Domain-dependent impairment of RUNX1 and p300 phosphorylation by leukemogenic PEBP2-β-SMMHC fusion protein. (A) Determination of regions within PEBP2-β-SMMHC necessary for the repression of p300 phosphorylation. Wild-type PEBP2-β or deletion variants of PEBP2-β-SMMHC fusion proteins were coexpressed in HEK293 cells with RUNX1 and FLAG-p300. Western blot analyses were performed using the indicated antibodies. (B) Schematic diagrams depicting different PEBP2-β-SMMHC deletion constructs used in panel A. The region delineated to be important in the inhibition of RUNX1 phosphorylation is also indicated.