The transcription factor nuclear factor I mediates repression of the GLUT4promoter by insulin

Insulin represses GLUT4 expression in 3T3-L1 adipocytes through an insulin response element located at bases -706 to -676 in the 5'-flanking sequence. Nuclear proteins related to the nuclear factor I (NF1) family of transcrip tion factors bind to this insulin response element. Mutations that disrupt binding of NF1 proteins to the insulin response element impair the insulin response in reporter gene assays. Insulin treatment of 3T3-L1 adipocytes in duces a rapid change in the level of phosphorylation of NF1 proteins, provi ding a potential mechanism for insulin's ability to regulate gene expressio n through NF1. Another as yet unidentified protein, not related to NF1, als o binds to the GLUT4 insulin response element and is able to mediate partia l repression of the GLUT4 promoter in reporter gene assays.