title: Mutations in homologous recombination genes rescue top3 slow growth in Saccharomyces cerevisiae.
abstract: In budding yeast, loss of topoisomerase III, encoded by the TOP3 gene, leads to a genomic instability phenotype that includes slow growth, hyper-sensitivity to genotoxic agents, mitotic hyper-recombination, increased chromosome missegregation, and meiotic failure. Slow growth and other defects of top3 mutants are suppressed by mutation of SGS1, which encodes the only RecQ helicase in S. cerevisiae. sgs1 is epistatic to top3, suggesting that the two proteins act in the same pathway. To identify other factors that function in the Sgs1-Top3 pathway, we undertook a genetic screen for non-sgs1 suppressors of top3 defects. We found that slow growth and DNA damage sensitivity of top3 mutants are suppressed by mutations in RAD51, RAD54, RAD55, and RAD57. In contrast, top3 mutants show extreme synergistic growth defects with mutations in RAD50, MRE11, XRS2, RDH54, and RAD1. We also analyzed recombination at the SUP4-o region, showing that in a rad51, rad54, rad55, or rad57 background top3Delta does not increase recombination to the same degree as in a wild-type strain. These results suggest that the presence of the Rad51 homologous recombination complex in a top3 background facilitates creation of detrimental intermediates by Sgs1. We present a model wherein Rad51 helps recruit Sgs1-Top3 to sites of replicative damage.
authors.affiliation: Department of Genetics and Development, Columbia University College of Physicians & Surgeons, New York, New York 10032-2704, USA.
authors.forename: Erika
authors.initials: E
authors.lastname: Shor
authors.forename: Serge
authors.initials: S
authors.lastname: Gangloff
authors.forename: Marisa
authors.initials: M
authors.lastname: Wagner
authors.forename: Justin
authors.initials: J
authors.lastname: Weinstein
authors.forename: Gavrielle
authors.initials: G
authors.lastname: Price
authors.forename: Rodney
authors.initials: R
authors.lastname: Rothstein
mesh_terms: D000251:Adenosine Triphosphatases; D004249:DNA Damage; D004265:DNA Helicases / Q000378:metabolism; D045643:DNA Repair Enzymes; D026942:DNA Topoisomerases; D004264:DNA Topoisomerases, Type I / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D051135:Rad51 Recombinase; D051721:Rad52 DNA Repair and Recombination Protein; D053484:RecQ Helicases; D011995:Recombination, Genetic / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C497197:RAD52 protein, S cerevisiae; C087191:RAD55 protein, S cerevisiae; D051721:Rad52 DNA Repair and Recombination Protein; D029701:Saccharomyces cerevisiae Proteins; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase; D000251:Adenosine Triphosphatases; C075468:RAD54 protein, S cerevisiae; C071451:RAD57 protein, S cerevisiae; C090472:SGS1 protein, S cerevisiae; D004265:DNA Helicases; D053484:RecQ Helicases; D026942:DNA Topoisomerases; C541336:RDH54 protein, S cerevisiae; D004264:DNA Topoisomerases, Type I; D045643:DNA Repair Enzymes