title: Transcription regulation by inflexibility of promoter DNA in a looped complex.
abstract: The gal operon of Escherichia coli is negatively regulated by repressor binding to bipartite operators separated by 11 helical turns of DNA. Synergistic binding of repressor to separate sites on DNA results in looping, with the intervening DNA as a topologically closed domain containing the two promoters. A closed DNA loop of 11 helical turns, which is in-flexible to torsional changes, disables the promoters either by resisting DNA unwinding needed for open complex formation or by impeding the processive DNA contacts by an RNA polymerase in flux during transcription initiation. Interaction between two proteins bound to different sites on DNA modulating the activity of the intervening segment toward other proteins by allostery may be a common mechanism of regulation in DNA-multiprotein complexes.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: H E
authors.initials: HE
authors.lastname: Choy
authors.forename: S W
authors.initials: SW
authors.lastname: Park
authors.forename: P
authors.initials: P
authors.lastname: Parrack
authors.forename: S
authors.initials: S
authors.lastname: Adhya
mesh_terms: D000494:Allosteric Regulation; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009690:Nucleic Acid Conformation; D009876:Operon; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial