Osmostress-induced transcription by Hot1 depends on a Hog1-mediated recruitment of the RNA Pol II.

In budding yeast, the mitogen-activated protein kinase (MAPK) Hog1 coordinates the transcriptional program required for cell survival upon osmostress. The Hot1 transcription factor acts downstream of the MAPK and regulates a subset of Hog1-responsive genes. In response to high osmolarity, Hot1 targets Hog1 to specific osmostress-responsive promoters. Here, we show that assembly of the general transcription machinery at Hot1-dependent promoters depends on the presence of Hot1 and active Hog1 MAPK. Unexpectedly, recruitment of RNA polymerase (Pol) II complex to target promoters does not depend on the phosphorylation of the Hot1 activator by the MAPK. Hog1 interacts with the RNA Pol II and with general components of the transcription machinery. More over, when tethered to a promoter as a LexA fusion protein, Hog1 activates transcription in a stress- regulated manner. Thus, anchoring of active Hog1 to promoters by the Hot1 activator is essential for recruitment and activation of RNA Pol II. The mammalian p38 also interacts with the RNA Pol II, which might suggest a conserved mechanism for regulation of gene expression by SAPKs among eukaryotic cells.