FIG. 2.

The E1 DBD binds cooperatively with E2. In 10-μl binding reactions, 0.8, 0.4, 0.2, and 0.1 ng of E1(142–308) were incubated alone (lanes 4 to 7) or in the presence of either 0.1 ng of full-length E2 (lanes 8 to 10) or 18 pg of the E2 DBD (lanes 11 to 13). The probe used in the binding reactions contained the BPV minimal ori with a high-affinity E2 binding site (BS12H). After 30 min of incubation at room temperature, the reaction mixtures were loaded directly onto a 5% polyacrylamide gel.