Y-Box-Binding Protein 3 (YBX3) Restricts Influenza A Virus by Interacting with Viral Ribonucleoprotein Complex and Imparing its Function

The influenza A virus (IAV) ribonucleoprotein (vRNP) complex consists of polymerase subunits, nucleoprotein (NP) and viral RNA and is responsible for RNA transcription and replication. Interactions between the vRNP complex and host factors play important roles in virus replication, pathogenicity and species tropism. In this study, Strep-tag affinity purification coupled with mass spectrometry was used to identify host factors that interact with IAV vRNP complex in infected human cells. We purified vRNP complex from HEK 293T cells infected with a recombinant mouse-adapted IAV (A/Chicken/Hubei/489/2004) containing a Strep-tag PB2 subunit and identified Y-box-binding protein 3 (YBX3) as a negative regulator of IAV replication. Overexpression of YBX3 inhibited the virus replication, viral protein expression and vRNA synthesis. Conversely, RNAi knockdown of YBX3 resulted in significantly increased virus growth rate. Furthermore, knockdown of YBX3 augmented the nuclear accumulation of NP and viral primary transcription in infected cells. Our results suggest that YBX3 restricts IAV replication by interacting with vRNP complex and subsequently imparing its function.