title: Heterogeneity in levels of vacuolating cytotoxin gene (vacA) transcription among Helicobacter pylori strains.
abstract: Broth culture supernatants from Tox+ Helicobacter pylori strains induce vacuolation of HeLa cells in vitro and contain VacA in concentrations that are higher than those found in supernatants from Tox- H. pylori strains. To investigate the basis for this phenomenon, we analyzed the transcription of the vacuolating cytotoxin gene (vacA) in eight Tox+ strains (each with a type s1/m1 vacA genotype) and nine Tox- strains (each with a type s2/m2 vacA genotype). Most of the Tox+ and Tox- strains tested used the same vacA transcriptional start point, but Tox+ strains yielded significantly stronger primer extension signal intensities than did Tox- strains (mean densitometry values of 15.8 +/- 1.9 versus 8.9 +/- 1.7, P = 0. 0016). Correspondingly, when we introduced vacA::xylE transcriptional fusions into the chromosomes of a Tox+ strain (60190) and a Tox- strain (86-313), the level of XylE activity in 60190 vacA::xylE was about 30-fold higher than that in 86-313 vacA::xylE. Sequence analysis and promoter exchange experiments indicated that the different levels of vacA transcription in these two strains cannot be explained solely by a difference in promoter strength. These data indicate that Tox+ and Tox- H. pylori strains typically differ not only in the VacA amino acid sequence but also in the level of vacA transcription.
authors.affiliation: Departments of Medicine and Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Forsyth
authors.forename: J C
authors.initials: JC
authors.lastname: Atherton
authors.forename: M J
authors.initials: MJ
authors.lastname: Blaser
authors.forename: T L
authors.initials: TL
authors.lastname: Cover
mesh_terms: D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000235:genetics*; D001427:Bacterial Toxins / Q000235:genetics*; D001483:Base Sequence; D016480:Helicobacter pylori / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D008969:Molecular Sequence Data; D010641:Phenotype; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C074689:VacA protein, Helicobacter pylori