Plasmid expression of mutS, -L and/or -H gene in Escherichia coli dam cells results in strains that display reduced mutation frequency.
Escherichia colidam cells have an active but non-directed mismatch repair system; therefore, assembly of MutSLH complex at a mismatched base pair can result in MutH-mediated cleavage of GATC sites in both DNA strands. Unpaired double-strand breaks on a fraction of the replication errors occurring in dam cells presumably cause cell death, selectively eliminating these putative mutants from the population. We show that E. colidam cells transformed with plasmids containing either the mutS, mutL or mutH gene display a mutation frequency three to eight times lower than that of the parental dam strain, due to increased mismatch-stimulated cell killing. Transformed strains are also more susceptible to killing by the base analogue 2-aminopurine. However, dam and dam transformed cells have similar duplication time, proportion of live/dead cells and morphology.
Jacquelín
Daniela K
DK
Centro de Investigaciones en Química Biológica de Córdoba, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
Martina
Mariana A
MA
Argaraña
Carlos E
CE
Barra
José L
JL
D015075:2-Aminopurine / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics*; D005798:Genes, Bacterial; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein / Q000235:genetics*; D009154:Mutation; D010957:Plasmids; D014169:Transformation, Bacterial
D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D015075:2-Aminopurine; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein