Role of the RNA-Binding Protein Tristetraprolin in Glucocorticoid-Mediated Gene Regulation

Division of Allergy and Clinical Immunology, Johns Hopkins University, Baltimore, MD 21224, USA.
The Journal of Immunology (Impact Factor: 4.92). 06/2008; 180(12):8342-53. DOI: 10.1016/j.jaci.2006.11.653
Source: PubMed


Glucocorticoids (GCs) are the mainstay of anti-inflammatory therapy. Modulation of posttranscriptional regulation (PTR) of gene expression by GCs is a relevant yet poorly characterized mechanism of their action. The RNA-binding protein tristetraprolin (TTP) plays a central role in PTR by binding to AU-rich elements in the 3'-untranslated region of proinflammatory transcripts and accelerating their decay. We found that GCs induce TTP expression in primary and immortalized human bronchial epithelial cells. To investigate the importance of PTR and the role of TTP in GC function, we compared the effect of GC treatment on genome-wide gene expression using mouse embryonic fibroblasts (MEFs) obtained from wild-type and TTP(-/-) mice. We confirmed that GCs induce TTP in MEFs and observed in TTP(-/-) MEFs a striking loss of up to 85% of GC-mediated gene expression. Gene regulation by TNF-alpha was similarly affected, as was the antagonistic effect of GC on TNF-alpha-induced response. Inflammatory genes, including cytokines and chemokines, were among the genes whose sensitivity to GCs was affected by lack of TTP. Silencing of TTP in WT MEFs by small interfering RNA confirmed loss of GC response in selected targets. Immunoprecipitation of ribonucleoprotein complexes revealed binding of TTP to several validated transcripts. Changes in the rate of transcript degradation studied by actinomycin D were documented for only a subset of transcripts bound to TTP. These results reveal a strong and previously unrecognized contribution of PTR to the anti-inflammatory action of GCs and point at TTP as a key factor mediating this process through a complex mechanism of action.

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Available from: Faoud Ishmael, Jan 07, 2015
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    • "RNA-IP was performed as described previously (Ishmael et al. 2008). Briefly, differentiated C2C12 cells in six-well plate (CellStar) were lysed in 250 μl of polysome lysis buffer (100 mM KCL, 5 mM MgCl2, 10 mM HEPES (pH 7.0), 0.5% Nonidet P-40, 1 mM DTT, 100 U/ml RNaseOUT (Invitrogen), 0.2% vanadyl-ribonucleoside complex (New England Biolabs), Protease Inhibitor Cocktail (Roche)) and centrifuged at 12000 rpm for 15 minutes at 4°C. "
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