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. 1997 Jan 2;16(1):203–209. doi: 10.1093/emboj/16.1.203

ATP-dependent resolution of R-loops at the ColE1 replication origin by Escherichia coli RecG protein, a Holliday junction-specific helicase.

A Fukuoh 1, H Iwasaki 1, K Ishioka 1, H Shinagawa 1
PMCID: PMC1169627  PMID: 9009281

Abstract

The RecG protein of Escherichia coli is a DNA helicase that promotes branch migration of the Holliday junctions. We found that overproduction of RecG protein drastically decreased copy numbers of ColE1-type plasmids, which require R-loop formation between the template DNA and a primer RNA transcript (RNA II) for the initiation of replication. RecG efficiently inhibited in vitro ColE1 DNA synthesis in a reconstituted system containing RNA polymerase, RNase HI and DNA polymerase I. RecG promoted dissociation of RNA II from the R-loop in a manner that required ATP hydrolysis. These results suggest that overproduced RecG inhibits the initiation of replication by prematurely resolving the R-loops formed at the replication origin region of these plasmids with its unique helicase activity. The possibility that RecG regulates the initiation of a unique mode of DNA replication, oriC-independent constitutive stable DNA replication, by its activity in resolving R-loops is discussed.

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Selected References

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