Figure 4.

Gel-mobility shift assays of C65F and C170F; 6, 12, 25, and 50 pmols of C65F (A, lanes 1–4) or C170F (B, lanes 6–9) were mixed with 25 pmols of ³²P-labeled synthetic 30-bp core-type DNA and incubated at room temperature for 20 min in 15 μl of buffer B (10 mM Tris, pH 7.5/50 mM NaCl/1 mM EDTA/1 mM DTT) plus 10% Ficoll. The reaction was analyzed by electrophoresis in 8% polyacrylamide (acrylamide:bis ratio 30:1). Lanes 5 and 10 show the DNA alone. (C) the same kind of analysis carried out under the same conditions, but in this case C65F (20 pmols) was mixed with 40 pmols of core-type DNA in the absence and presence of 40, 80, 120, 160, and 200 pmols of homologous (filled squares) or heterologous competitor (empty squares). The reaction was analyzed as above and quantitated by scanning the gels on a PhosphorImager (Molecular Dynamics).