SNMIB/Apollo protects leading-strand telomeres against NHEJ-mediated repair
SNMIB/Apollo protects leading-strand telomeres against NHEJ-mediated repair
复制标题
DOI：
10.1038/emboj.2010.58
复制
发表时间：
2010-07-07
期刊：
影响因子：
11.4
通讯作者：
Chang, Sandy
中科院分区：
文献类型：
--
作者：
Lam, Yung C.;Akhter, Shamima;Chang, Sandy
由于细胞无法区分端粒功能障碍的末端和DNA双链断裂，保护性保护性复合体的进行性端粒磨损或缺乏会引起DNA损伤反应。SNMIB/Apollo是一种保护素相关蛋白，是SMN1/PSO2核酸酶家族的成员，通过与TRF2的相互作用定位于端粒。在这里，我们建立了SNMIB/Apollo基因敲除的小鼠胚胎成纤维细胞(MEF)，以探讨SNMIB/Apollo在哺乳动物端粒中的功能。SNMIB/Apollo Null MEF显示G2染色单体类型融合的发生率增加，涉及由先导链DNA合成产生的端粒，反映在DNA复制后未能保护这些端粒。SNMIB/Apollo保守的核酸酶结构域中的突变未能抑制这一表型，表明其核酸酶活性是保护前导链端粒所必需的。当TRF2耗尽时，SNMIB/Apollo(-/-)ATM(-/-)MEF显示出强大的端粒融合，表明在这种情况下，ATM对于修复未封顶的端粒是必不可少的。我们的研究结果表明，SNM1B/Apollo的5‘-3’外切酶功能涉及在新复制的前导链端粒上产生3‘单链突出物，以保护它们免受非同源末端连接途径的影响。EMBO期刊(2010)29,2230-2241。DOI：10.1038/Intemj.2010.58；2010年6月15日在线发布
Progressive telomere attrition or deficiency of the protective shelterin complex elicits a DNA damage response as a result of a cell's inability to distinguish dysfunctional telomeric ends from DNA double-strand breaks. SNMIB/Apollo is a shelterin-associated protein and a member of the SMN1/PSO2 nuclease family that localizes to telomeres through its interaction with TRF2. Here, we generated SNMIB/Apollo knockout mouse embryo fibroblasts (MEFs) to probe the function of SNMIB/Apollo at mammalian telomeres. SNMIB/Apollo null MEFs exhibit an increased incidence of G2 chromatid-type fusions involving telomeres created by leading-strand DNA synthesis, reflective of a failure to protect these telomeres after DNA replication. Mutations within SNMIB/Apollo's conserved nuclease domain failed to suppress this phenotype, suggesting that its nuclease activity is required to protect leading-strand telomeres. SNMIB/Apollo(-/-)ATM(-/-) MEFs display robust telomere fusions when Trf2 is depleted, indicating that ATM is dispensable for repair of uncapped telomeres in this setting. Our data implicate the 5'-3' exonuclease function of SNM1B/Apollo in the generation of 3' single-stranded overhangs at newly replicated leading-strand telomeres to protect them from engaging the non-homologous end-joining pathway. The EMBO Journal (2010) 29, 2230-2241. doi:10.1038/emboj.2010.58; Published online 15 June 2010