title: Distinct Cdk1 requirements during single-strand annealing, noncrossover, and crossover recombination.
abstract: Repair of DNA double-strand breaks (DSBs) by homologous recombination (HR) in haploid cells is generally restricted to S/G2 cell cycle phases, when DNA has been replicated and a sister chromatid is available as a repair template. This cell cycle specificity depends on cyclin-dependent protein kinases (Cdk1 in Saccharomyces cerevisiae), which initiate HR by promoting 5'-3' nucleolytic degradation of the DSB ends. Whether Cdk1 regulates other HR steps is unknown. Here we show that yku70Δ cells, which accumulate single-stranded DNA (ssDNA) at the DSB ends independently of Cdk1 activity, are able to repair a DSB by single-strand annealing (SSA) in the G1 cell cycle phase, when Cdk1 activity is low. This ability to perform SSA depends on DSB resection, because both resection and SSA are enhanced by the lack of Rad9 in yku70Δ G1 cells. Furthermore, we found that interchromosomal noncrossover recombinants are generated in yku70Δ and yku70Δ rad9Δ G1 cells, indicating that DSB resection bypasses Cdk1 requirement also for carrying out these recombination events. By contrast, yku70Δ and yku70Δ rad9Δ cells are specifically defective in interchromosomal crossover recombination when Cdk1 activity is low. Thus, Cdk1 promotes DSB repair by single-strand annealing and noncrossover recombination by acting mostly at the resection level, whereas additional events require Cdk1-dependent regulation in order to generate crossover outcomes.
authors: Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milano, Italy.
authors: Camilla
authors: C
authors: Trovesi
authors: Marco
authors: M
authors: Falcettoni
authors: Giovanna
authors: G
authors: Lucchini
authors: Michela
authors: M
authors: Clerici
authors: Maria Pia
authors: MP
authors: Longhese
mesh_terms: D016203:CDC2 Protein Kinase / Q000235:genetics* / Q000378:metabolism; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D003434:Crossing Over, Genetic; D053903:DNA Breaks, Double-Stranded; D053904:DNA Breaks, Single-Stranded; D004268:DNA-Binding Proteins / Q000235:genetics; D016193:G1 Phase; D011995:Recombination, Genetic; D059767:Recombinational DNA Repair; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; C520769:YKU70 protein, S cerevisiae; C069930:rad9 protein; D016203:CDC2 Protein Kinase