Human exonuclease 1 and BLM helicase interact to resect DNA and initiate DNA repair
Human exonuclease 1 and BLM helicase interact to resect DNA and initiate DNA repair
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DOI：
10.1073/pnas.0809380105
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发表时间：
2008-11-04
影响因子：
11.1
通讯作者：
Kowalczykowski, Stephen C.
中科院分区：
文献类型：
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作者：
Nimonkar, Almitabh V.;Ozsoy, A. Zeynep;Kowalczykowski, Stephen C.
通过同源重组对双链DNA断裂进行无差错修复需要处理断裂末端。这些经过处理的末端是组装DNA链交换蛋白的底物，DNA链交换蛋白介导DNA链入侵。在这里，我们建立了人BLM解旋酶，RecQ家族的成员，刺激人外切酶1(HExo1)的核溶解活性，hExo1是一种5‘->；3’双链DNA外切酶。这种刺激是特异的，因为其他RecQ同源物无法刺激hExo1。HExo1对DNA切除的刺激不依赖于BLM解旋酶的活性，而是通过两种蛋白之间的相互作用来介导的。最后，我们证明了hExo1和BLM切除的DNA末端被人类RAD51用来促进同源DNA配对，而不是它的酵母或细菌对应物。这个体外系统概括了同源重组的初始步骤，并为BLM和Exo1在启动重组DNA修复中的作用提供了生化证据。
The error-free repair of double-stranded DNA breaks by homologous recombination requires processing of broken ends. These processed ends are substrates for assembly of DNA strand exchange proteins that mediate DNA strand invasion. Here, we establish that human BLM helicase, a member of the RecQ family, stimulates the nucleolytic activity of human exonuclease 1 (hExo1), a 5' --> 3' double-stranded DNA exonuclease. The stimulation is specific because other RecQ homologs fail to stimulate hExo1. Stimulation of DNA resection by hExo1 is independent of BLM helicase activity and is, instead, mediated by an interaction between the 2 proteins. Finally, we show that DNA ends resected by hExo1 and BLM are used by human Rad51, but not its yeast or bacterial counterparts, to promote homologous DNA pairing. This in vitro system recapitulates initial steps of homologous recombination and provides biochemical evidence for a role of BLM and Exo1 in the initiation of recombinational DNA repair.