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.

Abstract

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. Originally published Biochemical Journal, Vol. 338, No. 3, Mar 1999