The interaction between Vav1 and EBNA1 promotes survival of Burkitt's lymphoma cells by down-regulating the expression of Bim.

Vav1 is a guanine nucleotide exchange factor (GEF) predominantly expressed in hematopoietic cells, and functions in the development and antigen-stimulated response of lymphocytes. Burkitt's lymphoma (BL) is characterized as transformed B cell lymphoma, and is highly associated with Epstein-Barr virus (EBV). EBV nuclear antigen 1 (EBNA1) is the only viral protein expressed across all three types of latency and essential for the persistence of EBV genome. It is not clear yet how EBNA1 contributes to the growth advantage of latently infected cells such as in EBV+ lymphoma B cells. Here, we reported that Vav1 interacts with EBNA1 via its C-terminal SH3 domain. This interaction suppresses the expression of a pro-apoptotic Bcl-2 family member, Bim, resulting in the resistance of the BL cells to apoptotic inductions. Our data uncovered Vav1 as a novel target for EBNA1, and suggested a pro-survival role of Vav1 in the pathogenesis of EBV associated BLs.