The Yap1p-dependent Induction of Glutathione Synthesis in Heat Shock Response of Saccharomyces cerevisiae

Abstract

Glutathione is synthesized in two sequential reactions catalyzed by ␥-glutamylcysteine synthetase (GSH1 gene product) and glutathione synthetase (GSH2 gene product). The expression of GSH1 in Saccharomyces cerevisiae has been known to be up-regulated by Yap1p, a critical transcription factor for the oxidative stress response in yeast. The present study demonstrates that GSH2 expression is also regulated by Yap1p under oxidative stress-induced conditions. In addition to oxidative stress, expression of GSH1 and GSH2 was induced by heat shock stress in a Yap1p-dependent manner with subsequent increases in intracellular glutathione content. Oxygen respiration rate increased when cells were exposed to higher temperatures, and as a result, intracellular oxidation levels were increased. The heat shock-induced expression of GSH1 and GSH2 did not occur under anaerobic conditions. Furthermore, even under aerobic conditions, the heat shock response of these genes was not observed when cells were pretreated with KCN to block oxygen respiration. We speculate that heat shock stress enhances oxygen respiration, which in turn results in an increase in the generation of reactive oxygen species in mitochondria. This signal may be mediated by Yap1p, resulting in the elevation of intracellular glutathione levels.Stress-inducible proteins are synthesized by all organisms, and important functional insights of this group of proteins have been obtained from studies with the heat shock protein (HSP). 1A sudden increase in the temperature at which cells are growing induces the synthesis of a set of HSPs. When the temperature of Escherichia coli cells is increased from 30 to 42°C, the intracellular concentration of sigma factor 32 increases 15-20-fold. The sigma factor is one of the components of E. coli RNA polymerase, and substitution of a vegitative sigma factor ( 70 ) by 32 modifies the RNA polymerase to specifically recognize the promoter of HSP genes. In higher eukaryotes, a heat shock transcription factor is trimerized, phosphorylated, and translocated into the nucleus by heat shock stress and binds to the heat shock element (HSE) on the promoter of HSP genes to activate transcription (for a review, see Ref.

Oxidant-specific Folding of Yap1p Regulates Both Transcriptional Activation and Nuclear Localization

“…GSH1-lacZ expression was elevated by ϳ2-and 3.5-fold upon oxidative stress induced by H 2 O 2 or diamide, respectively, in the presence of wild-type Yap1p, consistent with the findings of other groups (28,30). Expression of C629A Yap1p increased GSH1 expression by 2-fold in the absence of oxidant, and this expression failed to increase in the face of H 2 O 2 exposure and was only modestly enhanced during diamide stress.…”

YcfR (BhsA) InfluencesEscherichia coliBiofilm Formation through Stress Response and Surface Hydrophobicity

“…Hence, ycfR induction may be related to a general effect of all the stresses or to the common mechanisms that the cells use to protect themselves against stress, as seen in plants (23), Saccharomyces cerevisiae (76), and bacteria (32); for example, it has been shown that both heavy metal stress (23) and heat shock stress (76) converge in the generation of oxygen-reactive species.…”

Activity of the Yap1 Transcription Factor in Saccharomyces cerevisiae Is Modulated by Methylglyoxal, a Metabolite Derived from Glycolysis

“…Several genes responsible for glutathione metabolism, such as glutathione synthesis (GSH1 and GSH2) and glutathionedependent antioxidant systems (GPX2 and GLR1), are up-regulated by Yap1 (19,25,55,58,67). In addition to its antioxidant function, glutathione is important in detoxifying many harmful xenobiotics.…”