title: Role of dioxin response element and nuclear factor-kappaB motifs in 2,3,7,8-tetrachlorodibenzo-p-dioxin-mediated regulation of Fas and Fas ligand expression.
abstract: We have demonstrated previously that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) up-regulates Fas and FasL in immune cells, although the molecular mechanisms remain unknown. We investigated the regulation of Fas or FasL promoter by TCDD in EL4 T cells using luciferase reporter constructs. We observed 20 +/- 5- and 14 +/- 4-fold induction of promoter activity for Fas and FasL, respectively, after TCDD exposure. The induction of luciferase was significantly reduced (2 +/- 1-fold) in the presence of alpha-naphthoflavone, an aryl hydrocarbon receptor (AhR) antagonist. We noted the presence of a dioxin response element (DRE) and five nuclear factor-kappaB (NF-kappaB) motifs on Fas promoter, and no DRE but two NF-kappaB motifs on FasL promoter. When we investigated the role of DRE and NF-kappaB, we observed varying levels of luciferase induction (9 +/- 2-fold for DRE and 8 +/- 2-fold for NF-kappaBs of Fas promoter and 6 +/- 3-fold for NF-kappaBs of FasL promoter). Mutations in DRE of Fas promoter or NF-kappaBs of FasL promoter led to decreased luciferase induction, further supporting our results. Probes for DRE or NF-kappaB motifs of Fas and/or FasL promoters demonstrated mobility shift in the presence of nuclear extract from TCDD-treated EL4 cells. Furthermore, we observed supershift in mobility when DRE and NF-kappaB probes were incubated in the presence of anti-mouse AhR, and anti-NF-kappaB (RelA/p65 and p50) antibodies, respectively. Administration of TCDD into mice caused significant increase in Fas and FasL transcripts in thymus and liver. These data demonstrate that TCDD regulates Fas and FasL promoters through DRE and/or NF-kappaB motifs via AhR.
authors.affiliation: Department of Pathology, University of South Carolina School of Medicine, Columbia, South Carolina, USA.
authors.forename: Narendra P
authors.initials: NP
authors.lastname: Singh
authors.forename: Mitzi
authors.initials: M
authors.lastname: Nagarkatti
authors.forename: Prakash S
authors.initials: PS
authors.lastname: Nagarkatti
mesh_terms: D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D017931:DNA Primers; D053222:Fas Ligand Protein / Q000187:drug effects / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D016399:Lymphoma, T-Cell; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000502:physiology*; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019014:fas Receptor / Q000187:drug effects / Q000235:genetics*
chemical_list: D017931:DNA Primers; D053222:Fas Ligand Protein; D016328:NF-kappa B; D000072317:Polychlorinated Dibenzodioxins; D019014:fas Receptor