AML1-ETO displaces the coactivator c-Jun from PU.1 by binding to the β₃β₄ region of PU.1.

(A) AML1-ETO physically binds to PU.1 in vitro. GST pull-down assay was performed using [³⁵S]-methionine–labeled in vitro–translated c-Jun (lane 1) or AML1-ETO (lane 4) incubated with equal amounts of bacterially expressed GST-PU.1 (lanes 2 and 5) or GST plus beads (lanes 3 and 6). GST-PU.1 or GST was recovered using glutathione-agarose beads and separated by SDS-PAGE prior to autoradiography. (B) AML1-ETO displaces c-Jun from binding to the β₃β₄ domain of PU.1. Saturating amounts of in vitro–translated c-Jun (20 μL) were incubated with GST-β₃β₄ and increasing amounts (from lanes 7-13) of in vitro–translated AML1-ETO (7.5-12.5 μL) were incubated. Densitometric quantification was also performed (given as percent input of the proteins).