Modulation of recombination and DNA repair by the RecG and PriA helicases of Escherichia coli K-12
Modulation of recombination and DNA repair by the RecG and PriA helicases of Escherichia coli K-12
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DOI：
10.1128/jb.178.23.6782-6789.1996
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发表时间：
1996-12-01
影响因子：
3.2
通讯作者：
Lloyd, RG
中科院分区：
文献类型：
--
作者：
AlDeib, AA;Mahdi, AA;Lloyd, RG
大肠杆菌的RecG蛋白是一种结构特异性的DNA解旋酶，它在基因重组中获得链交换中间体并驱动其分支沿DNA迁移。携带recG零突变的菌株显示重组和DNA修复减少，该表型的抑制子srgA位于meb附近，显示为priA的等位基因。抑制依赖于RecA、RecBCD、RecF、RuvAB和RuvC重组蛋白。对9个srgA突变进行了测序，结果显示它们指定的PriA突变蛋白具有位于或接近一个保守解旋酶基序的单氨基酸取代。根据recG srgA和srgA菌株的生存能力以及它们支持基于ColE1复制子的质粒复制的能力来判断，突变蛋白保留了催化原体组装的能力。多拷贝priA（+）质粒显著增加了recG菌株的重组和修复缺陷表型，并在recG srgA双突变株上赋予了类似的表型，但在ruvAB或温和型菌株上却没有。priA中的K230R、C446G和C477G替换消除了多拷贝效应。由此得出结论，PriA的3'-5' DNA解旋酶/转位酶活性抑制重组，而这种作用通常被RecG抵消。
The RecG protein of Escherichia coli is a structure-specific DNA helicase that tal gets strand exchange intermediates in genetic recombination and drives their branch migration along the DNA. Strains carrying null mutations in recG show reduced recombination and DNA repair, Suppressors of this phenotype, called srgA, were located close to metB and shown to be alleles of priA. Suppression depends on the RecA, RecBCD, RecF, RuvAB, and RuvC recombination proteins. Nine srgA mutations were sequenced and shown to specify mutant PriA proteins with single amino acid substitutions located in or close to one of the conserved helicase motifs. The mutant proteins retain the ability to catalyze primosome assembly, as judged by the viability of recG srgA and srgA strains and their ability to support replication of plasmids based on the ColE1 replicon. Multicopy priA(+) plasmids increase substantially the recombination- and repair-deficient phenotype of recG strains and confer similar phenotypes on recG srgA double mutants but not on ruvAB or mild-type strains, The multicopy effect is eliminated by K230R, C446G, and C477G substitutions in PriA. It is concluded that the 3'-5' DNA helicase/translocase activity of PriA inhibits recombination and that this effect is normally countered by RecG.