Regulation of RNA polymerase synthesis. Conditional lethal amber mutations in the beta subunit gene

Abstract

Amber mutations in the rpoB gene specifying the beta subunit of RNA polymerase coupled with conditional amber suppressors were used to restrict the synthesis of core RNA polymerase in strains of Escherichia coli. Such a restriction stimulated transcription of genetic units containing RNA polymerase subunit genes. Within the L10 transcription unit (genetic structure: promotor (PL10), rplJ (L10), rplL (L7/L12), attenuator, rpoB (beta), rpoC (beta'), terminator), the initiation of transcription at the promotor was enhanced and termination at the transcription attenuator was relaxed. Transcription of the genetic unit containing the rpoA gene (alpha) was also enhanced. In the strain containing a non-polar amber mutation, the synthesis rate of the beta' subunit protein during the restriction correlated with the level of transcription of the beta and beta' genes. In contrast, synthesis of L7/L12 ribosomal protein remained essentially unaltered in spite of the elevated levels of L10-L7/L12 mRNA.