Escherichia coli rep gene: identification of the promoter and N terminus of the rep protein.

The functional Escherichia coli rep gene, which encodes the Mr 67,000 Rep helicase, has been localized within a 2.55-kilobase sequence. Its regulatory region has been characterized by the use of rep-lacZ fusions. The direction of transcription of the rep gene is clockwise on the E. coli chromosome, as are the nearby ilvC and rho genes. The sequence of the rep control region was determined, and putative regulatory sequences were identified; no evidence for autoregulation of expression was obtained. Transcription of the gene was not enhanced during the SOS response. The location of the promoter and the beginning of the protein were confirmed by S1 nuclease mapping of the 5' end of rep mRNA and determination of the NH2-terminal sequence of the rep protein.