Western blot analysis after high-resolution 2-D gel electrophoresis (2-DGE) of Sp1 and its phosphorylated forms. Nuclear proteins (75 μg) isolated from untreated parental (A, E) and antifolate-resistant EDX^R0.03 cells (B, F), as well as pCPT-cGMP-treated EDX^R0.03 cells (C, G) and pCPT-cGMP plus okadaic acid (OA)-treated EDX^R0.03 cells (D, H) were subjected to high-resolution 2-DGE. The blots were then reacted with an antibody to Sp1 to detect nonphosphorylated (arrow) as well as phosphorylated forms of Sp1 (dashed arrow).