title: UV irradiation causes the loss of viable mitotic recombinants in Schizosaccharomyces pombe cells lacking the G(2)/M DNA damage checkpoint.
abstract: Elevated mitotic recombination and cell cycle delays are two of the cellular responses to UV-induced DNA damage. Cell cycle delays in response to DNA damage are mediated via checkpoint proteins. Two distinct DNA damage checkpoints have been characterized in Schizosaccharomyces pombe: an intra-S-phase checkpoint slows replication and a G(2)/M checkpoint stops cells passing from G(2) into mitosis. In this study we have sought to determine whether UV damage-induced mitotic intrachromosomal recombination relies on damage-induced cell cycle delays. The spontaneous and UV-induced recombination phenotypes were determined for checkpoint mutants lacking the intra-S and/or the G(2)/M checkpoint. Spontaneous mitotic recombinants are thought to arise due to endogenous DNA damage and/or intrinsic stalling of replication forks. Cells lacking only the intra-S checkpoint exhibited no UV-induced increase in the frequency of recombinants above spontaneous levels. Mutants lacking the G(2)/M checkpoint exhibited a novel phenotype; following UV irradiation the recombinant frequency fell below the frequency of spontaneous recombinants. This implies that, as well as UV-induced recombinants, spontaneous recombinants are also lost in G(2)/M mutants after UV irradiation. Therefore, as well as lack of time for DNA repair, loss of spontaneous and damage-induced recombinants also contributes to cell death in UV-irradiated G(2)/M checkpoint mutants.
authors.affiliation: Department of Biochemistry and Molecular Biology, University College London, London WC1E 6BT, United Kingdom. fekret.osman@bioch.ox.ac.uk
authors.forename: Fekret
authors.initials: F
authors.lastname: Osman
authors.forename: Irina R
authors.initials: IR
authors.lastname: Tsaneva
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Whitby
authors.forename: Claudette L
authors.initials: CL
authors.lastname: Doe
mesh_terms: D002453:Cell Cycle / Q000528:radiation effects; D064447:Checkpoint Kinase 2; D004260:DNA Repair / Q000528:radiation effects*; D004261:DNA Replication / Q000528:radiation effects; D018816:Genes, cdc / Q000528:radiation effects; D009154:Mutation / Q000528:radiation effects; D011494:Protein Kinases / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases; D011995:Recombination, Genetic / Q000528:radiation effects*; D012568:Schizosaccharomyces / Q000235:genetics* / Q000528:radiation effects; D029702:Schizosaccharomyces pombe Proteins; D014466:Ultraviolet Rays
chemical_list: D029702:Schizosaccharomyces pombe Proteins; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C578636:Cds1 protein, S pombe; D017346:Protein Serine-Threonine Kinases