RANBP3 and RAN orchestrate CRM1-mediated nuclear export of hepatitis B virus RNAs.

Nuclear export of viral RNAs is essential for the replication of hepatitis B virus (HBV). Our previous study demonstrated that ELAVL1 (embryonic lethal, abnormal vision, Drosophila-like 1) mediates the nuclear export of HBV RNAs via the chromosome region maintenance 1 (CRM1) pathway by recognizing and binding to the AUUUA motifs within these transcripts. Here, we identify Ras-related nuclear protein (RAN) and RAN-binding protein 3 (RANBP3) as critical downstream regulators of this CRM1-mediated RNA export pathway. We show that RANBP3 recruits RAN-GTP to assemble an export-competent quaternary complex (CRM1-HBV RNAs-RANBP3-RAN-GTP). The functional significance of this complex is underscored by the findings that its disruption, through knockdown of RANBP3/RAN, or by introducing CRM1 mutations that prevent cofactor binding, severely impairs HBV RNA export and viral replication. Together, our study thus elucidates a precise regulatory mechanism governing HBV RNA trafficking and highlights RANBP3 and RAN as potential antiviral targets.IMPORTANCEEfficient nuclear export of hepatitis B virus (HBV) RNAs is essential for viral replication, yet the regulatory mechanisms controlling this process remain poorly defined. This study identifies Ras-related nuclear protein (RAN) and RAN-binding protein 3 (RANBP3) as key host cofactors that drive chromosome region maintenance 1 (CRM1)-mediated export of HBV transcripts by assembling an export-competent complex with viral RNAs. Disrupting this pathway profoundly impairs RNA export and downstream steps of the viral life cycle. By defining how HBV harnesses the RANBP3-RAN-CRM1 axis for RNA trafficking, our work reveals a previously unrecognized layer of host dependency and highlights RANBP3 and RAN as promising targets for antiviral intervention.