Originally published as Genetics Published Articles Ahead of Print on January 16, 2005.
Genetics, Vol. 169, 1275-1289, March 2005, Copyright © 2005
doi:10.1534/genetics.104.036764
A Genetic Screen for top3 Suppressors in Saccharomyces cerevisiae Identifies SHU1, SHU2, PSY3 and CSM2
Four Genes Involved in Error-Free DNA Repair
Erika Shor1,
Justin Weinstein and
Rodney Rothstein2
Department of Genetics and Development, Columbia University College of Physicians & Surgeons, New York, New York 10032-2704
2 Corresponding author: Department of Genetics and Development, Columbia University College of Physicians & Surgeons, 701 W. 168th St., New York, NY 10032-2704.
E-mail: rothstein{at}cancercenter.columbia.edu
Helicases of the RecQ family and topoisomerase III are evolutionarily conserved proteins important for maintenance of genome stability. In Saccharomyces cerevisiae, loss of the TOP3 gene, encoding topoisomerase III, results in a phenotype of slow growth, DNA damage sensitivity, meiotic defects, and hyperrecombination. The sole RecQ helicase in budding yeast, Sgs1, interacts with Top3 both physically and genetically, and the two proteins are thought to act in concert in vivo. Much recent genetic and biochemical evidence points to the role of RecQ helicases and topoisomerase III in regulating homologous recombination (HR) during DNA replication. Previously, we found that mutations in HR genes partially suppress top3 slow growth. Here, we describe the analysis of four additional mutational suppressors of top3 defects: shu1, shu2, psy3, and csm2. These genes belong to one epistasis group and their protein products interact with each other, strongly suggesting that they function as a complex in vivo. Their mutant phenotype indicates that they are important for error-free repair of spontaneous and induced DNA lesions, protecting the genome from mutation. These mutants exhibit an epistatic relationship with rad52 and show altered dynamics of Rad52-YFP foci, suggesting a role for these proteins in recombinational repair.
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Copyright © 2005 by the Genetics Society of America.