A novel promoter architecture for microaerobic activation by the anaerobic transcription factor FNR.
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.
Marshall
F A
FA
Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
Messenger
S L
SL
Wyborn
N R
NR
Guest
J R
JR
Wing
H
H
Busby
S J
SJ
Green
J
J
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
D001426:Bacterial Proteins; D003470:Culture Media; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; D010100:Oxygen