FIG. 7.

Functional regulation of the c-myb promoter through the E2F element in asynchronous cells. (A) Schematic representation of the luciferase reporter plasmids used in panel B and Fig. 8. Wild-type (solid box) and mutant (dashed box) E2F and E2Fmyb-sp binding sites are shown as boxes; the presence of other elements in the c-myb promoter which were left unmodified is represented as semicircles labeled X and Y. (B) The indicated myb-Luc reporter plasmids containing wild-type or mutant E2F elements were cotransfected with pCMV-βgal into asynchronously growing Jurkat, U2OS, and NIH 3T3 cells; 40 h later, cell extracts were prepared and luciferase and β-galactosidase assays were performed. Luciferase values were normalized for β-galactosidase activity and represent the means of at least four different experiments. Luciferase activities of the indicated promoter reporter plasmids relative to cells transfected with myb(null)-Luc ± standard deviation (error bars) are shown.