A, serum-deprived SMC were stimulated with PDGF (25 ng/ml) and analyzed for Ser-133-phosphorylated CREB by Western blotting. Cohybridization for total CREB was employed as control. B, serum-deprived SMC were preincubated with vehicle or PD98059 (10 μmol/liter) for 30 min and stimulated with PDGF (25 ng/ml) for 15 min. Whole cell lysates were analyzed for Ser-133-phosphorylated CREB and phosphorylated p44/42 MAPK. Cohybridization for total CREB and total p44/42 MAPK was employed as control. C, quiescent SMC were stimulated with PDGF (25 ng/ml) for the indicated time points. Following chromatin immunoprecipitation (IP) using a Ser-133-phospho-CREB antibody (4 μg) or control IgG, PCR analysis was performed using primer pairs that cover the CRE sites between −79 and −46 of the NOR1 promoter. Total extract (Input) was used as positive PCR control. D, serum-deprived SMC were preincubated with vehicle or PD98059 (10 μmol/liter) for 30 min prior to stimulation with PDGF (25 ng/ml) for 30 min. Chromatin immunoprecipitation of Ser-133-phosphorylated CREB to the endogenous NOR1 promoter was performed as described in C. All autoradiograms shown are representative of three independently performed experiments. DMSO indicates Me2SO.