The Epstein-Barr virus origin of plasmid replication, oriP, contains both the initiation and termination sites of DNA replication

Epstein-Barr virus (EBV) oriP contains two components, a dyad symmetry element and a direct repeat element, that, in the presence of EBV nuclear antigen 1, are necessary and sufficient for plasmid replication. We have examined the replicative forms generated by EBV oriP using 2D gel electrophoresis. The patterns obtained from an oriP plasmid in a transfected cell line indicate that the site of initiation of DNA replication is at or very near the dyad symmetry element, while the direct repeats contain a replication fork barrier and the termination site. Thus, replication from oriP proceeds in a predominantly unidirectional manner. The patterns obtained from cells immortalized by EBV suggest that replication from oriP proceeds similarly in the viral genome.