Abstract
The Epstein-Barr virus (EBV) BamHI A mRNAs were originally identified in cDNA libraries from nasopharyngeal carcinoma, where they are expressed at high levels. The RNAs are differentially spliced to form several open reading frames and also contain the BARF0 open reading frame at the 3' end. One cDNA, RK-BARF0, included a potential endoplasmic reticulum-targeting signal peptide sequence. The RK-BARF0 protein is shown here to interact with the Notch4 ligand binding domain, using yeast two-hybrid screening, coimmunoprecipitation, and confocal microscopy. This interaction induces translocation of a portion of the full-length unprocessed Notch4 to the nucleus by using the Notch nuclear localization signal. These effects of RK-BARF0 on Notch intracellular location indicate that EBV possibly modulates Notch signaling. Unprocessed Notch4 was also detected in immunoprecipitated complexes from EBV-infected cells by using a rabbit antiserum raised against a BARF0-specific peptide. This finding provides additional evidence for expression of RK-BARF0 and its interaction with Notch during EBV infection. In EBV-infected, EBNA2-negative cells, RK-BARF0 induced the expression of EBV latent membrane protein 1 (LMP1), and this induction was dependent on the RK-BARF0/Notch interaction domain. The activation of LMP1 expression by RK-BARF0 may be responsible for expression of LMP1 in EBV latent infections in the absence of EBNA2.