Role of Hog-1 mitogen activated protein kinase in the Saccharomyces cerevisiae UV response

Abstract

The UV stress response in mammalian cells is characterized by transcriptional changes aimed at regulating cell growth, repair and survival. Previous studies have suggested that highly conserved mitogen-activated protein kinase (MAPK) pathways mediate UVinduced stress signalling. Here, we examined the role of the Hog-1 and Mpk-1 MAPKs in the Saccharomyces cerevisiae UV response. Deletion of both Hog-1 and Mpk-1 enhanced sensitivity to UVC-induced cell death. However, activation of these pathways by osmotic stress prior to irradiation failed to cross-protect wild type cells from death. A dosedependent upregulation of active Hog-1 was observed in response to UVC irradiation, but elevated expression caused by pre-treatment with hyper-osmotic medium correlated with a decrease in viability. We speculate that Hog-1, like its mammalian homologue, may also activate pro-apoptotic pathways when highly expressed.