title: Cdc2-cyclin B kinase activity links Crb2 and Rqh1-topoisomerase III.
abstract: The availability of a sister chromatid, and thus the cell cycle phase in which DNA double-strand breaks (DSBs) occur, influences the choice between homologous recombination (HR) or nonhomologous end joining (NHEJ). The sequential activation and destruction of CDK-cyclin activities controls progression through the cell cycle. Here we provide evidence that the major Schizosaccharomyces pombe CDK, Cdc2-cyclin B, influences recombinational repair of radiation-induced DSBs during the G(2) phase at two distinct stages. At an early stage in HR, a defect in Cdc2 kinase activity, which is caused by a single amino acid change in cyclin B, affects the formation of Rhp51 (Rad51(sp)) foci in response to ionizing radiation in a process that is redundant with the function of Rad50. At a late stage in HR, low Cdc2-cyclin B activity prevents the proper regulation of topoisomerase III (Top3) function, disrupting a recombination step that occurs after the assembly of Rhp51 foci. This effect of Cdc2-cyclin B kinase on Top3 function is mediated by the BRCT-domain-containing checkpoint protein Crb2, thus linking checkpoint proteins directly with recombinational repair in G(2). Our data suggest a model in which CDK activity links processing of recombination intermediates to cell cycle progression via checkpoint proteins.
authors.affiliation: Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Caspari
authors.forename: Johanne M
authors.initials: JM
authors.lastname: Murray
authors.forename: Antony M
authors.initials: AM
authors.lastname: Carr
mesh_terms: D016203:CDC2 Protein Kinase / Q000378:metabolism*; D017489:CDC28 Protein Kinase, S cerevisiae / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology* / Q000528:radiation effects; D002457:Cell Extracts; D002478:Cells, Cultured / Q000502:physiology / Q000528:radiation effects*; D019926:Cyclin B / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D018816:Genes, cdc / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism*; D017354:Point Mutation; D011233:Precipitin Tests; D011995:Recombination, Genetic; D012568:Schizosaccharomyces / Q000235:genetics / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins
chemical_list: D018797:Cell Cycle Proteins; D002457:Cell Extracts; C109867:Crb2 protein, S pombe; D019926:Cyclin B; D005656:Fungal Proteins; D009687:Nuclear Proteins; D029702:Schizosaccharomyces pombe Proteins; D016203:CDC2 Protein Kinase; D017489:CDC28 Protein Kinase, S cerevisiae; D004265:DNA Helicases; C106462:Rqh1 protein, S pombe; D004264:DNA Topoisomerases, Type I