C-terminal regions of topoisomerase IIalpha and IIbeta determine isoform-specific functioning of the enzymes in vivo.
C-terminal regions of topoisomerase IIalpha and IIbeta determine isoform-specific functioning of the enzymes in vivo.
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拓扑异构酶iialpha和IIBETA的C末端区域确定体内酶的同工型特异性功能。
DOI：
10.1093/nar/gkm102
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发表时间：
2007
影响因子：
14.9
通讯作者：
Christensen, Morten O
中科院分区：
文献类型：
--
作者：
Linka, Rene M;Porter, Andrew C G;Volkov, Arsen;Mielke, Christian;Boege, Fritz;Christensen, Morten O
拓扑异构酶II去除DNA代谢过程中产生的超螺旋和链烷，如转录和复制。脊椎动物细胞表达两种不同的遗传亚型(α和β)，它们的结构和生化活性相似，但生物学作用不同。拓扑异构酶IIα是细胞增殖所必需的，而拓扑异构酶IIβ只有在神经生长和脑发育方面才是必需的。为了确定导致这些差异的结构特征，我们交换了两个人类异构体(α1173-1531和β1186-1621)的不同C-末端区域(CTR)，并测试了所得杂交产物对人类细胞中条件拓扑异构酶IIα敲除的互补作用。所有带有αCTR的酶都能完全支持增殖。αCTR还促进了两个酶核心的染色体结合，并且本身是染色体结合的，表明在有丝分裂过程中发挥了酶靶向的作用。相比之下，携带βCTR的酶仅在极少数情况下支持增殖，并且在异常高水平表达时才能支持增殖。对发散的N-末端区域(α1-27和β1-43)的类似分析表明，在异构体特异性功能中没有作用。我们的结果表明，正是人类拓扑异构酶II的CTRs决定了它们在增殖细胞中的异构体特异性功能。它们还表明这两种异构体之间存在一些功能冗余。
Topoisomerase II removes supercoils and catenanes generated during DNA metabolic processes such as transcription and replication. Vertebrate cells express two genetically distinct isoforms (α and β) with similar structures and biochemical activities but different biological roles. Topoisomerase IIα is essential for cell proliferation, whereas topoisomerase IIβ is required only for aspects of nerve growth and brain development. To identify the structural features responsible for these differences, we exchanged the divergent C-terminal regions (CTRs) of the two human isoforms (α 1173-1531 and β 1186-1621) and tested the resulting hybrids for complementation of a conditional topoisomerase IIα knockout in human cells. Proliferation was fully supported by all enzymes bearing the α CTR. The α CTR also promoted chromosome binding of both enzyme cores, and was by itself chromosome-bound, suggesting a role in enzyme targeting during mitosis. In contrast, enzymes bearing the β CTR supported proliferation only rarely and when expressed at unusually high levels. A similar analysis of the divergent N-terminal regions (α 1-27 and β 1-43) revealed no role in isoform-specific functions. Our results show that it is the CTRs of human topoisomerase II that determine their isoform-specific functions in proliferating cells. They also indicate persistence of some functional redundancy between the two isoforms.