The adaptive response of Saccharomyces cerevisiae to mercury exposure

The budding yeast Saccharomyces cerevisiae has been shown to possess a number of discrete but overlapping adaptive stress responses. We show here that yeast has an adaptive stress response towards mercury and that this response overlaps to some extent with the H(2)O(2) and cadmium-inducible stress responses. Expression of the yeast GSH1 gene, encoding gamma-glutamylcysteine synthetase, is known to be regulated by hydrogen peroxide; in this study we show that expression of a GSH1-lacZ reporter gene is shown to be regulated by exposure to heavy metals, such as mercury and cadmium. Other redox-active metals, including copper and iron, were found not to induce GSH1 expression. We show that mercury-mediated regulation of the GSH1 gene is not by the same mechanism used by cadmium. Moreover, our experiments suggest the possibility that the oxidative stress produced by mercury exposure is similar to that produced by treatment with H(2)O(2), consistent with our finding that the Yap1 protein is also involved in the response of yeast towards mercury.