hnRNPH1 Inhibits Influenza Virus Replication by Binding Viral RNA

During the life cycle of the influenza virus, viral RNPs (vRNPs) are transported to the nucleus for replication. Given that a large number of progeny viral RNA occupies the nucleus, whether there is any host protein located in the nucleus that recognizes the viral RNA and inhibits the viral replication remains largely unknown. In this study, to explore the role of hnRNPH1 in influenza virus infection, we knocked down and over-expressed the hnRNPH1 proteins in 293T cells, then infected the cells with the influenza virus. The results showed that the host hnRNPH1 inhibits the replication of H1N1 and H9N2 influenza viruses by restraining the polymerase activity of viruses. hnRNPH1 contains two RNA recognition motifs (RRM1) and RRM2. Further studies indicated that hnRNPH1 specifically binds to the viral RNA of the PB1, PA, and NP genes. Mutation of the key residues tryptophan and tyrosine in RRM1 and RRM2 abolished the binding affinity to viral RNA and the suppression of polymerase activity of the influenza virus. All the results suggested that hnRNPH1 suppresses polymerase activity and replication of the influenza virus by binding viral RNA.