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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >The recombination hot spot χ activates RecBCD recombination by converting Escherichia coli to a recD mutant phenocopy
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The recombination hot spot χ activates RecBCD recombination by converting Escherichia coli to a recD mutant phenocopy

机译：重组热点χ通过将大肠杆菌转化为recD突变表型来激活RecBCD重组

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摘要

The products of the recB and recC genes are necessary for conjugal recombination and for repair of chromosomal double-chain breaks in Escherichia coli. The recD gene product combines with the RecB and RecC proteins to comprise RecBCD enzyme but is required for neither recombination nor repair. On the contrary, RecBCD enzyme is an exonuclease that inhibits recombination by destroying linear DNA. The RecD ejection model proposes that RecBCD enzyme enters a DNA duplex at a double-chain end and travels destructively until it encounters the recombination hot spot sequence χ·χ then alters the RecBCD enzyme by weakening the affinity of the RecD subunit for the RecBC heterodimer. With the loss of the RecD subunit, the resulting protein, RecBC(D~-), becomes deficient for exonuclease activity and proficient as a recombinagenic helicase. To test the model, genetic crosses between λ phage were conducted in cells containing χ on a nonhomologous plasmid. Upon delivering a double-chain break to the plasmid, λ recombined as if the cells had become recD mutants. The ability of χ to alter λ recombination in trans was reversed by overproducing the RecD subunit. These results indicate that χ can influence a recombination act without directly participating in it.
机译：recB和recC基因的产物对于大肠杆菌的结合重组和染色体双链断裂的修复是必需的。 recD基因产物与RecB和RecC蛋白结合，组成RecBCD酶，但重组或修复均不需要。相反，RecBCD酶是一种核酸外切酶，可通过破坏线性DNA来抑制重组。 RecD弹出模型建议RecBCD酶在双链末端进入DNA双链体并破坏性地传播，直到遇到重组热点序列χ·χ，然后通过削弱RecD亚基对RecBC异二聚体的亲和力来改变RecBCD酶。随着RecD亚基的丢失，所得蛋白质RecBC（D-）变得缺乏核酸外切酶活性，并熟练用作重组解旋酶。为了测试该模型，在非同源质粒上含有χ的细胞中进行了λ噬菌体之间的遗传杂交。传递双链断裂至质粒后，λ重组，好像细胞已成为recD突变体一样。通过过量产生RecD亚基逆转了χ改变反式中λ重组的能力。这些结果表明，χ可以在不直接参与的情况下影响重组行为。

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