Transcriptional Repression of the Interleukin-2 Gene by Vitamin D3: Direct Inhibition of NFATp/AP-1 Complex Formation by a Nuclear Hormone Receptor
| Autor: | I Alroy, Terri L. Towers, Leonard P. Freedman |
|---|---|
| Rok vydání: | 1995 |
| Předmět: |
Transcriptional Activation
Transcription Genetic Proto-Oncogene Proteins c-jun Receptors Retinoic Acid T-Lymphocytes Molecular Sequence Data Biology Calcitriol receptor Jurkat cells Cell Line Calcitriol Humans Amino Acid Sequence Promoter Regions Genetic Receptor Molecular Biology Transcription factor Psychological repression Base Sequence NFATC Transcription Factors Nuclear Proteins DNA Cell Biology Molecular biology DNA-Binding Proteins Transcription Factor AP-1 Enhancer Elements Genetic Retinoid X Receptors Nuclear receptor Vitamin D3 Receptor Mutation AP-1 Complex Interleukin-2 Receptors Calcitriol Proto-Oncogene Proteins c-fos Research Article Transcription Factors |
| Zdroj: | Molecular and Cellular Biology. 15:5789-5799 |
| ISSN: | 1098-5549 |
| DOI: | 10.1128/mcb.15.10.5789 |
| Popis: | T-lymphocyte proliferation is suppressed by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the active metabolite of vitamin D3, and is associated with a decrease in interleukin 2 (IL-2), gamma interferon, and granulocyte-macrophage colony-stimulating factor mRNA levels. We report here that 1,25(OH)2D3-mediated repression in Jurkat cells is cycloheximide resistant, suggesting that it is a direct transcriptional repressive effect on IL-2 expression by the vitamin D3 receptor (VDR). We therefore examined vitamin D3-mediated repression of activated IL-2 expression by cotransfecting Jurkat cells with IL-2 promoter/reporter constructs and a VDR overexpression vector and by DNA binding. We delineated an element conferring both DNA binding by the receptor in vitro and 1,25(OH)2D3-mediated repression in vivo to a short 40-bp region encompassing an important positive regulatory element, NF-AT-1, which is bound by a T-cell-specific transcription factor, NFATp, as well as by AP-1. VDR DNA-binding mutants were unable to either bind to this element in vitro or repress in vivo; the VDR DNA-binding domain alone, however, bound the element but also could not repress IL-2 expression. These results indicate that DNA binding by VDR is necessary but not sufficient to mediate IL-2 repression. By combining partially purified proteins in vitro, we observed the loss of the bound NFATp/AP-1-DNA complex upon inclusion of VDR or VDR-retinoid X receptor. Order of addition and off-rate experiments indicate that the VDR-retinoid X receptor heterodimer blocks NFATp/AP-1 complex formation and then stably associates with the NF-AT-1 element. This direct inhibition by a nuclear hormone receptor of transcriptional activators of the IL-2 gene may provide a mechanistic explanation of how vitamin derivatives can act as potent immunosuppressive agents. |
| Databáze: | OpenAIRE |
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