In vivo nicking and rejoining of nuclear DNA in ultraviolet-irradiated radiation-resistant and sensitive strains of Dictyostelium discoideum |
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Authors: | D L Welker and R A Deering |
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Institution: | (1) Department of Biochemistry and Biophysics, The Pennsylvania State University, 16802 University Park, Pennsylvania, USA;(2) Genetics Department, Research School of Biological Sciences, The Australian National University, 2601 Canberra City, ACT, Australia |
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Abstract: | Summary 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 singlestrand breaks in their nuclear DNA after a UV fluence of 15 J/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.Abbreviations used UV
ultraviolet light
- PBS
phosphate buffered saline
- cpm
counts per minute |
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