Stable replication of plasmids derived from Epstein–Barr virus in various mammalian cells

Abstract

Epstein–Barr virus (EBV) infects human B lymphocytes, transforming the infected cells into dividing blasts that can proliferate indefinitely (see ref. 1 for a review). The viral genome of 172 kilobase pairs (kbp) is a plasmid in most transformed cells^2–4. 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 DNA⁵. 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^6–8. 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.