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采用纯化酶活性分析和人细胞体外培养方法 ,研究砷对人 DNA修复关键酶—— DNA连接酶活性的影响。结果表明 :纯化人 DNA连接酶 和 在毫摩尔水平三价砷和五价砷存在下 ,酶活性增加。与此不同的是 ,经过微摩尔砷处理的人细胞核提取物的 DNA连接酶的活性即可被显著抑制。未经染砷处理的细胞核提取物的 DNA连接酶活性与纯化酶对砷的敏感性没有显著区别。说明砷的毒性与砷对 DNA连接酶的作用没有直接联系。因此 ,砷的促突变和对 DNA’损伤后修复的抑制 ,可能并非直接抑制修复酶所致 ,可能与砷所引起的细胞内信号传递和基因表达的改变及通过转录水平或翻译修饰的调节有关。
Purified enzyme activity analysis and in vitro culture of human cells were used to study the effect of arsenic on DNA ligase activity, a key enzyme in human DNA repair. The results showed that the enzyme activity increased in purified human DNA ligase and in the presence of trivalent arsenic and pentavalent arsenite at millimolar levels. In contrast, the DNA ligase activity of human nuclear extracts treated with micromolar arsenic can be significantly suppressed. DNA ligase activity of untreated arsenic-treated nuclear extracts was not significantly different from the sensitivity of purified enzymes to arsenic. Indicating that arsenic toxicity and arsenic DNA ligase is not directly linked. Therefore, arsenic mutation and inhibition of DNA repair after injury may not directly inhibit the repair enzyme may be caused by arsenic-induced changes in intracellular signaling and gene expression and through the regulation of transcription level or translational modification .