Biersack H, Jensen S, Gromova I, Nielsen I S, Westergaard O, Andersen A H
Department of Molecular and Structural Biology, University of Aarhus, Denmark.
Proc Natl Acad Sci U S A. 1996 Aug 6;93(16):8288-93. doi: 10.1073/pnas.93.16.8288.
DNA topoisomerase II is a nuclear enzyme essential for chromosome dynamics and DNA metabolism. In mammalian cells, two genetically and biochemically distinct topoisomerase II forms exist, which are designated topoisomerase II alpha and topoisomerase II beta. In our studies of human topoisomerase II, we have found that a substantial fraction of the enzyme exists as alpha/beta heterodimers in HeLa cells. The ability to form heterodimers was verified when human topoisomerases II alpha and II beta were coexpressed in yeast and investigated in a dimerization assay. Analysis of purified heterodimers shows that these enzymes maintain topoisomerase II specific catalytic activities. The natural existence of an active heterodimeric subclass of topoisomerase II merits attention whenever topoisomerases II alpha and II beta function, localization, and cell cycle regulation are investigated.
DNA拓扑异构酶II是一种对染色体动态变化和DNA代谢至关重要的核酶。在哺乳动物细胞中，存在两种在遗传和生化性质上不同的拓扑异构酶II形式，分别被命名为拓扑异构酶IIα和拓扑异构酶IIβ。在我们对人类拓扑异构酶II的研究中，我们发现在HeLa细胞中，相当一部分该酶以α/β异二聚体的形式存在。当人类拓扑异构酶IIα和IIβ在酵母中共同表达并在二聚化实验中进行研究时，形成异二聚体的能力得到了验证。对纯化的异二聚体的分析表明，这些酶保持着拓扑异构酶II特定的催化活性。每当对拓扑异构酶IIα和IIβ的功能、定位及细胞周期调控进行研究时，拓扑异构酶II活性异二聚体亚类的天然存在都值得关注。
