title: CD40-mediated transcriptional regulation of the IL-6 gene in B lymphocytes: involvement of NF-kappa B, AP-1, and C/EBP.
abstract: Engagement of CD40 by its ligand CD154 induces IL-6 production by B lymphocytes. We previously reported that this IL-6 production is dependent upon binding of the adapter protein TNF receptor-associated factor 6 to the cytoplasmic domain of CD40, while binding of TNF receptor-associated factors 2 and 3 is dispensable, as is the activation-induced nuclear translocation of NF-kappa B. The present study was designed to characterize CD40-mediated transcriptional control of the IL-6 gene in B cells. CD40 engagement on B lymphocytes activated the IL-6 promoter, and mutations in the putative binding sites for AP-1 and C/EBP transcription factors reduced this activation. Interestingly, a mutation in the putative NF-kappa B binding site completely abrogated the basal promoter activity, thus also rendering the promoter unresponsive to CD40 stimulation, suggesting that this site is required for binding of NF-kappa B constitutively present in the nucleus of mature B cells. The expression of dominant negative Fos or C/EBP alpha proteins, which prevent binding of AP-1 or C/EBP complexes to DNA, also reduced CD40-mediated IL-6 gene expression. Furthermore, CD40 stimulation led to phosphorylation of c-Jun on its activation domain, implicating CD40-mediated Jun kinase activation in the transcriptional regulation of IL-6 production.
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Mekhine
authors.initials: M
authors.lastname: Baccam
authors.forename: So-Youn
authors.initials: SY
authors.lastname: Woo
authors.forename: Charles
authors.initials: C
authors.lastname: Vinson
authors.forename: Gail A
authors.initials: GA
authors.lastname: Bishop
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D022762:CCAAT-Enhancer-Binding Proteins / Q000502:physiology*; D019013:CD40 Antigens / Q000502:physiology*; D002460:Cell Line; D007075:Immunoglobulin M / Q000096:biosynthesis; D015850:Interleukin-6 / Q000235:genetics* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000502:physiology*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000276:immunology; D017434:Protein Structure, Tertiary; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D018808:Transcription Factor AP-1 / Q000502:physiology*; D014158:Transcription, Genetic / Q000276:immunology*; D015533:Transcriptional Activation / Q000276:immunology
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D019013:CD40 Antigens; D007075:Immunoglobulin M; D015850:Interleukin-6; D016328:NF-kappa B; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D012694:Serine