ATP-dependent resolution of R-loops at the ColE1 replication origin by Escherichia coli RecG protein, a Holliday junction-specific helicase.
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.
Fukuoh
A
A
Department of Molecular Microbiology, Research Institute for Microbial Diseases, Osaka University, Suita, Japan.
Iwasaki
H
H
Ishioka
K
K
Shinagawa
H
H
D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D003086:Bacteriocin Plasmids / Q000235:genetics*; D004265:DNA Helicases / Q000235:genetics / Q000502:physiology*; D004261:DNA Replication / Q000502:physiology*; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D018628:Gene Dosage; D006868:Hydrolysis; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000378:metabolism; D018741:Replication Origin
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; C071446:RecG protein, E coli; D000255:Adenosine Triphosphate; D004265:DNA Helicases