Expression of a dominant-active mutant of FOXO3 results in up-regulation of Bim. BMCMCs were infected with a retrovirus encoding FOXO3(A3):ER and were left untreated (–) or incubated with 4-OHT (+) in the presence of SCF for the indicated time periods. The level of Bim was analyzed by Western blotting. As a control for possible toxic effects, uninfected cells were also treated with 4-OHT. Comparable results were obtained in at least 3 separate experiments. GAPDH indicates glyceraldehyde-3-phosphate dehydrogenase.