BIOLOGICAL FUNCTION OF MAMMALIAN TOPOISOMERASE II BETA

这项建议的主要目的是回答为什么哺乳动物发育中都需要两种具有相同酶性质的II型DNA拓扑异构酶。在这一中心主题下，有三个具体目标。目的I提出的假设是，这些活性是可以互换的，但拓扑异构酶IIα和β基因在时间和/或组织特异性调控上的差异是导致两者都有必要性的原因。AIM II旨在回答最近一项发现提出的问题，即小鼠体内β亚型的失活会阻止正常的轴突生长。报告基因(GFP)将与拓扑异构酶IIβ融合，以便在发育过程中详细监测这种异构体。最后，Aim III提出了一个假设，即异构体的不同C-末端结构域是它们不可缺少的原因。这一假说将通过一种异构体的C-末端结构域与另一种异构体的C-末端结构域互换来检验。

The main goal of this proposal is to answer the question why two typeII DNA topoisomerases with seemingly identical enzymatic properties are both needed in mammalian development. Under this central theme there are three specific aims. Aim I addresses the hypothesis that the activities are interchangeable but differences in temporal and/or tissue specific regulation of the topoisomerase II alpha and beta genes are responsible for the necessity of both. Aim II is directed at answering the question raised by the recent finding that inactivation of the beta isoform in the mouse prevents normal axon growth. A reporter gene (GFP) will be fused to topoisomerase II beta to allow detailed monitoring of this isoform during development. Finally, aim III addresses the hypothesis that the distinct C-terminal domain of the isoforms are responsible for their indispensability. This hypothesis will be tested through swapping of the C-terminal domain of one isoform by another.