Resection Activity of the Sgs1 Helicase Alters the Affinity of DNA Ends for Homologous Recombination Proteins in Saccharomyces cerevisiae.

The RecQ helicase family is critical during DNA damage repair and mutations in these proteins are associated with Bloom, Werner, or Rothmund-Thompson syndromes in man, leading to cancer pre-disposition and/or premature aging. In the budding yeast, Saccharomyces cerevisiae, mutations in the RecQ homologue, SGS1, phenocopy many of the defects observed ...
in the human syndromes. One challenge to studying RecQ helicases is that their disruption leads to a pleiotropic phenotype. Using yeast, we show that the separation-of-function allele of SGS1, sgs1-D664, has impaired activity at DNA ends resulting in a resection processivity defect. Compromising Sgs1 resection function in the absence of the Sae2 nuclease causes slow growth, which is alleviated by making the DNA ends accessible to Exo1 nuclease. Furthermore, fluorescent microscopy studies reveal that, when Sgs1 resection activity is compromised in sae2 cells, Mre11 repair foci persist. We suggest a model where the role of Sgs1 in end resection along with Sae2 is important for removing Mre11 from DNA ends during repair.
Date: Oct. 04, 2013
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