Carcinogen-induced insertion mutations in E. coli

Mutagenic effects of AAF have been examined by transforming competent E. coli cells with plasmid DNA which were regionally-modified with this carcinogen. Transposition of IS5 from chromosomal DNA to target sequences in the AAF-modified region was detected in six plasmids obtained from wild type and recA strains. A single GC addition was identified in an additional plasmid; no deletions were detected. The observed frequency of IS5 insertion, 2.5 X 10(-3), exceeds that reported for naturally-occurring IS5 transposition in E.coli. These results suggest that the frequency of recombinational events in E.coli can be increased by the presence of a DNA-carcinogen adduct.