The m6A Reader YTHDF2 Modulates Antiviral and Antibacterial Activity by Suppressing METTL3 Methylation-Modified STING in Fish

At present, N6-methyladenosine (m6A) modification has been proven to participate in a wide range of gene expression regulation, such as stability, translation, splicing, and output, among others, which has attracted much attention. Unlike mammals, however, the role of m6A in innate immunity of lower invertebrates has not yet been studied. In this study, we found that the total m6A level of Miichthys miiuy increased during Siniperca chuatsi rhabdovirus and Vibrio anguillarum infection, suggesting that m6A may play an important role in the immune process against pathogens in fish. In addition, our study shows that stimulator of IFN genes (STING) plays a dual immune function against viruses and bacteria in fish, and through degrading STING by identifying its m6A methylation site modified by methyltransferase-like 3 (METTL3), YTH domain family 2 (YTHDF2) can weaken the IRF3 and NF-κB-driven signaling pathway, thus weakening the innate immunity and promoting the infection of Siniperca chuatsi rhabdovirus and V. anguillarum to the M. miiuy. Although there have been reports on m6A modification of STING in mammals, it is still unclear whether there is also m6A modification in lower vertebrates, especially in fish. Therefore, our study provides a reference for filling the gap of m6A modification between fish and mammals.