RAD18 and poly(ADP-ribose) polymerase independently suppress the access of nonhomologous end joining to double-strand breaks and facilitate homologous recombination-mediated repair
RAD18 and poly(ADP-ribose) polymerase independently suppress the access of nonhomologous end joining to double-strand breaks and facilitate homologous recombination-mediated repair
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DOI：
10.1128/mcb.01243-06
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发表时间：
2007-04-01
影响因子：
5.3
通讯作者：
Takeda, Shunichi
中科院分区：
文献类型：
--
作者：
Saberi, Alihossein;Hochegger, Helfrid;Takeda, Shunichi
酿酒酵母RAD18基因是复制后修复所必需的，但不是同源重组(HR)所必需的，HR是酵母中主要的双链断裂(DSB)修复途径。因此，酵母rad18突变体对喜树碱(CPT)耐受，喜树碱是一种拓扑异构酶I抑制剂，它通过阻止复制来诱导DSB。令人惊讶的是，缺乏Rad18的哺乳动物细胞和鸡DT40细胞表现出对HR依赖的修复减少，并对CPT高度敏感。脊椎动物中主要的DSB修复途径--非同源末端连接(NHEJ)的缺失完全恢复了HR介导的DSB修复，表明脊椎动物Rad18调节NHEJ和HR之间的平衡。我们之前曾报道，NHEJ的缺失使聚(ADP-核糖)聚合酶1(PARP1)缺陷细胞的CPT敏感性正常化。RAD18和PARP1的同时缺失协同增加了CPT的敏感性，而NHEJ的额外失活使这种超敏反应正常化，表明它们的作用是平行的。总之，高等真核细胞分别使用PARP1和Rad18来抑制NHEJ在停滞复制叉处的HR反应中的毒性效应。
The Saccharomyces cerevisiae RAD18 gene is essential for postreplication repair but is not required for homologous recombination (HR), which is the major double-strand break (DSB) repair pathway in yeast. Accordingly, yeast rad18 mutants are tolerant of camptothecin (CPT), a topoisomerase I inhibitor, which induces DSBs by blocking replication. Surprisingly, mammalian cells and chicken DT40 cells deficient in Rad18 display reduced HR-dependent repair and are hypersensitive to CPT. Deletion of nonhomologous end joining (NHEJ), a major DSB repair pathway in vertebrates, in rad18-deficient DT40 cells completely restored HR-mediated DSB repair, suggesting that vertebrate Rad18 regulates the balance between NHEJ and HR. We previously reported that loss of NHEJ normalized the CPT sensitivity of cells deficient in poly(ADP-ribose) polymerase 1 (PARP1). Concomitant deletion of Rad18 and PARP1 synergistically increased CPT sensitivity, and additional inactivation of NHEJ normalized this hypersensitivity, indicating their parallel actions. In conclusion, higher-eukaryotic cells separately employ PARP1 and Rad18 to suppress the toxic effects of NHEJ during the HR reaction at stalled replication forks.