Plasmid expression of mutS, -L, and/or -H gene in E. coli dam sells results in strains that display reduced mutation frecuency

JACQUELÍN D K; MARTINA M A; ARGARAÑA C E; BARRA J L

MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS

Año: 2007 vol. 637 p. 197 - 204

0027-5107

Escherichia coli dam 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. coli dam cells transformed with plasmids containing either the mutS, mutL, or mutH gene display a mutation frequency 3-8 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.