title: The role of Sp1 in IL-1beta and H. pylori-mediated regulation of H,K-ATPase gene transcription.
abstract: Helicobacter pylori infection of the gastric body induces transient hypochlorhydria and contributes to mucosal progression toward gastric carcinoma. Acid secretion is mediated by parietal cell H,K-ATPase, in which the catalytic alpha-subunit (HKalpha) promoter activity in transfected gastric epithelial [gastric adenocarcinoma (AGS)] cells is repressed by H. pylori through NF-kappaB p50 homodimer binding to the promoter. IL-1beta, an acid secretory inhibitor whose mucosal level is increased by H. pylori, upregulates HKalpha promoter activity in AGS cells. Because IL-1beta also activates NF-kappaB signaling, we investigated disparate HKalpha regulation by H. pylori and IL-1beta, testing the hypothesis that IL-1beta-induced HKalpha promoter activation is mediated by the transcription factor Sp1. DNase I footprinting revealed Sp1 binding to the HKalpha promoter at -56 to -39 bp. IL-1beta stimulated the activity of three HKalpha promoter constructs containing NF-kappaB and Sp1 sites transfected into AGS cells and also stimulated a construct containing only an Sp1 site. This stimulation was abrogated by mutating the HKalpha promoter Sp1 binding site. Gelshift assays showed that IL-1beta increased Sp1 but not p50 binding to cognate HKalpha probes and that Sp1 also interacts with an HKalpha NF-kappaB site when bound to its cognate HKalpha cis-response element. H. pylori did not augment Sp1 binding to an HKalpha Sp1 probe, and small interfering RNA-mediated knockdown of Sp1 expression abrogated IL-1beta-induced HKalpha promoter stimulation. We conclude that IL-1beta upregulates HKalpha gene transcription by inducing Sp1 binding to HKalpha Sp1 and NF-kappaB sites and that the H. pylori perturbation of HKalpha gene expression is independent of Sp1-mediated basal HKalpha transcription.
authors.affiliation: Medical Univ. of South Carolina, Charleston, SC 29425, USA.
authors.forename: Arindam
authors.initials: A
authors.lastname: Saha
authors.forename: Charles E
authors.initials: CE
authors.lastname: Hammond
authors.forename: Monika
authors.initials: M
authors.lastname: Gooz
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Smolka
mesh_terms: D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D016480:Helicobacter pylori / Q000502:physiology*; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D011485:Protein Binding; D015398:Signal Transduction; D016329:Sp1 Transcription Factor / Q000378:metabolism*
chemical_list: D053583:Interleukin-1beta; D016328:NF-kappa B; D016329:Sp1 Transcription Factor; D048049:Extracellular Signal-Regulated MAP Kinases; D017506:H(+)-K(+)-Exchanging ATPase
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