Nutrients and the Pkh1/2 and Pkc1 protein kinases control mRNA decay and P-body assembly in yeast.

Regulated mRNA decay is essential for eukaryotic survival but the mechanisms for regulating global decay and coordinating it with growth, nutrient, and environmental cues are not known. Here we show that a signal transduction pathway containing the Pkh1/Pkh2 protein kinases and one of their effector kinases, Pkc1, is required for and regulates global mRNA decay at the deadenylation step in Saccharomyces cerevisiae. Additionally, many stresses disrupt protein synthesis and release mRNAs from polysomes for incorporation into P-bodies for degradation or storage. We find that the Pkh1/2-Pkc1 pathway is also required for stress-induced P-body assembly. Control of mRNA decay and P-body assembly by the Pkh-Pkc1 pathway only occurs in nutrient-poor medium, suggesting a novel role for these processes in evolution. Our identification of a signaling pathway for regulating global mRNA decay and P-body assembly provides a means to coordinate mRNA decay with other cellular processes essential for growth and long-term survival. Mammals may use similar regulatory mechanisms because components of the decay apparatus and signaling pathways are conserved.