Conformational changes modulate the activity of human RAD51 protein
Conformational changes modulate the activity of human RAD51 protein
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DOI：
10.1016/j.jmb.2004.02.022
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发表时间：
2004-04-02
影响因子：
5.6
通讯作者：
West, SC
中科院分区：
文献类型：
--
作者：
Liu, YL;Stasiak, AZ;West, SC
同源重组是哺乳动物细胞DNA双链断裂修复的主要途径。同源重组缺陷可导致高水平的染色体易位或缺失，这可能促进细胞转化和癌症的发展。这个过程的一个关键组成部分是RAD51。与细菌同源物RecA相比，人RAD51蛋白在体外表现出低水平的链交换活性。然而，高盐的存在会刺激这种活动。在这里，我们研究了这种增产的机理基础。我们发现，高离子强度有利于rad51 -单链DNA （ssDNA）核蛋白丝与裸露的双链DNA共聚集，形成一个复合体，在这个复合体中寻找同源序列。高离子强度允许RAD51与ssDNA和双链DNA （dsDNA）的不同结合，因此ssDNA-RAD51的相互作用不受影响，而RAD51与dsDNA之间的相互作用则不稳定。最重要的是，高盐诱导了RAD51的构象变化，导致ssDNA上形成延长的核蛋白丝。这些延伸的细丝模仿大肠杆菌RecA-ssDNA细丝的活性形式，表现出有效的链交换活性。(C) 2004 Elsevier Ltd.版权所有。
Homologous recombination provides a major pathway for the repair of DNA double-strand breaks in mammalian cells. Defects in homologous recombination can lead to high levels of chromosomal translocations or deletions, which may promote cell transformation and cancer development. A key component of this process is RAD51. In comparison to RecA, the bacterial homologue, human RAD51 protein exhibits low-level strand-exchange activity in vitro. This activity can, however, be stimulated by the presence of high salt. Here, we have investigated the mechanistic basis for this stimulation. We show that high ionic strength favours the co-aggregation of RAD51-single-stranded DNA (ssDNA) nucleoprotein filaments with naked duplex DNA, to form a complex in which the search for homologous sequences takes place. High ionic strength allows differential binding of RAD51 to ssDNA and double-stranded DNA (dsDNA), such that ssDNA-RAD51 interactions are unaffected, whereas those between RAD51 and dsDNA are destabilised. Most importantly, high salt induces a conformational change in RAD51, leading to the formation of extended nucleoprotein filaments on ssDNA. These extended filaments mimic the active form of the Escherichia coli RecA-ssDNA filament that exhibits efficient strand-exchange activity. (C) 2004 Elsevier Ltd. All rights reserved.