title: Mechanism of 1α,25-dihydroxyvitamin D(3)-dependent repression of interleukin-12B.
abstract: Interleukin 12 (IL-12) is a heterodimeric, pro-inflammatory cytokine that plays a central role in activation and differentiation of CD4(+) T cells into interferon-γ secreting T-helper type 1 cells. IL-12B, a gene encoding the larger subunit of active IL-12, has been reported to be down-regulated by the nuclear hormone 1α,25-dihydroxyvitamin D(3) (1α,25(OH)(2)D(3)), but the mechanism of the regulation is unknown. In this study, we have examined the molecular mechanism of transcriptional regulation of the IL-12B gene by 1α,25(OH)(2)D(3) in lipopolysaccharide (LPS)-treated human monocytes (THP-1). Quantitative RT-PCR showed that IL-12B mRNA displays a cyclical expression profile and is down-regulated 2.8-fold during the first 8h and even 12.1-fold 24h after exposure to 1α,25(OH)(2)D(3). Gel shift and quantitative chromatin immunoprecipitation (ChIP) assays demonstrated vitamin D receptor (VDR) binding to genomic regions 480 and 6300bp upstream of the IL-12B transcription start site (TSS). Quantitative ChIP assays also revealed that together with VDR and its partner RXR the above regions recruited the co-repressor NCOR2/SMRT and histone deacetylase 3 leading to a decreased histone 4 acetylation and increased histone 3 trimethylation at the IL-12B promoter and its TSS. We suggest that these repressive epigenetic changes eventually cause down-regulation of IL-12 expression. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.
authors.affiliation: Department of Biosciences, University of Eastern Finland, FI-70211 Kuopio, Finland.
authors.forename: Petra
authors.initials: P
authors.lastname: Gynther
authors.forename: Sari
authors.initials: S
authors.lastname: Toropainen
authors.forename: Juha M
authors.initials: JM
authors.lastname: Matilainen
authors.forename: Sabine
authors.initials: S
authors.lastname: Seuter
authors.forename: Carsten
authors.initials: C
authors.lastname: Carlberg
authors.forename: Sami
authors.initials: S
authors.lastname: Väisänen
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D019295:Computational Biology; D044127:Epigenesis, Genetic / Q000187:drug effects; D020869:Gene Expression Profiling; D015894:Genome, Human / Q000235:genetics; D006801:Humans; D053762:Interleukin-12 Subunit p40 / Q000235:genetics* / Q000378:metabolism; D008024:Ligands; D008969:Molecular Sequence Data; D055503:Protein Multimerization / Q000187:drug effects; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D047488:Retinoid X Receptors / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D024363:Transcription Initiation Site; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: C500879:IL12B protein, human; D053762:Interleukin-12 Subunit p40; D008024:Ligands; D018167:Receptors, Calcitriol; D012097:Repressor Proteins; D047488:Retinoid X Receptors; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C118756:dihydroxy-vitamin D3; D014807:Vitamin D