Nocentini S
UMR Curie/CNRS 218 et LRC no. 1 du CEA, Institut Curie, Section de Recherche, Paris, France.
Radiat Res. 1999 Apr;151(4):423-32.
The repair kinetics for rejoining of DNA single- and double-strand breaks after exposure to UVC or gamma radiation was measured in cells with deficiencies in DNA ligase activities and in their normal counterparts. Human 46BR cells were deficient in DNA ligase I. Hamster EM9 and EM-C11 cells were deficient in DNA ligase III activity as a consequence of mutations in the XRCC1 gene. Hamster XR-1 cells had mutation in the XRCC4 gene, whose product stimulates DNA ligase IV activity. DNA single- and double-strand breaks were assessed by the comet assay in alkaline conditions and by the technique of graded-field gel electrophoresis in neutral conditions, respectively. 46BR cells, which are known to re-ligate at a reduced rate the DNA single-strand breaks incurred during processing of damage induced by UVC but not gamma radiation, were shown to have a normal repair of radiation-induced DNA double-strand breaks. EM9 cells exhibited a reduced rate of rejoining of DNA single-strand breaks after exposure to ionizing radiation, as reported previously, as well as UVC radiation. EM-C11 cells were deficient in the repair of radiation-induced-DNA single-strand breaks but, in contrast to EM9 cells, demonstrated the same kinetics as the parental cell line in the resealing of DNA breaks resulting from exposure to UVC radiation. Both EM9 and EM-C11 cells displayed a significant defect in rejoining of radiation-induced-DNA double-strand breaks. XR-1 cells were confirmed to be highly deficient in the repair of radiation-induced DNA double-strand breaks but appeared to rejoin DNA single-strand breaks after UVC and gamma irradiation at rates close to normal. Taken together these results indicate that: (1) DNA ligase I is involved only in nucleotide excision repair; (2) DNA ligase IV plays an important role only in repair of DNA double-strand breaks; and (3) DNA ligase III is implicated in base excision repair and in repair of DNA double-strand breaks, but probably not in nucleotide excision repair.
在DNA连接酶活性有缺陷的细胞及其正常对照细胞中，测量了暴露于紫外线C（UVC）或γ辐射后DNA单链和双链断裂重新连接的修复动力学。人类46BR细胞缺乏DNA连接酶I。仓鼠EM9和EM-C11细胞由于XRCC1基因突变而缺乏DNA连接酶III活性。仓鼠XR-1细胞的XRCC4基因发生了突变，其产物可刺激DNA连接酶IV的活性。分别通过碱性条件下的彗星试验和中性条件下的梯度场凝胶电泳技术评估DNA单链和双链断裂。已知46BR细胞在处理UVC而非γ辐射诱导的损伤过程中产生的DNA单链断裂时，重新连接的速率降低，但显示出对辐射诱导的DNA双链断裂具有正常的修复能力。如先前报道的那样，EM9细胞在暴露于电离辐射以及UVC辐射后，DNA单链断裂重新连接的速率降低。EM-C11细胞在修复辐射诱导的DNA单链断裂方面存在缺陷，但与EM9细胞不同的是，在重新封闭UVC辐射导致的DNA断裂方面，其动力学与亲本细胞系相同。EM9和EM-C11细胞在重新连接辐射诱导的DNA双链断裂方面均表现出明显缺陷。XR-1细胞被证实高度缺乏对辐射诱导的DNA双链断裂的修复能力，但在UVC和γ辐射后，其重新连接DNA单链断裂的速率似乎接近正常。综合这些结果表明：（1）DNA连接酶I仅参与核苷酸切除修复；（2）DNA连接酶IV仅在DNA双链断裂的修复中起重要作用；（3）DNA连接酶III与碱基切除修复以及DNA双链断裂的修复有关，但可能不参与核苷酸切除修复。
