Viral N6-methyladenosine upregulates replication and pathogenesis of human respiratory syncytial virus [SeV]

N6-methyladenosine (m6A) is the most abundant internal RNA modification catalyzed by host RNA methyltransferases. As obligate intracellular parasites, many viruses acquire m6A methylation in their RNAs. However, the biological functions of viral m6A methylation are poorly understood. Here, we found that viral m6A methylation serves as a molecular marker for host innate immunity to discriminate self from nonself RNA and that this novel biological function of viral m6A methylation is universally conserved in non-segmented negative-sense (NNS) RNA viruses. Using m6A methyltransferase (METTL3)-knockout cells, we produced m6A-deficient virion RNA from the representative members of the families Pneumoviridae, Paramyxoviridae, and Rhabdoviridae and found that these m6A-deficient viral RNAs triggered significantly higher levels of type I interferon compared to the m6A-sufficient viral RNAs, in a RIG-I dependent manner. Reconstitution of the RIG-I pathway revealed that m6A-deficient virion RNA induced higher expression of RIG-I, bound to RIG-I more efficiently, enhanced RIG-I ubiquitination, and facilitated RIG-I conformational rearrangement and oligomerization. Furthermore, the m6A binding protein YTHDF2 sequesters m6A-sufficient virion RNA which suppresses type I interferon signaling pathway. Collectively, our results suggest that NNS RNA viruses acquire m6A in viral RNA as a common strategy to evade host innate immunity. Overall design: A few other (NNS) RNA viruses including RSV and hMPV has been sequenced and published before by us. Here, we performed m6A-seq of Sendai virus (SeV). Total RNA were purified from SeV-infected A549 cell lines and subject to m6A-IP-MeRIP-seq.