Sp1 activates PDGF-D transcription and mRNA expression. (A) SMCs were transfected with 30 μg Sp1 expression vector CMV-Sp1 or backbone vector CMV-gutless. Semiquantitative RT-PCR (left) or real-time PCR (right) was performed after 24 hours. (B) Transient cotransfection of CMV-Sp1 (1-3 μg) or the corresponding amount of CMV-gutless together with 10 μg p1168PDGF-Dluc to demonstrate Sp1 dependence. Promoter activity was assessed after 24 hours. Results are expressed as fold induction compared with backbone vector. (C) SMCs were cotransfected with 3 μg of Sp1 plasmid or dominant-negative Sp1 (pEBG-DN-Sp1), respectively, together with 10 μg p1168PDGF-Dluc. Luciferase activity was determined after 24 hours. The data are representative of at least 2 independent experiments. Error bars represent SEM performed in duplicate or triplicate. *P < .05 relative to control using Student t test.