Regulation of the hypertonic stress response by the 3’ mRNA cleavage and polyadenylation complex

Abstract

AbstractMaintenance of osmotic homeostasis is one of the most aggressively defended homeostatic setpoints in physiology. One major mechanism of osmotic homeostasis involves the upregulation of proteins that catalyze the accumulation of solutes called organic osmolytes. To better understand how osmolyte accumulation proteins are regulated, we conducted forward genetic screen inC. elegansfor mutants with no induction of osmolyte biosynthesis gene expression (Nio mutants).nio-3mutants encoded a missense mutation incpf-2/CstF64 whilenio-7mutants encoded a missense mutation insymk-1/Symplekin. Bothcpf-2andsymk-1are nuclear components of the highly conserved 3’ mRNA cleavage and polyadenylation complex.cpf-2andsymk-1block the hypertonic induction ofgpdh-1and other osmotically induced mRNAs, suggesting they act at the transcriptional level. We generated a functional auxin-inducible degron (AID) allele forsymk-1and found that acute, post-developmental degradation in the intestine and hypodermis was sufficient to cause the Nio phenotype.symk-1andcpf-2exhibit genetic interactions that strongly suggest they function through alterations in 3’ mRNA cleavage and/or alternative polyadenylation. Consistent with this hypothesis, we find that inhibition of several other components of the mRNA cleavage complex also cause a Nio phenotype.cpf-2andsymk-1specifically affect the osmotic stress response since heat shock-induced upregulation of ahsp-16.2::GFPreporter is normal in these mutants. Our data suggest a model in which alternative polyadenylation of one or more mRNAs is essential to regulate the hypertonic stress response.