Autogenous posttranscriptional regulation of RNA polymerase beta and beta' subunit synthesis in Escherichia coli

Abstract

Bacterial strains carrying poorly suppressed amber mutations in the RNA polymerase beta subunit gene (rpoB) exhibit regulatory compensation. This compensation allows these strains to produce an adequate content of RNA polymerase to support a near normal rate of growth despite the poorly suppressed amber mutation. The primary compensatory mechanism permitting the elevated expression functions by permitting a much more efficient (up to threefold) loading of ribosomes at the beta cistron translation initiation site on the mRNA. This result supports the concept that the production of beta and beta' RNA polymerase subunits are autogenously regulated at the level of mRNA translation; this translational mechanism is clearly distinct from the transcriptional mechanism regulating beta and beta' expression described previously (P. P. Dennis, Proc. Natl. Acad. Sci. U.S.A. 74:5416-5420, 1977).