title: A novel promoter architecture for microaerobic activation by the anaerobic transcription factor FNR.
abstract: The yfiD gene of Escherichia coli has an unusual promoter architecture in which an FNR dimer located at -93.5 inhibits transcription activation mediated by another FNR dimer bound at the typical class II position (-40.5). In vitro transcription from the yfiD promoter indicated that FNR alone can downregulate yfiD expression. Analysis of yfiD::lac reporters showed that five turns of the DNA helix between FNR sites was optimal for downregulation. FNR heterodimers, in which one subunit carried a defective repression surface, revealed that the upstream subunit of the -40.5 dimer and the downstream subunit of the -93.5 dimer were most important for downregulating yfiD expression. Deletion of the C-terminal domain of the alpha-subunit of RNA polymerase (RNAP) did not affect FNR-mediated repression, suggesting that repression is mediated through FNR-FNR and not FNR-RNAP interactions. Maximum yfiD::lac expression was observed in cultures exposed to 10 microM oxygen. More or less oxygen reduced expression dramatically. This pattern of response was dependent on the combination of a high-affinity site at the activating class II position and a lower affinity site at the upstream position.
authors.affiliation: Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
authors.forename: F A
authors.initials: FA
authors.lastname: Marshall
authors.forename: S L
authors.initials: SL
authors.lastname: Messenger
authors.forename: N R
authors.initials: NR
authors.lastname: Wyborn
authors.forename: J R
authors.initials: JR
authors.lastname: Guest
authors.forename: H
authors.initials: H
authors.lastname: Wing
authors.forename: S J
authors.initials: SJ
authors.lastname: Busby
authors.forename: J
authors.initials: J
authors.lastname: Green
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003470:Culture Media; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D007506:Iron-Sulfur Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D010100:Oxygen / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; D010100:Oxygen