FIG. 1.

(A) Schematic representation of the regulatory region of the human IR gene with HMGI-Y, Sp1, and C/EBPβ binding sites (uppercase) within C2 and E3 promoter elements. Contiguous binding sites are separated by shills. -, site on the minus strand. (B) EMSA of radiolabeled fragments C2 and E3 (0.2 ng each) with 2.5 ng of either HMGI-Y or pure Sp1, in the presence of 2.0 μg of BSA or 0.5 μg of 3T3-L1 nuclear extract (NE) and 0.2 μg of poly(dI-dC) as the competitor DNA. In supershift assays the protein was preincubated with 1 μg of the polyclonal antibody to HMGI-Y (lanes 2 and 9), Sp1 (lanes 4 and 11), or C/EBPβ (lanes 6 and 13) before addition of the probe. A, B, and C indicate binding of Sp1, C/EBPβ, and HMGI-Y, respectively.