Mitomycin C-induced bidirectional transcription from the colicin E1 promoter region in plasmid ColE1

Treatment of a colicinogenic culture with mitomycin C induces convergent transcription from two adjacent promoters at the beginning of the colicin E1 gene. S1-mapping and primer extension assays indicate that the mitomycin C-inducible transcripts correspond to colicin E1 mRNA (cea mRNA) and to a transcript, designated RNA-C, that may code for an entry exclusion function. Nucleotide sequences that strongly resemble a consensus sequence for LexA protein binding sites span the transcription start points for cea mRNA and RNA-C. These putative operator sequences overlap by one base pair and bind LexA protein (Ebina, Y., Takahara, Y., Kishi, F., Nakazawa, A. and Brent, R. (1983) J. Biol. Chem. 258, 13258-13261). The data suggest that mitomycin C-induced bidirectional transcription from the cea mRNA and RNA-C promoters is controlled by the SOS regulatory system of Escherichia coli.