DNA strand invasion promoted by Escherichia coli RecT protein
DNA strand invasion promoted by Escherichia coli RecT protein
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DOI：
10.1074/jbc.273.20.12274
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发表时间：
1998-05-15
影响因子：
4.8
通讯作者：
Kolodner, RD
中科院分区：
文献类型：
--
作者：
Noirot, P;Kolodner, RD
大肠杆菌的RecT蛋白是RecE途径促进的RecA非依赖性重组事件所需的DNA配对蛋白。发现RecT蛋白在不存在Mg 2+的情况下与单链DNA（ssDNA）和双链DNA（dsDNA）结合。在Mg ~（2+）存在下，RecT与dsDNA的结合受到强烈抑制，而与ssDNA的结合仅在很小程度上受到抑制。RecT促进单链寡核苷酸转移到超螺旋同源双链体中以形成D（置换）环。D-环的形成发生在不存在的Mg 2+和在1 mM Mg 2+，但被抑制的Mg 2+的浓度增加，并不需要一个高能量的辅因子。链转移介导的RecT-ssDNA核蛋白复合物与裸露的双链DNA反应，并防止RecT-dsDNA核蛋白复合物的形成。最后，RecT介导超螺旋DNA和具有同源3 '-单链尾的线性dsDNA底物之间的接合分子的形成。总之，这些结果表明，RecT是不是一个螺旋不稳定的蛋白质促进再退火反应，而是一种新型的配对蛋白能够促进重组的DNA链侵入机制。这些结果与RecE（核酸外切酶VIII）和RecT可以促进大肠杆菌中RecA非依赖性双链断裂修复的观察一致。杆菌
The RecT protein of Escherichia coli is a DNA-pairing protein required for the RecA-independent recombination events promoted by the RecE pathway. The RecT protein was found to bind to both single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) in the absence of Mg2+. In the presence of Mg2+, RecT binding to dsDNA was inhibited drastically, whereas binding to ssDNA was inhibited only to a small extent. RecT promoted the transfer of a single-stranded oligonucleotide into a supercoiled homologous duplex to form a D (displacement)-loop. D-loop formation occurred in the absence of Mg2+ and at 1 mM Mg2+ but was inhibited by increasing concentrations of Mg2+ and did not require a high energy cofactor. Strand transfer was mediated by a RecT-ssDNA nucleoprotein complex reacting with a naked duplex DNA and was prevented by the formation of RecT-dsDNA nucleoprotein complexes. Finally, RecT mediated the formation of joint molecules between a supercoiled DNA and a linear dsDNA substrate with homologous 3'-single-stranded tails. Together these results indicate that RecT is not a helix-destabilizing protein promoting a reannealing reaction but rather is a novel type of pairing protein capable of promoting recombination by a DNA strand invasion mechanism. These results are consistent with the observation that RecE (exonuclease VIII) and RecT can promote RecA-independent double-strand break repair in E. coli.