Cobalt enhances DNA cleavage mediated by human topoisomerase IIα in vitro and in cultured cells
Cobalt enhances DNA cleavage mediated by human topoisomerase IIα in vitro and in cultured cells
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DOI：
10.1021/bi035472f
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发表时间：
2004-01-27
期刊：
影响因子：
2.9
通讯作者：
Osheroff, N
中科院分区：
文献类型：
--
作者：
Baldwin, EL;Byl, JAW;Osheroff, N
尽管钴是人类必需的微量元素，但这种金属在较高浓度下具有遗传毒性和致突变性。用钴处理细胞会产生 DNA 链断裂和共价蛋白质-DNA 复合物。然而，这些影响的基础尚不清楚。由于钴引起的毒性事件与拓扑异构酶 II 毒物相似，因此检查了该金属对人类拓扑异构酶 IIα 的影响。当裂解反应中钴 (II) 取代镁 (II) 时，酶介导的 DNA 裂解水平增加 6-13 倍。钴 (II) 刺激在存在镁 (II) 的情况下观察到的所有 DNA 位点的裂解，并且该酶在几个“钴特异性”位点切割 DNA。钴 (II) 存在下 DNA 裂解水平的增加部分是由于酶介导的重新连接速率的降低。拓扑异构酶 IIalpha 在含有钴 (II) 的反应中保留了许多催化特性，包括对抗癌药物依托泊苷的敏感性以及松弛和连接 DNA 的能力。最后，在纯化系统和人 MCF-7 细胞中，在镁 (II) 存在的情况下，钴 (II) 会刺激拓扑异构酶 IIα 介导的 DNA 裂解。这些发现表明，钴 (11) 在体外和培养细胞中是一种拓扑异构酶 H 毒物，并表明该金属的至少一些基因毒性作用是通过拓扑异构酶 IIα 介导的。
Although cobalt is an essential trace element for humans, the metal is genotoxic and mutagenic at higher concentrations. Treatment of cells with cobalt generates DNA strand breaks and covalent protein-DNA complexes. However, the basis for these effects is not well understood. Since the toxic events induced by cobalt resemble those of topoisomerase II poisons, the effect of the metal on human topoisomerase IIalpha was examined. The level of enzyme-mediated DNA scission increased 6-13-fold when cobalt(II) replaced magnesium(II) in cleavage reactions. Cobalt(II) stimulated cleavage at all DNA sites observed in the presence of magnesium(II), and the enzyme cut DNA at several "cobalt-specific" sites. The increased level of DNA cleavage in the presence of cobalt(II) was partially due to a decrease in the rate of enzyme-mediated religation. Topoisomerase IIalpha retained many of its catalytic properties in reactions that included cobalt(II), including sensitivity to the anticancer drug etoposide and the ability to relax and decatenate DNA. Finally, cobalt(II) stimulated topoisomerase IIalpha-mediated DNA cleavage in the presence of magnesium(II) in purified systems and in human MCF-7 cells. These findings demonstrate that cobalt(11) is a topoisomerase H poison in vitro and in cultured cells and suggest that at least some of the genotoxic effects of the metal are mediated through topoisomerase IIalpha.