Figure 5.

In the mammalian expression plasmid GAL4 DBD/ETO, ETO is fused with the GAL4 DBD (amino acids 1–147). The firefly luciferase reporter gene is driven by the TK promoter with four copies of the GAL4 DNA-binding site upstream. (A) ETO exhibited potent, dose-dependent, transcriptional repression. (B) GAL4 DBD alone partially relieved repression by GAL4 DBD/ETO, due to competition for GAL4 binding sites. When AML1/ETO or RARα LBD, both driven by the cytomegalovirus promoter, were cotransfected with GAL4 DBD/ETO, the repressive effects of ETO were almost abrogated. The AML1/ETO fusion and RARα LBD may compete with ETO for HuN-CoR binding, leading to relief of repression.