Deletions at stalled replication forks occur by two different pathways
Deletions at stalled replication forks occur by two different pathways
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DOI：
10.1093/emboj/16.11.3332
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发表时间：
1997-06-02
期刊：
影响因子：
11.4
通讯作者：
Michel, B
中科院分区：
文献类型：
--
作者：
Bierne, H;Ehrlich, SD;Michel, B
复制阻断诱导大肠杆菌中的非同源缺失。这些缺失的形成机制进行了研究。使用携带两个相反方向的大肠杆菌复制终止子（Ter位点）的pBR 322-mini-oriC杂合质粒。至少去除pBR 322阻断位点（命名为Ter 1）的缺失以每代2x 10（-6）的频率发生。它们分为tyro等大的类别：连接无同源性序列的缺失，以及连接3-10 bp同源性序列的缺失。前一类中约95%的缺失是由于两个Ter位点之前的序列融合造成的，这表明阻断复制叉在其形成中的直接作用。在topA 10突变体中没有发现这些缺失，表明拓扑异构酶I介导的过程。相反，连接短同源序列的缺失不受topA 10突变的影响。然而，这第二类缺失的发生率在缺乏核酸外切酶V活性的recD突变体中增加了10倍，这表明线性分子是其形成的中间体。此外，类似的50%，这些缺失仅仅聚集在区域侧翼的Ter 1位点。我们认为它们是通过修复在被阻断的复制叉处断裂的分子而产生的。
Replication blockage induces non-homologous deletions in Escherichia coli. The mechanism of the formation of these deletions was investigated. A pBR322-mini-oriC hybrid plasmid carrying two E.coli replication terminators (Ter sites) in opposite orientations was used. Deletions which remove at least the pBR322 blocking site (named Ter1) occurred at a frequency of 2x10(-6) per generation. They fall into tyro equally large classes: deletions that join sequences with no homology, and others that join sequences of 3-10 bp of homology. Some 95% of the deletions in the former class resulted from the fusion of sequences immediately preceding the two Ter sites, indicating a direct role for blocked replication forks in their formation. These deletions were not found in a topA10 mutant, suggesting a topoisomerase I-mediated process. In contrast, deletions joining short homologous sequences were not affected by the topA10 mutation. However, the incidence of this second class of deletions increased 10-fold in a recD mutant, devoid of exonuclease V activity, This indicates that linear molecules are intermediates in their formation. In addition, similar to 50% of these deletions mere clustered in the region flanking the Ter1 site. We propose that they are produced by repair of molecules broken at the blocked replication forks.