The EBNA2-EBF1 complex promotes oncogenic MYC expression levels and metabolic processes required for cell cycle progression of Epstein-Barr virus-infected B cells

Epstein-Barr virus (EBV) is a human tumor virus, which preferentially infects resting human B cells. Upon infection in vitro, EBV activates and immortalizes these cells. The viral latent protein EBV nuclear antigen (EBNA) 2 is essential for B cell activation and immortalization; it targets and binds the cellular and ubiquitously expressed DNA binding protein CBF1, thereby transactivating a plethora of viral and cellular genes. In addition, EBNA2 uses its N-terminal dimerization (END) domain to bind early B cell factor (EBF) 1, a pioneer transcription factor specifying the B cell lineage. We found that EBNA2 exploits EBF1 to support key metabolic processes and to foster cell cycle progression of infected B cells in their first cell cycles upon activation. An 1-helix within the END domain was found to promote EBF1 binding. EBV mutants lacking the 1-helix in EBNA2 can infect and activate B cells efficiently, but the activated cells fail to complete the early S phase of their initial cell cycle. Expression of MYC, target genes of MYC and E2F as well as multiple metabolic processes linked to cell cycle progression are impaired in EBV{Delta}1 infected B cells. Our findings indicate that EBF1 controls B cell activation via EBNA2 and, thus, has a critical role in regulating the cell cycle of EBV infected B cells. This is a function of EBF1 going beyond its well-known contribution to B cell lineage specification. Significance statementEpstein-Barr virus (EBV) infects primary B cells and establishes life-long latent infection in these cells. EBV nuclear antigen (EBNA) 2 drives early processes of B cell activation and cell cycle entry. The surface of the N-terminal dimerization domain of EBNA2 exposes a five amino acid -helix (1) that recruits EBF1 to activate MYC and downstream targets of both MYC and E2F to support critical metabolic processes in infected B cells and to drive them through S phase in the first cell cycle post-infection. Our study demonstrates how EBNA2 exploits EBF1, a key factor of B cell lineage specification to initiate proliferation and high-lights the 1-helix as a potential Achilles heel of the virus at the stage when latent infection is established.