title: Repression and activation of promoter-bound RNA polymerase activity by Gal repressor.
abstract: By binding to the DNA site OE at position -60.5 in the gal operon, the GalR protein activates transcription from the P2 promoter located on the opposite face of DNA (position -5) and represses transcription from the P1 promoter located on the same face (position +1). GalR increases RNA polymerase binding at P2 and inhibits isomerization at P1 by forming a GalR-DNA-RNA polymerase ternary complex in each case. The specific effect of GalR at one promoter is independent of the presence of the other promoter. The enhancement or repression is also not the intrinsic property of a promoter; the regulation can be reversed by switching the angular orientation of the promoters relative to OE. Both enhancement and repression appear to require the same interaction between RNA polymerase alpha-subunit and GalR and/or the same interaction between RNA polymerase alpha-subunit and DNA in the ternary complexes. We have discussed how GalR might exert opposite effects in the steps involved in the formation of the open complex from free RNA polymerase and DNA.
authors.affiliation: Department of Molecular Biology, Odense University, Denmark.
authors.forename: H E
authors.initials: HE
authors.lastname: Choy
authors.forename: R R
authors.initials: RR
authors.lastname: Hanger
authors.forename: T
authors.initials: T
authors.lastname: Aki
authors.forename: M
authors.initials: M
authors.lastname: Mahoney
authors.forename: K
authors.initials: K
authors.lastname: Murakami
authors.forename: A
authors.initials: A
authors.lastname: Ishihama
authors.forename: S
authors.initials: S
authors.lastname: Adhya
mesh_terms: D001665:Binding Sites; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005690:Galactose / Q000378:metabolism; D005786:Gene Expression Regulation; D008957:Models, Genetic; D009154:Mutation; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D029968:Escherichia coli Proteins; C050993:Galactose repressor proteins; D012097:Repressor Proteins; D012321:DNA-Directed RNA Polymerases; D005690:Galactose