FIG. 6.

SP-1 binds to the c-myc and c-myb E2F elements. (A) Complex formation in assays employing X50-7 nuclear extracts and a radiolabeled E2Fmyb-m7-9 probe. Reaction mixtures were incubated in the absence (None) or in the presence of the indicated antibodies (Ab). (B) Binding of recombinant SP-1 to a TK-SP1 or to the indicated E2F elements. Binding reactions were performed with 0.5 footprint units of baculovirus-generated SP-1 (Promega). (C) Competition analysis of complexes formation in assays using X50-7 nuclear extracts and either an E2Fmyb-wt (lanes 1 to 7) or E2Fdhfr (lanes 8 to 14) probe. Reaction mixtures were incubated in the absence or in the presence of the indicated antibodies: anti-SP-1 (lanes 2, 3, 5, 9, 10, and 13), preimmune anti-DP-1 (P.I.; lanes 3, 4, 10, and 11), anti-DP-1 (lanes 5 to 7 and 12 to 14), and anti-c-Myc (lanes 7 and 14).