(A) PU.1 binding and PU.1-mediated Csf1r promoter activity of MLL deletion mutants. The PU.1-, menin-, and LEDGF-interacting domains and the results for interaction with PU.1 and PU.1-mediated transactivation of Csf1r-luc are indicated. ND, not determined (B–C) Pu.1 binding. 293T cells were co-transfected with wild-type or mutants of HA-tagged MLL and FLAG-tagged PU.1 (B), or with wild-type or mutants of FLAG-tagged MLL and HA-tagged PU.1 (C). Anti-FLAG antibody immunoprecipitates (IP:FLAG) or cell lysates (Input) were subjected to immunoblotting with anti-HA or anti-FLAG antibodies. (D) PU.1-mediated Csf1r promoter-driven transcription. SaOS2 cells were transfected with the Csf1r–luciferase construct and PU.1, together with deletion mutants of MLL. Luciferase activity was analyzed 24 h after transfection. Error bars represent SD (n = 3).