Orren David K, Theodore Shaji, Machwe Amrita
Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536, USA.
Biochemistry. 2002 Nov 19;41(46):13483-8. doi: 10.1021/bi0266986.
The loss of function of WRN, a DNA helicase and exonuclease, causes the premature aging disease Werner syndrome. A hallmark feature of cells lacking WRN is genomic instability typified by elevated illegitimate recombination events and accelerated loss of telomeric sequences. In this study, the activities of WRN were examined on a displacement loop (D-loop) DNA substrate that mimics an intermediate formed during the strand invasion step of many recombinational processes. Our results indicate that this model substrate is specifically bound by WRN and efficiently disrupted by its helicase activity. In addition, the 3' end of the inserted strand of this D-loop structure is readily attacked by the 3'-->5' exonuclease function of WRN. These results indicate that D-loop structures are favored sites for WRN action. Thus, WRN may participate in DNA metabolic processes that utilize these structures, such as recombination and telomere maintenance pathways.
WRN是一种DNA解旋酶和核酸外切酶，其功能丧失会导致早衰疾病——沃纳综合征。缺乏WRN的细胞的一个标志性特征是基因组不稳定，其典型表现为非法重组事件增加以及端粒序列加速丢失。在本研究中，我们在一个替代环（D环）DNA底物上检测了WRN的活性，该底物模拟了许多重组过程的链侵入步骤中形成的中间体。我们的结果表明，这种模型底物能被WRN特异性结合，并被其解旋酶活性有效破坏。此外，该D环结构插入链的3'端很容易受到WRN的3'→5'核酸外切酶功能的攻击。这些结果表明，D环结构是WRN发挥作用的有利位点。因此，WRN可能参与利用这些结构的DNA代谢过程，如重组和端粒维持途径。
