Transactivation of the human insulin receptor gene by the CAAT/enhancer binding protein

Within human insulin receptor gene there are three consensus binding sites for the CAAT/enhancer binding protein (C/EBP). Two sites are located in the 5' flanking region and the other is in the first intron. We have studied the ability of these sequences to be regulated by C/EBP. A eukaryotic expression vector containing these sequences can be transactivated in a dose-dependent manner by a C/EBP expression vector when co-transfected into NIH-3T3 cells. In addition, double stranded oligonucleotides corresponding to two of these sequences can bind C/EBP in a gel retardation assay. These two oligonucleotides can complete with each other to bind C/EBP. These findings suggest that this transcription factor may play a role in the regulation of insulin receptor gene expression in vivo.