BLM helicase facilitates telomere replication during leading strand synthesis of telomeres.
BLM helicase facilitates telomere replication during leading strand synthesis of telomeres.
复制标题
DOI：
10.1083/jcb.201410061
复制
发表时间：
2015-07-20
期刊：
影响因子：
--
通讯作者：
Schildkraut CL
中科院分区：
文献类型：
--
作者：
Drosopoulos WC;Kosiyatrakul ST;Schildkraut CL
BLM解旋酶通过解析在前导链合成过程中可以在富含G的重复序列中形成的G-四链体结构来促进端粒复制。基于其在体外解旋活性的G-四链体（G4）DNA，布卢姆综合征相关的解旋酶BLM被提出参与端粒复制，通过帮助叉进展通过G-丰富的端粒DNA。用复制DNA的单分子分析（SMARD）来确定BLM解旋酶对端粒复制的贡献。在BLM缺陷细胞中，从端粒内的起点开始的复制叉通过前导链合成复制富含G的链，与邻近的亚端粒相比，通过端粒移动得更慢。在G4稳定剂的存在下，通过端粒的分叉进展进一步减慢。使用G4特异性抗体，我们发现BLM或另一种G4解旋解旋酶Werner综合征相关解旋酶WRN的缺乏导致细胞中G4结构增加。重要的是，任一解旋酶的缺乏导致端粒中检测到的G4 DNA比全基因组中检测到的G4 DNA增加更大。总的来说，我们的研究结果是一致的BLM解旋酶促进端粒复制，解决G4结构的复制过程中形成的G-丰富的链的前导链合成。
BLM helicase facilitates telomere replication by resolving G-quadruplex structures that can form in the G-rich repeats during leading strand synthesis. Based on its in vitro unwinding activity on G-quadruplex (G4) DNA, the Bloom syndrome–associated helicase BLM is proposed to participate in telomere replication by aiding fork progression through G-rich telomeric DNA. Single molecule analysis of replicated DNA (SMARD) was used to determine the contribution of BLM helicase to telomere replication. In BLM-deficient cells, replication forks initiating from origins within the telomere, which copy the G-rich strand by leading strand synthesis, moved slower through the telomere compared with the adjacent subtelomere. Fork progression through the telomere was further slowed in the presence of a G4 stabilizer. Using a G4-specific antibody, we found that deficiency of BLM, or another G4-unwinding helicase, the Werner syndrome-associated helicase WRN, resulted in increased G4 structures in cells. Importantly, deficiency of either helicase led to greater increases in G4 DNA detected in the telomere compared with G4 seen genome-wide. Collectively, our findings are consistent with BLM helicase facilitating telomere replication by resolving G4 structures formed during copying of the G-rich strand by leading strand synthesis.