Escherichia coli RNase II: Characterization of the promoters involved in the transcription of rnb

The mb gene encodes ribonuclease II (RNase II), one of the two major Escherichia coli exonucleases involved in mRNA degradation. In this paper, the mb transcript is characterized regarding its promoter and terminator regions. The combined results from S1 nuclease protection analysis, DNase I footprinting and gene fusions with IacZ have shown that rnb is expressed from two promoters. S1 nuclease protection analysis and DNA footprinting have shown that rnb has two promoters, P1 and P2. Transcriptional and translational lacZ reporter fusions, constructed to the mb gene, revealed that P2, the mb proximal promoter, is stronger than pi. However, PZ is not transcribed in vitro, suggesting that an additional factor is required in vivo. The 3' end of the mb transcript mapped to a stem-loop structure immediately after the translated region.