The bvg‐dependent promoters show similar behaviour in different Bordetella species and share sequence homologies

Abstract

The expression of the virulence-associated genes in Bordetella species is co-ordinately regulated by the gene products encoded by the bvg locus. In Bordetella pertussis the expression of this locus is regulated by the P1, P2, P3 and P4 promoters which are located in a 350 bp DNA fragment also containing the PFHA promoter. Here we report the transcriptional regulation of the bvg locus and the fha gene in Bordetella parapertussis and a sequence analysis of the bvg-regulated promoters. The Pp1, Pp2, Pp4 and PpFHA promoters are indistinguishable, both in transcription initiation sites and environmental regulation, from the corresponding promoters of B. pertussis, while the Pp3 promoter is not active. Sequence homologies from nine bvg-regulated promoters show a conserved dinucleotide, 5'-TG-3', at approximately one turn of helix upstream of the -10 5'-A.AaTat-3' region, and a 5'-TTTCC-3' sequence in the -90 region. Since the nucleotide sequence of the inactive Pp3 promoter shows several base substitutions with respect to the found sequence homologies, it is likely that some of these bases play an essential role in promoter activity.

Molecular characterization of Bordetella bronchiseptica filamentous haemagglutinin and its secretion machinery The GenBank accession numbers for the sequences reported in this paper are AF111794, AF111796, AF111797 and AF111798.

“…3 Two additional sites in the upstream region have been proposed to play important roles in transcriptional control. A TG sequence that has been previously identified (Scarlato et al, 1991) as a common feature of Bvg-regulated promoters is located upstream of the k11 position described above and remains conserved among these fhaB sequences. The second regulatory element consists of an imperfect inverted TTTCCTA repeat located at position k82 to k95 that is involved in binding of the phosphorylated transcription factor BvgA-P (Boucher et al, 1997 ;Karimova & Ullmann, 1997).…”

“…They also indicate that the nucleotide differences upstream of the transcriptional start site in the three species do not have a net effect on FHA promoter activity ; however, their possible effect on transcript stability and processing was not addressed. It is interesting to note that the nucleotide found at the k11 position in nine other Bvgregulated promoters is also an A (Scarlato et al, 1991). This nucleotide lies at the fourth position of a sequence in the k10 region, 5h-CAG(A\G)CT-3h, which bears some resemblance to the prokaryotic σ(!…”

“…In a fashion similar to that of B. pertussis Fha44, most of B. bronchiseptica Fha44 was not amenable to N-terminal Edman degradation, suggesting that the N-terminal residue of the B. bronchiseptica FHA is also blocked. In the first few cycles, minute chromatographic peaks corresponding to the QGLVP sequence were detectable (data not shown), (Roy et al, 1990 ;Scarlato et al, 1991). A dash indicates no corresponding nucleotide for this position.…”

“…Sequence comparison of the "180 bp promoter\ regulatory regions located 5h to the B. pertussis and B. bronchiseptica fhaB genes revealed a number of differences, most of which are located upstream of the transcriptional start site defined for B. pertussis fhaB 70 nt upstream of the ATG (Roy & Falkow, 1991 ;Scarlato et al, 1991) (Fig. 3).…”

“…A dash indicates no corresponding nucleotide for this position. Boxed regions indicate k10 promoter element and conserved TG located at k25 (Scarlato et al, 1991). An EcoRI site was incorporated into the reverse (anti-sense) PCR primer which led to changes in the fhaB sequence (underlined) and in the predicted protein sequence (hollow letters).…”