CK 2‐dependent inhibitory phosphorylation is relieved by Ppt 1 phosphatase for the ethanol stress‐specific activation of Hsf 1 in S accharomyces cerevisiae

Summary Ethanol, the major fermentation product of S accharomyces cerevisiae , has long been known as an inducer of heat shock response, but the underlying mechanisms by which ethanol activates heat shock transcription factor ( HSF ) are not well understood. We demonstrate that CK 2‐dependent phosphorylation on S 608 is an ethanol stress‐specific repression mechanism of Hsf 1, which does not affect the basal or heat‐induced activity of Hsf 1. This repression is relieved by dephosphorylation by Ppt 1 which directly interacts with Hsf 1 via its tetratricopeptide repeat ( TPR ) domain. In response to ethanol stress, PPT1 deletion and CK 2 overexpression exert synergistic inhibitory effects on Hsf 1 activation, whereas Hsf 1 S 608 A mutant shows enhanced activation. Therefore, regulation of the Hsf 1 S 608 phosphorylation status by reciprocal actions of CK 2 and Ppt 1 might play an important role to determine Hsf 1 sensitivity towards ethanol stress.