Transcription frequency modulates the efficiency of an attenuator preceding the rpoBC RNA polymerase genes of Escherichia coli: possible autogenous control.
AUTOR(ES)
Steward, K L
RESUMO
Expression of the rpoBC genes encoding the beta and beta' RNA polymerase subunits of Escherichia coli is autogenously regulated. Although previous studies have demonstrated a post-transcriptional feedback mechanism, complex transcriptional controls of rpoBC expression may also contribute. We show that an attenuator (rpoBa) separating the ribosomal protein (rpl) genes from the rpoBC genes in the rplKAJLrpoBC gene cluster is modulated in its efficiency in response to changes in the frequency of transcription initiated by promoters located upstream. A series of rplJLrpoBalacZ transcriptional fusions was constructed on lambda vectors in which transcription into the rpoBa attenuator was varied by using a variety of promoters with different strengths. beta-galactosidase assays performed on monolysogens of the recombinant phage show that with transcription increasing over a 40-fold range, readthrough of rpoBa decreases from 61% to 19%. In contrast, two other well-characterized terminators show nearly constant efficiencies over a similar range of transcription frequencies. Using a set of phage P22 ant promoter variants with single-nucleotide changes in the promoter consensus sequences also demonstrates that the modulation of rpoBa function appears to be unrelated to the phenomenon of 'factor-independent antitermination' reported by others. The implications for autogenous control of RNA polymerase synthesis are discussed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=334231Documentos Relacionados
- Evidence that rifampicin can stimulate readthrough of transcriptional terminators in Escherichia coli, including the attenuator of the rpoBC operon.
- Control features within the rplJL-rpoBC transcription unit of Escherichia coli.
- An internal region of rpoB is required for autogenous translational regulation of the beta subunit of Escherichia coli RNA polymerase.
- Mutations in rpoBC Suppress the Defects of a Sinorhizobium meliloti relA Mutant
- Effect of rifampicin on expression of lacZ fused to promoters or terminators of the E.coli rpoBC operon.