RRC ID 29843
Author Subia NL, Kogoma T.
Title Concatemer formation of ColE1-type plasmids in mutants of Escherichia coli lacking RNase H activity.
Journal J Mol Biol
Abstract rnh mutants harboring pBR322 were found to contain several slowly migrating DNA species when examined by agarose gel electrophoresis. The plasmid DNA from rnh mutants included large molecules, i.e. plasmids two, three or four times the size of a single plasmid unit. That this DNA contained concatemeric plasmid joined in a head-to-tail fashion was determined by digestion with restriction endonucleases that cleaved the monomeric plasmid DNA at a unique site. This treatment resulted in migration of the plasmid DNA at a mobility identical to that of linearized monomeric plasmid by agarose gel electrophoresis. This was confirmed by electron microscopy. Plasmid concatemer formation was detected with several high-copy-number (relaxed type) plasmids but not with low-copy-number (stringent) plasmids. Concatemer formation was dependent on RecA+ and RecF+ functions since several recA and recF mutations abolished concatemer formation. ColE1-type plasmids were previously shown to replicate in rnh mutants in the absence of DNA polymerase I (PolI) activity. This DNA PolI-independent plasmid replication was also examined for its dependence on the recF and recA gene products. rnh- polA(Ts) recF- strains were efficiently transformed with these plasmids at 30 degrees C and 42 degrees C, indicating the presence of DNA PolI-independent replication under recF- conditions. The presence or absence of plasmid replication in rnh- polA- recA(Ts) strains was also examined by measuring the increase in total amounts of plasmid. The results indicated that DNA PolI-independent replication occurred in these triple mutants at 42 degrees C as well as at 30 degrees C. It was concluded that the recombination event giving rise to concatemer formation was not essential for DNA PolI-independent replication in rnh mutants.
Volume 189(3)
Pages 389-99
Published 1986-6-5
DOI 10.1016/0022-2836(86)90311-6
PII 0022-2836(86)90311-6
PMID 3023625
MeSH Bacterial Proteins / genetics DNA Polymerase I / metabolism DNA Replication DNA, Bacterial Electrophoresis, Agar Gel Endoribonucleases / metabolism* Escherichia coli / enzymology* Escherichia coli / genetics Mutation* Nucleic Acid Conformation Plasmids* Rec A Recombinases / genetics Ribonuclease H
IF 4.76
Times Cited 11
Prokaryotes E. coli ME9133 ME9146 ME9120 ME9225 ME9226 ME9229 ME9224 ME9218 ME9219 ME9186 ME9176 ME9170 ME9174 ME9142 ME9149 ME9150