Control features within the rplJL-rpoBC transcription unit of Escherichia coli.

Abstract

Gene fusions constructed in vitro have been used to examine transcription regulatory signals from the operon which encodes ribosomal proteins L10 and L7/12 and the RNA polymerase P and #I subunits (the rplJL-rpoBC operon). Portions of this operon, which were obtained by in vitro deletions, have been placed between the ara promoter and the lacZ gene in the gene-fusion plasmid pMC81 developed by M. Casadaban and S. Cohen. The effect of the inserted DNA segment on the expression of the IacZ gene (in the presence and absence of arabinose) permits the localization of regulatory signals to discrete regions of the rpIJL-rpoBC operon. An element that reduces the level of distal gene expression to one-sixth is located on a fragment which spans the rplL-rpoB intercistronic region. This strongly supports the idea that there is an attenuator in this region. The terminator for the operon is located on a fragment which spans the 3' end of the rpoC gene. (13) or by the elicitation of the stringent response (9). The observed differential regulation of these cotranscribed genes has led to suggestions of attenuation or of mRNA processing as extra control devices (6,7,14,15). It has also been proposed that rpoBC may in fact have a second promoter that functions independently of the primary promoter for the rplJL-rpoBC transcript (7, 13).We have constructed hybrid plasmids between DNA fragments derived from selected segments of the rplJL-rpoBC region and the plasmid pMC81. These hybrid plasmids have been used to study the regulatory features contained in this region. MATERIALS AND METHODSBacterial Strains, Plasmids, and Enzymes. Strain HB133 (endoI-, rBMB, ara-, strA, lac-) and plasmid pBR322 (ampr, tetr) (16) were obtained from H. Boyer; strain MO1000 (r + m , recB, recC, sbcA, gal-, thi-, Atrp-tonB) was obtained from M. Oishi. Strain MC1000 (rjmj, AlacIPOZY, galK, galU, Aara-leu, strA) and plasmid pMC81 (colEl:tn3:araIO-trpBlacZ) (1)

A chaperone network controls the heat shock response in E. coli

“…2C; Barry et al 1979). The synthesis of these proteins declined only twofold by 10 min after overexpression of GroE/S from the Ptet promoter, as compared with the four-to fivefold repression of HtpG synthesis, indicating that GroEL/S has a specific repression component for 32 -mediated transcription.…”

Transcription mapping of the Escherichia coli chromosome by electron microscopy

“…The increase in interpolymerase spacing occurred at a position corresponding to a strong transcription attenuation site between the rpl genes and rpoB (3,4). After this site, transcripts were spaced nearly 1 kbp apart.…”

“…Transcription initiation on rpl strands 1 and 2 was fairly precise (slope = 1.14), and it was only after the rpl genes that the distribution of transcripts differed between the two strands (slope = 2.59). The position of this discontinuity corresponds to the location of the transcription attenuation site between rplL and rpoB (3,4). Attenuation was apparently more efficient on strand 2 than on strand 1. Another exception to coordinate transcription on sister strands was seen near oriC (Fig.…”

Differential regulation of the two-component regulatory system senX3-regX3 in Mycobacterium tuberculosis

“…Thus, RegX3 may serve as a master regulatory switch, providing a common means by which to transduce the signals of P i depletion and nutrient starvation, thereby inducing the stringent response, which is critical for Mtb persistence in the host (Dahl et al, 2003). The presence of multiple promoters to provide fine-tuning of gene expression is not unusual within bacterial operons (Barry et al, 1979;Fornwald et al, 1987;Taylor et al, 1984). For example, in addition to the principal promoter (Dorman, 1995), which regulates the transcription of the DNA gyrase genes, the Mtb operon containing the essential genes gyrB and gyrA also includes a promoter within the intergenic region between these two genes (Unniraman et al, 2002).…”