Stable replication of plasmids derived from Epstein-Barr virus in various mammalian cells. 
Epstein-Barr virus (EBV) infects human B lymphocytes, transforming the infected cells into dividing blasts that can proliferate indefinitely.  The viral genome of 172 kilobase pairs (kbp) is a plasmid in most transformed cells.  We have identified a region of EBV DNA, termed oriP (nucleotides 7,333-9,109 of strain B95-8), which acts in cis to permit linked DNAs to replicate as plasmids in cells containing EBV DNA.  We have postulated the existence of a trans-acting gene allowing oriP function.  Here we report that this gene lies in a 2.6-kbp region of the viral genome (nucleotides 107, 567-110, 176) which encodes the EBNA-1 antigen.  We show that circular DNAs containing oriP, the EBNA-1 gene and a selectable marker replicate autonomously in cells derived from at least four developmental lineages and from at least three species.  We also find that the one-third of the EBNA-1 gene repetitive in sequence is not essential for the trans-acting function that EBNA-1 gives oriP.