Chan G L, Little J B
Mutat Res. 1979 Dec;63(2):401-12. doi: 10.1016/0027-5107(79)90072-1.
Clonogenic survival response to 254-nm ultraviolet light was measured in 2 strains of repair-proficient normal human fibroblasts and 4 strains of xeroderma pigmentosum (XP) fibroblasts belonging to complementation groups A, C, D and variant. In all strains except XPA, cells irradiated in plateau phase and subcultured immediately were much more resistant to the lethal effect of UV than cells irradiated in the exponential phase of growth. Typically, 10-20% of plateau-phase cells were extremely resistant. When the cultures were held in plateau phase for 24 h after irradiation and before subculture, there was a further enhance of survival. By use of a UV-specific endonuclease assay, no difference was found in the number of DNA lesions induced in exponentially growing and plateau cultures by the same dose of UV light. Thus plateau-phase cells appear to be more efficient in their DNA-repair capability than cells in exponential growth. XP group A cells were uniquely found to be deficient in the processes which lead to plateau-phase resistance. Since plateau-phase repair was not lacking in XP groups C, D and variant, it may be related to a DNA-repair process different from that which is responsible for the overall UV sensitivity of these cells.
在2株修复功能正常的正常人成纤维细胞和4株属于互补组A、C、D及变异型的着色性干皮病（XP）成纤维细胞中，测定了对254纳米紫外线的克隆形成存活反应。在除XPA外的所有菌株中，处于平台期照射并立即传代培养的细胞比处于生长指数期照射的细胞对紫外线的致死效应具有更强的抗性。通常，10%至20%的平台期细胞具有极强的抗性。当培养物在照射后且传代培养前在平台期保持24小时时，存活率进一步提高。通过使用紫外线特异性核酸内切酶测定法，发现相同剂量的紫外线在指数生长期和平板期培养物中诱导的DNA损伤数量没有差异。因此，平台期细胞在DNA修复能力上似乎比指数生长期的细胞更有效。独特的是，发现XP组A细胞在导致平台期抗性的过程中存在缺陷。由于XP组C、D及变异型细胞并不缺乏平台期修复，所以它可能与一种不同于导致这些细胞总体紫外线敏感性的DNA修复过程有关。
