Regulation of interleukin-8 gene at a distinct site of its promoter by CCAAT enhancer-binding protein homologous protein in prostaglandin E2-treated human T cells.
For a long period of time, the transcription factor CCAAT/enhancer-binding protein homologous protein (CHOP) has been thought to inhibit transcriptional activity for its ability to interact with CCAAT enhancer-binding protein family factors, thus preventing their binding to DNA. We have previously shown that in human T lymphocytes the CHOP phosphorylation induced by prostaglandin E(2) (PGE(2))-increased interleukin-8 (IL-8) gene expression. Given the CHOP positive role in the regulation of transcription, here we have investigated the molecular mechanism(s) by which CHOP increases IL-8 gene activity under PGE(2) stimulus. Transfection experiments with mutants showed both that the CHOP transactivation domain is essential for IL-8 transcription and that the IL-8/activator protein 1 (AP-1) promoter mutated in NF-kappaB and NF-IL-6, but not in the AP-1 site, harbors essential CHOP-responsive elements. CHOP silencing confirmed its role in the IL-8 transcriptional regulation and protein production, whereas c-Jun small interfering RNA experiments showed that the PGE(2)-induced activation of IL-8 promoter is mainly c-Jun-independent. Moreover, PGE(2) induced CHOP-DNA complexes only when the entire IL-8/AP-1 promoter or the wild type sequences encompassing the AP-1 upstream region were employed. Mutations introduced in these sequences prevented the DNA-CHOP complex formation. The IL-8/AP-1 mutant promoter lacking the sequence immediately upstream the AP-1 site is PGE(2)-unresponsive. Finally, chromatin immunoprecipitation data confirmed in vivo that PGE(2) induces CHOP binding to the IL-8 promoter. Taken together, our results suggest that the increased expression of CHOP in response to PGE(2) exerts a positive transcriptional regulation of the IL-8 promoter mediated by direct binding to a novel consensus site.
Cucinotta
Maria
M
Department of Experimental Pathology and Microbiology, University of Messina, Messina 98100, Italy.
Visalli
Maria
M
Aguennouz
Mohamed
M
Valenti
Andrea
A
Loddo
Saverio
S
Altucci
Lucia
L
Teti
Diana
D
D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics; D015232:Dinoprostone / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics*; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D013601:T-Lymphocytes / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D051742:Transcription Factor CHOP / Q000378:metabolism
D022762:CCAAT-Enhancer-Binding Proteins; C497249:DDIT3 protein, human; D016209:Interleukin-8; D018808:Transcription Factor AP-1; D051742:Transcription Factor CHOP; D015232:Dinoprostone
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