Genes rapidly reactivate expression following thermal stress exposure

Heat waves don’t just exhaust people—they force cells to rethink what they can afford to do. For years, scientists have mapped cellular stress responses, but how cells dynamically sense temperature and reversibly rewire gene regulation has remained less clear.

A new study from the University of Osaka, published in Molecular Cell, identifies a temperature-reading mechanism inside the nucleus that tunes pre-mRNA splicing during thermal stress and then restores it afterward. The work centers on nuclear stress bodies, membrane-free hubs that orchestrate the splicing of hundreds of pre-mRNAs during recovery.

Under heat stress, cells reduce certain activities to conserve energy and protect vital functions. Splicing, however, must be adjusted in the short term and then normalized when conditions improve—requiring a control system that can switch quickly and then back again.

Lead author Tsuyoshi Ueno and colleagues focused on CLK1, a splicing regulator known to associate with nuclear stress bodies during recovery from heat. The key question was how CLK1 is recruited (or excluded) depending on temperature, enabling splicing to match the cell’s current needs.

Their experiments, performed in living cells and cell-free systems, reveal a phosphorylation circuit with distinct “on” and “off” states. CLK1 is phosphorylated at a specific serine under normal conditions, becomes dephosphorylated during heat stress, and is rephosphorylated during recovery.

This molecular toggling determines CLK1’s localization: dephosphorylation drives its exclusion from nuclear stress bodies, whereas rephosphorylation promotes its recruitment. Importantly, the enzymes controlling these steps are spatially and functionally coordinated.

PP1 executes CLK1 dephosphorylation, while RIOK2 rephosphorylates CLK1 during recovery. The missing piece was how PP1 activity itself is regulated by temperature, and the study points to PPP1R2, an intrinsically disordered PP1 subunit that acts as a reversible thermosensor.

Together, the authors describe a multi-component heat-sensing mechanism that synchronizes opposing enzymatic activities to coordinate temperature-dependent splicing. Beyond explaining a fundamental control system, the findings may guide future work on stress-related diseases where splicing regulation goes awry.