Physical association of GATA-1 with RUNX1 and with RUNX1-ETO. (A) Interaction of GATA-1 and RUNX1 in IP assays. HEK293T cells were cotransfected with pCMV-RUNX1 1-381, pEF-GATA-1, and pCMV-CBFβ, as indicated. Cellular extracts were immunoprecipitated (IP) using either rat anti–GATA-1 (N6) or rabbit anti-RUNX1 (rhd). Immunoprecipitates were immunoblotted (IB) with the indicated antibodies. (B) Interaction of GATA-1 and RUNX1-ETO. Immunoprecipitation–immunoblot assays were performed as in panel A, except that cells were transfected with pCMV-RUNX1-ETO instead of pCMV-RUNX1 1-381. (C) Participation of GATA-1, RUNX1, and CBFβ in a common complex. Immunoprecipitations were performed with rat anti–GATA-1 (N6) as in panel A, followed by immunoblotting with the indicated antibodies.