PARP-mediated repair, homologous recombination, and back-up non-homologous end joining-like repair of single-strand nicks.
PARP-mediated repair, homologous recombination, and back-up non-homologous end joining-like repair of single-strand nicks.
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DOI：
10.1016/j.dnarep.2013.04.004
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发表时间：
2013-07
期刊：
影响因子：
3.8
通讯作者：
Monnat, Raymond J., Jr.
中科院分区：
文献类型：
--
作者：
Metzger, Michael J.;Stoddard, Barry L.;Monnat, Raymond J., Jr.
染色体DNA双链断裂(DSB)可引起同源重组(HR)和非同源重组(NHEJ)。最近，我们发现单链NICK可显著降低NHEJ的毒性和致突变效应，从而诱导HR。为了进一步研究DSB和NICK诱导的修复的异同，我们在人类细胞中使用了一个集成的报告系统来测量由归巢内切酶I-anII和设计的切割相同靶点的NICASE变异体产生的HR和NHEJ，重点关注PARP和HR修复途径。阻断单链断裂修复的PARP抑制剂使NICK诱导的HR增加1.7倍，但不影响DSB诱导的HR或muNHEJ。此外，PALB2 WD40结构域在反式中的表达对DSB和NICK诱导的HR起显性-负性抑制作用，使细胞对PARP抑制敏感，并揭示了NICK的另一种突变修复途径。因此，虽然DSB和NICK诱导的HR都使用共同的途径，但它们的底物由细胞因子进行不同的处理。这些结果还表明，PARP和BRCA的合成致死性可能是由于通过一种容易出错的NHEJ样机制修复缺口，当PARP和HR通路都被阻断时，这种机制是活跃的。
Double-strand breaks (DSBs) in chromosomal DNA can induce both homologous recombination (HR) and non-homologous recombination (NHEJ). Recently we showed that single-strand nicks induce HR with a significant reduction in toxicity and mutagenic effects associated with NHEJ. To further investigate the differences and similarities of DSB- and nick-induced repair, we used an integrated reporter system in human cells to measure HR and NHEJ produced by the homing endonuclease I-AniI and a designed ‘nickase’ variant that nicks the same target site, focusing on the PARP and HR repair pathways. PARP inhibitors, which block single-strand break repair, increased the rate of nick-induced HR up to 1.7-fold but did not affect DSB-induced HR or mutNHEJ. Additionally, expression of the PALB2 WD40 domain in trans acted as a dominant-negative inhibitor of both DSB- and nick-induced HR, sensitized cells to PARP inhibition, and revealed an alternative mutagenic repair pathway for nicks. Thus, while both DSB- and nick-induced HR use a common pathway, their substrates are differentially processed by cellular factors. These results also suggest that the synthetic lethality of PARP and BRCA may be due to repair of nicks through an error prone, NHEJ-like mechanism that is active when both PARP and HR pathways are blocked.
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