EBV epitranscriptome reprogramming by METTL14 is critical for viral-associated tumorigenesis

Epstein-Barr virus (EBV) is a ubiquitous oncogenic virus that induces many cancers. N6-Methyladenosine (m6A) modification regulates many cellular processes. We explored the role of m6A in EBV gene regulation and associated cancers. We have comprehensively defined m6A modification of EBV latent and lytic transcripts. Furthermore, m6A modification demonstrated a functional role in regulation of the stability of viral transcripts. The methyltransferase METTL14 was induced at the transcript and protein levels, and knock-down of METTL14 led to decreased expression of latent EBV transcripts. METTL14 was also significantly induced in EBV-positive tumors, promoted growth of EBV-transformed cells and tumors in Xenograft animal models. Mechanistically, the viral-encoded latent oncoprotein EBNA3C activated transcription of METTL14, and directly interacted with METTL14 to promote its stability. This demonstrated that EBV hijacks METTL14 to drive EBV-mediated tumorigenesis. METTL14 is now a new target for development of therapeutics for treatment of EBV-associated cancers. Author summary Epstein-Barr virus (EBV) is a ubiquitous oncogenic virus that contributes to approximately 2% of all cancers by modulating a myriad of host cell activities. M6A is the most abundant RNA modification which is important for infection with HIV-1, HCV, Zika virus, KSHV and SV40 virus. The role of m6A modification and the associated enzymes in EBV infection and related oncogenic activities has not been explored. We investigated the role of m6A modification on EBV-infection and examined its effects on the proliferative activities of the virus which contributes to cancer. We showed that the m6A methyltransferase METTL14 is an important factor in EBV-induced oncogenesis. METTL14 was dramatically increased in EBV latently infected cells. Knock-down of METTL14 led to decreased latent viral gene expression. The essential EBV latent antigen EBNA3C was up-regulated by METTL14-mediated m6A modification, and its expression led to a feedback loop in up-regulation of METTL14 transcription, and the stability of its protein. We now provide a more comprehensive understanding of EBV and the host cell RNA processing machinery critical for regulation of EBV activities to maintain latent infection and its oncogenic properties.