Both Epstein-Barr viral nuclear antigen 2 (EBNA2) and activated Notch1 transactivate genes by interacting with the cellular protein RBP-J kappa

The Epstein-Barr viral nuclear antigen 2 (EBNA2) plays a key role during establishment and maintenance of B cell immortalization after Epstein-Barr virus (EBV) infection. EBNA2 acts as a transactivator of cellular and viral genes. We studied two EBNA2 regulated viral promoters (TP1 promoter and LMP/TP2 promoter) in detail to learn more about the molecular mechanisms of EBNA2-mediated transactivation. In both promoters we could identify at least one binding site for the cellular repressor protein RBP-J kappa. EBNA2 is tethered to the EBNA2 responsive promoter elements by interaction with this cellular protein. Although necessary, the binding of RBP-J kappa is not sufficient for EBNA2-mediated transactivation. At least two further cellular proteins, which are different in the studied promoters are important for efficient transactivation. The identification of RBP-J kappa as central mediator of EBNA2 transactivation suggested an interference of EBNA2 with the highly conserved Notch receptor signal transduction pathway. We could show that an activated form of the Notch receptor can transactivate a reporter construct containing a hexamer of the two RBP-J kappa binding sites of the TP1 promoter supporting the idea that EBNA2 acts as a functional equivalent of an activated Notch receptor.