USE OF MAMMALIAN DNA REPAIR-DEFICIENT MUTANTS TO ASSESS THE EFFECTS OF TOXIC METAL-COMPOUNDS ON DNA
USE OF MAMMALIAN DNA REPAIR-DEFICIENT MUTANTS TO ASSESS THE EFFECTS OF TOXIC METAL-COMPOUNDS ON DNA
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DOI：
10.1016/0006-2952(84)90289-2
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发表时间：
1984-01-01
影响因子：
5.8
通讯作者：
COSTA, M
中科院分区：
文献类型：
--
作者：
CHRISTIE, NT;CANTONI, O;COSTA, M
利用中国仓鼠卵巢细胞的野生型和修复缺陷细胞系（Em9）来评估金属对DNA损伤的细胞毒性反应。碱性洗脱研究表明，CaCrO4和HgCl2都能诱导DNA单链断裂。CaCrO4和HgCl2处理也诱导了完整的中国仓鼠卵巢细胞的DNA交联。突变细胞被认为在修复聚合酶中有缺陷，因此对各种在DNA中产生损伤的物质（如x射线和紫外线）表现出更大的敏感性，与野生型细胞相比，对HgCl2和CaCrO4的细胞毒性反应也表现出更大的敏感性。例如，与修复缺陷细胞相比，暴露于CaCrO4 6小时或HgCl2 1小时后，野生型细胞的IC50（产生50%生长抑制的浓度）分别是3.4倍或1.8- 3.9倍。与野生型细胞相比，突变型细胞对主要作用位点不在DNA水平的药物（即两性霉素B、三氟哌嗪和环己亚胺）的生长抑制并不更敏感。10 μ m暴露诱导的DNA交联。在野生型细胞中，CaCrO4暴露6小时后，在24小时内几乎完全修复，而在同样暴露的突变细胞中，这种损伤最初更为明显，并且在缺乏CaCrO4的情况下，仅在24小时恢复性后部分修复。CaCrO4诱导的单链断裂修复在野生型和突变型细胞中更为迅速和相似。由于Hg（II）抑制单链断裂的修复，因此无法研究该药物诱导的损伤修复；然而，在非常低的浓度下(1。与野生型细胞相比，突变细胞中203Hg（II）与DNA的结合更大。从培养基中去除203Hg（II）后，相对于细胞中存在的总203Hg(II)，突变细胞通常保留更多与DNA结合的203Hg。CaCrO4和HgCl2的一个重要毒性作用涉及对DNA的损伤，因为这些金属引起可测量的DNA损伤的浓度与它们各自的细胞毒性浓度一致，DNA修复缺陷突变体既表现出增强的细胞毒性，又表现出金属诱导病变的修复能力下降。这项研究可能应用于癌变的研究。
Wild-type and repair-deficient cell lines (Em9) of Chinese hamster ovary cells were utilized to assess cytotoxic responses towards metals that produce lesions in DNA. Alkaline elution studies indicated that both CaCrO4 and HgCl2 induced single-strand breaks in the DNA. CaCrO4 and HgCl2 treatments of intact Chinese hamster ovary cells also caused the induction of DNA cross links. The mutant cells, which are thought to have a defect in the repair polymerase enzyme and therefore exhibit greater sensitivity towards a variety of agents that produce lesions in the DNA such as X-rays and UV-light, also displayed a greater sensitivity, compared to wild-type cells, towards the cytotoxic response of HgCl2 and CaCrO4. For example, the IC50 (concentration producing a 50% growth inhibition) following exposure for 6 h to CaCrO4 or 1 h to HgCl2 was 3.4-fold or 1.8- to 3.9-fold greater in wild-type cells compared to repair-deficient cells respectively. Mutant cells compared to wild-type cells were not more sensitive to growth inhibition by agents whose primary site of action was not at the DNA level (i.e., amphotericin B, trifluoroperazine and cycloheximide). The DNA crosslinks induced by exposure to 10 .mu.M CaCrO4 for 6 h were almost completely repaired in wild-type cells within 24 h, whereas in similarly exposed mutant cells this lesion was initially more pronounced and was only partially repaired following a 24-h recovery period in the absence of CaCrO4. The repair of single-strand breaks induced by CaCrO4 was more rapid and similar in both wild-type and mutant cells. Since Hg(II) inhibits repair of single-strand breaks, repair of this lesion induced by this agent could not be studied; however, at very low concentrations (1 .mu.M) binding of 203Hg(II) to DNA was greater in the mutant cells compared to the wild-type cells. Following removal of 203Hg(II) from the media, mutant cells generally retained more 203Hg bound to DNA relative to the total 203Hg(II) present in the cell. An important toxic action of CaCrO4 and HgCl2 involves injury to DNA since the concentrations of these metals causing measurable DNA damage were consistent with their respective cytotoxic concentrations and DNA repair-deficient mutants displayed both enhanced cytotoxicity and decreased repair of metal-induced lesions. [This research may have applications to the study of carcinogenesis.].