Prompt repair of hydrogen peroxide-induced DNA lesions prevents catastrophic chromosomal fragmentation.
Prompt repair of hydrogen peroxide-induced DNA lesions prevents catastrophic chromosomal fragmentation.
复制标题
迅速修复过氧化氢诱导的DNA病变可防止灾难性的染色体碎片。
DOI：
10.1016/j.dnarep.2016.03.012
复制
发表时间：
2016-05
期刊：
影响因子：
3.8
通讯作者：
Kuzminov A
中科院分区：
文献类型：
--
作者：
Mahaseth T;Kuzminov A
过氧化氢 (H2O2, HP) 造成的体内铁依赖性 DNA 氧化损伤会诱导大量的单链 (ss) 断裂和碱基修饰。 HP 还会引起罕见的双链 DNA 断裂，其与细胞杀伤的关系尚不清楚。由于过氧化氢仅使生长细胞中的染色体断裂，因此这些双链断裂被认为代表复制叉在直接或切除 ss 断裂时崩溃，并且是完全可修复的。我们最近报道过氧化氢通过诱导灾难性的染色体断裂来杀死大肠杆菌，而氰化物（CN）则增强了杀死和断裂的作用。值得注意的是，CN+HP 诱导的染色体双链断裂的极高密度使得复制叉不太可能参与。在这里，我们表明，这种大规模碎片通过 ss 断裂修复或碱基切除修复的失活而进一步放大，表明未修复的初级 DNA 损伤直接转化为双链断裂。事实上，阻断 DNA 复制仅将 CN+HP 诱导的断裂降低约 2 倍，而不影响存活。一旦氰化物被去除，大肠杆菌中的重组修复可以修复几个双链断裂，但无法修复遍布整个染色体的约 100 个断裂。因此，氧化损伤诱导的双链断裂发生在未修复的原代单链DNA损伤位点，与复制无关并且具有高度致死性，支持了稳定DNA-铁复合物位点上聚集的单链断裂模型。
Iron-dependent oxidative DNA damage in vivo by hydrogen peroxide (H2O2, HP) induces copious single-strand(ss)-breaks and base modifications. HP also causes infrequent double-strand DNA breaks, whose relationship to the cell killing is unclear. Since hydrogen peroxide only fragments chromosomes in growing cells, these double-strand breaks were thought to represent replication forks collapsed at direct or excision ss-breaks and to be fully reparable. We have recently reported that hydrogen peroxide kills Escherichia coli by inducing catastrophic chromosome fragmentation, while cyanide (CN) potentiates both the killing and fragmentation. Remarkably, the extreme density of CN+HP-induced chromosomal double-strand breaks makes involvement of replication forks unlikely. Here we show that this massive fragmentation is further amplified by inactivation of ss-break repair or base-excision repair, suggesting that unrepaired primary DNA lesions are directly converted into double-strand breaks. Indeed, blocking DNA replication lowers CN+HP-induced fragmentation only ~2-fold, without affecting the survival. Once cyanide is removed, recombinational repair in E. coli can mend several double-strand breaks, but cannot mend ~100 breaks spread over the entire chromosome. Therefore, double-strand breaks induced by oxidative damage happen at the sites of unrepaired primary one-strand DNA lesions, are independent of replication and are highly lethal, supporting the model of clustered ss-breaks at the sites of stable DNA-iron complexes.