Replication Fork Reversal after Replication-Transcription Collision
Replication Fork Reversal after Replication-Transcription Collision
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DOI：
10.1371/journal.pgen.1002622
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发表时间：
2012-04-01
期刊：
影响因子：
4.5
通讯作者：
Michel, Benedicte
中科院分区：
文献类型：
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作者：
De Septenville, Anne L.;Duigou, Stephane;Michel, Benedicte
复制叉停滞是公认的遗传不稳定性的来源，而转录是复制障碍的最突出原因之一。我们在这里分析的重组蛋白在大肠杆菌中的复制-转录头上的碰撞时，诱导在一个特定的网站由一个高度表达的核糖体操纵子（rrn）的反转的要求。RecBC是在这些增加的复制-转录碰撞的条件下细胞活力所需的唯一重组蛋白。在其不存在的情况下，叉断裂发生在碰撞位点，并且所得线性DNA不被修复并且被RecJ核酸外切酶缓慢降解。在缺乏RecA和RecD的细胞中也观察到致死叉断裂，即当同源重组和RecBCD复合物的有效核酸外切酶V活性都失活时，通过RecBC解旋酶和RecJ核酸外切酶的组合作用，所得线性DNA缓慢降解。主要的线性片段的大小表明，DNA降解减慢遇到另一个rrn操纵子。当recB和recA recD突变体中的霍利迪连接解离酶RuvABC失活时，线性DNA的量减少了近两倍，这表明部分线性DNA是通过霍利迪连接的解离形成的。我们的研究结果表明，复制叉逆转发生后，复制转录头上的碰撞，我们建议，它促进了行动的辅助复制解旋酶，驱逐障碍。
Replication fork arrest is a recognized source of genetic instability, and transcription is one of the most prominent causes of replication impediment. We analyze here the requirement for recombination proteins in Escherichia coli when replication-transcription head-on collisions are induced at a specific site by the inversion of a highly expressed ribosomal operon (rrn). RecBC is the only recombination protein required for cell viability under these conditions of increased replication-transcription collisions. In its absence, fork breakage occurs at the site of collision, and the resulting linear DNA is not repaired and is slowly degraded by the RecJ exonuclease. Lethal fork breakage is also observed in cells that lack RecA and RecD, i.e. when both homologous recombination and the potent exonuclease V activity of the RecBCD complex are inactivated, with a slow degradation of the resulting linear DNA by the combined action of the RecBC helicase and the RecJ exonuclease. The sizes of the major linear fragments indicate that DNA degradation is slowed down by the encounter with another rrn operon. The amount of linear DNA decreases nearly two-fold when the Holliday junction resolvase RuvABC is inactivated in recB, as well as in recA recD mutants, indicating that part of the linear DNA is formed by resolution of a Holliday junction. Our results suggest that replication fork reversal occurs after replication-transcription head-on collision and we propose that it promotes the action of the accessory replicative helicases that dislodge the obstacle.