Novel Architectural Features of Bordetella Pertussis Fimbrial Subunit Promoters and Their Activation by the Global Virulence Regulator BvgA

Mol Microbiol. 2010 Sep;77(5):1326-40. doi: 10.1111/j.1365-2958.2010.07293.x.

Abstract

A prominent feature of the promoters of Bordetella pertussis fimbrial subunit genes fim2, fim3 and fimX is the presence of a 'C-stretch', a monotonic run of C residues. The C-stretch renders these genes capable of phase variation, through spontaneous variations in its length. For each of these we determined the length of the C-stretch that gave maximal transcriptional activity, and found that the three optimized promoters align perfectly, with identical distances between conserved upstream sequences and the downstream -10 elements and transcriptional start sites. We also demonstrated, for Pfim3, that the conserved sequence corresponds to BvgA binding sites. The more upstream of the two binding sites is predicted to be high affinity, by comparison to a functionally derived consensus BvgA-binding sequence. The other binding site is a fairly poor match to this consensus, with 10 of 14 bp belonging to the C-stretch. Interestingly, the centre of this downstream site of BvgA binding coincides exactly with the centre of the expected typical location of a -35 sequence. However, the lack of a recognizable -35 element (CCCCCC versus TTGACA), and the occupation of this site by BvgA∼P suggest that activation of the fim promoters involves unusual interactions among BvgA, RNA polymerase and promoter DNA.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Bordetella pertussis / genetics*
  • Bordetella pertussis / metabolism
  • Bordetella pertussis / pathogenicity*
  • Conserved Sequence
  • Enhancer Elements, Genetic
  • Fimbriae, Bacterial / genetics*
  • Fimbriae, Bacterial / metabolism*
  • Molecular Sequence Data
  • Promoter Regions, Genetic*
  • Protein Binding
  • Protein Subunits / biosynthesis
  • Protein Subunits / genetics
  • Transcription Factors / metabolism*
  • Transcription Initiation Site
  • Transcriptional Activation
  • Virulence

Substances

  • Bacterial Proteins
  • BvgA protein, Bacteria
  • Protein Subunits
  • Transcription Factors