Regulatory elements downstream of the promoter of an rRNA gene of E. coli

Abstract

Previously we have shown that plasmid constructs carrying a resporter gene fused to the P 2 promoter of the E. coli rrnB gene exhibited a strange two-phase kinetics of expression depending on the physiological conditions of the cell if a short DNA region downstream of the promoter was present between the promoter and the reporter gene (Lukacsovich et al. (1987) J. Bacteriol. 169, 272–277). Insertion of a synthetic oligonucleotide corresponding to the first half of this region into constructs where the reporter directly follows the prometer, leads to a complete blocks of expression in vivo, while in vitro - in a purified system - transciption is not inhibited. Band-shift experiments indicate that the putative regulatory region downstream of the promoter specifically binds protein(s) present in total bacterial extracts.