Non-enzymatic roles for the URE2 glutathione S-transferase in the response of Saccharomyces cerevisiae to arsenic
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The response of Saccharomyces cerevisiae to arsenic involves a large ensemble of genes, many of which are associated with glutathione-related metabolism. The role of the glutathione S-transferase (GST) product of the URE2 gene involved in resistance of S. cerevisiae to a broad range of heavy metals was investigated. Glutathione peroxidase activity, previously reported for the Ure2p protein, was unaffected in cell-free extracts of an ure2Δ mutant of S. cerevisiae. Glutathione levels in the ure2Δ mutant were lowered about threefold compared to the isogenic wild-type strain but, as in the wild-type strain, increased 2–2.5-fold upon addition of either arsenate (AsV) or arsenite (AsIII). However, lack of URE2 specifically caused sensitivity to arsenite but not to arsenate. The protective role of URE2 against arsenite depended solely on the GST-encoding 3′-end portion of the gene. The nitrogen source used for growth was suggested to be an important determinant of arsenite toxicity, in keeping with non-enzymatic roles of the URE2 gene product in GATA-type regulation.
KeywordsUre2 Glutathione S-transferase GATA regulation Arsenic detoxification
Nitrogen catabolite repression
NADPH-dependent glutamate dehydrogenase
NAD+-dependent glutamate dehydrogenase
We are grateful to Ivan Tarassov for providing the p413 vector, to Ales Vancura for pET23b-URE2 and pET23b-URE2(ΔN) plasmids, and to Emmanuelle Boy-Marcotte for the FPS1-lacZ fusion plasmid. Work in S.V.’s laboratory is supported by REALISE, the Alsace Research Network in Environmental Sciences. The present study was supported by CNRS ATIP to S.V., by the National Science Fund of Bulgarian Ministry of Education and Science (Project No. Б-BУ-201/06) and by a visiting scientist grant of the European Doctoral College of Strasbourg to A.K. T.T. was the recipient of an Agence Universitaire de la Francophonie PhD grant and a member of the European Doctoral College of Strasbourg.
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