AML1-ETO works as a repressor or an activator of transcription. (A) Binding of AML1-ETO at sites associated with repressed genes leads to displacement of AML1 (that binds DNA as heterodimer with core-binding factor β [CBFβ] to sites with a slightly different motif) and recruitment of CoR complexes that lead to reduced transcription. (B) Binding of AML1-ETO at sites associated with activated genes occurs in combination with other transcription factors (AP1 characterized in this study) and recruitment of coactivator (CoA) complexes. In this case, AML1 is not displaced and stays at its own binding site, and the amount of AML1-ETO present is less than observed at repressed genes.