title: The essential activities of the bacterial sigma factor.
abstract: Transcription is the first and most heavily regulated step in gene expression. Sigma (σ) factors are general transcription factors that reversibly bind RNA polymerase (RNAP) and mediate transcription of all genes in bacteria. σ Factors play 3 major roles in the RNA synthesis initiation process: they (i) target RNAP holoenzyme to specific promoters, (ii) melt a region of double-stranded promoter DNA and stabilize it as a single-stranded open complex, and (iii) interact with other DNA-binding transcription factors to contribute complexity to gene expression regulation schemes. Recent structural studies have demonstrated that when σ factors bind promoter DNA, they capture 1 or more nucleotides that are flipped out of the helical DNA stack and this stabilizes the promoter open-complex intermediate that is required for the initiation of RNA synthesis. This review describes the structure and function of the σ70family of σ proteins and the essential roles they play in the transcription process.
authors.affiliation: Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.|Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Davis
authors.affiliation: Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.|Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Kesthely
authors.affiliation: Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.|Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.
authors.forename: Emily A
authors.initials: EA
authors.lastname: Franklin
authors.affiliation: Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.|Department of Biology, University of New Brunswick, Fredericton, NB E3B 5A3, Canada.
authors.forename: Shawn R
authors.initials: SR
authors.lastname: MacLellan
mesh_terms: D001419:Bacteria / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000737:chemistry / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D012808:Sigma Factor; D012321:DNA-Directed RNA Polymerases
keywords: ARN polymérase; RNA polymerase; bacteria; bactérie; expression génique; facteur sigma; gene expression; sigma factor; transcription