Abstract

Adherence of Helicobacter pylori to the gastric epithelial cell line AGS strongly induces expression of fliK encoding a flagellar hook-length control protein. FliK has a role in triggering dissociation of the alternate sigma factor, σ28, from a nonfunctional σ28-FlgM complex, releasing free, functional σ28. The σ28-RNA polymerase initiates transcription of cagA, the major virulence gene, from a promoter identified in this study. Consequently, significant up-regulation of cagA was observed in AGS-adhered H. pylori. Direct binding of σ28 to the cagA promoter was demonstrated by chromatin immunoprecipitation and the transcription start site was identified by 5′ RACE (rapid amplification of complementary DNA ends). The σ28-dependent cagA promoter was active specifically in AGS-adhered H. pylori, and this motif might be associated with high cagA expression and severity of disease. These results also indicate that H. pylori has evolved to integrate expression of the major virulence gene cagA with the flagellar regulatory circuit, essential for colonization of the human host.

You do not currently have access to this article.