Identification of EMSA complex components by antibody interference. Parental 32Dcl3, 32Dβ8, and 32Dαβ cell lines were treated, and the lysates prepared as described in Materials and Methods. Lysates obtained from cells treated with 200 pmol/L mGM-CSF were treated with STAT5a, STAT5b, STAT3, STAT1, or preimmune serum before incubation with radiolabeled DR probe. EMSA was then performed on 5.3% polyacrylamide gels, which were visualized by autoradiography.