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

MARIANI ME, JACQUELIN DK, ARGARAÑA CE, BARRA JL.; MARTINA MA; ARGARAÑA CE; BARRA JL

ELSEVIER SCIENCE BV

Año: 2008 vol. 637 p. 197 - 197

scherichia 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 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.