Identification of an N6-methyladenosine-mediated positive feedback loop that promotes Epstein-Barr virus infection.

N6-methyladenosine (m6A) is among the most abundant mRNA modifications, particularly in eukaryotes, and is found in mammals, plants and even some viruses. Although essential for the regulation of many biological processes, the exact role of m6A modification in virus-host interactions remains largely unknown. Here, using m6A -immunoprecipitation and sequencing, we find that Epstein-Barr virus (EBV) infection decreases the m6A modification of transcriptional factor KLF4 mRNA and subsequently increases its protein level. Mechanistically, EBV immediate-early protein BZLF1 interacts with the promoter of m6A methyltransferase METTL3, inhibiting its expression. Subsequently, the decrease of METTL3 reduces the level of KLF4 mRNA m6A modification, preventing its decay by the m6A reader protein YTHDF2. As a result, KLF4 protein level is upregulated and, in turn, promotes EBV infection of nasopharyngeal epithelial cells. Thus, our results suggest the existence of a positive feedback loop formed between EBV and host molecules via cellular mRNA m6A levels, and this feedback loop acts to facilitate viral infection. This mechanism contains multiple potential targets for controlling viral infectious diseases.