title: Domain movements of the enhancer-dependent sigma factor drive DNA delivery into the RNA polymerase active site: insights from single molecule studies.
abstract: Recognition of bacterial promoters is regulated by two distinct classes of sequence-specific sigma factors, σ(70) or σ(54), that differ both in their primary sequence and in the requirement of the latter for activation via enhancer-bound upstream activators. The σ(54) version controls gene expression in response to stress, often mediating pathogenicity. Its activator proteins are members of the AAA+ superfamily and use adenosine triphosphate (ATP) hydrolysis to remodel initially auto-inhibited holoenzyme promoter complexes. We have mapped this remodeling using single-molecule fluorescence spectroscopy. Initial remodeling is nucleotide-independent and driven by binding both ssDNA during promoter melting and activator. However, DNA loading into the RNA polymerase active site depends on co-operative ATP hydrolysis by the activator. Although the coupled promoter recognition and melting steps may be conserved between σ(70) and σ(54), the domain movements of the latter have evolved to require an activator ATPase.
authors.affiliation: Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK, Department of Life Sciences, Sir Alexander Fleming Building, Imperial College, London SW72AZ, UK and School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Amit
authors.initials: A
authors.lastname: Sharma
authors.forename: Robert N
authors.initials: RN
authors.lastname: Leach
authors.forename: Christopher
authors.initials: C
authors.lastname: Gell
authors.forename: Nan
authors.initials: N
authors.lastname: Zhang
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Burrows
authors.forename: Dale A
authors.initials: DA
authors.lastname: Shepherd
authors.forename: Sivaramesh
authors.initials: S
authors.lastname: Wigneshweraraj
authors.forename: David Alastair
authors.initials: DA
authors.lastname: Smith
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhang
authors.forename: Martin
authors.initials: M
authors.lastname: Buck
authors.forename: Peter G
authors.initials: PG
authors.lastname: Stockley
authors.forename: Roman
authors.initials: R
authors.lastname: Tuma
mesh_terms: D020134:Catalytic Domain; D004247:DNA / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism*; D005456:Fluorescent Dyes; D009711:Nucleotides / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D051877:RNA Polymerase Sigma 54 / Q000737:chemistry* / Q000378:metabolism; D013698:Templates, Genetic; D014158:Transcription, Genetic
chemical_list: D005456:Fluorescent Dyes; D009711:Nucleotides; D004247:DNA; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54