ESCHERICHIA-COLI RECG AND RECA PROTEINS IN R-LOOP FORMATION
ESCHERICHIA-COLI RECG AND RECA PROTEINS IN R-LOOP FORMATION
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DOI：
10.1002/j.1460-2075.1995.tb07233.x
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发表时间：
1995-05-15
期刊：
影响因子：
11.4
通讯作者：
KOGOMA, T
中科院分区：
文献类型：
--
作者：
HONG, XK;CADWELL, GW;KOGOMA, T
缺乏RNase HI的大肠杆菌rnhA突变体表现出组成型稳定的DNA复制，cSDR，其被认为是从在RNase HI不存在下稳定的R环开始的。我们发现rnhA和recG突变的组合对细胞是致命的。抑制RecG蛋白的解旋酶活性并抑制霍利迪连接的反向分支迁移的recG突变赋予类似于rnhA突变体的表型。因此，recG突变体显示cSDR活性，并且recG polA双突变体与rnhA polA双突变体一样是不可活的。这些结果表明，RecG解旋酶具有防止R环形成的作用。一个模型，R-环形成的同化RNA转录到双链体DNA进行了讨论。该模型进一步假设RecA蛋白催化该同化反应，并且RecG蛋白在该反应中抵消RecA，通过其解旋酶活性解析R环，或两者兼而有之。
Escherichia coli rnhA mutants devoid of RNase HI exhibit constitutive stable DNA replication, cSDR, which is thought to be initiated from R-loops stabilized in the absence of RNase HI. We found that a combination of an rnhA and a recG mutation is lethal to the cell. recG mutations that inactivate the helicase activity of RecG protein and inhibit reverse branch migration of Holliday junctions impart phenotypes resembling those of rnhA mutants. Thus, recG mutants display cSDR activity, and recG polA double mutants are inviable as are rnhA polA double mutants. These results suggest that the RecG helicase has a role in preventing R-loop formation. A model that R-loops are formed by assimilation of RNA transcripts into the duplex DNA is discussed. The model further postulates that RecA protein catalyzes this assimilation reaction and that RecG protein counteracts RecA in this reaction, resolves R-loops by its helicase activity, or does both.