Mirzayans R, Paterson M C
Molecular Genetics and Carcinogenesis Laboratory, Cross Cancer Institute, Edmonton, Alb., Canada.
Mutat Res. 1991 Mar;262(3):151-7. doi: 10.1016/0165-7992(91)90015-v.
The extent of DNA-excision repair was determined in human fibroblast strains from clinically normal and xeroderma pigmentosum complementation group A (XP-A) donors after irradiation with 254-nm ultraviolet (UV) light. Repair was monitored by the use of 1-beta-D-arabinofuranosylcytosine (araC), a potent inhibitor of DNA synthesis, and alkaline sucrose velocity sedimentation to quantitate DNA single-strand breaks. In this approach, the number of araC-accumulated breaks in post-UV incubated cultures becomes a measure of the efficiency of a particular strain to perform long-patch excision repair. The maximal rate of removal of araC-detectable DNA lesions equalled approximately 1.8 sites/10(8) dalton/h in the normal strains (GM38, GM43), while it was more than 10-fold lower in both XP-A strains (XP4LO, XP12BE) examined. In normal fibroblasts the number of lesions removed during the first 4 h after irradiation saturated at approximately 10 J/m2. In contrast, the residual amount of repair in the excision-deficient cells increased as a linear function of UV fluence over a range 5-120 J/m2. Thus we conclude that the repair of araC-detectable UV photoproducts in XP group A fibroblasts is limited by availability of damaged regions in the genome to repair complexes.
在用254纳米紫外线（UV）照射后，测定了来自临床正常和着色性干皮病A互补组（XP - A）供体的人成纤维细胞株中的DNA切除修复程度。通过使用DNA合成的有效抑制剂1-β-D-阿拉伯呋喃糖基胞嘧啶（araC）以及碱性蔗糖速度沉降法来监测修复情况，以定量DNA单链断裂。在这种方法中，紫外线照射后培养的细胞中araC积累的断裂数量成为衡量特定细胞株进行长片段切除修复效率的指标。在正常细胞株（GM38、GM43）中，araC可检测到的DNA损伤的最大去除速率约为1.8个位点/10⁸道尔顿/小时，而在所检测的两种XP - A细胞株（XP4LO、XP12BE）中，该速率则低10倍以上。在正常成纤维细胞中，照射后最初4小时内去除的损伤数量在约10 J/m²时达到饱和。相比之下，在5 - 120 J/m²范围内，切除缺陷细胞中的修复残留量随紫外线通量呈线性增加。因此我们得出结论，XP A组成纤维细胞中araC可检测到的紫外线光产物的修复受到基因组中损伤区域对修复复合物可用性的限制。
