Fig. 2. PKA induction of TTF1 transcriptional activity in PKA- and PKA+ cells. Increasing amounts of TTF1 cDNA plasmid were transiently cotransfected with TTF1-CAT reporter cDNA in the presence () or absence () of 2.5 µg of the C-PKA expression vector in A126 (A) or COS7 (B). Inset in A, CAT activity as function of C-PKA plasmid concentration in the presence of 0.2 µg of the TTF1 expression plasmid. The results represent means of four independent experiments and are expressed as a percentage of CAT enzymatic activity; bars, SD.