Stringent Control of Esherichia coli rnpB Gene Transcription in Vivo in Multicopy Plasmids

Abstract

Stringent control of the Escherichia coli mpB gene expression in plasmids has been examined in vivo. The stringent response was analyzed by directly observing metabolically unstable transcript derived from the internally deleted mpB gene. During amino acid starvation the transcription of the mpB gene was repressed in wild type E. coli but not in relaxed strains carrying the reL4-mutation. Thus, expression of the mpB gene is under stringent control at transcriptional level and its regulation is reWdependent. In the course of this study, it was also demonstrated that the overexpressed primary Ml RNA transcripts from the mpB gene in the multicopy plasmids are rapidly processed to mature Ml RNA and their processing does not require the intact sequences of M1 RNA.