E2F1 is a potent positive regulator of δ-catenin transcription. (A) β-catenin/LEF-1, NICD (a binding protein of RBP-Jkappa), and E2F1, together with a different human δ-catenin-lucferase vector (BK1, 3, 4, 5), were co-transfected into 4 different cell lines (MEFs, SH-SY5Y, CWR22-Rv1, and MDCK cells) as indicated. E2F1 induced dramatic increases in δ-catenin-luciferase activity regardless of cell types and reporter vectors used. (B) E2F1 increased δ-catenin-luciferase activities in a concentration-dependent manner. The expression of E2F1 was confirmed using Western blot analysis (bottom panel).