FIG. 5.

RPA outcompetes E1 for the binding of ssDNA. A radiolabeled 31-nt oligonucleotide (2 fmol) was incubated at 25°C for 20 min with purified BPV1 E1 (10 pmol), RPA (ranging from 0 to 15 fmol), or both proteins, as indicated. The reaction mixtures were cross-linked with glutaraldehyde and subjected to nondenaturing PAGE and phosphorimager analysis. E1 (on the left) indicates the migration of the probe with E1 alone. RPA-1 indicates the migration of the probe with RPA alone, while RPA-2 indicates a second shift of the probe with RPA when higher concentrations of RPA were used. The migration of the probe alone is also indicated (Free Probe).