RecBCD, SbcCD and ExoI process a substrate created by convergent replisomes to complete DNA replication
RecBCD, SbcCD and ExoI process a substrate created by convergent replisomes to complete DNA replication
复制标题
DOI：
10.1111/mmi.14242
复制
发表时间：
2019-06-01
影响因子：
3.6
通讯作者：
Courcelle, Justin
中科院分区：
文献类型：
--
作者：
Hamilton, Nicklas A.;Wendel, Brian M.;Courcelle, Justin
准确完成染色体上的DNA复制需要RecBCD和结构特异性的SbcCD和ExoI核酸酶。然而，该反应发生的底物和机制仍不清楚。在这里，我们表明这些补全酶在含有两个复制体的质粒底物上起作用，但在含有一个复制体的质粒上不起作用。双复制体质粒上的补全需要RecBCD，但不需要RecA，并且在没有RecA的情况下没有断裂的中间体积累，这表明在没有任何双链断裂的情况下，补全反应正常进行。此外，与染色体类似，我们发现当正常的完成反应被阻止时，异常的reca介导的重组过程会导致扩增，从而驱动与双复制体底物相关的大多数不稳定性。这些观察结果表明，SbcCD、ExoI和RecBCD在体内作用的底物是由两个趋同复制体特异性地产生的，并表明RecBCD在完成复制中的功能独立于双链断裂修复，并可能促进趋同复制分叉链的连接。
The accurate completion of DNA replication on the chromosome requires RecBCD and structure specific SbcCD and ExoI nucleases. However, the substrates and mechanism by which this reaction occurs remains unknown. Here we show that these completion enzymes operate on plasmid substrates containing two replisomes, but are not required for plasmids containing one replisome. Completion on the two-replisome plasmids requires RecBCD, but does not require RecA and no broken intermediates accumulate in its absence, indicating that the completion reaction occurs normally in the absence of any double-strand breaks. Further, similar to the chromosome, we show that when the normal completion reaction is prevented, an aberrant RecA-mediated recombination process leads to amplifications that drive most of the instabilities associated with the two-replisome substrates. The observations imply that the substrate SbcCD, ExoI and RecBCD act upon in vivo is created specifically by two convergent replisomes, and demonstrate that the function of RecBCD in completing replication is independent of double-strand break repair, and likely promotes joining of the strands of the convergent replication forks.