Clarke D J, Johnson R T, Downes C S
Department of Zoology, University of Cambridge, UK.
J Cell Sci. 1993 Jun;105 ( Pt 2):563-9. doi: 10.1242/jcs.105.2.563.
Yeast temperature-sensitive mutants of DNA topoisomerase II are incapable of chromosome condensation and anaphase chromatid segregation. In mammalian cells, topoisomerase II inhibitors such as etoposide (VP-16-123) have similar effects. Unfortunately, conclusions drawn from work with mammalian cells have been limited by the fact that the standard inhibitors of topoisomerase II also generate DNA strand breaks, which when produced by other agents (e.g. ionizing radiation) are known to affect progression into and through mitosis. Here we show that the anti-tumour agent ICRF-193, recently identified as a topoisomerase II inhibitor operating by a non-standard mechanism, generates neither covalent complexes between topoisomerase II and DNA, nor adjacent DNA strand breaks, in mitotic HeLa. However, the drug does prevent anaphase segregation in HeLa and PtK2 cells, with effects similar to those of etoposide. We therefore conclude that topoisomerase II function is required for anaphase chromosome segregation in mammalian cells, as it is in yeast.
DNA拓扑异构酶II的酵母温度敏感突变体无法进行染色体浓缩和后期染色单体分离。在哺乳动物细胞中，拓扑异构酶II抑制剂如依托泊苷（VP - 16 - 123）具有类似的作用。不幸的是，从哺乳动物细胞研究中得出的结论受到以下事实的限制：拓扑异构酶II的标准抑制剂也会产生DNA链断裂，而当由其他试剂（如电离辐射）产生时，已知会影响进入有丝分裂及在有丝分裂过程中的进程。在此我们表明，最近被鉴定为通过非标准机制起作用的拓扑异构酶II抑制剂的抗肿瘤药物ICRF - 193，在有丝分裂的HeLa细胞中既不会在拓扑异构酶II与DNA之间产生共价复合物，也不会产生相邻的DNA链断裂。然而，该药物确实会阻止HeLa和PtK2细胞中的后期分离，其作用与依托泊苷类似。因此我们得出结论，正如在酵母中一样，拓扑异构酶II的功能对于哺乳动物细胞中的后期染色体分离是必需的。
