Mammalian CST averts replication failure by preventing G-quadruplex accumulation
Mammalian CST averts replication failure by preventing G-quadruplex accumulation
复制标题
哺乳动物 CST 通过阻止 G 四链体积累来避免复制失败
DOI：
10.1093/nar/gkz264
复制
发表时间：
2019
影响因子：
14.9
通讯作者：
Wang Feng
中科院分区：
文献类型：
--
作者：
Zhang Miaomiao;Wang Bing;Li Tingfang;Liu Rui;Xiao Yingnan;Geng Xin;Li Guang;Liu Qiang;Price Carolyn M;Liu Yang;Wang Feng
人类CST(CTC1-STN1-TEN1)是一种类似RPA的复合体，与富含G的单链DNA结合，有助于解决端粒和基因组范围内的复制问题。我们之前的研究表明，CST在体外可以结合和破坏G-四链(G4)DNA，这表明CST可能通过解析G4结构来阻止复制。在这里，我们证明了CST结合和展开G4的效率与RPA相似。在细胞中，CST在G4稳定时被招募到端粒和非端粒染色质，即使当ATR/ATM通路被抑制时也是如此。STN1缺失会增加G4的积累，并减缓大量基因组DNA的复制。在端粒，STN1缺失和G4稳定共同导致多个端粒FISH信号和端粒丢失，这是端粒双链复制缺陷的特征。链特异性端粒FISH表明C链DNA优先丢失，而对领先和滞后链端粒复制过程中BrdU摄取的分析表明，滞后端粒优先复制不足。综上所述，这些结果表明冈崎的片段合成受阻。总体而言，我们的发现表明，CST通过在复制分叉之前和在滞后链模板上解析G4结构，在维持基因组完整性方面发挥了新的作用。
Human CST (CTC1-STN1-TEN1) is an RPA-like complex that associates with G-rich single-strand DNA and helps resolve replication problems both at telomeres and genome-wide. We previously showed that CST binds and disrupts G-quadruplex (G4) DNAin vitro, suggesting that CST may preventin vivoblocks to replication by resolving G4 structures. Here, we demonstrate that CST binds and unfolds G4 with similar efficiency to RPA. In cells, CST is recruited to telomeric and non-telomeric chromatin upon G4 stabilization, even when ATR/ATM pathways were inhibited. STN1 depletion increases G4 accumulation and slows bulk genomic DNA replication. At telomeres, combined STN1 depletion and G4 stabilization causes multi-telomere FISH signals and telomere loss, hallmarks of deficient telomere duplex replication. Strand-specific telomere FISH indicates preferential loss of C-strand DNA while analysis of BrdU uptake during leading and lagging-strand telomere replication shows preferential under-replication of lagging telomeres. Together these results indicate a block to Okazaki fragment synthesis. Overall, our findings indicate a novel role for CST in maintaining genome integrity through resolution of G4 structures both ahead of the replication fork and on the lagging strand template.