title: Hyperactive Cdc2 kinase interferes with the response to broken replication forks by trapping S.pombe Crb2 in its mitotic T215 phosphorylated state.
abstract: Although it is well established that Cdc2 kinase phosphorylates the DNA damage checkpoint protein Crb2(53BP1) in mitosis, the full impact of this modification is still unclear. The Tudor-BRCT domain protein Crb2 binds to modified histones at DNA lesions to mediate the activation of Chk1 by Rad3ATR kinase. We demonstrate here that fission yeast cells harbouring a hyperactive Cdc2CDK1 mutation (cdc2.1w) are specifically sensitive to the topoisomerase 1 inhibitor camptothecin (CPT) which breaks DNA replication forks. Unlike wild-type cells, which delay only briefly in CPT medium by activating Chk1 kinase, cdc2.1w cells bypass Chk1 to enter an extended cell-cycle arrest which depends on Cds1 kinase. Intriguingly, the ability to bypass Chk1 requires the mitotic Cdc2 phosphorylation site Crb2-T215. This implies that the presence of the mitotic phosphorylation at Crb2-T215 channels Rad3 activity towards Cds1 instead of Chk1 when forks break in S phase. We also provide evidence that hyperactive Cdc2.1w locks cells in a G1-like DNA repair mode which favours non-homologous end joining over interchromosomal recombination. Taken together, our data support a model such that elevated Cdc2 activity delays the transition of Crb2 from its G1 to its G2 mode by blocking Srs2 DNA helicase and Casein Kinase 1 (Hhp1).
authors.affiliation: Genome Biology Group, College of Natural Sciences, School of Biological Sciences, Bangor University, Brambell Building, Deiniol Road, Bangor LL57 2UW, Wales, United Kingdom.
authors.forename: Salah Adam
authors.initials: SA
authors.lastname: Mahyous Saeyd
authors.affiliation: Genome Biology Group, College of Natural Sciences, School of Biological Sciences, Bangor University, Brambell Building, Deiniol Road, Bangor LL57 2UW, Wales, United Kingdom.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Ewert-Krzemieniewska
authors.affiliation: Genome Biology Group, College of Natural Sciences, School of Biological Sciences, Bangor University, Brambell Building, Deiniol Road, Bangor LL57 2UW, Wales, United Kingdom.
authors.forename: Boyin
authors.initials: B
authors.lastname: Liu
authors.affiliation: Genome Biology Group, College of Natural Sciences, School of Biological Sciences, Bangor University, Brambell Building, Deiniol Road, Bangor LL57 2UW, Wales, United Kingdom t.caspari@bangor.ac.uk.
authors.forename: Thomas
authors.initials: T
authors.lastname: Caspari
mesh_terms: D034961:Antigens, Nuclear / Q000378:metabolism; D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism*; D002166:Camptothecin / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D000071877:Checkpoint Kinase 1; D004265:DNA Helicases / Q000378:metabolism; D004260:DNA Repair; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D016193:G1 Phase / Q000235:genetics; D059565:G2 Phase Cell Cycle Checkpoints / Q000235:genetics*; D000072200:Ku Autoantigen; D008938:Mitosis / Q000235:genetics; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012568:Schizosaccharomyces / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D059004:Topoisomerase I Inhibitors / Q000494:pharmacology
chemical_list: D034961:Antigens, Nuclear; D018797:Cell Cycle Proteins; C109867:Crb2 protein, S pombe; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D029702:Schizosaccharomyces pombe Proteins; D059004:Topoisomerase I Inhibitors; D011494:Protein Kinases; C088232:hhp1 protein, S pombe; D000071877:Checkpoint Kinase 1; C000605873:Chk1 protein, S pombe; D016203:CDC2 Protein Kinase; C469447:cdc2 protein, S pombe; D004265:DNA Helicases; D000072200:Ku Autoantigen; C468289:Srs2 protein, S pombe; D002166:Camptothecin