Role of Gal11, a component of the RNA polymerase II mediator in stress-induced hyperphosphorylation of Msn2 in Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, the Msn2 transcription factor is a key element in mediating the environmental stress response (ESR), leading to the induction of 100-200 genes through the cis-acting Stress Response Element (STRE) in response to various physico-chemical stresses and nutritional variations. This activation is accompanied by a stress-induced hyperphosphorylation of Msn2. By a systematic screening we identified two proteins essential in this process: (i) the cyclin-dependent Ssn3/Srb10 protein kinase, part of a module of the RNA polymerase II mediator, which has already been shown to be involved in hyperphosphorylation and degradation of Msn2 upon stress, and (ii) Gal11, a component of the mediator.