Requirement of Rrm3 Helicase for Repair of Spontaneous DNA Lesions in Cells Lacking Srs2 or Sgs1 Helicase

Abstract

The Rrm3 DNA helicase of Saccharomyces cerevisiae interacts with proliferating cell nuclear antigen and is required for replication fork progression through ribosomal DNA repeats and subtelomeric and telomeric DNA. Here, we show that rrm3 srs2 and rrm3 sgs1 mutants, in which two different DNA helicases have been inactivated, exhibit a severe growth defect and undergo frequent cell death. Cells lacking Rrm3 and Srs2 arrest in the G₂/M phase of the cell cycle with 2N DNA content and frequently contain only a single nucleus. The phenotypes of rrm3 srs2 and rrm3 sgs1 mutants were suppressed by disrupting early steps of homologous recombination. These observations identify Rrm3 as a new member of a network of pathways, involving Sgs1 and Srs2 helicases and Mus81 endonuclease, suggested to act during repair of stalled replication forks.

We thank Meng-Er Huang, Dan Mazur, and Christopher Putnam for helpful comments on the manuscript, Vincent Pennaneach for discussions, Karen Oegema and Ashad Desai for help with microscopy, Virginia Zakian and Jorge Torres (Princeton University) for communication of unpublished results, and Dennis Young for FACS analysis.

This work was supported by National Institutes of Health grant GM26017 to R.D.K.