title: In vivo nicking and rejoining of nuclear DNA in ultraviolet-irradiated radiation-resistant and sensitive strains of Dictyostelium discoideum.
abstract: Some aspects of DNA repair in several radiation-resistant and radiation-sensitive strains of Dictyostelium discoideum were investigated by using alkaline sucrose gradients to analyze for the production and resealing of single-strand breaks following irradiation with 254 nm UV. All radiation-resistant strains and all mutants assayed that are sensitive to both UV and 60Co gamma rays produced single-strand breaks in their nuclear DNA after a UV fluence of 15 M/m2. Mutants at the radC locus which are sensitive to UV but as resistant as their parental strains to 60Co gamma rays produced many fewer single-strand breaks in their DNA after irradiation with UV. Thus, the radC mutations alter a repair pathway specific for UV-induced DNA damage and presumably affect the activity of a UV-damage-specific endonuclease involved in excision repair. All radiation-resistant strains and all of our mutants sensitive to gamma rays rejoined much of their DNA during a three-hour post-UV-irradiation incubation, suggesting that these strains have at least a partially intact excision repair system.
mesh_terms: D002499:Centrifugation, Density Gradient; D004260:DNA Repair; D004023:Dictyostelium / Q000235:genetics* / Q000528:radiation effects; D009154:Mutation; D010641:Phenotype; D011836:Radiation Tolerance; D014466:Ultraviolet Rays