Expression of different bacterial cytotoxins is controlled by two global transcription factors, CRP and Fis, that co-operate in a shared-recruitment mechanism

Amanda E Rossiter, Rita E Godfrey, Jack A Connolly, Stephen J W Busby, Ian R Henderson, Douglas F Browning

Research output: Contribution to journalArticlepeer-review


Pet is a cytotoxic autotransporter protein secreted by the pathogenic enteroaggregative Escherichia coli strain 042. Expression of Pet is co-dependent on two global transcription regulators: CRP (cyclic AMP receptor protein) and Fis (factor for inversion stimulation). At the pet promoter CRP binds to a single site centred at position -40.5 upstream of the start site for transcription. Due to the suboptimal positioning of this site, CRP alone activates transcription poorly and requires Fis to bind upstream to promote full activation. Here, we show that CRP and Fis control the expression of other important autotransporter toxins, namely Sat from uropathogenic E. coli (UPEC) and SigA from Shigella sonnei, and that this regulation has been conserved in different pathogens. Furthermore, we investigate the mechanism of Fis-mediated co-activation, exploiting a series of semi-synthetic promoters, with similar architecture to the pet promoter. We show that, when bound at position -40.5, CRP recruits RNA polymerase inefficiently and that Fis compensates by aiding polymerase recruitment through a direct protein-protein interaction. We demonstrate that other suitably positioned upstream transcription factors, which directly recruit RNA polymerase, can also compensate for the inappropriate positioning of CRP. We propose that this is a simple 'shared-recruitment' mechanism, by which co-dependence of promoters on two transcription factors could evolve.

Original languageEnglish
Pages (from-to)323-35
Number of pages13
JournalThe Biochemical Journal
Issue number2
Publication statusPublished - 1 Mar 2015
Externally publishedYes


  • 5' Flanking Region
  • Amino Acid Substitution
  • Bacterial Proteins/chemistry
  • Bacterial Toxins/genetics
  • Cyclic AMP Receptor Protein/chemistry
  • DNA-Directed RNA Polymerases/chemistry
  • Electrophoretic Mobility Shift Assay
  • Enterotoxins/genetics
  • Escherichia coli K12/enzymology
  • Escherichia coli Proteins/chemistry
  • Factor For Inversion Stimulation Protein/chemistry
  • Gene Expression Regulation, Bacterial
  • Models, Molecular
  • Mutation
  • Promoter Regions, Genetic
  • Protein Interaction Domains and Motifs
  • Response Elements
  • Serine Endopeptidases/genetics
  • Shigella sonnei/enzymology
  • Sigma Factor/chemistry
  • Transcription, Genetic
  • Uropathogenic Escherichia coli/enzymology


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