Identification of the origin of replication of bovine papillomavirus and characterization of the viral origin recognition factor E1.

Expression of the viral polypeptides E1 and E2 is necessary and sufficient for replication of BPV in mouse C127 cells. By providing these factors from heterologous expression vectors we have identified a minimal origin fragment from BPV that contains all the sequences required in cis for replication of BPV in short term replication assays. This same sequence is also required for stable replication in the context of the entire viral genome. The identified region is highly conserved between different papillomaviruses, and is unrelated to the previously identified plasmid maintenance sequences. The minimal ori sequence contains a binding site for the viral polypeptide E1, which we identify as a sequence specific DNA binding protein, but surprisingly, an intact binding site for the viral transactivator E2 at the ori is not required. The isolated origin shows an extended host region for replication and replicates efficiently in both rodent and primate cell lines.