An architectural RNA builds a reaction crucible through molecular concentration and activated enzyme selection

HSATIII arcRNA–nuclear stress bodies recruit activated CLK1 via ASAP, enabling enhanced SRSF phosphorylation by concentrating SRSFs and CLK1 while selectively selecting catalytically active CLK1.

• Why it matters: It remains unclear how arcRNAs organize functional proteins inside membraneless organelles to create biochemically active reaction sites during stress recovery.
• What they did: The study identified ASAP as a recruitment factor that recognizes Ser341-phosphorylated, catalytically activated CLK1, and used biochemical reconstitution to test how an HSATIII-bound SRSF platform affects phosphorylation.
• The result: The conserved SRSF–ASAP–CLK1 interaction network in humans and mice suggests primate-specific HSATIII arcRNAs co-opted an existing pathway to establish nSB reaction-crucible function.

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