A Third Viral Nuclear Protein in Lymphoblasts Immortalized by Epstein--Barr Virus

Most sera from patients with rheumatoid arthritis as well as some sera from normal Epstein-Barr virus (EBV)-infected people detect a 140-kDa protein on immunoblots of EBV-infected lymphoblasts. The 140-kDa protein is a nuclear protein characteristic of latent EBV infection. Sera reactive with this protein identify a distinctive globular nuclear antigen. Although the 140-kDa protein is encoded by EBV, it is not encoded by genes that encode the two previously described EBV nuclear antigens (EBNA) or the latent-infection membrane protein. The 140-kDa protein is therefore designated EBNA3. The EBV genes, including the gene encoding EBNA3, that are characteristically expressed in latent infection are likely to play a role in the maintenance of persistent latent viral infection or in the cell proliferation caused by virus infection.