STUB1 inhibited transcriptional activity of RUNX1. 293T cells were cotransfected with pMSCFR-luc and expression vectors for RUNX1, CBFB, and STUB1. Transfection efficiency was normalized using fluorometric quantitation of enhanced green fluorescent protein in a cotransfection of pMYs-IG. All luciferase assays were performed in duplicates (data are shown as the mean ± S.E., *, p = 0.0054; **, p = 0.0055).