DESCRIPTION: The EBV genome is present in EBV-positive tumor cells and latently infected B cells as a plasmid that replicates once per cell cycle during S phase in parallel with the cellular chromosomes. Replication and maintenance of EBV plasmids in these cells requires only one viral protein, the EBV nuclear antigen-1 (EBNA-1). A complete description of the mechanism by which EBNA-1 supports the replication and maintenance of EBV genomes in dividing cells is central to understanding how this virus causes latent infections and the relationship of EBV with tumor cells. Three of the long-term goals of this laboratory are to determine how the binding of EBNA-1 to its recognition elements in the latent cycle origin of DNA replication (oriP) leads to the initiation of DNA replication, to understand how this event is regulated in a cell-cycle dependent manner, and to determine how EBV plasmids are stably maintained in dividing cells. In addition to its role in latent cycle DNA replication and plasmid maintenance, EBNA-1 negatively regulates its own promoter during latency and this activity is of considerable interest with respect to the ability of EBV to cause latent infections in vivo. The specific aims of this proposal are: 1) to identify the minimal DNA fragment that contains oriP replicator activity and determine which nucleotides within the fragment are required for replicator function; 2) to determine if EBV DNA latent cycle DNA replication is subject to the same controls that regulate cellular DNA replication and if oriP region I is required for the regulated replication of oriP plasmids; 3) to characterize the physical interaction of EBNA-1 with cellular proteins importin-alpha and p32, and determine if these interactions are required for EBNA-1 autoregulation; 4) to determine if an evolutionarily-conserved eukaryotic cell protein interacts with EBNA-1 in EBV-infected B cells and is involved in the replication or maintenance of EBV genomes in latently-infected B cells and tumor cells, or viral gene regulation.