Transcription factor NF1 mediates repression of the GLUT4 promoter by cyclic-AMP

Prolonged treatment of 3T3-L1 adipocytes with 8-Br-cAMP decreases expressio n of GLUT4, the insulin-responsive glucose transporter. Expression of a pro moter-reporter gene construct that contained 785 base pairs of 5'-fIanking region of the murine GLUT4 gene was down regulated by 8-Br-cAMP (p < 0.001) , whereas expression of constructs that contained 641 or 469 base pairs of 5'-flanking region was not. A reporter gene construct in which bases -706 t o -676 were deleted was not repressed by 8-Br-cAMP, thereby identifying a 3 0 bp region as necessary for repression of the GLUT4 promoter by 8-Br-cAMP. Mutations in this regulatory element that disrupt binding of the transcrip tion factor NF1 abolish the 8-Br-cAMP-induced repression of the gene. Altho ugh insulin and cAMP both repress the GLUT4 promoter through this cis-eleme nt, they appear to do this through different mechanisms, as treatment with 8-Br-cAMP does not induce the phosphorylation of NF1 that is induced by ins ulin treatment. (C) 1999 Academic Press.