Regulation global sumoylation by a MAP kinase Hog1 and its potential role in osmo‐tolerance in yeast (802.17)

Abstract

Sumoylation, a post‐translational protein modification by small ubiquitin‐like modifier (SUMO), has been implicated in many stress responses. Here we analyzed the potential role of sumoylation in osmo‐response in yeast. We find that osmotic stress induces rapid accumulation of sumoylated species in normal cells. Interestingly, disruption of MAP kinase Hog1 leads to a much higher level of accumulation of sumoylated conjugates that are independent of new protein synthesis. We also find that the accumulation of sumoylated species is dependent on a SUMO ligase Siz1. Notably, overexpression of SIZ1 in Hog1‐disruptive mutants (hog1[[Unsupported Character ‐ Symbol Font □]]) but not in wild type cells leads to a markedly increased and prolonged accumulation of sumoylated species. Examination of osmo‐tolerance of mutants that display either an increase or a decrease in the global sumoylation level revealed an inverse relationship between accumulation of sumoylated conjugates and somo‐tolerance. Further investigation has shown that many of the sumoylated species induced by hyperosmotic stress are actually poly‐sumoylated. Together, these findings indicated that abnormal accumulation of poly‐sumoylated conjugates is harmful for osmo‐tolerance, and suggest that Hog1 promotes adaptation to hyperosmotic stress partially via regulation of global sumoylation level.