Importance of the Sgs1 helicase activity in DNA repair of Saccharomyces cerevisiae

The Saccharomyces cerevisiae Sgs1 protein, together with Schizosaccharomyce s pombe Rqh1 and the human Bloom and Werner proteins, is a DNA helicase of the Escherichia coli RecQ family. Mutation of SGS1 causes premature aging i n yeast cells, including the accumulation of extrachromosomal rDNA circles. We have recently shown that Sgs1p interacts with the DNA repair Rad16p pro tein and is epistatic to Rad16p for UVC, 4-NQO and H2O2 lesions. Therefore we tested sgs1 strains containing mutations in the helicase and C-terminal domains. We demonstrate here that the helicase activity of the Sgs1 is impo rtant for most elements of the sgs1 mutation phenotype, including sensitivi ty to UVC, 4-NQO, H2O2, MMS and hydroxyurea.