title: Stimulation of recombination between homologous sequences on plasmid DNA and chromosomal DNA in Escherichia coli by N-acetoxy-2-acetylaminofluorene.
abstract: A plasmid containing a wild-type lac operon and a tetracycline-resistance gene was covalently modified by N-acetoxy-2-acetylaminofluorene and used to transform two series of Lac- Escherichia coli cell types. Each set contained wild-type and repair-deficient mutants. One set of cells contained a lacY mutation and the other a deletion of the entire lac operon. Survival and mutagenesis of the plasmid were measured as a function of the N-acetoxy-2-acetylaminofluorene concentration. The results indicate that when no homologous sequences are present in the chromosomal DNA, mutations occur at a low frequency: at 10% survival the frequency was 1-2 X 10(-4) mutants per transformant. When homologous sequences, the lacY allele, are present in the chromosomal DNA, Lac- plasmids are found at a high frequency in a recA-dependent, lexA-independent fashion: at 10% survival the frequency was 5-10 X 10(-2) mutants per transformant. Southern blot analysis of the restriction enzyme profiles of the resulting plasmid and host-cell DNA sequences showed recombinational transfer of host sequences to the N-acetoxy-2-acetylamino-fluorene-treated plasmid had occurred. When the host chromosomes contained Lac+ homologous sequences no mutants were found, indicating that the results were not caused by error-prone recombination.
mesh_terms: D015073:2-Acetylaminofluorene / Q000031:analogs & derivatives*; D000099:Acetoxyacetylaminofluorene / Q000494:pharmacology*; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D009154:Mutation / Q000187:drug effects; D010957:Plasmids; D011938:Rec A Recombinases / Q000235:genetics; D011995:Recombination, Genetic / Q000187:drug effects*
chemical_list: D004269:DNA, Bacterial; D000099:Acetoxyacetylaminofluorene; D015073:2-Acetylaminofluorene; D011938:Rec A Recombinases