Context-dependent cooperation between nuclear factor κB (NF-κB) and the glucocorticoid receptor at a TNFAIP3 intronic enhancer: a mechanism to maintain negative feedback control of inflammation.
TNF expression is elevated in asthma and other inflammatory airway diseases that are commonly treated with glucocorticoid-based therapies, but the impact of glucocorticoids on negative feedback control of TNF is not well understood. We analyzed the effect of dexamethasone, a potent synthetic glucocorticoid, on TNF-regulated gene expression in cultured airway epithelial cells. Although dexamethasone-mediated activation of the glucocorticoid receptor (GR) potently repressed expression of IL1β, IL8, and several other pro-inflammatory TNF targets, the expression of anti-inflammatory TNF targets such as TNFAIP3 (A20) and NFKBIA was selectively spared or augmented by dexamethasone treatment. Despite divergent effects on gene expression, GR and NF-κB occupancy at the TNFAIP3 locus and GR-repressed targets was similar. A co-occupied intronic TNFAIP3 regulatory element mediated cooperative enhancement of transcription by GR and NF-κB that required the presence of a functional GR binding site (GBS). GBS exchanges between reporters for TNFAIP3 and FKBP5, a canonical GR-induced target, revealed substantial latitude in the GBS sequence requirements for GR/NF-κB cooperation, suggesting that the TNFAIP3 GBS acts primarily as a docking site in this context. Supporting this notion, a selective GR ligand with only weak agonist activity for induction of FKBP5 enabled robust GR/NF-κB cooperative induction of a mutant TNFAIP3 reporter harboring the FKBP5 GBS. Taken together, our data support a model in which the expression of anti-inflammatory targets of TNF is maintained during treatment with glucocorticoids through context-dependent cooperation between GR and NF-κB.
From the Department of Medicine, National Jewish Health, Denver, Colorado 80206.
Mohammed O
MO
Altonsy
Sarah K
SK
Sasse
Tzu L
TL
Phang
Anthony N
AN
Gerber
D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000276:immunology; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation / Q000235:genetics* / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000276:immunology; D007438:Introns; D016328:NF-kappa B / Q000276:immunology*; D009687:Nuclear Proteins / Q000235:genetics* / Q000276:immunology; D011965:Receptors, Glucocorticoid / Q000276:immunology*; D015533:Transcriptional Activation; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D011965:Receptors, Glucocorticoid; D014409:Tumor Necrosis Factor-alpha; C076529:TNFAIP3 protein, human; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3
Chromatin Immunoprecipitation (ChiP); Cooperativity; Glucocorticoid Receptor; NF-kappa B (NF-KB); Negative Feedback; TNFAIP3; Transcription Enhancers