Tumour necrosis factor-alpha regulates expression of the CCAAT-enhancer-binding proteins (C/EBPs) alpha and beta and determines the occupation of the C/EBP site in the promoter of the insulin-responsive glucose-transporter gene in 3T3-L1 adipocytes.
We have demonstrated previously that treatment of 3T3-L1 adipocytes with tumour necrosis factor-alpha (TNF) results in a rapid (4 h) and significant (75-80%) reduction in the rate of transcription of the GLUT4 gene. Control of GLUT4 gene transcription has been suggested at least in part to reside with the CCAAT-enhancer-binding protein (C/EBP) family (alpha, beta and delta isoforms) of transcription factors. Using electrophoretic mobility shift assays, we have examined the ability of TNF to alter the occupation of the C/EBP site in the GLUT4 promoter. The data suggest that in fully differentiated adipocytes the C/EBP site is a ligand for predominantly alpha/alpha homodimers; however, after exposure to TNF, a shift in occupancy of the site occurs and the ligands become alpha/beta heterodimers and beta/beta homodimers. Partner selection in dimer formation appears to be controlled by selective translocation of the beta-isoform from the cytosol to the nucleus after exposure of the cells to TNF.
Department of Biochemistry, School of Medicine, East Carolina University, Greenville, NC 27858, USA.
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D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D004247:DNA; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000235:genetics*; D009124:Muscle Proteins; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D011994:Recombinant Proteins; C495693:Slc2a4 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D004247:DNA