Abstract

Heterogeneous nuclear ribonucleoproteins (hnRNPs) play important roles in the life cycle of influenza A virus (IAV). Our previous mass spectrometry analysis identified cellular hnRNP D as a novel interaction partner of the IAV polymerase basic 2 (PB2) protein. However, the functional implications of hnRNP D in IAV replication and the underlying mechanisms remained unknown. In this study, we confirmed that hnRNP D directly interacts with the PB2 protein of the A/Puerto Rico/8/1934 (PR8, H1N1) strain, while also binding to other proteins within viral ribonucleoprotein complexes (vRNPs). These interactions collectively inhibit vRNPs assembly and viral polymerase activity. However, we have found that hnRNP D enhances the viral titer of IAV in A549 cells. Mechanistically, hnRNP D suppresses the activation of the interferon (IFN)-β promoter, and the mRNA levels of downstream factors in the type I IFN signaling pathway. In detail, hnRNP D inhibits IFN-β promoter activation induced by crucial antiviral proteins and interacts strongly with the interferon regulatory factor 3 (IRF3). More importantly, hnRNP D blocks the binding of TANK-binding kinase 1 (TBK1) to IRF3, thereby impeding the phosphorylation and activation of IRF3. Collectively, we unveil a novel viral immune evasion strategy by which IAV hijacks a host RNA-binding protein, hnRNP D, to facilitate self-replication. This work not only elucidates the intricate trade-off mechanisms in virus-host interaction but also identifies hnRNP D as a potential therapeutic target aimed at bolstering antiviral immunity.