m6A epigenetic modification of viral RNA is critical for the transmission cycle of mosquito-borne flaviviruses

Abstract

Arboviruses maintain alternative transmission routes between arthropods and vertebrates through precise dual-host adaptation of their viral genome. However, how epigenetic modifications impact flavivirus transmission cycle remains obscure. Depleting the m6A modification complex revealed that m6A modifications preferentially facilitate mosquito-borne flaviviruses (MBFs) propagation in vertebrates but not in mosquitoes. Stem loop I (SLI) deletion in the MBF 3’ UTR decreased m6A expression and viral propagation in vertebrates but not in mosquitoes, indicating viral genome component–epigenetic modification interplay. Mechanistically, m6A modification in stress granules was found to be driven by dynamic SLI–cellular G3BP1 interaction. The m6A-methylated viral genome is ejected by G3BP1 and undergoes viral assembly. Chemical perturbation of m6A modification via METTL3 inhibition potently blocked MBF proliferation in mice and abolished mouse–mosquito viral transmission. Overall, m6A modification is indispensable for efficient arthropod-to-vertebrate transmission of MBF, highlighting its potential as a target for antiviral and transmission-control strategies.