Differential expression and role of two dithiol glutaredoxins Grx1 and Grx2 in Schizosaccharomyces pombe.

Glutaredoxins are glutathione-specific thiol oxidoreductases. The regulation and the role of grx1(+) and grx2(+) genes encoding dithiol glutaredoxins were analyzed in Schizosaccharomyces pombe. When tested in the same genetic background including mating type, the grx1 null mutant became sensitive to hydrogen peroxide, whereas grx2 mutant became highly sensitive to paraquat, a superoxide generator. The grx1grx2 double mutant showed additive phenotype of each single mutant. The grx1(+) gene expression was induced by various stresses such as oxidants, salts, and heat, and increased in the stationary phase, whereas grx2(+) stayed constitutive. The induction was mediated via Spc1 MAP kinase path involving both Atf1 and Pap1 transcription factors. Sub-cellular fractionation as well as fluorescence microscopy revealed that Grx1 resides mainly in the cytosol, whereas Grx2 is in mitochondria. These results suggest distinct roles for Grx1 and Grx2 in S. pombe in mediating glutathione-dependent redox homeostasis.

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