EMSAs with nuclear extracts from different cell lines show different levels of Sp1 and Sp3 binding to the GC-/GA-rich oligonucleotide.

(A) Oligonucleotide sequence used for electrophoretic mobility shift assays. (B-E) HeLa and PC3 nuclear extracts, 10 μg each, were used in each lane with approximately 5 fmoles of labeled oligonucleotide. Competitions were done with 100-fold excess of cold oligonucleotides, and 2 μg of polyclonal antibodies were employed when required. On the left are indicated the Sp1 and Sp3 specific bands: mSp1 and mSp3 = multiple Sp1 and Sp3; lSp3 = long Sp3 isoforms; sSp3 = short Sp3 isoforms. Sp1/DNA complex is identified with asterisks. Panels C and E are simply overexposures of the autoradiograms shown in panels B and D. HeLa (B,C) and PC3 (D,E) nuclear extracts show that both Sp1 and Sp3 bind to the GC-/GA-rich oligonucleotide, albeit with different efficiencies.