Figure 14.

Functional role of HBE and CRE sites within the proximal promoter of IGF-I gene in glucagon-induced IGF-I promoter activity in αT3 cells. Site-directed mutation and PCR-based truncation were conducted in (A) the HBE site (as “mHBE” and “ΔHBE,” respectively) and (B) CRE site (as “mCRE” and “ΔCRE,” respectively) within the IGF-I promoter of pIGF1(-112).Luc. After that, the constructs with HBE and CRE mutation/truncation were used for co-transfection studies in αT3 cells together with the expression vector for HNF1α and CREB, respectively, followed by a 24-h treatment with glucagon (100 nM). In these experiments, parallel transfection with the wild type pIGF1(-112).Luc was used as the control. After drug treatment, cell lysate was prepared and used for luciferase activity measurement.