Figure 7. Hypoxia-inducible factor-1 (HIF-1) binds to the hypoxia response element (HRE) in the 3β-hydroxysteroid dehydrogenase type 1 (Hsd3b1) promoter. Electromobility shift assay was used to determine the binding of the HIF-1 protein present in TM3 Leydig cells treated or not with 250 µM CoCl₂ for 24 hours. The HIF-1 binding was competed/supershifted (Ss) by an HIF-1 antiserum (HIF-1). HIF-1 binding was also challenged by increasing doses (black triangles; molar excesses of 5x and 25x) of unlabeled oligonucleotides corresponding to the wild-type –1012-bp HRE (wt) or the –1012-bp HRE mutated from CACGT to CAATT (mut). P.I. indicates preimmune serum.