FIG. 1.

(A) MEF2 and ATF sites are required for EGF induction of the c-jun promoter. HeLa cells were transiently transfected with the c-jun pGL3-luciferase reporter plasmids, as indicated, and pCMV-β-galactosidase as an internal control. After transfection, the cells were serum starved and treated with or without EGF (100 ng/ml) for 3 h before preparing cell lysates for luciferase and β-galactosidase assays. The fold induction of luciferase activity in EGF-treated cells relative to untreated cells is shown. Values shown are the averages of at least two separate experiments done in duplicate ± standard errors of the means. (B) c-jun promoter constructs. The positions of binding sites for the transcription factors SP1, CTF, ATF, and MEF2 are indicated. The ATF site was previously referred to as an AP1-like element. The regions of the c-jun promoter in each construct are indicated. Point mutations in the ATF or MEF2 sites are indicated (x). LUC, luciferase.