The CCT chaperonin is a context-dependent regulator of RNA-binding protein phase transitions

RNA-binding proteins (RBPs) undergo regulated phase transitions during oogenesis that are critical for maternal mRNA regulation. In C. elegans , the CCT chaperonin prevents ectopic condensation of RBPs in maturing oocytes, including MEX-3 and CAR-1 . Here, we show that CCT differentially affects oocyte RBP condensation depending on protein identity and cellular context. Depletion of CCT did not cause ectopic condensation of the P-granule proteins GLH-1 and PGL-1 . During heat stress, CCT depletion reduced MEX-3 and CAR-1 condensation, opposite from the phenotype in normally maturing oocytes. These findings reveal CCT as a context-dependent regulator of RBP phase transitions in oocytes.