Role of the sigma 70 subunit of RNA polymerase in transcriptional activation by activator protein PhoB in Escherichia coli
Autor: | Hideo Shinagawa, Soo-Ki Kim, M Amemura, Kozo Makino, Atsuo Nakata |
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Rok vydání: | 1993 |
Předmět: |
DNA
Bacterial inorganic chemicals Transcription Genetic Protein subunit Molecular Sequence Data Restriction Mapping Sigma Factor Biology chemistry.chemical_compound Bacterial Proteins RNA polymerase Gene expression Escherichia coli Genetics Amino Acid Sequence Cloning Molecular Promoter Regions Genetic RNA polymerase II holoenzyme Gene Alleles Base Sequence Promoter DNA-Directed RNA Polymerases Gene Expression Regulation Bacterial Molecular biology Cell biology Regulon chemistry Mutagenesis Electrophoresis Polyacrylamide Gel DNA Transcription Factors Developmental Biology |
Zdroj: | Genes & Development. 7:149-160 |
ISSN: | 1549-5477 0890-9369 |
Popis: | Transcription of the genes belonging to the phosphate (pho) regulon in Escherichia coli, which are induced by phosphate starvation, requires the specific activator protein PhoB in addition to the RNA polymerase holoenzyme containing the major sigma-factor sigma 70. To study the mechanism of transcriptional activation and identify the subunit of RNA polymerase involved in specific interaction with PhoB, we attempted to isolate rpoA and rpoD mutants that are specifically defective in the expression of the pho genes. We isolated two rpoD mutants with such properties, but no rpoA mutant with similar properties. The rpoD mutations altered amino acids within and near the first helix of the putative helix-turn-helix (HTH) motif in the carboxy-terminal region of sigma 70. Activities of the pho promoters in vivo were severely reduced in these mutants, whereas those of the PhoB-independent promoters were affected only marginally at most. The reconstituted mutant RNA polymerase holoenzymes were severely defective in transcribing the pstS gene, one of the pho genes, whereas they were efficient in transcribing the PhoB-independent promoters. Phosphorylated PhoB, which binds to the pho promoters with high affinity, mediated the specific binding of the wild-type holoenzyme to the pstS promoter, but it did not mediate the binding of the mutant holoenzymes. These results suggest that PhoB promotes specific interaction between RNA polymerase and the pho promoters for transcriptional activation, and the first helix of the putative HTH motif plays an essential role in the interaction, probably by making direct contact with PhoB. |
Databáze: | OpenAIRE |
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