Mycobacterial Ku and ligase proteins constitute a two-component NHEJ repair machine
Mycobacterial Ku and ligase proteins constitute a two-component NHEJ repair machine
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DOI：
10.1126/science.1099824
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发表时间：
2004-10-22
期刊：
影响因子：
56.9
通讯作者：
Doherty, AJ
中科院分区：
文献类型：
--
作者：
Della, M;Palmbos, PL;Doherty, AJ
在哺乳动物细胞中，修复DNA双链。通过非同源末端连接（NHEJ）的断裂（DSB）对于基因组稳定性至关重要。虽然NHEJ的末端桥接和连接步骤已经在体外重建，但对连接前发生的末端加工反应知之甚少。最近，在原核生物中发现了功能上同源的末端桥接和连接活性。与聚合酶和核酸酶的同源性一致，我们证明了结核分枝杆菌DNA连接酶D（Mt-Lig）具有独特的多种核苷酸转移酶活性，包括缺口填充聚合酶，末端转移酶和引物酶，也是一种3'至5'核酸外切酶。这些酶活性允许Mt-Ku和Mt-Lig蛋白在体外连接不相容的DSB末端，以及在酵母中在体内重建NHEJ。这些结果表明，原核Ku和连接酶形成真正的NHEJ系统，其编码DSB修复所需的所有识别、加工和连接活性。
In mammalian cells, repair of DNA double-strand. breaks (DSBs) by nonhomologous end-joining (NHEJ) is critical for genome stability. Although the end-bridging and ligation steps of NHEJ have been reconstituted in vitro, little is known about the end-processing reactions that occur before ligation. Recently, functionally homologous end-bridging and ligation activities have been identified in prokarya. Consistent with its homology to polymerases and nucleases, we demonstrate that DNA ligase D from Mycobacterium tuberculosis (Mt-Lig) possesses a unique variety of nucleotidyl transferase activities, including gap-filling polymerase, terminal transferase, and primase, and is also a 3' to 5' exonuclease. These enzyme activities allow the Mt-Ku and Mt-Lig proteins to join incompatible DSB ends in vitro, as well as to reconstitute NHEJ in vivo in yeast. These results demonstrate that prokaryotic Ku and ligase form a bona fide NHEJ system that encodes all the recognition, processing, and ligation activities required for DSB repair.