The minimum essential domain of β/SMMHC for protection of RUNX1. (A) Various deletion constructs of RUNX1 were coexpressed in P19 cells with either β165 or β/SMMHC, and WCEs were subjected to Western blotting. Numbers at the top represent what amino acids remain in the mutant protein. (B) RUNX1 expression plasmid (1 μg) was cotransfected with expression plasmids for various PEBP2β informs (1 μg) as well as those for deletion constructs of β/SMMHC (1 μg) and WCEs were subjected to Western blotting. (C) Schematic diagram of β/SMMHC derived constructs.