FIGURE 6.

MEK1 activity promotes C/EBPβ binding to the RCAN1–4 promoter. EMSA was performed with nuclear extracts from neonatal rat ventricular myocytes infected with a Cn and/or constitutively active MEK1 adenovirus as indicated. A C/EBPβ consensus site (A) or template 2 (B) were used for EMSA. Excess cold C/EBPβ consensus binding template was used as a competitor in both experiments. C, neonatal rat ventricular myocytes were infected with Ad-RCAN1.4-Luc along with control adenoviruses or Ad-Cn as indicated. Two days after infection, cultures were treated with dimethyl sulfoxide (vehicle) or the MEK1 inhibitor U0126 (10 μm) for 4 h and then assayed for luciferase activity. Transfections were carried out in triplicate. Error bars indicate S.D. con, control.