Mechanism of nonhomologous end-joining in mycobacteria: a low-fidelity repair system driven by Ku, ligase D and ligase C
Mechanism of nonhomologous end-joining in mycobacteria: a low-fidelity repair system driven by Ku, ligase D and ligase C
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DOI：
10.1038/nsmb915
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发表时间：
2005-04-01
影响因子：
16.8
通讯作者：
Glickman, MS
中科院分区：
文献类型：
--
作者：
Gong, CL;Bongiorno, P;Glickman, MS
DNA双链断裂（DSB）可以通过同源重组（HR）或非同源末端连接（NHEJ）修复。这两种途径在真核生物中都是有效的，但细菌被认为只依赖HR。在这里，我们提供了直接的证据，分枝杆菌有一个强大的NHEJ途径，需要Ku和一个专门的多功能ATP依赖性DNA连接酶（LigD）。平端和互补5 '-突出端DSB的NHEJ具有高度致突变性（类似于50%错误率）。对单个NHEJ事件产生的重组连接的分析强调了几种DNA末端重塑活动的参与，包括5'突出端的模板依赖性填充、在平端处的单核苷酸的非模板化添加和溶核切除。LigD本身在体外具有模板依赖性和模板非依赖性聚合酶功能，其在体内构成NHEJ的分子特征。另一种ATP依赖性DNA连接酶（LigC）为平端DSB的LigD非依赖性易错修复提供了后备机制。我们推测NHEJ允许分枝杆菌逃避遗传毒性宿主防御。
DNA double-strand breaks (DSBs) can be repaired either via homologous recombination (HR) or nonhomologous end-joining (NHEJ). Both pathways are operative in eukaryotes, but bacteria had been thought to rely on HR alone. Here we provide direct evidence that mycobacteria have a robust NHEJ pathway that requires Ku and a specialized polyfunctional ATP-dependent DNA ligase (LigD). NHEJ of blunt-end and complementary 5'-overhang DSBs is highly mutagenic (similar to 50% error rate). Analysis of the recombination junctions ensuing from individual NHEJ events highlighted the participation of several DNA end-remodeling activities, including template-dependent fill-in of 5' overhangs, nontemplated addition of single nucleotides at blunt ends, and nucleolytic resection. LigD itself has the template-dependent and template-independent polymerase functions in vitro that compose the molecular signatures of NHEJ in vivo. Another ATP-dependent DNA ligase (LigC) provides a backup mechanism for LigD-independent error-prone repair of blunt-end DSBs. We speculate that NHEJ allows mycobacteria to evade genotoxic host defense.