Regulation of synthesis and activity of a mutant RNA polymerase in Escherichia coli.

The expression of the genes specifying the beta and beta' subunits of RNA polymerase (nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.7.6) was examined in an Escherichia coli strain bearing a temperature-sensitive mutation in the beta' subunit gene. A shift to 42 degrees results in a restriction of RNA chain initiation and a cessation of RNA synthesis. A shift to 39 degrees results in only partial restriction, allowing RNA and protein synthesis to continue. The partial restriction produces a 5- to 6-fold increase in the relative transcription rate of the beta and beta' genes and a concomitant increase in the relative synthesis rate of the beta and beta' proteins. The transcription rate of ribosomal protein genes was also increased somewhat. These results indicate that the genes specifying the beta and beta' subunits of RNA polymerase are regulated at the level of transcription and that this regulation is related to the transcription of ribosomal protein genes. Furthermore, the results indicate that this regulation of the beta and beta' RNA polymerase subunit genes is somehow triggered by a reduction in the ability of RNA polymerase to initiate transcription on the bacterial chromosome.