The Partition Code: How RNA Modifications Set the Address of Transcripts Among Membraneless Compartments: Covalent RNA Marks Set a Measurable, Reversible Spatial Address Among Membraneless Compartments-A Variable to Perturb, Not Just Observe.

Where a transcript goes among a cell's membraneless compartments-stress granules, P-bodies, paraspeckles, nuclear speckles-is an addressable, rewritable property that this article proposes chemical modifications of RNA help write. The code's output depends on the transcript's role: for client messenger RNAs, an apparent partition coefficient (Kpart), its enrichment in a condensate; for the rare long noncoding RNAs acting as architectural scaffolds, the saturation concentration that decides whether the compartment forms at all. This client/scaffold asymmetry is the framework's central proposal, its scaffold arm as yet untested. Only m6A has cellular partitioning evidence; A-to-I editing sets nuclear address by a related route, and the remaining marks are candidates or structure-based predictions. The value is a variable and a falsifiable test: perturb a mark at fixed sequence and state, and ask whether the address moves. It reframes scattered epitranscriptomic and condensate biology as one control problem.