title: Efficiency of formation of pyrimidine dimers in SV40 chromatin in vitro.
abstract: The efficiency of formation of pyrimidine dimers by 254-nm light was studied in mixtures of SV40 chromatin and DNA extracted from that chromatin. At high doses (beyond 380 J/m2), fewer dimers are formed in chromatin than in DNA for a given dose of radiation. This difference is about 10% as saturation with pyrimidine dimers is approached at 6840 J/m2. Conversely, at biologically repairable doses (up to 40 J/m2, less than 2 dimers/genome), significantly more dimers are produced in the chromatin than in the DNA. A maximum increase of about 50% occurs at doses producing 0.5--20 dimers/genome. With isolated nucleosomes from this chromatin, a maximum increase in dimer formation of 77% was observed. Therefore, the increased dimer formation in the whole chromatin can be wholly accounted for in the nucleosome portion.
mesh_terms: D000818:Animals; D002460:Cell Line; D002843:Chromatin / Q000528:radiation effects*; D004247:DNA / Q000528:radiation effects; D004279:DNA, Viral / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D000882:Haplorhini; D007668:Kidney; D008836:Micrococcal Nuclease; D009707:Nucleosomes / Q000528:radiation effects; D011740:Pyrimidine Dimers / Q000528:radiation effects*; D013539:Simian virus 40 / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D002843:Chromatin; D004279:DNA, Viral; D009707:Nucleosomes; D011740:Pyrimidine Dimers; D004247:DNA; D008836:Micrococcal Nuclease