Figure 7. Silencing of Sp1 and Sp3 reduces A3G promoter activity. (A) HeLa cells were transfected with 150 and 300 ng of unspecific, Sp1-specific or Sp3-specific siRNA. After 48 h, cells were harvested and Sp1 and Sp3 proteins were detected by western blot analysis. As loading control, protein levels of tubulin are shown. (B) HeLa cells were cotransfected with reporter plasmid pGL3-Basic containing 180 or 150 bp of the A3G promoter and siRNA. Hundred nanogram of unspecific siRNA (control), Sp1-specific siRNA (Sp1), Sp3-specific siRNA (Sp3) or a mixture of 50 ng Sp1-specific plus 50 ng Sp3-specific siRNA (Sp1+Sp3) were used. Firefly luciferase activities after 48 h were normalized to coexpressed renilla luciferase activities. Mean values (±SD) of a representative experiment performed in triplicate are shown.