AML1 DNA binding in UT7-Mpl cells. AML1 DNA binding is independent of TPO stimulation. Nuclear extracts were prepared from 1 × 10⁷ UT7-Mpl cells either nonstimulated (lane 1) or stimulated with 10 nM TPO for 1 hour (lane 2). The γ³²P-labeled IEX-1 probe was incubated with 10 μg of the nuclear extracts and subjected to electrophoretic mobility shift analysis. Where indicated, either antibody to AML1 (lane 3), unlabeled wild-type probe (lane 4), or the unlabeled AML1 mutated probe (lane 5) was added to the binding reaction mixtures. The asterisk indicates the nonspecific complex formed. The arrows indicate the complexes supershifted in the presence of an anti-AML1 antibody (αAML1). Rabbit IgG antibody was used as control for the supershift.