title: The severe slow growth of Deltasrs2 Deltarqh1 in Schizosaccharomyces pombe is suppressed by loss of recombination and checkpoint genes.
abstract: Our interest in the Schizosaccharomyces pombe RecQ helicase, rqh1+, led us to investigate the function of a related putative DNA helicase, srs2+. We identified the srs2+ homolog in S.pombe, and found that srs2+ is not essential for cell viability. A Deltasrs2 Deltarqh1 double mutant grows extremely slowly with aberrant shaped cells and low viability. This slow growth does not appear to be related to stalled replication, as Deltasrs2 Deltarqh1 cells showed higher survival rates, compared with Deltarqh1, when stalled forks were increased by UV irradiation or hydroxy urea treatment. Consistent with this result, we found that Deltasrs2 Deltarqh1 cells progress through S-phase with a slight delay, but undergo a checkpoint-dependent arrest presumably at G2/M. Further, we found that Deltasrs2 Deltarqh1 slow growth is related to recombination, as loss of either the rhp51+ or rhp57+ recombination genes improves cell growth in the double mutant. Deltasrs2 is also synthetic lethal with Deltarhp54, another homologous recombination gene. This lethality is suppressed in a Deltarhp51 background. Together, these results demonstrate a clear genetic interaction between rqh1+, srs2+ and the genes of the homologous recombination pathway.
authors.affiliation: Department of Environmental Health Sciences, Columbia University, Mailman School of Public Health and College of Physicians and Surgeons, Kolb Building, Room 114, 722 West 168th Street, New York, NY 10032, USA.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Maftahi
authors.forename: Justin C
authors.initials: JC
authors.lastname: Hope
authors.forename: Lissette
authors.initials: L
authors.lastname: Delgado-Cruzata
authors.forename: Christine S
authors.initials: CS
authors.lastname: Han
authors.forename: Greg A
authors.initials: GA
authors.lastname: Freyer
mesh_terms: D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D004265:DNA Helicases / Q000235:genetics*; D004261:DNA Replication / Q000187:drug effects / Q000528:radiation effects; D017353:Gene Deletion; D005800:Genes, Fungal / Q000235:genetics; D005804:Genes, Lethal / Q000235:genetics; D018816:Genes, cdc; D006918:Hydroxyurea / Q000494:pharmacology; D010641:Phenotype; D011995:Recombination, Genetic / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D012568:Schizosaccharomyces / Q000166:cytology / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D013489:Suppression, Genetic / Q000235:genetics*; D014466:Ultraviolet Rays
chemical_list: D029702:Schizosaccharomyces pombe Proteins; D004265:DNA Helicases; C106462:Rqh1 protein, S pombe; C468289:Srs2 protein, S pombe; D006918:Hydroxyurea