The investigation examined the expression and function of MG53 in bladder cancer. MG53 is a member of the tripartite motif family of E3 ubiquitin ligases, which regulate metabolic homeostasis and tumor-associated signaling. In bladder cancer cells, the team assessed proliferation, invasion, glycolytic metabolism, intracellular reactive oxygen species, or ROS, and apoptosis.

Co-immunoprecipitation and ubiquitination assays were used to investigate the interaction between MG53 and AMPKα. Overexpression of MG53 reduced cell proliferation, invasion, and glycolytic metabolism in bladder cancer cells. It was also accompanied by increased intracellular ROS accumulation and a higher apoptotic rate.

The cells showed increased levels of cleaved caspase-3 and a higher Bax-to-Bcl-2 ratio, while the decrease in glycolytic metabolism was consistent with attenuation of the Warburg effect. These measurements link MG53 overexpression with reduced proliferative and invasive behavior, altered metabolism, and increased cell death in the experimental systems. The reported results do not establish the order in which all of these changes occurred or whether each one directly caused another.

Biochemical experiments identified AMPKα as a molecular target of MG53. Co-immunoprecipitation indicated that MG53 and AMPKα interacted, while ubiquitination assays showed that MG53 promoted AMPKα ubiquitination. The authors further demonstrated that MG53 drove AMPKα toward proteasomal degradation.

Together, the experiments support a mechanism in which elevated MG53 reduces AMPKα abundance, attenuates glycolytic metabolism, and suppresses bladder cancer-cell proliferation and invasion. The evidence comes from molecular assays and bladder cancer-cell experiments; the supplied study summary does not provide the full range of experimental controls or the complete sequence of downstream events. Findings from xenograft models extended the cell results to an in vivo setting.

In those animal models, MG53 overexpression inhibited tumor growth, supporting a suppressive role for the protein in the experimental bladder cancer system. The work identifies MG53 as a candidate therapeutic target, but the researchers explicitly stated that its translational value remains to be established in future preclinical and clinical studies. Accordingly, the results provide a mechanistic and preclinical basis for further investigation of MG53-mediated AMPKα degradation, rather than evidence that MG53-directed treatment is ready for clinical use.

Subject of Research: Preclinical study of MG53-mediated AMPKα degradation in bladder cancer.

Article Title: MG53 suppresses the progression of bladder cancer through E3 ubiquitin ligase-mediated degradation of AMPKα

Article References: He, X., Zhang, H., Zhang, Y., Wu, J., Wang, T., Liu, Y., Jin, K., Tang, W., Ye, Q., & Wang, Q. (2026). MG53 suppresses the progression of bladder cancer through E3 ubiquitin ligase-mediated degradation of AMPKα. Medical Oncology, 43(11), Article 337. https://doi.org/10.1007/s12032-026-03448-7

Image Credits: AI Generated

DOI: 10.1007/s12032-026-03448-7

Keywords: MG53, TRIM72, bladder cancer, AMPKα, E3 ubiquitin ligase, protein degradation, glycolytic metabolism, reactive oxygen species, apoptosis, xenograft models, suppresses, progression

Ubiquitin is a small, highly conserved 76-amino-acid protein whose covalent attachment to other proteins was once viewed mainly as a destruction tag. The canonical ubiquitination reaction proceeds through a three-enzyme cascade: a ubiquitin-activating enzyme (E1) charges ubiquitin in an ATP-dependent thioester reaction, a ubiquitin-conjugating enzyme (E2) transfers the activated ubiquitin, and a ubiquitin ligase (E3) catalyzes formation of an isopeptide bond between the ubiquitin C-terminal glycine and a lysine side chain on the substrate. When the substrate lysine receives a single ubiquitin, the modification is called monoubiquitination; when ubiquitin chains are built on that first ubiquitin, often through its lysine 48 or lysine 63 residues, the result is polyubiquitination. The two outcomes are functionally distinct, and the review emphasizes that monoubiquitination is not simply an intermediate step but a signal in its own right.

The authors draw a sharp contrast with the better-known story of histone monoubiquitination. Histones, the proteins around which DNA is wrapped, carry monoubiquitin marks at specific residues that primarily regulate chromatin structure and transcription. Non-histone monoubiquitination, by comparison, touches a far broader range of substrates and processes. The review organizes these into six major arenas: the DNA damage response, transcriptional regulation, signal transduction, endocytic trafficking, autophagy and immunity. In each case, a single ubiquitin acts as a portable molecular address label, changing where a protein goes, what it binds, or how long it survives without necessarily committing it to degradation.

The mechanistic logic is subtle. Unlike lysine-48-linked polyubiquitin, which flags proteins to the 26S proteasome for destruction, a monoubiquitin mark typically alters protein behavior in other ways. It can create binding sites for ubiquitin-binding domains on partner proteins, mediate incorporation of proteins into membranes or vesicles, control protein complex assembly and disassembly, or adjust enzymatic activity. Specificity is achieved through a combination of E3 ligase recognition motifs, docking sequences on substrates, and spatial organization within the cell. Deubiquitylating enzymes, which cleave ubiquitin from substrates, provide the counterweight, and the balance between writing and erasing monoubiquitin marks determines the functional state of hundreds of proteins at any moment.

Among the most consequential examples is the DNA damage response. Monoubiquitination of proliferating cell nuclear antigen, the sliding clamp that tethers DNA polymerases, serves as a master switch that redirects DNA synthesis from high-fidelity replication to translesion synthesis, allowing the replication machinery to bypass lesions that would otherwise stall it. This single modification therefore influences both genome stability and mutation rate, with direct implications for cancer initiation and treatment resistance. The review also discusses monoubiquitination of repair factors and signaling proteins that coordinate the cellular decision between repair, cell-cycle arrest and programmed death after DNA injury.

In signal transduction and membrane traffic, monoubiquitination acts as a routing signal. Receptors at the cell surface are monoubiquitinated after ligand binding, which directs them into the endocytic pathway and toward degradation or recycling, thereby tuning the intensity and duration of signaling. The same principle governs the trafficking of transporters, adhesion molecules and viral proteins. In autophagy, monoubiquitin marks on selective cargo receptors and on components of the autophagy machinery help determine what the cell consumes during stress. The immune system exploits the chemistry as well, with monoubiquitination modulating receptor signaling, antigen presentation and inflammatory pathways, and pathogens in turn have evolved strategies to hijack or block these marks.

The review’s therapeutic argument rests on the observation that dysregulated monoubiquitination is implicated in a wide range of human diseases. Aberrant monoubiquitin marks on tumor suppressors, oncogenes and cell-cycle regulators contribute to uncontrolled proliferation and metastasis. Faulty monoubiquitination of neuronal proteins is linked to protein aggregation and impaired synaptic function in neurodegenerative conditions. In immune and inflammatory disorders, miswritten monoubiquitin signals disturb the thresholds that normally keep immune activation in check. Because each mark is written by a specific E3 ligase and erased by specific deubiquitylating enzymes, the pathway offers many discrete intervention points rather than a single blunt target.

That granularity is already visible in the clinic. Proteasome inhibitors such as bortezomib exploit ubiquitin-dependent degradation in multiple myeloma, and a growing pharmacopeia of E3 ligase modulators and deubiquitylating enzyme inhibitors is in development for cancer and immune disease. The review suggests that monoubiquitination-specific mechanisms, distinct from polyubiquitination and proteasomal degradation, could support next-generation drugs with greater precision and fewer side effects. It also highlights technical advances, including ubiquitin remnant mass spectrometry and ubiquitin-chain-specific enrichment methods, that are expanding the catalog of monoubiquitinated substrates and making the modification tractable for drug discovery.

The authors, led by Kedian Chen, Haoguo Wang, Siqi Zhang and Siyao Qu with corresponding authors Chengzhong Xing, Pengcheng Jiang, Lei Qiao and Jingwei Liu, frame the review as a bridge between fundamental ubiquitin biochemistry and translational medicine. They acknowledge open questions, including how monoubiquitination sites are selected among competing lysines, how writers and erasers are themselves regulated, and how monoubiquitin signals are decoded differently in different cellular contexts. Answering these questions, they argue, will be essential for converting the growing mechanistic knowledge into reliable biomarkers and therapies.

For a modification that involves adding a single 8.5-kilodalton protein to a lysine residue, monoubiquitination has turned out to carry remarkable regulatory weight. The review’s synthesis makes clear that the field has moved past the era when ubiquitin was seen only as a destruction tag, and that the single-ubiquitin signal now stands alongside phosphorylation and acetylation as a central axis of cellular control. As the catalog of monoubiquitinated non-histone proteins grows and the disease connections multiply, the authors conclude, understanding and manipulating this modification may become a defining challenge for molecular medicine in the coming decade.

Subject of Research: Non-histone protein monoubiquitination: from cellular functions to mechanism and therapeutic potential of human diseases

Article Title: Non-histone protein monoubiquitination: from cellular functions to mechanism and therapeutic potential of human diseases

Article References: Chen, K., Wang, H., Zhang, S., Qu, S., Chang, X., Li, S., Li, A., Chen, X., Wang, S., Di, X., Wang, R., Xing, C., Jiang, P., Qiao, L., & Liu, J. (2026). Non-histone protein monoubiquitination: from cellular functions to mechanism and therapeutic potential of human diseases. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06479-5

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06479-5

Keywords: monoubiquitination, non-histone proteins, ubiquitin, post-translational modification, E3 ubiquitin ligase, deubiquitylating enzymes, DNA damage response, autophagy, endocytic trafficking, cancer therapy, Non-histone, protein

Protein arginine methylation is carried out by a family of enzymes called protein arginine methyltransferases, or PRMTs. These enzymes transfer methyl groups onto the nitrogen atoms of arginine residues, generating distinct chemical outcomes depending on the enzyme involved. Type I PRMTs produce asymmetric dimethylarginine marks, type II enzymes generate symmetric dimethylation, and type III and type IV PRMTs add monomethyl or terminal methyl modifications respectively. The substrates are remarkably diverse. PRMTs decorate histones, the spool-like proteins around which DNA is wound, thereby shaping gene expression programs, but they also modify a vast array of nonhistone proteins, altering their enzymatic activity, their ability to bind partner molecules, their subcellular localization and, crucially for the story told in this review, their recognition by the protein degradation machinery.

Ubiquitination is the second half of the dialogue. In this process, the small 76-amino-acid protein ubiquitin is attached to lysine residues on target proteins through a cascade involving an activating enzyme, a conjugating enzyme and, most importantly for specificity, a ubiquitin ligase known as an E3. Depending on how ubiquitin chains are assembled and linked, the consequence can be proteasomal destruction of the tagged protein or, alternatively, a non-degradative change in trafficking, interaction or activity. Deubiquitinases, the enzymes that remove ubiquitin marks, add a further layer of reversibility. Together, methylation and ubiquitination therefore represent two of the most versatile post-translational modification systems in the cell, and the review’s central thesis is that they constantly influence one another rather than operating on separate tracks.

The crosstalk runs in both directions. In one direction, arginine methylation can change how readily a protein is recognized by E3 ubiquitin ligases. Methylation of an arginine residue can mask or reshape the local surface of a protein, sometimes blocking the docking of a ligase and thereby protecting the protein from ubiquitination and degradation. In other contexts, the same chemical mark does the opposite: it creates or exposes a recognition element that recruits the ubiquitination machinery, accelerating the destruction of the tagged protein. This means a single methylation event can function as either a stabilizing shield or a degradation signal, depending on the protein and the cellular setting, a context dependence that the authors identify as one of the field’s central challenges.

The reverse direction is equally consequential. E3 ubiquitin ligases and deubiquitinases can act directly on the PRMT enzymes themselves, controlling their abundance, stability and, by extension, the overall methylation landscape of the cell. When a ligase tags a PRMT for proteasomal degradation, the methyl marks that enzyme would have deposited begin to fade, changing the fate of dozens of downstream substrates. Conversely, when deubiquitinases rescue a PRMT from degradation, methylation-dependent signaling is sustained or amplified. The result is a feedback architecture in which each system tunes the other, creating what the authors describe as a dynamic, bidirectional network rather than a simple linear pathway.

What makes this network medically important is its reach into nearly every hallmark of cancer. The review connects methylation-ubiquitin crosstalk to tumor invasion and metastasis, to the uncontrolled proliferation of malignant cells, to apoptosis, the programmed cell death that many therapies try to trigger, and to ferroptosis, an iron-dependent form of cell death that has become a major focus of cancer research. It also implicates the network in DNA repair and the maintenance of genomic stability, in the metabolic reprogramming that allows tumors to fuel their growth, in the acquisition of drug resistance and in immune escape, the process by which cancer cells avoid detection by cytotoxic T cells and other immune effectors. By determining whether key signaling proteins are stabilized or destroyed, the crosstalk effectively sets the gain on the molecular circuits that govern how cancer cells grow, move, survive stress and respond to treatment.

The therapeutic implications are considerable. PRMT inhibitors have already entered clinical development for several malignancies, and the review argues that understanding the ubiquitination dimension of PRMT biology could explain why single-agent approaches sometimes fall short and how resistance emerges. If methylation protects an oncogenic protein from degradation, then blocking the methyltransferase should destabilize that protein; if ubiquitination destroys a tumor suppressor only after it has been methylated, then the therapeutic logic inverts. The authors highlight several forward-looking strategies, including dual-function inhibitors designed to hit both modification systems at once, small-molecule degraders that exploit the ubiquitin-proteasome machinery to eliminate disease-driving proteins, and engineered nanobodies that could be tailored to disrupt specific methylation-dependent recognition events. They also point to combination approaches in which modulation of the methylation-ubiquitin network is paired with immune checkpoint blockade, with the goal of making tumors more visible to the immune system while simultaneously undermining their survival circuits.

The authors are careful to emphasize the obstacles. The crosstalk is highly context-dependent: the same methylation event can stabilize one protein and destabilize another, and the same ligase can behave as an oncogene in one tumor type and a tumor suppressor in another. Mapping these relationships across dozens of PRMT substrates and hundreds of E3 ligases will require systematic approaches, including proteomics methods that can simultaneously read methylation and ubiquitination states on the same molecules. Achieving therapeutic precision is a second challenge, since both PRMTs and ubiquitination enzymes have many normal physiological roles, and indiscriminate interference risks toxicity. The review frames these difficulties not as reasons for pessimism but as a research agenda, identifying the mapping of context-specific crosstalk nodes as a priority for the field.

For readers following the broader post-translational modification literature, the review situates arginine methylation within a family of cross-regulated marks that increasingly includes phosphorylation, acetylation and O-GlcNAcylation, each of which has been shown to influence protein stability in ways analogous to the mechanisms described here. What distinguishes the methylation-ubiquitin axis is the depth of its documented involvement in cancer-relevant pathways and the growing availability of chemical tools to probe it. As PRMT inhibitors mature clinically and as degrader technologies expand, the points of contact between these two systems are likely to become some of the most closely watched nodes in cancer pharmacology.

The review, Protein arginine methylation and ubiquitination: A prominent crosstalk and its functions in cancer, was published in Genes & Diseases, a peer-reviewed journal focused on the molecular bases of human disease. Its synthesis suggests that the next phase of work will move from cataloging individual methylation-ubiquitin pairs to modeling the network as a whole, with the aim of predicting how a given tumor will respond when one arm of the dialogue is therapeutically silenced. If that predictive understanding can be achieved, the molecular conversation between arginine methylation and ubiquitination may shift from an object of study to a set of actionable targets in the clinic.

Subject of Research: Crosstalk between protein arginine methylation and ubiquitination in cancer biology and therapy

Article Title: Decoding a molecular dialogue: How arginine methylation and ubiquitination shape cancer

Article References: Decoding a molecular dialogue: How arginine methylation and ubiquitination shape cancer. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: arginine methylation, ubiquitination, PRMT, post-translational modification, cancer, E3 ubiquitin ligase, deubiquitinase, ferroptosis, drug resistance, immune escape, proteasome, Genes & Diseases

That gap has now been substantially closed. A team of researchers led by Marco Jost of Harvard Medical School, working alongside colleagues including Seth Rakoff-Nahoum, Emily Balskus of Harvard University and the Howard Hughes Medical Institute, and Michael Fischbach of Stanford University, has deployed genome-scale CRISPR screening to systematically identify the regulators of AHR signaling in a human hepatocyte model. The study, published in Genome Biology, represents one of the most comprehensive efforts to date to chart the wiring diagram of this enigmatic receptor. Rather than examining candidate genes one at a time, the team perturbed virtually every gene in the human genome and measured the consequences for AHR activity, allowing the data to reveal the regulatory architecture on an unbiased, genome-wide scale.

The technical approach at the heart of the study is CRISPR interference, or CRISPRi, a refined application of the gene-editing technology that does not cut DNA. Instead, a catalytically dead form of the Cas9 protein is guided to specific genes, where it acts as a reversible brake on transcription, silencing expression without altering the underlying genetic code. By delivering a genome-wide library of guide RNAs into cells engineered so that AHR activation produces a measurable fluorescent or luminescent readout, the researchers could simultaneously test the effect of losing each of roughly twenty thousand human genes on the signaling pathway. Genes whose silencing boosted the readout are candidate negative regulators of AHR; those whose silencing dampened the signal are candidate positive regulators. The beauty of the method lies in its parallelism: thousands of regulatory hypotheses are tested in a single experiment, and the strength of each guide RNA’s enrichment or depletion across the population quantifies the effect.

The results provided immediate validation that the screens had captured genuine biology. Among the hits recovered were the core components of the canonical AHR pathway itself, including the receptor, its nuclear translocator partner ARNT, and factors involved in ligand binding and receptor degradation. This internal consistency mattered, because a screen that failed to rediscover the known players could not be trusted to reveal unknown ones. But beyond the expected genes, the datasets surfaced a large and previously unmapped network of regulators, many of which had never been connected to AHR biology. The breadth of the hit list carried its own message: AHR signaling is not an isolated detoxification circuit but a process deeply interwoven with the general machinery of human cells, touching protein synthesis, trafficking, degradation, and chromatin regulation.

One of the study’s most striking findings concerns the fate of the receptor protein itself. The team identified the E3 ubiquitin ligase UBR5 as a factor that sustains AHR signaling by counteracting the degradation of ligand-bound AHR. Ubiquitin ligases are the enzymes that tag proteins with ubiquitin marks, often condemning them to destruction by the proteasome, and the interplay between AHR and the ubiquitin-proteasome system has long been known to shape receptor levels. What the new work adds is a specific, experimentally validated node within that system: when UBR5 function was compromised, ligand-activated AHR was degraded more readily, and the downstream transcriptional program weakened. In other words, UBR5 acts as a guardian of the activated receptor, extending the window during which AHR can drive gene expression after it encounters its chemical triggers.

The screens also probed how regulation depends on context, a question of particular importance for a receptor that responds to chemically diverse ligands ranging from environmental toxins to microbially derived metabolites such as urolithins, the gut bacterial products that the team included in their chemical analyses. By repeating CRISPRi screens with different inducing molecules, the researchers could classify regulators into those that act generally across all ligands and those whose effects are specific to particular inducers. This distinction is more than a technical curiosity. General regulators represent the pathway’s universal infrastructure, while ligand-specific and cell-type-specific regulators offer potential points of selective manipulation. A drug aimed at a general node would shift AHR activity everywhere; one aimed at a context-specific node could, in principle, tune the receptor’s response to microbial metabolites in the gut without disturbing its detoxification duties in the liver.

That therapeutic logic runs throughout the study’s conclusions. Because AHR sits at the interface of environment, diet, microbiome, and immunity, pharmaceutical interest in the receptor has grown steadily, with attempts to modulate it for inflammatory bowel disease, autoimmune conditions, and metabolic disorders. The obstacle has always been specificity: blunt activation or inhibition of AHR produces widespread effects, some beneficial and some harmful. By identifying cell-type-specific and ligand-specific regulatory components, the new map provides a catalog of candidate targets for more surgical interventions. The authors frame these context-dependent nodes as potential handles for manipulating AHR signaling in a targeted manner for therapeutic benefit, a framing that turns a basic-science dataset into a starting point for drug discovery.

The study also carries implications for understanding host-microbe interactions, one of the most active frontiers in biology. Gut bacteria generate a pharmacopeia of small molecules, and AHR is one of the principal receptors through which these metabolites communicate with the host immune system. Microbial ligands of AHR have been implicated in maintaining the intestinal barrier, calibrating immune responses, and protecting against colitis. A complete regulatory map of the pathway in human cells gives researchers a systematic way to ask how host genetics shapes sensitivity to microbial chemistry, and why individuals or disease states might differ in their responses to the same bacterial metabolites. The integration of chemical screening with genetic screening in this work, including the use of a urolithin library prepared specifically for the study, exemplifies the kind of combined approach that the field of host-microbe chemical biology increasingly demands.

Methodologically, the work demonstrates how far functional genomics has come in dissecting signaling pathways that were once studied gene by gene over decades. The researchers supplemented their primary genome-wide screens with focused sublibrary screens, individual validation assays using independently designed guide RNAs, transcriptional measurements, and biochemical analyses of receptor protein turnover, including western blot experiments documented with full-length unprocessed scans. The classification of hits by activation phenotype across multiple inducers, and the assessment of regulator activity across different cell types, turned a flat list of genes into a structured network with layers of general, ligand-specific, and cell-type-specific control. The datasets, released openly with the article, include raw and analyzed screen data, guide RNA sequences, and primer sequences, providing a resource that other laboratories can mine and reanalyze.

What emerges from the study is a picture of AHR as a receptor embedded in a dense web of cellular governance, its activity shaped not only by which ligand is present but by an extensive cast of proteins controlling its expression, abundance, localization, and longevity. The identification of UBR5 as a protector of the activated receptor offers a mechanistic vignette of how that governance works at the level of protein stability, while the broader network suggests that perturbations far removed from the canonical pathway could nonetheless modulate how human cells respond to the chemical world. For a receptor whose dysfunction has been tied to metabolic and inflammatory disease, and whose normal function depends on a constant dialogue between the body and its microbial inhabitants, the new regulatory map is both a reference atlas and a hypothesis engine. It transforms AHR from a well-studied but incompletely understood sensor into a system whose vulnerabilities and control points can, for the first time, be surveyed in their entirety.

Subject of Research: Genome-scale CRISPR identification of regulators of aryl hydrocarbon receptor signaling in human cells

Article Title: Identification of regulators of aryl hydrocarbon receptor signaling in human cells by genome-scale CRISPR screening

Article References: Verma, M., Adamthwaite, M. L., Desai, K., Ding, Y., Wang, X., Bae, M., Rakoff-Nahoum, S., Balskus, E. P., Fischbach, M. A., & Jost, M. (2026). Identification of regulators of aryl hydrocarbon receptor signaling in human cells by genome-scale CRISPR screening. Genome Biology. https://doi.org/10.1186/s13059-026-04299-1

Image Credits: AI Generated

DOI: 10.1186/s13059-026-04299-1

Keywords: aryl hydrocarbon receptor, CRISPR screening, gene regulation, transcription factor, UBR5, E3 ubiquitin ligase, gut microbiome, microbial metabolites, xenobiotic detoxification, host-microbe interactions, inflammatory disease, hepatocytes

To understand why this matters, it helps to start with PROTACs, or PROteolysis TArgeting Chimeras. These bifunctional molecules are the flagship technology of targeted protein degradation, one of the most exciting areas of modern drug discovery. A PROTAC has two business ends: one binds a protein that scientists want eliminated, and the other recruits an E3 ubiquitin ligase, the cellular machinery that tags unwanted proteins for destruction by the proteasome. By physically dragging the target protein into contact with the ligase, a PROTAC catalyzes the formation of a protein-protein interaction that would never happen naturally, triggering the cell’s own waste-disposal system to chew up the target. Unlike conventional inhibitors, which merely block a protein’s activity and must be present at high concentrations to keep it suppressed, degraders can eliminate the protein altogether and work catalytically, so a single molecule can destroy many copies of its target.

The problem is that this power comes with a loss of control. Because PROTACs act anywhere they reach in the body, they can degrade their target proteins in healthy tissues as well as diseased ones, producing side effects that are difficult to predict. The field has therefore been searching for ways to impose spatiotemporal control, meaning the ability to restrict drug activity to a specific place at a specific time. Light is the most attractive remote trigger for this purpose, since it can be focused on a tissue with exquisite precision and switched on and off at will. Photocaging strategies, in which a light-sensitive chemical group masks a drug’s activity until illumination releases it, have been applied to PROTACs before, but earlier systems suffered from weak contrast between the dark and illuminated states, or required high-energy ultraviolet light that damages cells and penetrates poorly into tissue.

The team behind the new work, led by Dmytro Havrylyuk, David K. Heidary and Edith C. Glazer at North Carolina State University, together with colleagues at the University of Kentucky, took a different approach by building the light switch out of a metal. Their RuPHOTACs use ruthenium(II) coordination complexes as photocages wrapped around the PROTAC scaffold. Ruthenium complexes have a distinctive photochemistry: when they absorb light, they can undergo ligand photodissociation, cleanly releasing the molecule attached to the metal. Crucially, the absorption properties of these complexes can be tuned so that the release is driven by low-energy red light rather than damaging ultraviolet wavelengths. Red light penetrates deeper into biological tissue and is far gentler on living cells, which is why the authors emphasize that their systems are optimized for biological applications rather than merely demonstrated in a cuvette.

To prove the concept, the researchers targeted bromodomain-containing proteins, a family of epigenetic regulators that read acetylation marks on histones and help control gene expression. These proteins, particularly members of the BET family, are major targets in cancer research because many tumors depend on them to drive the expression of growth-promoting genes. In the dark, the ruthenium cage keeps the RuPHOTAC inert; when illuminated with red light, the cage releases the active degrader, which then recruits the E3 ligase and drags the bromodomain protein to the proteasome. The team showed that the compounds strongly reduced not only the levels of the bromodomain targets themselves but also the abundance of two important downstream proteins, c-MYC and PIM1, both of which are transcriptional targets of BET proteins and both of which are heavily implicated in cancer progression. Knocking down c-MYC in particular is a longstanding goal in oncology, since the protein has been notoriously difficult to drug with conventional small molecules.

The quantitative performance of the new compounds is what sets the study apart. The authors report that the RuPHOTACs achieve the highest selectivity for activation in the light versus the dark reported for photocontrolled degraders, meaning that in the absence of light the molecules are essentially silent, while a brief illumination unleashes full degrading activity. They also show improved potency against the target proteins compared with prior systems, so less compound is needed to achieve the same degree of degradation. Most strikingly, the increased efficacy extends to animal work: using low-energy red light, the team demonstrated increased efficacy in vivo, a critical benchmark because many photochemical technologies that shine in cell culture fail when confronted with the optical and biological complexity of a living organism.

Measuring protein degradation sounds simple but is surprisingly tricky, and the study introduces an elegant solution to a chronic measurement problem. Traditional assays often rely on antibodies or fluorescent tags that report total protein abundance, but those signals conflate two opposing processes: the destruction of existing protein molecules and the continuous production of new ones. If a drug slows protein synthesis as a side effect, or if the cell ramps up production to compensate for degradation, the apparent degradation rate becomes distorted. To disentangle these effects, the researchers created fusion proteins in which the target of interest is fused to Dendra2, a photoconvertible fluorescent protein. Dendra2 can be switched from a green to a red fluorescent state by light, allowing the researchers to mark a defined cohort of pre-existing protein molecules and then watch that cohort disappear over time as the PROTAC does its work.

This bifunctional reporter system offers several advantages over previously described PROTAC reporters. Because the photoconverted molecules are already synthesized, any change in the red fluorescence signal reflects true degradation rather than changes in new protein production. At the same time, the green signal tracks newly synthesized protein, so the researchers can monitor both destruction and replenishment simultaneously in the same living cell. Importantly, the approach does not perturb translation, proteostasis, or cell health, meaning the measurements reflect normal cellular physiology rather than artifacts introduced by the measurement itself. The authors argue that this makes the system superior to prior reporter strategies for live-cell analysis of protein degradation, and it could become a standard tool for the broader targeted degradation community, which has long struggled with assay artifacts.

The study also carries a broader message about the role of metals in chemical biology. Ruthenium is not a component of any natural biomolecule, and metal complexes are often viewed with suspicion in drug development because of concerns about stability and toxicity. Yet the work demonstrates that incorporating a metal component within an organic PROTAC confers multiple concrete advantages: a clean and efficient photorelease mechanism, absorption profiles compatible with low-energy red light, and tunable photophysical properties that organic photocages struggle to match. The researchers suggest that this design philosophy, using coordination chemistry as an engineering platform for light-controlled drugs, could extend well beyond the specific bromodomain targets validated here, potentially allowing any PROTAC scaffold to be fitted with a ruthenium switch.

Caveats remain, as they always do at this stage of translation. The work was supported by the National Institutes of Health and the Kentucky Cabinet for Health and Family Services, and the authors declare no competing interests, but moving from validated compounds in cells and animal models toward clinical candidates will require extensive safety evaluation of the ruthenium payloads, optimization of light delivery to internal organs, and pharmacokinetic studies that the current paper does not address. The article itself was shared early as a peer-reviewed accepted manuscript subject to further editorial processing. Even so, the combination of near-total dark-state silence, red-light activation, in vivo efficacy, and a genuinely improved measurement technology makes RuPHOTACs one of the most complete demonstrations to date that protein degradation can be placed under remote optical control. For a field racing to make degraders safer and more precise, that is a result worth watching closely.

Subject of Research: Light-activated ruthenium photocaged PROTACs for spatiotemporally controlled targeted protein degradation

Article Title: RuPHOTACs provide photocontrol over protein degradation with optimized properties for biological applications

Article References: Havrylyuk, D., LaMore, A. P., Al-Hamaly, M. A., Blackburn, J. S., Heidary, D. K., & Glazer, E. C. (2026). RuPHOTACs provide photocontrol over protein degradation with optimized properties for biological applications. Nature Communications. https://doi.org/10.1038/s41467-026-78110-x

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78110-x

Keywords: targeted protein degradation, PROTACs, RuPHOTACs, ruthenium photocages, photochemistry, E3 ubiquitin ligase, bromodomain proteins, c-MYC, Dendra2 reporter, red light activation, chemical biology, cancer research

The research, conducted by Juhong Xie, Jiayi Lei, Qinxue Zhu, Bin Gui, Yongming Li, Yaping Wang, and Rong Huang, began with an observation made in an earlier study. Using random mutagenesis in the rare minnow, Gobiocypris rarus, a small laboratory model fish widely used in Chinese aquatic disease research, the team had identified a gene whose variation was associated with susceptibility to hemorrhagic disease. That gene encoded a protein resembling an E3 ubiquitin ligase, the class of enzymes responsible for attaching ubiquitin tags to target proteins. In the new work, detailed domain and amino acid sequence analyses confirmed that the gene truly encodes a functional E3 ubiquitin ligase, and because close relatives of the gene are found only in fish, the team designated it NHRE3, a fish-specific member of this enzyme family.

Ubiquitination is one of the cell’s most versatile regulatory tools. By stringing chains of ubiquitin, a small regulatory protein, onto specific lysine residues of a target protein, E3 ligases determine that protein’s fate. K48-linked polyubiquitin chains, in particular, serve as a molecular kiss of death: they are recognized by the proteasome, the cell’s protein-shredding machinery, and the tagged protein is rapidly degraded. Viruses have learned to exploit this system extensively. In mammals, viral proteins frequently hijack the ubiquitin pathway to dismantle signaling molecules that would otherwise trigger interferon production, the body’s first chemical alarm against infection. The question the Chinese team posed was whether fish viruses use similar tricks, and if so, through what molecular intermediaries.

The first clue came from genetics. The researchers generated rare minnows in which the nhre3 gene was knocked out, producing nhre3-null animals. When these fish were challenged with GCRV, they displayed significantly enhanced resistance to the virus compared with normal fish. In other words, removing NHRE3 made the fish harder to infect, which strongly implied that the ligase normally works in the virus’s favor. This was a striking result, because it suggested that a host-encoded enzyme was acting as an accomplice to viral infection, suppressing the very defenses it might have been expected to support. Such pro-viral host factors are prized targets for intervention, since blocking them can bolster immunity without directly attacking the virus itself.

To find out what NHRE3 actually does at the molecular level, the team turned to immunoprecipitation followed by mass spectrometry, a technique that pulls a bait protein out of the cell along with everything it physically associates with. The screen identified interferon-stimulated gene 15, or ISG15, as an NHRE3-interacting protein. ISG15 is one of the most strongly induced genes during antiviral responses across vertebrates, and in mammals it functions both as a free intracellular protein and as a modifier conjugated onto other proteins in a process called ISGylation. Its precise antiviral role in fish, however, had remained poorly understood, which made the discovery of its interaction with NHRE3 doubly significant: it implicated ISG15 in fish antiviral defense while simultaneously suggesting a mechanism by which that defense could be undermined.

Subsequent biochemical experiments established the full pathway. NHRE3 possesses genuine E3 ubiquitin ligase activity, and it uses that activity to catalyze K48-linked polyubiquitination of ISG15. Once tagged with these destruction chains, ISG15 is routed to the proteasome and degraded. The logic of the system is therefore elegantly sinister: the host produces ISG15 to fight the virus, and NHRE3, a fish-specific enzyme, eliminates ISG15 before it can do its job, thereby promoting GCRV infection. The knockout fish, lacking NHRE3, retain their ISG15 and consequently mount a stronger antiviral response, which explains their enhanced resistance to hemorrhagic disease.

Because the antiviral mechanism of ISG15 in fish had not been clearly defined, the researchers went on to investigate what ISG15 actually does downstream. Their experiments revealed that fish ISG15 can interact with IRF3, interferon regulatory factor 3, a central transcription factor in the innate antiviral response. In mammals and other vertebrates, IRF3 is activated when viral nucleic acids are detected by pattern-recognition receptors; once activated, it translocates to the nucleus and switches on the transcription of interferons and a broad panel of antiviral effector genes. The new study found that fish ISG15 promotes the expression of innate immune factors downstream of IRF3, thereby amplifying the antiviral program and exerting its protective effect against GCRV. This positions ISG15 not merely as a passive marker of interferon activity but as an active participant in the signaling cascade that drives it.

The comparison with mammalian immune evasion strategies is where the study acquires its broader evolutionary resonance. In mammals, viruses that target the ISG15 system generally do so in one of two ways: they inhibit ISGylation, the conjugation of ISG15 onto host and viral proteins, or they induce deISGylation, the enzymatic removal of ISG15 from its targets. Both strategies tinker with the modification process itself. The mechanism described in the fish study is different in kind. Here, the virus benefits from a host-encoded, fish-specific ubiquitin ligase that removes ISG15 from the cell entirely by sending it to the proteasome. The authors suggest that this may represent a more primitive or more diverse form of innate immune regulation, one in which the balance of the antiviral response is governed by the stability of ISG15 itself rather than by its conjugation state.

That interpretation carries implications for how scientists think about the origins of antiviral immunity. The immunological arms race between hosts and pathogens is ancient, predating the divergence of the major vertebrate lineages by hundreds of millions of years. Fish occupy a pivotal position in that history, and discovering that a fish-specific enzyme mediates viral immune escape through protein degradation suggests that the repertoire of evasion strategies available to viruses may be broader, and older, than the mammalian-focused literature implies. It also underscores the degree to which lineage-specific innovations, in this case a ubiquitin ligase found only in fish, can shape the outcome of infection in ways that have no direct parallel in laboratory mammals.

For aquaculture, the practical implications are immediate. Grass carp hemorrhagic disease remains a serious threat to one of the world’s largest freshwater aquaculture industries, and GCRV has proven difficult to control through conventional means. The NHRE3-ISG15 axis offers a concrete molecular target: strategies that inhibit NHRE3 activity, stabilize ISG15, or enhance IRF3-driven antiviral gene expression could plausibly be developed into breeding markers, feed additives, or therapeutic approaches that strengthen fish resistance to GCRV. The nhre3 knockout minnows generated in the study provide a proof of principle that removing this single gene measurably improves survival in the face of viral challenge. More broadly, the work demonstrates the value of studying host-pathogen interactions in non-mammalian systems, where the molecular logic of immunity may differ in instructive ways. By tracing the fate of a single protein, ISG15, from induction to ubiquitination to proteasomal destruction, the researchers have assembled a complete evasion circuit and, in doing so, illuminated one of the more ancient strategies in the long war between viruses and vertebrate hosts.

Subject of Research: A fish-specific E3 ubiquitin ligase that suppresses antiviral immunity by ubiquitinating ISG15

Article Title: A fish-specific E3 ubiquitin ligase NHRE3 suppresses antiviral immunity by degrading ISG15 via ubiquitination

Article References: Xie, J., Lei, J., Zhu, Q., Gui, B., Li, Y., Wang, Y., & Huang, R. (2026). A fish-specific E3 ubiquitin ligase NHRE3 suppresses antiviral immunity by degrading ISG15 via ubiquitination. PLOS Pathogens, 22(9), e1014544. https://doi.org/10.1371/journal.ppat.1014544

Image Credits: AI Generated

DOI: 10.1371/journal.ppat.1014544

Keywords: NHRE3, ISG15, E3 ubiquitin ligase, grass carp reovirus, antiviral immunity, ubiquitination, proteasome, innate immunity, aquaculture, rare minnow, IRF3, immune evasion

The research, led by Chenxi Li, Yingying Qin and Yajuan Yang of Shandong University and collaborating institutions in China, focused on what happens when mouse primordial germ cells lose RAD54 like, or RAD54L. The team found that without this factor, the cells proliferate poorly, leaving an insufficient pool of germ cells and ultimately impairing fertility. The defect traces back to a specific molecular hazard: the accumulation of topoisomerase I cleavage complexes, abbreviated TOP1ccs, which are among the most common and most dangerous lesions that arise during DNA replication.

To appreciate why TOP1ccs matter, it helps to understand what topoisomerase I normally does. As the two strands of the double helix are prised apart for copying, the DNA ahead of the replication machinery becomes overwound, like a rope twisted too tightly. Topoisomerase I relieves this torsional stress by nicking one strand of the DNA, allowing it to swivel freely, and then sealing the break again. The enzyme normally completes this cut-and-paste cycle in a fraction of a second. Occasionally, however, the enzyme becomes trapped mid-cycle, covalently bonded to the DNA at the nick it just created. That trapped enzyme-DNA adduct is the TOP1 cleavage complex, and if it is not removed promptly, the approaching replication fork collides with it, converting a transient intermediate into a double-strand break and stalling DNA synthesis.

Cells possess dedicated machinery to clear these protein-DNA adducts, and the new study adds a surprising player to that list. The researchers showed that RAD54L promotes the degradation of TOP1ccs through the ubiquitin-proteasome pathway, the cellular recycling system that tags unwanted proteins with chains of ubiquitin and delivers them to the proteasome for destruction. The key to this activity lies in a partnership between RAD54L and tripartite motif-containing protein 21, or TRIM21, which the authors identify as a newly recognized E3 ubiquitin ligase responsible for clearing TOP1ccs. E3 ligases are the enzymes that confer specificity on the ubiquitin system, deciding which targets get marked for degradation. In this case, TRIM21 appears to be the enzyme that flags trapped topoisomerase I for removal.

The mechanistic twist is that RAD54L does not itself ligate ubiquitin. Instead, it interacts with TRIM21 and stabilizes the protein, keeping sufficient TRIM21 available to do its clearing work. When RAD54L is absent, TRIM21 is not maintained properly, TOP1ccs accumulate, and the resulting DNA damage escalates. In RAD54L-deficient primordial germ cells, this cascade of events exacerbates DNA damage, undermines proliferation and erodes the reproductive reserve. The finding reframes RAD54L, historically viewed as a homologous recombination factor that helps search for and invade homologous DNA templates during double-strand break repair, as also acting upstream of repair, at the stage of removing the lesions that would otherwise create breaks in the first place.

Primordial germ cells are an especially revealing setting for this kind of analysis. These cells undergo rapid mitotic divisions during embryonic development, and their genome must be transmitted faithfully across generations. High levels of replication, combined with the metabolic demands of a growing embryo, make TOP1ccs a constant threat. The DNA damage response mechanisms that protect somatic cells have been studied extensively, but the regulatory networks that safeguard the germline during this early mitotic phase have remained largely unexplored. By showing that a defect in a single DNA damage response factor can compromise the founding population of the germline, the study connects genome maintenance at the molecular level to fertility at the organismal level.

The experimental logic of the work follows a path familiar to genome stability researchers but with distinctive results. Mice lacking RAD54L in their germ cells show proliferation defects in the primordial germ cell population. The DNA damage observed in these cells is not random; it is specifically tied to TOP1cc accumulation, which means the damage is preventable if the trapped complexes are cleared. The demonstration that RAD54L stabilizes TRIM21 provides a coherent causal chain: loss of RAD54L destabilizes the E3 ligase, the ligase can no longer ubiquitinate trapped topoisomerase I efficiently, the adducts persist, replication forks collide with them, and DNA damage mounts until cells falter or die.

The discovery also resonates with a broader and clinically important theme in cancer medicine. Drugs called topoisomerase I poisons, including camptothecin and its clinical derivatives irinotecan and topotecan, work precisely by stabilizing the TOP1 cleavage complex, trapping the enzyme on DNA and forcing tumor cells into lethal collisions between replication forks and the drug-stabilized adducts. Understanding how healthy cells, and particularly vulnerable populations like germ cells, clear TOP1ccs has implications for how such treatments affect fertility and for how resistance to these drugs emerges. A pathway involving RAD54L and TRIM21 that governs the lifespan of TOP1ccs could, in principle, influence both the toxicity and the efficacy of these widely used chemotherapeutics, although the new study addresses physiology rather than treatment outcomes.

TRIM21 itself carries an interesting scientific history. Long studied in immunology as an antibody receptor inside cells, it has more recently been appreciated as a versatile quality-control factor that recognizes and ubiquitinates a range of intracellular targets. Its identification here as the E3 ligase for TOP1cc clearance in germ cells extends that repertoire into genome maintenance and adds a new dimension to how the ubiquitin system participates in the DNA damage response. The RAD54L-TRIM21 axis suggests that repair factors may do more than mend breaks after they occur; some may actively manage the burden of endogenous lesions so that breaks are less likely to arise at all.

For the field of reproductive biology, the study fills in a piece of a larger puzzle: how the mitotic phase of gametogenesis, before meiosis begins, is protected against the wear and tear of rapid proliferation. The authors frame their results as extending understanding of the regulatory mechanisms that safeguard genome integrity during this process, and the practical significance is clear. A diminished primordial germ cell pool is a diminished reproductive reserve, and the work points to TOP1cc accumulation as one preventable driver of that loss. As with any mouse study, translating the findings to human fertility will require further work, but the core machinery of topoisomerase I, the ubiquitin-proteasome system and the DNA damage response is conserved across mammals, making the pathway a plausible target for future investigations into reproductive health and the side effects of topoisomerase-targeting therapies.

Subject of Research: The role of RAD54L and TRIM21 in clearing topoisomerase I cleavage complexes to maintain genome stability in primordial germ cells

Article Title: RAD54L counteracts topoisomerase I cleavage complexes by stabilizing E3 ligase TRIM21 to maintain genome stability

Article References: Li, C., Wang, S., Xu, W., Kong, Z., Wen, C., Zhao, S., Cao, L., Chen, Z.-J., Zhao, S., Qin, Y., & Yang, Y. (2026). RAD54L counteracts topoisomerase I cleavage complexes by stabilizing E3 ligase TRIM21 to maintain genome stability. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06458-w

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06458-w

Keywords: RAD54L, TRIM21, topoisomerase I cleavage complexes, primordial germ cells, genome stability, DNA damage response, ubiquitin-proteasome pathway, replication stress, fertility, gametogenesis, E3 ubiquitin ligase, DNA repair

The research, led by Junrui Luo and Zhiqiang Liu at Henan Polytechnic University in Jiaozuo, China, focused on TRIM37, a member of the tripartite motif family of E3 ubiquitin ligases. These enzymes act as molecular quality-control agents, attaching small ubiquitin protein tags to specific target molecules, which then marks those targets for destruction or alters their behavior. TRIM37 had already been implicated in cancer development and in maintaining the health of centrioles, the barrel-shaped structures from which cilia are built. But its precise role in the assembly of primary cilia, a process biologists call ciliogenesis, had remained murky until now.

To probe that role, the team worked with two widely used laboratory cell lines: human retinal pigment epithelial cells, known as RPE1 cells, which are a standard model for studying cilia, and HK2 cells, a human kidney cell line. Both of these cell types normally grow prominent primary cilia when they exit the active cell cycle and settle into a quiescent state. When the researchers used RNA interference to knock down TRIM37 expression, they observed a striking effect: the fraction of cells that managed to grow cilia dropped significantly, and the cilia that did form were noticeably shorter than normal. Importantly, the team verified that this defect was not simply a side effect of altered cell cycle progression, ruling out one obvious alternative explanation.

A key clue to the mechanism came from the location of the protein itself. Using fluorescence microscopy, the researchers found that TRIM37 accumulates at the basal body, the modified centriole that anchors the cilium to the cell and serves as the gateway through which building blocks are ferried into the growing organelle. This strategic positioning suggested that TRIM37 might be doing more than just housekeeping at the cilium’s foundation. It hinted that the protein could be actively managing the local environment needed for ciliary assembly, possibly by coordinating the delivery or removal of materials at the base of the structure.

That suspicion led the investigators to autophagy, the cell’s internal recycling program. During autophagy, the cell engulfs damaged proteins and organelles in double-membraned vesicles called autophagosomes, which then fuse with lysosomes, the acidic compartments where the cargo is broken down and its components are returned for reuse. Autophagy has a complicated, two-sided relationship with cilia: at moderate levels it can help clear inhibitors of ciliary assembly, but excessive or insufficient autophagic activity can disrupt cilium formation. The researchers discovered that when TRIM37 was depleted, cells accumulated LC3-II, a lipidated form of a protein that decorates autophagosomal membranes, along with p62, also known as SQSTM1, a cargo receptor that shuttles tagged material into autophagosomes. At the same time, levels of Beclin1 and WIPI2, two proteins essential for launching the autophagy program, declined, indicating that the initiation of autophagy itself was being suppressed.

To determine whether the accumulated autophagic machinery was actually working, the team deployed bafilomycin A1, a toxin that blocks the final step of autophagy by preventing the acidification of lysosomes and the fusion of autophagosomes with them. By comparing autophagic flux, the complete throughput of the recycling pipeline, in the presence and absence of this blocker, the researchers confirmed that TRIM37-deficient cells suffered from genuine flux impairment. An independent immunofluorescence assay measuring the colocalization of LC3 with LAMP2, a lysosomal membrane protein, painted the same picture: autophagosome formation was reduced, and the fusion of autophagosomes with lysosomes was defective. In other words, losing TRIM37 did not merely slow the recycling line at one checkpoint; it jammed the entire conveyor belt.

The next question was whether TRIM37’s enzymatic activity, its ability to transfer ubiquitin tags, was required for these effects. The researchers performed functional complementation experiments, re-introducing TRIM37 variants into depleted cells and testing whether the protein could rescue normal cilium growth and autophagic balance. The results were unambiguous: only a version of TRIM37 with intact E3 ubiquitin ligase activity could restore normal ciliogenesis and autophagic homeostasis. A catalytically dead variant could not. This finding elevated TRIM37 from a passive structural component to an active enzymatic regulator whose chemical function is the linchpin of the whole process.

Having established that TRIM37’s ligase activity was essential, the team searched for the critical substrate and found it in p62, the very cargo receptor that had piled up in TRIM37-depleted cells. The experiments showed that TRIM37 directly mediates the ubiquitination of SQSTM1/p62, promoting its turnover and thereby keeping autophagic activity within the proper range. When TRIM37 is absent, p62 accumulates unchecked, and the resulting imbalance disrupts both the initiation of autophagy and the maturation of autophagosomes, which in turn sabotages the carefully choreographed process of cilium construction.

The most convincing demonstration of this regulatory axis came from a double-knockdown experiment. When the researchers simultaneously depleted both TRIM37 and SQSTM1/p62, the ciliogenesis defects and autophagic abnormalities caused by losing TRIM37 alone were substantially alleviated. This genetic epistasis experiment, a classic strategy for ordering genes into a pathway, showed that p62 acts downstream of TRIM37 and that removing the problematic accumulation of p62 can compensate for the loss of its regulator. Together, the findings define a novel TRIM37–SQSTM1/p62–autophagy signaling axis that modulates mammalian ciliogenesis, adding a new branch to the molecular regulatory network that biologists have been mapping for decades.

The implications of this work extend beyond basic cell biology. TRIM37 is already known as the gene mutated in mulibrey nanism, a rare inherited growth disorder, and its involvement in centriole maintenance and tumorigenesis has made it a subject of intense interest. By connecting this ubiquitin ligase to the autophagy machinery and to ciliary assembly, the study offers a mechanistic framework that could eventually inform research into ciliopathies, kidney disease, and cancers in which autophagy and ciliary signaling go awry. It also underscores a growing theme in modern cell biology: organelle construction is not an isolated program but an integrated process that depends on the cell’s recycling systems running at exactly the right tempo. As researchers continue to untangle the connections between ubiquitination, autophagy, and cilia, the TRIM37–p62 axis identified here provides a clear example of how a single enzymatic regulator can coordinate two fundamental cellular systems to build one of the cell’s most important sensory structures.

Subject of Research: Regulation of primary ciliogenesis by the E3 ubiquitin ligase TRIM37 through p62 ubiquitination and autophagy control

Article Title: Ciliogenesis is regulated by TRIM37 through ubiquitinating p62 and controlling the autophagy pathway

Article References: Luo, J., Zhang, X., Zhao, C., Zhang, Y., Chen, W., Wang, Z., Li, S., & Liu, Z. (2026). Ciliogenesis is regulated by TRIM37 through ubiquitinating p62 and controlling the autophagy pathway. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06454-0

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06454-0

Keywords: TRIM37, ciliogenesis, primary cilia, autophagy, p62, SQSTM1, ubiquitination, E3 ubiquitin ligase, basal body, autophagic flux, ciliopathies, cell biology

The core problem the researchers set out to solve is a bottleneck familiar to anyone working in targeted protein degradation. Proteomics-based approaches can, in principle, reveal every protein whose abundance changes when a compound is applied, but they are expensive and slow, making them impractical as a first-pass screen for large chemical libraries. Target-based biochemical assays such as AlphaLISA or TR-FRET require purified proteins and, crucially, prior knowledge of which target-E3 pair to test—an assumption that defeats the purpose of hunting for glues against unknown or classically undruggable substrates like transcription factors and scaffold proteins. Phenotypic screens, meanwhile, are biologically rich but cannot easily distinguish a true degrader from an ordinary inhibitor, forcing laborious downstream mechanistic deconvolution. What the field needed was a cheap, fast, and mechanistically informative primary readout.

The team’s answer was to make the transcriptome itself the universal readout. Gene expression signatures are high-dimensional proxies for cellular state, a principle demonstrated at scale by the L1000 platform and made affordable by DRUG-seq, which skips RNA purification and uses direct cell lysis with multiplexed library preparation. The researchers employed an optimized version, DRUG-seq2, which they report offers superior sensitivity for low-abundance regulatory transcripts—a critical feature when the signals of interest come from immature, weak molecular glues. In their workflow, Hep3B liver cancer cells were seeded in 96-well plates, treated with compounds at a uniform concentration of 1 micromolar for 24 hours, and processed through the miniaturized sequencing protocol. The library comprised 117 compounds: 11 commercial molecular glues serving as validated benchmarks and 106 in-house candidates synthesized by two collaborative research groups, all rationally designed to modulate the cereblon (CRBN) E3 ligase.

A deceptively simple but essential innovation lies in how the baseline is defined. Because DRUG-seq2 relies on direct lysis, technical noise can swamp the subtle transcriptional ripples produced by nascent glues. Before any analysis, the team performed systematic pairwise Pearson correlation analysis across all DMSO vehicle wells on each plate, excluding any replicate with a correlation coefficient below 0.95. By constructing the reference transcriptome solely from high-consensus control wells, they established a robust, self-consistent zero-point that maximizes statistical power to resolve low-magnitude perturbations. Downstream, differential expression analysis with DESeq2—flagging genes with absolute log2 fold change greater than 1 and adjusted p-value below 0.05—was paired with gene set enrichment analysis (GSEA) built from six curated collections, including Hallmark, Reactome, KEGG, Gene Ontology Biological Process, C6, and the C3 transcription factor target set. This two-layer design means even compounds with few or zero individual differentially expressed genes can still betray coordinated pathway-level activity.

The mechanistic heart of the platform is a genetic benchmark: an isogenic pair of Hep3B cell lines, one wild-type and one in which CRBN has been knocked out via CRISPR-Cas9. The researchers established a stable Cas9-expressing parent line, introduced single-guide RNAs targeting CRBN, and isolated single-cell clones. Clone 3 emerged as the definitive knockout after rigorous validation. Treatment with CC-90009, a clinical molecular glue that degrades the translation termination factor GSPT1, provided the proof: in wild-type cells the drug rapidly and almost completely eliminated GSPT1 protein, while in the knockout the effect vanished entirely, along with the drug’s cytotoxic potency, which showed a pronounced right-shift in the IC50 curve. Any compound whose transcriptional signature collapses in the knockout is therefore flagged as CRBN-dependent—a hallmark of a genuine glue—whereas signals that persist likely reflect off-target toxicity, conventional inhibition, or hijacking of a different E3 ligase such as VHL or DCAF16.

Screening the full library revealed a strikingly polarized activity spectrum. Roughly 20 percent of the compounds were transcriptionally inert, producing zero differentially expressed genes under the test conditions. At the other extreme, the high-activity cluster was dominated by known glues: SJ3149, which targets CK1α, elicited the most profound response, followed by lenalidomide, BMS-986397, and a MYC degrader. For most of these, transcriptional activity was almost completely abolished in the CRBN knockout, exactly as expected for classic glues. Encouragingly, one in-house compound, LC-02-047-P1, landed among the potent performers, marking it as a promising novel candidate. Conversely, compounds such as LC-02-105 and LC-02-033 displayed a paradoxical knockout-amplified phenotype, indicating CRBN-independent mechanisms and allowing the team to filter out molecules whose intrinsic scaffold toxicity overwhelmed any degradation function.

The pathway-level analysis added mechanistic texture that raw gene counts alone could not provide. Potent GSPT1 degraders such as CC-90009 upregulated regulators of the integrated stress response—DDIT3 (CHOP), GDF15, TRIB3, DDIT4, and PPP1R15A—consistent with the biology of translation termination failure: ribosomes stall at stop codons, collide, and trigger the ZAKα-mediated ribotoxic stress response, which in turn activates ATF4 and suppresses the translational apparatus to mitigate proteotoxic stress. GSEA of CC-90009 confirmed enrichment of integrated stress response, proteasome, and apoptosis pathways alongside downregulation of translation machinery. LC-02-047-P1, by contrast, showed metabolic rather than stress-related regulatory characteristics, hinting that its degraded target might be an upstream switch governing multiple metabolic pathways. The enrichment layer also rescued latent hits: LC-02-051 performed modestly in the differential expression analysis but ranked near the top in pathway enrichment, and its signal was completely blocked by CRBN knockout—suggesting a genuine but weak glue worth optimizing. Even CC-92480 yielded an instructive anomaly, showing slightly expanded enrichment in knockout cells, which the authors attribute to the absence of its high-affinity target IKZF1 in Hep3B, pushing the compound toward non-canonical substrates or generic xenobiotic stress.

To translate these multidimensional data into decisions, the researchers built a scatterplot integrating transcriptional potency (differential gene counts) with functional breadth (enriched pathway counts) across both wild-type and knockout conditions, then stratified the library into four tiers. Tier one comprises potent glues with high wild-type activity that nearly vanishes upon CRBN loss—the highest priorities for optimization. Tier two captures intermediate and latent leads whose coordinated functional signals suggest seed scaffolds needing structural refinement. Tier three contains active but E3-independent perturbators, likely conventional inhibitors, and tier four collects inert compounds. The spatial logic is intuitive: strong glues such as SJ3149, lenalidomide, CC-90009, and LC-02-047-P1 occupy the upper-right quadrant and collapse toward the origin in the knockout, while pharmacologically inert molecules cluster near the origin in both conditions and target-independent agents stubbornly refuse to move. The thresholds, the authors note, can be customized for different libraries.

Proteomic cross-validation demonstrated that the transcriptomic tiers predict real degradation events. Tandem mass tag quantitative proteomics of LC-02-047-P1-treated Hep3B cells revealed marked downregulation of CSNK1A1 (CK1α), and western blotting across Hep3B, Huh7, and HepG2 hepatocellular carcinoma lines confirmed near-complete, selective CK1α degradation with no effect on GSPT1. A decisive control sealed the case: cells engineered to express a non-degradable GSPT1 mutant abolished CC-90009’s activity but left LC-02-047-P1’s CK1α degradation untouched, proving the candidate acts entirely independently of GSPT1. The weaker tier-two compound LC-02-051 produced only minor proteomic perturbation, with TPM3 changes failing statistical validation—consistent with its latent classification. On scalability, the economics are compelling: the platform costs less than 100 RMB (roughly 14 US dollars) per sample, about 2 percent of standard TMT proteomics, with an end-to-end turnaround of three to four weeks even beyond 1,000 compounds.

The authors are candid about limitations. The single 24-hour window captures an integrated cellular state—primary degradation consequences blended with secondary cascades and stress responses—rather than the immediate transcriptional footprints of neosubstrate depletion, and future iterations will incorporate time-resolved profiling. Transcriptomic signatures also remain an indirect proxy for protein-level events, so candidate leads must ultimately be confirmed by quantitative proteomics and structural biology demonstrating direct ternary complex formation. The choice of screening cell line matters too, since E3 and substrate abundance dictate sensitivity; the authors suggest abundance-matched models, such as VHL-high or DCAF15-high backgrounds, for targeted campaigns. Even so, the GPS platform fills a genuine gap, bridging high-volume chemical screening and low-throughput mechanistic validation, and offering the field a practical roadmap for converting molecular glue discovery from a lucky accident into an engineering discipline.

Subject of Research: High-throughput transcriptomic screening for the discovery of CRBN-dependent molecular glue degraders

Article Title: A scalable, high-throughput glue perturbation screening platform for molecular glue discovery

Article References: Huang, D., Shuang, Z., Chen, L., Ouyang, H., Yang, P., Huang, L., Lu, W., Shi, M., Ding, X., Jiang, B., & Wu, W. (2026). A scalable, high-throughput glue perturbation screening platform for molecular glue discovery. iScience, 29(10), Article 117600. https://doi.org/10.1016/j.isci.2026.117600

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.117600

Keywords: molecular glue degraders, targeted protein degradation, CRBN, DRUG-seq2, transcriptomics, gene set enrichment analysis, CRISPR knockout, E3 ubiquitin ligase, proteomics, drug discovery, GSPT1, CK1α

The significance of the finding lies in the mechanism. Rather than simply blocking cadmium from entering plant tissues, NnRNF217 appears to work by neutralizing the chemical fallout that cadmium leaves behind. When plants take up cadmium, the metal disrupts cellular redox balance and triggers an avalanche of reactive oxygen species, highly reactive molecules such as hydrogen peroxide and superoxide radicals that shred membranes, damage DNA, and push cells toward death. The research team found that plants engineered to express the lotus gene showed markedly higher activity of catalase and superoxide dismutase, the two frontline enzymes responsible for dismantling these dangerous molecules, and correspondingly lower levels of accumulated reactive oxygen species under cadmium stress.

Lotus was a logical place to hunt for such a gene. The plant is a multifunctional aquatic crop of enormous economic, medicinal, and ornamental value across Asia, yet its paddies and ponds are increasingly threatened by cadmium contamination in agricultural soils. Previous studies have documented heavy metal accumulation in lotus roots in regions such as the Dongting Lake area of China, and the plant has even been explored as a candidate for phytoremediation, the use of plants to clean up polluted environments. Understanding how lotus copes at the molecular level with cadmium could therefore pay dividends both for protecting the crop and for designing cleanup strategies.

To find the gene, the researchers took a systematic approach. They constructed a cDNA library from lotus, a collection of DNA copies representing all the genes the plant actively transcribes, and screened it in yeast to identify candidates that might confer cadmium tolerance. That screen flagged NnRNF217, which encodes a member of the RBR family of E3 ubiquitin ligases. These enzymes are the enforcement arm of the ubiquitin-proteasome system, the cellular machinery that tags specific proteins for destruction or modification. RBR-type ligases are particularly interesting because of their unusual catalytic architecture, which involves a distinctive RING-between-RING domain arrangement that shuttles ubiquitin onto target proteins through a two-step transfer mechanism.

With the candidate in hand, the team moved to functional testing. They expressed NnRNF217 in yeast and confirmed that the gene enhanced the single-celled organism’s tolerance to cadmium while increasing its accumulation of the metal. They then transferred the gene into Arabidopsis thaliana, the standard workhorse of plant genetics, and observed the same pattern: transgenic lines carrying the lotus gene tolerated cadmium exposure better than wild-type controls and accumulated more cadmium in their tissues. That combination, greater tolerance alongside greater accumulation, is a hallmark of plants that can both soak up a toxin and survive its consequences, a profile that is highly relevant for phytoremediation applications.

To understand what was happening inside the engineered plants, the researchers turned to RNA sequencing, a technique that measures the activity of thousands of genes at once. The comparative transcriptomic analysis revealed that overexpression of NnRNF217 significantly modulated the expression of genes associated with antioxidant defense, suggesting that the lotus ligase reprograms the plant’s stress-response network rather than acting on cadmium directly. The physiological assays then confirmed the functional consequences of that reprogramming. Catalase and superoxide dismutase activities were induced to a greater extent in the transgenic lines than in wild-type plants, and the overexpressing lines showed significantly lower levels of hydrogen peroxide, superoxide radicals, and total reactive oxygen species when exposed to cadmium.

The result adds a new dimension to what plant biologists know about RBR-type E3 ligases. This family of enzymes has been implicated in a wide range of plant processes, from immune responses against bacterial pathogens to drought and aluminum tolerance. A tobacco RBR ligase called NtRNF217, a relative of the lotus gene, has been shown to regulate resistance to the wilt pathogen Ralstonia solanacearum, while a soybean ariadne-like ubiquitin ligase enhances aluminum tolerance in Arabidopsis. The new study extends this family’s portfolio into heavy metal detoxification, and specifically into the oxidative-stress arm of the cadmium response, expanding the current understanding of how RBR-type ubiquitin ligases contribute to cadmium tolerance in plants.

The broader context makes the work timely. Recent assessments published in Science have warned that global soil pollution by toxic metals threatens both agriculture and human health, and cadmium ranks among the most concerning of these contaminants because it is readily taken up by crop plants and accumulates in edible tissues. Plant scientists have pursued several strategies to manage the problem, including breeding varieties that exclude cadmium from their grains, engineering enhanced phytochelatin and glutathione pathways that sequester the metal, and identifying transporter genes that control where cadmium goes within the plant. The NnRNF217 study points to a complementary approach: bolstering the antioxidant systems that determine whether a plant survives the metal’s presence long enough to be useful, whether as a crop or as a remediation tool.

There are also practical implications for lotus itself. Because the gene was isolated from lotus and shown to function in a distantly related plant, it provides a valuable molecular reference for further investigation into cadmium accumulation and tolerance in lotus crops. Breeders could potentially use NnRNF217 as a marker or a direct engineering target to develop lotus varieties that thrive in contaminated waterways, protecting yields of a crop that is prized for its edible rhizomes and seeds. The fact that the gene increases cadmium accumulation as well as tolerance suggests it could also strengthen lotus’s credentials as a phytoremediation species, capable of extracting the metal from polluted sediments while remaining healthy enough to complete the cleanup.

Much work remains before the finding translates from the greenhouse to the field. The study was conducted in yeast and Arabidopsis, and the researchers note that their results provide a reference for further investigation into cadmium tolerance in lotus rather than a finished solution. Key open questions include which proteins NnRNF217 tags with ubiquitin, how the ligase is regulated during cadmium stress, and whether the same antioxidant-boosting effect holds true in lotus itself and in other crop species. The datasets generated during the study are available from the corresponding authors on reasonable request, and the work was supported by the National Natural Science Foundation of China, the Natural Science Foundation of Hunan Province, and the Scientific Research Fund of Hunan Provincial Education Department. Still, the image of a gene from a flower revered for emerging unstained from muddy waters helping plants endure one of agriculture’s nastiest pollutants is hard to resist, and it may prove to be more than poetic.

Subject of Research: Identification of the RBR-type E3 ubiquitin ligase NnRNF217 from lotus and its role in cadmium tolerance through reactive oxygen species scavenging

Article Title: The RBR-type E3 ligase NnRNF217 from Nelumbo nucifera enhances cadmium tolerance by ROS scavenging

Article References: Gu, T., Lu, X., Fang, S., Li, Y., Liu, Y., Wang, L., Chen, S., Gao, Y., & Peng, J. (2026). The RBR-type E3 ligase NnRNF217 from Nelumbo nucifera enhances cadmium tolerance by ROS scavenging. Plant and Soil. https://doi.org/10.1007/s11104-026-09146-7

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09146-7

Keywords: cadmium tolerance, Nelumbo nucifera, E3 ubiquitin ligase, RBR-type ligase, reactive oxygen species, oxidative stress, catalase, superoxide dismutase, Arabidopsis thaliana, transcriptomics, heavy metal detoxification, lotus