title: CDK targets Sae2 to control DNA-end resection and homologous recombination.
abstract: DNA double-strand breaks (DSBs) are repaired by two principal mechanisms: non-homologous end-joining (NHEJ) and homologous recombination (HR). HR is the most accurate DSB repair mechanism but is generally restricted to the S and G2 phases of the cell cycle, when DNA has been replicated and a sister chromatid is available as a repair template. By contrast, NHEJ operates throughout the cell cycle but assumes most importance in G1 (refs 4, 6). The choice between repair pathways is governed by cyclin-dependent protein kinases (CDKs), with a major site of control being at the level of DSB resection, an event that is necessary for HR but not NHEJ, and which takes place most effectively in S and G2 (refs 2, 5). Here we establish that cell-cycle control of DSB resection in Saccharomyces cerevisiae results from the phosphorylation by CDK of an evolutionarily conserved motif in the Sae2 protein. We show that mutating Ser 267 of Sae2 to a non-phosphorylatable residue causes phenotypes comparable to those of a sae2Delta null mutant, including hypersensitivity to camptothecin, defective sporulation, reduced hairpin-induced recombination, severely impaired DNA-end processing and faulty assembly and disassembly of HR factors. Furthermore, a Sae2 mutation that mimics constitutive Ser 267 phosphorylation complements these phenotypes and overcomes the necessity of CDK activity for DSB resection. The Sae2 mutations also cause cell-cycle-stage specific hypersensitivity to DNA damage and affect the balance between HR and NHEJ. These findings therefore provide a mechanistic basis for cell-cycle control of DSB repair and highlight the importance of regulating DSB resection.
authors: The Wellcome Trust and Cancer Research UK Gurdon Institute, and Department of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.
authors: Pablo
authors: P
authors: Huertas
authors: Felipe
authors: F
authors: Cortés-Ledesma
authors: Alessandro A
authors: AA
authors: Sartori
authors: Andrés
authors: A
authors: Aguilera
authors: Stephen P
authors: SP
authors: Jackson
mesh_terms: D020816:Amino Acid Motifs; D017489:CDC28 Protein Kinase, S cerevisiae / Q000378:metabolism*; D002453:Cell Cycle; D002460:Cell Line; D002470:Cell Survival; D017124:Conserved Sequence; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004706:Endodeoxyribonucleases / Q000378:metabolism; D004720:Endonucleases; D005090:Exodeoxyribonucleases / Q000378:metabolism; D006801:Humans; D009154:Mutation; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D051721:Rad52 DNA Repair and Recombination Protein / Q000378:metabolism; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: C497197:RAD52 protein, S cerevisiae; D051721:Rad52 DNA Repair and Recombination Protein; C107849:SAE2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D010768:Phosphoserine; D017489:CDC28 Protein Kinase, S cerevisiae; D004706:Endodeoxyribonucleases; D004720:Endonucleases; D005090:Exodeoxyribonucleases; C094191:MRE11 protein, S cerevisiae