The arrested state of processing bodies supports mRNA regulation in early development

Abstract

ABSTRACTBiomolecular condensates that form via liquid-liquid phase separation can exhibit diverse physical states. Despite considerable progress, the relevance of condensate physical states forin vivobiological function remains limited. Here, we investigated the physical properties ofin vivoprocessing bodies (P bodies) and their impact on mRNA storage in matureDrosophilaoocytes. We show that the conserved DEAD-box RNA helicase Me31B forms P body condensates which adopt a less dynamic, arrested physical state. We demonstrate that structurally distinct proteins and hydrophobic and electrostatic interactions, together with RNA and intrinsically disordered regions, regulate the physical properties of P bodies. Finally, using live imaging, we show that the arrested state of P bodies is required to prevent the premature release ofbicoid(bcd) mRNA, a body axis determinant, and that P body dissolution leads tobcdrelease. Together, this work establishes a role for arrested states of biomolecular condensates in regulating cellular function in a developing organism.