PMID:15743945

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Citation

Ozgenc, AI, Szekeres, ES and Lawrence, CW (2005) In vivo evidence for a recA-independent recombination process in Escherichia coli that permits completion of replication of DNA containing UV damage in both strands. J. Bacteriol. 187:1974-84

Abstract

We have investigated recombination mechanisms promoting the completion of replication in the face of unrepaired DNA damage by transforming an isogenic set of uvrA6 excision-defective Escherichia coli strains with pUC-based plasmids in which each strand carried, at staggered positions, a single thymine-thymine pyrimidine (6-4) pyrimidinone lesion. The distance between the lesions was 28 or 8 bp in one orientation relative to the unidirectional ColE1 origin of replication or, in the other orientation, 30 or 10 bp. C-C mismatches placed opposite each of the T-T photoproducts permit unambiguous detection of the three events that can lead to the completion of replication: sister-strand recombination, translesion replication (TR) on the leading strand, and TR on the lagging strand. We find that E. coli possesses a largely constitutive, recA-independent sister-strand recombination mechanism that allows 9% or more of these severely compromised plasmids to be fully replicated. In one orientation, such recombination depends partly on recG and priA but not on ruvA, ruvB, ruvC, or mutS and is largely independent of recF. In the other orientation, recombination is dependent on none of the genes. The strains used did not contain the cryptic phage encoding recET, which encodes enzymes that promote interplasmid recombination. The nature of the recA-independent recombination mechanism is not known but could perhaps result from a template-strand-switching, or copy choice, process.

Links

PubMed PMC1064058 Online version:10.1128/JB.187.6.1974-1984.2005

Keywords

Adenosine Triphosphatases/genetics; Adenosine Triphosphatases/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; DNA Helicases/genetics; DNA Helicases/metabolism; DNA Polymerase II/metabolism; DNA Replication/genetics; DNA, Bacterial/genetics; DNA-Binding Proteins/genetics; DNA-Binding Proteins/metabolism; Endodeoxyribonucleases/genetics; Endodeoxyribonucleases/metabolism; Escherichia coli/genetics; Escherichia coli/radiation effects; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Exodeoxyribonucleases/genetics; Plasmids/genetics; Prophages/genetics; Recombination, Genetic/genetics; Ultraviolet Rays

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