Peroxisome proliferator-activated receptor gamma-dependent repression of the inducible nitric oxide synthase gene.
The peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the nuclear receptor superfamily that activates target gene transcription in a ligand-dependent manner. In addition, liganded PPARgamma can inhibit transcription of genes induced by gamma interferon (IFN-gamma) and/or lipopolysaccharides (LPSs), including the inducible nitric oxide synthase (iNOS) gene. Inhibition of the iNOS promoter is achieved partially through antagonizing the activities of NF-kappaB, AP-1, and STAT1, which are known to mediate effects of LPS and IFN-gamma. Previous studies have suggested that transrepression of these factors by nuclear receptors involves competition for limiting amounts of the general coactivators CREB-binding protein (CBP) and p300. CBP and p300 are thought to be recruited to nuclear receptors through bridging factors that include SRC-1, although CBP also interacts directly with PPARgamma through its amino terminus. These observations have raised questions concerning the involvement of SRC-1-like factors in CBP recruitment and transrepression. We here provide evidence that PPARgamma's ability to repress iNOS transcription requires the ligand-dependent charge clamp that mediates interactions with CBP and SRC-1. Single amino acid mutations in PPARgamma that abolished ligand-dependent interactions with SRC-1 and CBP not only resulted in complete loss of transactivation activity but also abolished transrepression. Conversely, a CBP deletion mutant containing the SRC-1 interaction domain but lacking the N-terminal PPARgamma interaction domain was inactive as a PPARgamma coactivator and failed to rescue transrepression. Together, these findings are consistent with a model in which transrepression by PPARgamma is achieved by targeting CBP through direct interaction with its N-terminal domain and via SRC-1-like bridge factors.
Li
M
M
Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla 92093-0651, USA.
Pascual
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G
Glass
C K
CK
D000818:Animals; D001665:Binding Sites; D050882:CREB-Binding Protein; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D005786:Gene Expression Regulation; D051548:Histone Acetyltransferases; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D009154:Mutation; D019001:Nitric Oxide Synthase / Q000235:genetics* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D056920:Nuclear Receptor Coactivator 1; D010766:Phosphorylation; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D000077154:Rosiglitazone; D013844:Thiazoles / Q000494:pharmacology; D045162:Thiazolidinediones; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D013844:Thiazoles; D045162:Thiazolidinediones; D015534:Trans-Activators; D014157:Transcription Factors; D000077154:Rosiglitazone; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D050882:CREB-Binding Protein; C494364:Crebbp protein, mouse; D051548:Histone Acetyltransferases; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1