Transactivation properties of Gal4-fusion constructs containing full-length wild-type or (Ser¹⁶⁹ → Ala) mutant p45: effect of 8-Br-cAMP. BHK cells were transfected with 100 ng of the reporter pGAL4-Luc, 50 ng of the β-galactosidase expression vector pRSV-βGal (internal control), and the indicated amounts of transactivator plasmid [pGal4/p45(wt), triangles; pGal4/p45(mut), squares; pSG424, diamonds]. The total amount of transfected DNA was kept constant by the addition of carrier DNA. Half of the cultures were treated with 1 mmol/L 8-Br-cAMP for 8 hours before harvesting to activate endogenous A-kinase (dashed lines and filled symbols). Reporter gene activities were determined as described in Materials and Methods; luciferase activity was normalized to β-galactosidase activity in each sample to correct for transfection efficiencies. Results represent the mean ± SD of three independent experiments.