FIG. 3.

Transcriptional activation of CBE reporter genes by the cAMP/PKA/CREB signaling pathway. (A) Activation of CBE reporter genes by cAMP-elevating agents. 293T and PC12 cells were transfected with p3xCBE-Luc (1 μg) and treated with or without forskolin plus IBMX (as indicated at the bottom). (B) CREB-dependent activation of the CBE reporter gene by PKA in PC12 cells. PC12 cells were transfected with the PKAc expression plasmid (0.1 μg) and various luciferase reporter plasmids (1 μg of each), together with dominant negative mutant CREBR287L (1 μg). (C) CREB-dependent activation of CBE reporter genes by PKA in Ba/F3 cells. Ba/F3 cells were electroporated with the PKAc expression plasmid (0.45 μg) and CBE luciferase reporter plasmid (3 μg), together with CREBR287L (0, 1.5 and 4 μg; shown as a triangle). Twenty hours after transfection, cell lysates were prepared and analyzed by luciferase assays. Data shown are representative results from three independent experiments performed in duplicate (in PC12 cells) or quadruplicate (in Ba/F3 cells). Luciferase activities are plotted in arbitrary units per microgram of total protein.