Abstract
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 E. coli strain bearing a temperature-sensitive mutation in the .beta.'' subunit gene. A shift to 42.degree. C results in a restriction of RNA chain initiation and a cessation of RNA synthesis. A shift to 39.degree. C 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. Apparently, the genes specifying the .beta. and .beta.'' subunits of RNA polymerase are regulated at the level of transcription and this regulation is related to the transcription of ribosomal protein genes. This regulation of the .beta. and .beta.'' RNA polymerase subunit genes is apparently somehow triggered by a reduction in the ability of RNA polymerase to initiate transcription on the bacterial chromosome.