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

The Saccharomyces cerevisiae Sgs1 protein, together with Schizosaccharomyces 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 in yeast cells, including the accumulation of extrachromosomal rDNA circles. We have recently shown that Sgs1p interacts with the DNA repair Rad16p protein 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 important for most elements of the sgs1 mutation phenotype, including sensitivity to UVC, 4-NQO, H2O2, MMS and hydroxyurea.