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

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.