Interaction between DEAD-box RNA helicase 10 and influenza PB1 polymerase selectively regulates influenza A virus replication

Abstract

ABSTRACT Identifying the host factors that mediate avian influenza virus adaptation in mammals is important for monitoring zoonotic potential. Although viral polymerase adaptations are known to influence cross-species transmission, the engagement of specific host factors with divergent viral polymerases remains to be explored. We examined human DEAD-box RNA helicases (DDXs) as potential regulators of influenza polymerase activity. A screen of 16 DDXs identified DDX10 as a factor that selectively enhanced the polymerase activity and replication of human-adapted H1N1 viruses, including the 2009 pandemic strain, but not avian-origin H9N2 viruses. This differential activity was associated with DDX10 showing stronger interaction with human-origin PB1 (Cal04/H1N1) than with avian-origin PB1 (BJ16/H9N2). Strain specificity was mediated by two residues (336 and 364) within the PB1 catalytic domain: introducing H1N1-type residues (I336 and I364) into H9N2-PB1 conferred DDX10 responsiveness, while reciprocal mutations in H1N1-PB1 abolished it. This work defines DDX10 as a potential host factor that differentially supports influenza polymerase activity, revealing a specific molecular interface that contributes to the replication efficiency of distinct viral subtypes in human cells and providing insight into host-adaptive mechanisms. IMPORTANCE This study identifies DDX10 as a strain-specific host factor that differentially regulates influenza A virus replication. By demonstrating that DDX10 selectively enhances human-adapted H1N1 viruses over avian-origin H9N2 viruses through direct interaction with the viral PB1 protein, and by mapping two critical residues (positions 336 and 364) in PB1 that govern this selectivity, our work provides a mechanistic framework for understanding how a single host factor can modulate viral fitness and host adaptation. These findings have important implications for predicting cross-species transmission potential and may guide the development of host-targeted antiviral strategies. This study identifies DDX10 as a strain-specific host factor that differentially regulates influenza A virus replication. By demonstrating that DDX10 selectively enhances human-adapted H1N1 viruses over avian-origin H9N2 viruses through direct interaction with the viral PB1 protein, and by mapping two critical residues (positions 336 and 364) in PB1 that govern this selectivity, our work provides a mechanistic framework for understanding how a single host factor can modulate viral fitness and host adaptation. These findings have important implications for predicting cross-species transmission potential and may guide the development of host-targeted antiviral strategies.