Recombination is essential for viability of an Escherichia coli dam (DNA adenine methyltransferase) mutant
Marinus, Martin G.
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UMass Chan Affiliations
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Keywords
Base Pair Mismatch
Crosses, Genetic
*DNA Helicases
DNA Repair
DNA-Binding Proteins
Endodeoxyribonucleases
Escherichia coli
*Escherichia coli Proteins
Exodeoxyribonuclease V
Exodeoxyribonucleases
Gene Expression Regulation, Bacterial
Gene Expression Regulation, Enzymologic
*Mutation
Rec A Recombinases
*Recombination, Genetic
SOS Response (Genetics)
Site-Specific DNA-Methyltransferase (Adenine-Specific)
Life Sciences
Medicine and Health Sciences
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Abstract
Double mutants of Escherichia coli dam (DNA adenine methyltransferase) strains with ruvA, ruvB, or ruvC could not be constructed, whereas dam derivatives with recD, recF, recJ, and recR were viable. The ruv gene products are required for Holliday junction translocation and resolution of recombination intermediates. A dam recG (Holliday junction translocation) mutant strain was isolated but at a very much lower frequency than expected. The inviability of a dam lexA (Ind(-)) host was abrogated by the simultaneous presence of plasmids encoding both recA and ruvAB. This result indicates that of more than 20 SOS genes, only recA and ruvAB need to be derepressed to allow for dam mutant survival. The presence of mutS or mutL mutations allowed the construction of dam lexA (Ind(-)) derivatives. The requirement for recA, recB, recC, ruvA, ruvB, ruvC, and possibly recG gene expression indicates that recombination is essential for viability of dam bacteria probably to repair DNA double-strand breaks. The effect of mutS and mutL mutations indicates that DNA mismatch repair is the ultimate source of most of these DNA breaks. The requirement for recombination also suggests an explanation for the sensitivity of dam cells to certain DNA-damaging agents.
Source
J Bacteriol. 2000 Jan;182(2):463-8.