Stress-induced map kinase Hog1 is part of transcription activation complexes

In response to hyperosmotic environments, most eukaryotic cells activate a specialized mitogen-activated protein (MAP) kinase pathway. In S. cerevisiae, the key protein kinase, Hog1, coordinates the transcriptional induction of a variety of genes devoted to osmoadaptation and general stress protection. Depending on the promoter context, Hog1 can function through a variety of structurally unrelated transcription factors. Using chromatin precipitation assays, we discovered that the kinase itself becomes intimately linked with promoter regions during stress responses. This interaction is dependent on the presence of stress-mediating transcriptional activators. In turn, Hog1 modulates promoter association of at least one of these factors. Additional findings highlight the possibility that Hog1 constitutes an integral part of the upstream activation complex, perhaps targeting not only the activator but also components of the general transcription machinery.