Regulation of B cell receptor signalling by Epstein-Barr virus nuclear antigens

The cancer-associated Epstein-Barr virus (EBV) latently infects and immortalises B lymphocytes. EBV latent membrane protein 2A and EBV-encoded microRNAs are known to manipulate B cell receptor signalling to control cell growth and survival and suppress lytic replication. Here, we show that the EBV transcription factors EBNA2, 3A, 3B and 3C bind to genomic sites around multiple B cell receptor (BCR) pathway genes, regulate their expression and affect BCR signalling. EBNA2 regulates the majority of BCR pathway genes associated with binding sites, where EBNA3 proteins regulate only 42% of targets predicted by binding. Both EBNA2 and 3 proteins predominantly repress BCR pathway gene expression and target some common genes. EBNA2 and at least one EBNA3 protein repress the central BCR components CD79A and CD79B and the downstream genes BLNK, CD22, CD72, NFATC1, PIK3CG and RASGRP3. Studying repression of CD79B, we show that EBNA2 decreases transcription by disrupting binding of Early B cell Factor-1 to the CD79B promoter. Consistent with repression of BCR signalling, we demonstrate that EBNA2 and EBNA3 proteins suppress the basal or active BCR signalling that culminates in NFAT activation. Additionally, we show that EBNA2, EBNA3A and EBNA3C expression can result in reductions in the active serine 473 phosphorylated form of Akt in certain cell contexts, consistent with transcriptional repression of the PI3K-Akt BCR signalling arm. Overall, we identify EBNA2, EBNA3A and EBNA3C-mediated transcription control of BCR signalling as an additional strategy through which EBV may control the growth and survival of infected B cells and maintain viral latency.

Automated summary

The Epstein-Barr virus (EBV), associated with cancer, manipulates the B cell receptor signaling pathway to control cell growth and survival. EBV transcription factors EBNA2, 3A, 3B, and 3C were found to bind to genomic sites around B cell receptor pathway genes, regulating their expression and affecting B cell receptor signaling. EBNA2 and EBNA3 predominantly repress the expression of B cell receptor pathway genes and target common genes. EBNA2 and at least one EBNA3 protein repress the central components of the B cell receptor pathway and downstream genes. This study reveals a mechanism through which EBV controls the growth and survival of infected B cells and maintains viral latency.