N -Methyladenosine Negatively Regulates Human Respiratory Syncytial Virus Replication.

N-methyladenosine (mA) is the most abundant internal modification described in eukaryotic mRNA and several viral RNA including human respiratory syncytial virus (HRSV). Here, we evaluated the impact of mA writers, erasers and readers on HRSV genomic RNA accumulation and inclusion bodies assembly during viral replication. We observed that the METTL3/METTL14 mA writer complex plays a negative role in HRSV protein synthesis and viral titers, while mA erasers FTO and ALKBH5 had the opposite effect. We also observed that mA readers YTHDF1-3 bind to the viral genomic RNA inducing a decrease in its intracellular levels and thus, inhibiting viral replication. Finally, we observed that overexpression of YTHDFs proteins caused a decrease in the size of inclusion bodies (IBs), accompanied by an increase in their number. METTL3 knockdown cells showed an opposite effect indicating that the dynamics of IBs assembly and coalescence are strongly affected by mA readers in a mechanism dependent on mA writers. Taken together, our results demonstrated that the mA modification negatively affects HRSV replication, possibly through a mechanism involving the assembly of inclusion bodies, the main factories of viral genomic RNA synthesis.