Figure 3.

Identification of bHLH proteins in the activator complex binding to the secretin E box. HIT nuclear extract was assayed by gel mobility shift. Binding reactions, containing 4 μg of nuclear extract, were initiated before the addition of 2 μl of IgG-purified anti-BETA2 antibodies, 0.2 μl of anti-Pan1, 0.02 μl of anti-Pan2, or 0.02 μl of anti-USF. Complex 1 disappears with anti-BETA2, anti-Pan1, or anti-Pan2. Complex 2 disappears with anti-USF.