FIG. 5.

E-box elements are required for full activity of the E2F3a promoter in response to stimulation of cell proliferation. Effects of mutation of Myc binding sites on growth stimulated the expression of the E2F3a promoter. REF52 cells were transfected with 4 μg of the wild-type E2F3a-luciferase plasmid (□) or the mutant E2F3a (E-box−)-luciferase plasmid (■), together with 2 μg of CMV–β-galactosidase. Transfected cells were treated as described in Fig. 2, and the luciferase and β-galactosidase activities were measured. The luciferase activity was normalized to the β-galactosidase activity.