Expression of the Helicobacter pylori virulence factor vacuolating cytotoxin A (vacA) is influenced by a potential stem-loop structure in the 5′ untranslated region of the transcript

Karin R. Amilon, Darren P. Letley, Jody A. Winter, Karen Robinson, John C. Atherton*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The vacuolating cytotoxin, VacA, is an important virulence factor secreted by the gastric pathogen Helicobacter pylori. Certain vacA genotypes are strongly associated with disease risk, but the association is not absolute. The factors determining vacA gene expression are not fully understood, and the mechanisms of its regulation are elusive. We have identified a potential mRNA stem-loop forming structure in the 5′ untranslated region (UTR) of the vacA transcript. Using site-directed mutagenesis, we found that disruption of the stem-loop structure reduced steady-state mRNA levels between two- and sixfold (P=0.0005) and decreased mRNA half-life compared with wild type (P=0.03). This led to a marked reduction in VacA protein levels and overall toxin activity. Additionally, during stressful environmental conditions of acid pH or high environmental salt concentrations, when general transcription of vacA was decreased or increased respectively, the stabilising effects of the stem-loop were even more pronounced. Our results suggest that the stem-loop structure in the vacA 5′ UTR is an important determinant of vacA expression through stabilisation of the vacA mRNA transcript and that the stabilising effect is of particular importance during conditions of environmental stress.

Original languageEnglish
Pages (from-to)831-846
JournalMolecular Microbiology
Volume98
Issue number5
Early online date10 Sept 2015
DOIs
Publication statusPublished - Dec 2015
Externally publishedYes

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