Transcriptional potential of AML1 mutants. (A) Transcriptional activities of the AML1 mutants in HeLa cells. Cells were transfected with 5 μg pM-CSF-R-luc, 3 μg FLAG-tagged AML1 or AML1 mutant expression vector, 1 μg CBFβ expression vector, and 0.25 μg pRL-tk as an internal control to normalize luciferase activities for transfection efficiency. (B) Transcriptional activities of the AML1 mutants in U937 cells. Cells were transfected with 2 μg pM-CSF-R-luc reporter plasmid, the indicated amounts of AML1 expression constructs, and 0.2 μg pRL-tk as an internal control to normalize luciferase activities for evaluation of transfection efficiency. The expression vector containing wild-type AML1 (0.2 μg) was cotransfected with increasing doses (0, 0.1, 0.2, 0.4, and 0.6 μg) of expression vectors containing CBFβ-MYH11 or various AML1 mutations. Each value represents the mean of 3 independent experiments. The error bars indicate the mean ± standard deviation.