Fig. 3. Sp1 and Sp3 transcription factor confer Sp1-site dependent VEGF/VPF promoter transactivation in a comparable fashion in Drosophila SL2 cells. Analysis of CAT expression derived from transiently transfected -88/+54 bp wild-type (wt) or -88/+54 Sp1 site-mutated (Sp1 mut) VEGF/VPF promoter-based construct (carrying critical 2 nucleotide mutations within the Sp1 sites; 5 µg each) along with expression vectors encoding Sp1 (pPacUSp1, 0.3 µg), Sp3 (pPacUSp3, 0.3 µg) and/or empty vector (pPacUbx, to compensate for differences in co-transfected DNA). The fold increase in CAT activity was calculated on the basis of data obtained from cells co-transfected with empty vector alone. Schematic representations of the wild-type and the mutated sequence are shown at the top (Sp1 sites underlined), the two nucleotide mutations are indicated by enlarged letter size. The data displayed represent the means±s.d. of five independent duplicate experiments. (Student's t-test; n.s., not significant; ^** P<0.01, compared to cells transfected with the wt vector).