Lankinen M H, Vilpo L M, Vilpo J A
Department of Clinical Chemistry, Tampere University Hospital, Finland.
Mutat Res. 1996 Jun 10;352(1-2):31-8. doi: 10.1016/0027-5107(95)00172-7.
Ionizing irradiation and UV-irradiation cause DNA damage. Ionizing irradiation induces single-strand breaks, much less abundantly double-strand breaks, alkali-labile sites, and various oxidized purines and pyrimidines. UV-irradiation, on the other hand, causes cyclobutane pyrimidine dimers, (6-4) photoproducts, and various monomeric base damages. The deposition of energy in DNA may result directly in single-strand breaks (predominant form after ionizing radiation), or the strand breaks may be generated during the repair process (predominant form after UV-irradiation). We investigated the formation and repair of DNA single-strand breaks in human blood granulocytes and lymphocytes by the single-cell gel electrophoresis or comet assay. The induction and repair of DNA lesions by gamma-irradiation was comparable in human blood granulocytes and lymphocytes. The finding is consistent with the expression of the pertinent base excision repair proteins in these cells. In contrast to gamma-irradiation, fewer single-strand breaks were observed immediately after UV-irradiation; the maximum number of breaks were seen when the cells were incubated for 30-60 min. After an incubation period of 150 min, a significant reduction of single-strand breaks was noted. It is conceivable that the first 30-60 min represented a period during which the incision-excision phase of nucleotide excision repair (NER) predominated. After that, strand joining was dominant, evidently representing the synthesis and ligation phase of NER. These results indicate that the approx. 30 different polypeptides required for complete NER are functional in these mature blood cells. This is the first demonstration of the expression of global NER in human granulocytes.
电离辐射和紫外线辐射会导致DNA损伤。电离辐射会诱导单链断裂，双链断裂的情况则少得多，还会产生碱不稳定位点以及各种氧化的嘌呤和嘧啶。另一方面，紫外线辐射会导致环丁烷嘧啶二聚体、（6-4）光产物以及各种单体碱基损伤。DNA中的能量沉积可能直接导致单链断裂（电离辐射后的主要形式），或者链断裂可能在修复过程中产生（紫外线辐射后的主要形式）。我们通过单细胞凝胶电泳或彗星试验研究了人类血液粒细胞和淋巴细胞中DNA单链断裂的形成和修复。γ辐射对DNA损伤的诱导和修复在人类血液粒细胞和淋巴细胞中具有可比性。这一发现与这些细胞中相关碱基切除修复蛋白的表达一致。与γ辐射不同，紫外线辐射后立即观察到的单链断裂较少；在细胞孵育30 - 60分钟时观察到断裂数量最多。孵育150分钟后，单链断裂显著减少。可以想象，最初的30 - 60分钟代表了核苷酸切除修复（NER）的切口 - 切除阶段占主导的时期。在此之后，链连接占主导，显然代表了NER的合成和连接阶段。这些结果表明，完整NER所需的约30种不同多肽在这些成熟血细胞中发挥功能。这是首次在人类粒细胞中证明全局NER的表达。
