Hepatitis B virus core protein dimer-dimer interface is critical for viral replication

Hepatitis B virus (HBV) core protein (HBc) serves pivotal roles in the viral life cycle, particularly serving as the basic unit for capsid assembly, and is closely associated with HBV genome replication and progeny virion production. Previous studies have demonstrated that HBc has at least two functional interfaces; two HBc monomers form a homodimer via an intradimer interface, and then 90 or 120 homodimers form an icosahedral capsid via a dimer-dimer interface. In the present study, the role of the HBc dimer-dimer interface in HBV replication was investigated. A panel of residues located at the dimer-dimer interface were identified based on the crystal structure of HBc. Native gel electrophoresis and western blotting revealed that, despite mutations in the dimer-dimer interface, HBc formed a capsid-like structure, whereas mutations at amino acid residues 23–39 completely disrupted capsid assembly. Using denaturing gel electrophoresis, Southern and Northern blotting, and quantitative polymerase chain reaction, it was demonstrated that none of the mutations in the dimer-dimer interface supported pregenomic RNA encapsidation or DNA replication. In addition, these mutants interacted with the wild-type (WT) HBc monomer and inhibited WT genome replication and virion production in a dose-dependent manner. However, the quantity of covalently closed circular DNA in the nucleus was not affected. The present study highlighted the importance of the HBc dimer-dimer interface for normal capsid function and demonstrated that the HBc dimer-dimer interface may be a novel antiviral target.