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Publisher Summary Epstein–Barr virus (EBV) is a gamma-herpes-4-virus and was the first herpes virus to be completely sequenced. Several diseases are associated with EBV, including Hodgkin's and post-transplant lymphomas, oral hairy leukoplakia, and nasopharyngeal carcinomas. EBV has a double-stranded 172-kb DNA genome. Upon infection, the genome circularizes and persists as an episome in infected cells. More than 70 open reading frames exist, which encode proteins expressed during lytic and latent EBV infection. Lytic proteins encode viral proteins, which are necessary for the production of infectious virions, whereas latent proteins are needed to set up persistent infection by transforming and immortalizing host cells. EBV also encodes non-translated RNAs (e.g., EBER1 and EBER2), which are almost ubiquitously expressed and highly abundant in EBV-infected cells. Four EBV latency programs have been described with distinct sets of expressed proteins and viral RNAs: (1) Latency 0 : EBER1 and EBER2 but no expression of proteins; (2) Latency 1 (true latency program): EBER1 and EBER2, EBNA1; (3) Latency 2 (default program): EBER1 and EBER2 and expression of EBNA1, latent membrane protein (LMP)-1, LMP2A, LMP2B; and (4) Latency 3 (growth program): EBER1 and EBER2 and expression of EBNA-leader protein (LP), EBNA 2–6, LMP1, LMP2A, LMP2B. The role of most EBV proteins has been characterized mainly in vitro using lymphoblastoid cell lines. |
