Structural, functional, and genetic comparisons of Epstein-Barr virus nuclear antigen 3A, 3B, and 3C homologues encoded by the rhesus lymphocryptovirus

EBNA-3A, -3B, and -3C are three latent infection nuclear proteins important for Epstein-Barr virus (EBV)induced B-cell immortalization and the immune response to EBV infection. All three are hypothesized to function as transc riptional transactivators, but little is known about their precise mechanis m of action or their role in EBV pathogenesis, We have cloned and studied t he three EBNA-3 homologues from a closely related lymphocryptovirus (LCV) w hich naturally infects rhesus monkeys. The rhesus LCV EBNA-3A, -3B, and -3C homologues have 37, 40, and 36% amino acid identity with the EBV genes, re spectively, Function, as measured by in vitro assays, also appears to be co nserved with the EBV genes, since the rhesus LCV EBNA-3s can interact with the transcription factor RBP-J kappa and the rhesus LCV EBNA-3C encodes a Q /P-rich domain with transcriptional activation properties. In order to bett er understand the relationship between these EBV and rhesus LCV latent infe ction genes, we asked if the rhesus LCV EBNA-3 locus could be recombined in to the EBV genome and if it could substitute for the EBV EBNA-3s when assay ed for human B-cell immortalization. Recombination between the EBV genome a nd rhesus LCV DNA was reasonably efficient. However, these studies suggest that the rhesus LCV EBNA-3 locus was not completely interchangeable with th e EBV EBNA-3 locus for B-cell immortalization and that at least one determi nant of the species restriction for LCV-induced B-cell immortalization maps to the EBNA-3 locus. The overall conservation of EBNA-3 structure and func tion between EBV and rhesus LCV indicates that rhesus LCV infection of rhes us monkeys can provide an important animal model for studying the role of t he EBNA-3 genes in LCV pathogenesis.