Effects of recJ, recQ, and recFOR mutations on recombination in nuclease-deficient recB recD double mutants of Escherichia coli
Effects of recJ, recQ, and recFOR mutations on recombination in nuclease-deficient recB recD double mutants of Escherichia coli
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DOI：
10.1128/jb.187.4.1350-1356.2005
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发表时间：
2005-02-01
影响因子：
3.2
通讯作者：
Brcic-Kostic, K
中科院分区：
文献类型：
--
作者：
Ivancic-Bace, I;Salaj-Smic, E;Brcic-Kostic, K
大肠杆菌的两种主要重组途径（RecBCD和RecF）具有不同的重组机制，它们在重组的启动中独立起作用。双链DNA末端和断裂的早期重组过程需要三种基本的酶活性：解旋酶，5‘- >3’外切酶，以及将RecA蛋白装载到单链DNA尾部。RecBCD酶执行所有这些活动，而RecF途径的重组机制由RecQ（解旋酶），RecJ（5‘- >3’外切酶）和RecFOR （reca -单链DNA细丝形成）组成。recB（核酸酶缺陷）突变体的重组途径是一种杂交，因为它包括RecBCD和RecF重组机制的元件。在这项研究中，对recB（核酸酶缺陷）recD双突变体的重组进行了遗传分析。我们发现，该突变体在紫外线和伽马照射后的共轭重组和DNA修复高度依赖于recJ，部分依赖于recFOR，独立于recQ。这些结果表明，在核酸酶缺陷的recB - recD双突变体中操作的重组途径也是一种杂交。我们认为解旋酶和RecA装载活性属于RecBCD重组机制，而recj介导的5‘- >3’外切酶是RecF重组机制的一个组成部分。
The two main recombination pathways in Escherichia coli (RecBCD and RecF) have different recombination machineries that act independently in the initiation of recombination. Three essential enzymatic activities are required for early recombinational processing of double-stranded DNA ends and breaks: a helicase, a 5'-->3' exonuclease, and loading of RecA protein onto single-stranded DNA tails. The RecBCD enzyme performs all of these activities, whereas the recombination machinery of the RecF pathway consists of RecQ (helicase), RecJ (5'-->3' exonuclease), and RecFOR (RecA-single-stranded DNA filament formation). The recombination pathway operating in recB (nuclease-deficient) mutants is a hybrid because it includes elements of both the RecBCD and RecF recombination machineries. In this study, genetic analysis of recombination in a recB (nuclease-deficient) recD double mutant was performed. We show that conjugational recombination and DNA repair after UV and gamma irradiation in this mutant are highly dependent on recJ, partially dependent on recFOR, and independent of recQ. These results suggest that the recombination pathway operating in a nuclease-deficient recB recD double mutant is also a hybrid. We propose that the helicase and RecA loading activities belong to the RecBCD recombination machinery, while the RecJ-mediated 5'-->3' exonuclease is an element of the RecF recombination machinery.