FIGURE 4.

ZnPP associates with transcription factors Sp1 and Egr1 but not DNA. In A, increasing amounts of nuclear proteins extracted from HepG2 cells were incubated with 5 μm ZnPP, and then separated on an agarose gel. The protein complexes bound to ZnPP, shown as retention on the gel, were visualized under UV light. Varying amounts of bovine serum albumin (BSA) or rabbit IgG incubated with ZnPP served as controls. In B, the nuclear proteins were incubated with IgG, or anti-Sp1 and Egr1 antibodies and further incubated with ZnPP. The ZnPP-protein complexes were separated on the agarose gel and visualized under UV light. In C, the DNA fragments SE and non-SE were incubated with 5 μm ZnPP or vehicle, respectively, and then separated using PAGE. The ZnPP complex was visualized under UV light. In D, after the ZnPP bands shown in C were photographed, the gel was further stained with ethidium bromide and visualized under UV light to evaluate the migration of free DNA and DNA bound by ZnPP.