Epstein-Barr virus latent membrane protein 2A exploits Notch1 to alter B-cell identity in vivo

Expression of latent membrane protein 2 (LMP2A) during B-cell development leads to global alterations in gene transcription similar to those seen in Hodgkin Reed-Sternberg cells of Hodgkin lymphoma (HL). Along with the consistent detection of LMP2A in Epstein-Barr virus- associated HL, this implicates a role for LMP2A in the pathogenesis of HL. We have shown that LMP2A constitutively activates the Notch1 pathway to autoregulate the LMP2A promoter. To determine whether constitutive activation of the Notch pathway is important for LMP2Amediated alterations in B-cell development in vivo, TgE-LMP2A-transgenic mice were intercrossed with mice expressing loxP-flanked Notch1 genes and Cre recombinase. B cells from TgE Notch1^lox/lox- CD19^+/Cre mice have an increase in immunoglobulin M and CD43 and a decrease in CD5 expression in the bone marrow compared with TgE Notch1^lox/lox mice, indicating the LMP2A signal for developmental aberrations is impaired in the absence of Notch1. Real-time reverse-transcribed polymerase chain reaction analysis reveals that LMP2A requires the Notch1 pathway to alter levels of B cell-specific transcription factors, E2A and EBF. Interestingly, Notch1 appears to be important for LMP2A-mediated survival in low interleukin- 7. We propose that LMP2A and the Notch1 pathway may cooperate to induce the alterations in B-cell identity seen in Hodgkin Reed-Sternberg cells.