In vivo nicking and rejoining of nuclear DNA in ultraviolet-irradiated radiation-resistant and sensitive strains of Dictyostelium discoideum
✍ Scribed by Welker, D. L. ;Deering, R. A.
- Publisher
- Springer
- Year
- 1979
- Tongue
- English
- Weight
- 412 KB
- Volume
- 167
- Category
- Article
- ISSN
- 0026-8925
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✦ Synopsis
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.