Genetic analysis of pertussis toxin promoter activation in Bordetella pertussis.
Bordetella pertussis regulates expression of its virulence factors such as pertussis toxin (Ptx) via the bvg locus, which encodes a two-component system composed of a sensor protein, BvgS, and a transcription activator, BvgA. We used a ptx-lac fusion on the B. pertussis chromosome to analyse promoter activation by alteration of specific sequences upstream of and within the promoter. Our data demonstrate that a pair of heptanucleotide inverted repeats separated by a turn of the DNA helix within the upstream repeat region (centred around nucleotide -136.5) are crucial cis-activating elements, and probably represent the initial BvgA-binding site. In addition, we demonstrate that the sequence between these repeats and the promoter plays a role in activation. Our data are most consistent with a model of co-operative binding of BvgA dimers to this intervening region and interaction with RNA polymerase at the promoter to activate ptx transcription. In the core promoter region both the non-consensus 21 bp spacing and the specific sequence between the -35 and -10 elements are crucial for promoter activity.
Marques
R R
RR
Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore 21201-1159, USA.
Carbonetti
N H
NH
D001483:Base Sequence; D001886:Bordetella pertussis / Q000235:genetics*; D002876:Chromosomes, Bacterial; D004269:DNA, Bacterial; D007763:Lac Operon; D008969:Molecular Sequence Data; D037342:Pertussis Toxin; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D017384:Sequence Deletion; D015533:Transcriptional Activation; D010566:Virulence Factors, Bordetella / Q000235:genetics*
D004269:DNA, Bacterial; D011993:Recombinant Fusion Proteins; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin