Cyclic AMP-dependent initiation and rho-dependent termination of colicin E1 gene transcription

Abstract

We have analyzed the initiation and termination sites of transcription in vivo of the colicin E1 gene in Escherichia coli cells by S1-mapping assay and RNA blot hybridization. According to the S1-mapping assay, the transcription was initiated at about 75 base pairs upstream from the NH2-terminal codon of the gene. The initiation site corresponded with one of the two promoters which were previously determined by in vitro transcription experiments (Ebina, Y., Kishi, F., Miki, T., Kagamiyama, H., Nakazawa, T., and Nakazawa, A. (1981) Gene 15, 119-126). Transcription in vivo of the colicin E1 gene was stimulated by cyclic AMP in the adenylate cyclase-defective mutant cells. Two transcripts of the colicin E1 gene, approximately 1700 and 2200 nucleotides, were detected by the blot hybridization. Since initiation of the transcription started at one site in vivo, these results indicated two termination sites. The location of the termination sites were approximately 60 and 560 base pairs downstream from the COOH-terminal codon of the gene as judged by S1-mapping assay. In vitro transcription experiments with rho-factor strongly suggested that the termination in the proximal terminator was rho-dependent. In the terminator structure, there is the sequence CAAACAAA which is homologous to a common sequence CAATCAA found in other rho-dependent terminators.