HKUST Scientists Uncover Breakthrough in RNA Silencing Mechanism

In a groundbreaking study from The Hong Kong University of Science and Technology (HKUST), researchers have elucidated the molecular intricacies that govern the exceptional precision of the human enzyme DICER in processing microRNAs (miRNAs). This enzyme’s ability to execute highly accurate cleavage of RNA substrates has profound implications for understanding gene regulation and the molecular mechanisms underlying a range of human diseases, including cancer, immune disorders, and genetic pathologies. The findings, published in the esteemed journal Nature, reveal a sophisticated dual-pocket recognition system within DICER that orchestrates cleavage fidelity with unprecedented detail.

RNA molecules, composed of the ribonucleotides adenine (A), uracil (U), guanine (G), and cytosine (C), are central to cellular function, conveying genetic information and regulating gene expression. Among these molecules, miRNAs are short regulatory RNAs integral to the RNA-induced silencing complex (RISC), modulating gene expression by guiding the silencing machinery to specific messenger RNA targets. DICER’s role is to cleave precursor double-stranded RNAs into these active miRNA fragments, a process that demands both specificity and precision to maintain cellular homeostasis.

Despite the fundamental nature of DICER in RNA silencing pathways, the precise molecular determinants enabling its striking accuracy had remained elusive. Through a combination of advanced biochemical assays and high-resolution cryogenic electron microscopy (cryo-EM), the HKUST team—led by Professor Tuan Anh Nguyen and his PhD students Minh Khoa Ngo and Cong Truc Le—captured atomic-level snapshots of DICER engaged with various RNA substrates. These structural insights unveil the enzyme’s dynamic conformational shifts prior to cleavage, illustrating how DICER meticulously aligns RNA molecules within its catalytic core.

Central to this process are two distinct 5′-end binding pockets within the enzyme’s structure, each demonstrating a nucleotide preference that influences cleavage positioning. Previously recognized was a pocket favoring uracil (U) at the RNA’s 5′-end, guiding the enzyme’s cutting action. Remarkably, the HKUST team identified a second, guanine (G)-preferring pocket, which together with the U-favored site forms a dual-pocket framework. This dual recognition system enables DICER to discern subtle sequence variations, thereby refining the cleavage site selection to single-nucleotide accuracy.

The discovery of this dual-pocket mechanism fundamentally reshapes our understanding of how DICER accommodates diverse RNA sequences, providing a molecular basis for how the enzyme maintains cleavage fidelity across a spectrum of substrates. By modulating the interaction between RNA 5′-end identity and DICER’s structural elements, the enzyme can “read” the RNA code, ensuring that genetic messages are processed correctly and efficiently. This nuanced control is crucial, given that miscleavage can lead to aberrant gene regulation with potentially deleterious biological consequences.

Moreover, the conformational plasticity observed in the cryo-EM structures suggests that DICER undergoes a series of dynamic adjustments to engage its RNA substrates optimally. These rearrangements position RNA strands precisely within the enzyme’s catalytic pocket before cleavage, underscoring a highly orchestrated interplay between protein domains and RNA elements. This interplay highlights an evolved molecular sophistication enabling robust and reliable gene regulatory outcomes.

Beyond broadening our molecular understanding, these insights carry significant translational potential. By elucidating the detailed mechanisms underlying DICER function, this research paves the way for improved RNA-based therapeutics. Precise manipulation of DICER activity could enhance gene silencing technologies, which are increasingly employed in treating genetic disorders and cancers. Furthermore, understanding the structural basis for DICER’s cleavage fidelity informs efforts to diagnose and potentially remediate diseases stemming from dysfunctional RNA processing pathways.

Professor Nguyen emphasized the broader implications of this work, stating that the findings not only illuminate fundamental RNA biology but also establish a platform for novel therapeutic innovations. The dual-pocket recognition model could inspire the design of small molecules or engineered proteins tailored to modulate DICER activity or specificity, offering a route to finely tuned gene regulatory interventions.

The study also addresses long-standing questions about how DICER discriminates among a vast array of RNA substrates differing only subtly in sequence and structure. By integrating 5′-end nucleotide identity, RNA motif recognition, and enzymatic domain movements, DICER exemplifies a molecular machine of remarkable flexibility and precision. These findings highlight the enzyme’s evolved capacity to adapt its activity to diverse regulatory contexts within the cell.

In addition to revealing these mechanistic details, the research underscores the power of combining biochemical experimentation with cutting-edge structural biology techniques, such as cryo-EM, to resolve dynamic protein-RNA interactions at near-atomic resolution. This integrative approach sets a precedent for future studies of RNA-processing enzymes and other nucleic acid-binding proteins.

The HKUST team’s findings mark a significant advance in the field of RNA biology, shedding new light on the molecular choreography that orchestrates gene silencing pathways. By defining the structural basis for DICER’s precision, the study opens avenues for both fundamental biological research and the development of next-generation RNA therapeutics aimed at correcting aberrant gene expression profiles implicated in human disease.

News Publication Date: 4-Mar-2026

Web References: https://www.nature.com/articles/s41586-026-10211-5

References: 10.1038/s41586-026-10211-5