Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA.
Mol Microbiol. 2021 Jun;115(6):1122-1137. doi: 10.1111/mmi.14655. Epub 2020 Dec 19.
Most, but not all, homologous genetic recombination in bacteria is mediated by the RecA recombinase. The mechanistic origin of RecA-independent recombination has remained enigmatic. Here, we demonstrate that the RarA protein makes a major enzymatic contribution to RecA-independent recombination. In particular, RarA makes substantial contributions to intermolecular recombination and to recombination events involving relatively short (<200 bp) homologous sequences, where RecA-mediated recombination is inefficient. The effects are seen here in plasmid-based recombination assays and in vivo cloning processes. Vestigial levels of recombination remain even when both RecA and RarA are absent. Additional pathways for RecA-independent recombination, possibly mediated by helicases, are suppressed by exonucleases ExoI and RecJ. Translesion DNA polymerases may also contribute. Our results provide additional substance to a previous report of a functional overlap between RecA and RarA.
大多数（但并非全部）细菌中的同源基因重组是由 RecA 重组酶介导的。RecA 非依赖性重组的机制起源仍然是个谜。在这里，我们证明了 RarA 蛋白对 RecA 非依赖性重组有重要的酶促贡献。具体来说，RarA 对分子间重组以及涉及相对较短（<200bp）同源序列的重组事件做出了重大贡献，而 RecA 介导的重组效率低下。这些影响在基于质粒的重组测定和体内克隆过程中都得到了体现。即使 RecA 和 RarA 都不存在，重组的残余水平仍然存在。由解旋酶介导的可能的 RecA 非依赖性重组的其他途径被外切核酸酶 ExoI 和 RecJ 抑制。跨损伤 DNA 聚合酶也可能有贡献。我们的结果为 RecA 和 RarA 之间存在功能重叠的先前报告提供了更多依据。
