title: Srs2 plays a critical role in reversible G2 arrest upon chronic and low doses of UV irradiation via two distinct homologous recombination-dependent mechanisms in postreplication repair-deficient cells.
abstract: Differential posttranslational modification of proliferating cell nuclear antigen (PCNA) by ubiquitin or SUMO plays an important role in coordinating the processes of DNA replication and DNA damage tolerance. Previously it was shown that the loss of RAD6-dependent error-free postreplication repair (PRR) results in DNA damage checkpoint-mediated G(2) arrest in cells exposed to chronic low-dose UV radiation (CLUV), whereas wild-type and nucleotide excision repair-deficient cells are largely unaffected. In this study, we report that suppression of homologous recombination (HR) in PRR-deficient cells by Srs2 and PCNA sumoylation is required for checkpoint activation and checkpoint maintenance during CLUV irradiation. Cyclin-dependent kinase (CDK1)-dependent phosphorylation of Srs2 did not influence checkpoint-mediated G(2) arrest or maintenance in PRR-deficient cells but was critical for HR-dependent checkpoint recovery following release from CLUV exposure. These results indicate that Srs2 plays an important role in checkpoint-mediated reversible G(2) arrest in PRR-deficient cells via two separate HR-dependent mechanisms. The first (required to suppress HR during PRR) is regulated by PCNA sumoylation, whereas the second (required for HR-dependent recovery following CLUV exposure) is regulated by CDK1-dependent phosphorylation.
authors: Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan. hishida@biken.osaka-u.ac.jp
authors: Takashi
authors: T
authors: Hishida
authors: Yoshihiro
authors: Y
authors: Hirade
authors: Nami
authors: N
authors: Haruta
authors: Yoshino
authors: Y
authors: Kubota
authors: Hiroshi
authors: H
authors: Iwasaki
mesh_terms: D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism; D016203:CDC2 Protein Kinase / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D004261:DNA Replication; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D016195:G2 Phase / Q000528:radiation effects; D017353:Gene Deletion; D005800:Genes, Fungal; D008954:Models, Biological; D009154:Mutation; D010766:Phosphorylation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011836:Radiation Tolerance / Q000235:genetics / Q000502:physiology; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D034961:Antigens, Nuclear; D004271:DNA, Fungal; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; C546594:POL30 protein, S cerevisiae; D018809:Proliferating Cell Nuclear Antigen; C063607:RAD18 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; C061376:SRS2 protein, S cerevisiae; D016203:CDC2 Protein Kinase; D004265:DNA Helicases