Figure 7.
Role of ERK in cyclin D1 gene promoter activity and DNA synthesis in HepG2 cells. Tymidine incorporation into DNA has been evaluated as described in MATERIALS AND METHODS on HepG2 cells pretreated 15 min with the mitogen-activated protein kinase kinase inhibitors PD98059 (PD) and U0126 (U0) (10 μM) and then stimulated 6 h with vehicle (C) or E2 (10 nM) (a). Luciferase assay detection on HepG2 cells transfected with pXP2-D1–2966-luciferase and than stimulated 6 h with vehicle (C) or E2 (10 nM) after 15 min of pretreatment with the MAP kinase pathway inhibitors PD98059 (PD) and U0126 (U0) (10 μM) (b). Data are expressed as percentage of variation with respect to the controls and are the means ± SD of four independent experiments. *P < 0.001, compared with respective control values (C), determined using Student's t test. °P < 0.001, compared with respective E2 values, determined using Student's t test.