The effect of rifampicin upon the transcription of RNA polymerase β-gene in Escherichia coli

Abstract

We studied the rate of synthesis of beta-and beta'-subunits of DNA-dependent RNA polymerase and the rate of beta-polypeptide mRNA synthesis in rifampicin-treated bacteria. The chosen antibiotic doses did not significantly inhibit the total RNA and protein synthesis in rifampicin-sensitive bacteria. For RNA-DNA hybridization experiments a pOD162 plasmid was constructed carrying a fragment of the rpoB gene and no other chromosome DNA regions. It was found that low doses of rifampicin cause an absolute and a relative increase in the rate of synthesis of the specific mRNA for the beta-subunit, suggesting a stimulation of the corresponding gene transcription and excluding the possibility of a less pronounced inhibition of the rpoB gene expression compared to that of most other genes. However the relative acceleration of transcription is substantially higher than the absolute one. The stimulating effect of rifampicin on the beta-polypeptide synthesis is also demonstrated in a coupled system of transcription and translation directed by lambda rifd47 DNA. The possible mechanisms of the rifampicin action are discussed.

The Primary Structure of Escherichia coli RNA Polymerase

“…EcoRI fragments were obtained from the DNA of POD-162 and pJB-35 plasmids [19] and of 1, rifd 47 phage by EcoRI restriction endonuclease digestion. The fragments were separated either by centrifugation in a sucrose gradient, similar to the procedure described in [20], or by preparative horizontal electrophoresis in 1 % agarose blocks [21].…”

Evidence that rifampicin can stimulate readthrough of transcriptional terminators inEscherichia coli,including the attenuator of therpoBCoperon

“…absolute increase in the rate of synthesis of S and W' (and other polymerase subunits) without a parallel effect on the ribosomal proteins L7/12 encoded upstream in the 55' operon (12)(13)(14)(15)(16). In fact the transcription of the rpoBC genes is strongly stimulated, while that of the rplKAJL region and other ribosomal RNA and protein genes displays weak stimulation (17,18,8). It is possible that post-transcriptional events play a minor role in the effects of rifampicin on a and a' synthesis (8,18,19), but the main effects in vivo are clearly transcriptional (17).…”

Expression of accumulated capacity for initiation of chromosome and minichromosome replication in dnaA mutants of Escherichia coli

“…The minimal salts medium contained (per liter of distilled, deionized water): 2 g of NH4Cl, 6 g of Na2HPO4, 3 25 and 33°C, balanced growth was obtained after approximately 16 h of growth in Casamino Acidssupplemented glucose minimal medium or after 48 h of incubation in glucose minimal medium. In the case of F62 (pAL2), incubation was for 5 h at 33°C after overnight growth at 25°C.…”

“…This conclusion is also consistent with the suppression of dnaA by mutations in rpoB (1,2), but it is difficult to reconcile with the findings of Tippe-Schindler et al (26), and those reported here, that exposure to rifampin yields a slight enhancement of DNA synthesis at intermediate temperatures. This latter finding might be explained by the observation that low concentrations of rifampin are capable of stimulating the synthesis of mRNA for RNA polymerase subunits (3). Because rifampin is absorbed slowly into E. coli K-12 cells (21), the addition of rifampin to PC5 may have resulted in a transient increase in the levels of functional RNA polymerase before the intracellular concentration of the drug became inhibitory.…”