An mRNA decapping mutant deficient in P body assembly limits mRNA stabilization in response to osmotic stress

Abstract

Yeast is exposed to changing environmental conditions and must adapt its genetic program to provide a homeostatic intracellular environment. An important stress for yeast in the wild is high osmolarity. A key response to this stress is increased mRNA stability primarily by the inhibition of deadenylation. We previously demonstrated that mutations in decapping activators (edc3â † lsm4â †C), which result in defects in P body assembly, can destabilize mRNA under unstressed conditions. We wished to examine whether mRNA would be destabilized in the edc3â † lsm4â †C mutant as compared to the wild-Type in response to osmotic stress, when P bodies are intense and numerous. Our results show that the edc3â † lsm4â †C mutant limits the mRNA stability in response to osmotic stress, while the magnitude of stabilization was similar as compared to the wild-Type. The reduced mRNA stability in the edc3â † lsm4â †C mutant was correlated with a shorter PGK1 poly(A) tail. Similarly, the MFA2 mRNA was more rapidly deadenylated as well as significantly stabilized in the ccr4â † deadenylation mutant in the edc3â † lsm4â †C background. These results suggest a role for these decapping factors in stabilizing mRNA and may implicate P bodies as sites of reduced mRNA degradation.