Replication stress-induced chromosome breakage is correlated with replication fork progression and is preceded by single-stranded DNA formation.
Replication stress-induced chromosome breakage is correlated with replication fork progression and is preceded by single-stranded DNA formation.
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DOI：
10.1534/g3.111.000554
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发表时间：
2011-10
期刊：
影响因子：
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通讯作者：
Brewer BJ
中科院分区：
文献类型：
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作者：
Feng W;Di Rienzi SC;Raghuraman MK;Brewer BJ
复制压力造成的染色体断裂被认为是复制叉进展缺陷或复制叉“坍塌”的直接结果。然而，直接和全基因组范围的证据表明，倒塌的复制叉会导致染色体断裂，这一点仍然缺乏。我们先前的研究表明，酵母复制检查点突变体Mec1-1在短暂暴露于羟基脲(HU)的复制障碍后，无法完成DNA复制，在复制叉处积累了单链DNA(SsDNA)，并使其染色体碎片化。在这项研究中，通过通过单链DNA检测跟踪全基因组的复制分叉进程，并通过直接定位HU暴露后的染色体断裂，我们验证了Mec1细胞的染色体断裂发生在折叠的复制分叉的假设。我们证明染色体断裂的位置确实与复制分叉位置相关。此外，在染色体断裂之前可以检测到单链DNA，这表明单链DNA积累是折叠复制叉处双链断裂的常见前兆。
Chromosome breakage as a result of replication stress has been hypothesized to be the direct consequence of defective replication fork progression, or “collapsed” replication forks. However, direct and genome-wide evidence that collapsed replication forks give rise to chromosome breakage is still lacking. Previously we showed that a yeast replication checkpoint mutant mec1-1, after transient exposure to replication impediment imposed by hydroxyurea (HU), failed to complete DNA replication, accumulated single-stranded DNA (ssDNA) at the replication forks, and fragmented its chromosomes. In this study, by following replication fork progression genome-wide via ssDNA detection and by direct mapping of chromosome breakage after HU exposure, we have tested the hypothesis that the chromosome breakage in mec1 cells occurs at collapsed replication forks. We demonstrate that sites of chromosome breakage indeed correlate with replication fork locations. Moreover, ssDNA can be detected prior to chromosome breakage, suggesting that ssDNA accumulation is the common precursor to double strand breaks at collapsed replication forks.