IL-3–induced activation of the reporter gene in Ba/F3 cells. Cells were transfected with 50 μg of the reporter gene carrying 0.8-kb promoter region linked to luciferase gene and 5 μg of pSV2neo by electroporation. After culture in the presence of 1 mg/mL G418 for 2 weeks, a pool of G418-resistant cells was starved for 16 hours in the absence of growth factor and then stimulated with (•) or without (○) 10 ng/mL IL-3 for the indicated periods. Cell extracts were prepared and luciferase activity was measured.