title: Region 2.5 of the Escherichia coli RNA polymerase sigma70 subunit is responsible for the recognition of the 'extended-10' motif at promoters.
abstract: At some bacterial promoters, a 5'-TG-3' sequence element, located one base upstream of the -10 hexamer element, provides an essential motif necessary for transcription initiation. We have identified a mutant of the Escherichia coli RNA polymerase sigma70 subunit that has an altered preference for base sequences in this 'extended -10' region. We show that this mutant sigma70 subunit substantially increases transcription from promoters bearing 5'-TC-3' or 5'-TT-3' instead of a 5'-TG-3' motif, located one base upstream of the -10 hexamer. The mutant results from a single base pair substitution in the rpoD gene that causes a Glu to Gly change at position 458 of sigma70. This substitution identifies a functional region in sigma70 that is immediately adjacent to the well-characterized region 2.4 (positions 434-453, previously shown to contact the -10 hexamer). From these results, we conclude that this region (which we name region 2.5) is involved in contacting the 5'-TG-3' motif found at some bacterial promoters: thus, extended -10 regions are recognized by an extended region 2 of the RNA polymerase sigma70 subunit.
authors.affiliation: School of Biochemistry, The University of Birmingham, Edgbaston, UK.
authors.forename: K A
authors.initials: KA
authors.lastname: Barne
authors.forename: J A
authors.initials: JA
authors.lastname: Bown
authors.forename: S J
authors.initials: SJ
authors.lastname: Busby
authors.forename: S D
authors.initials: SD
authors.lastname: Minchin
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D004269:DNA, Bacterial / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D011993:Recombinant Fusion Proteins; D012808:Sigma Factor; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases