HBeAg Precursor Proteins Interact with APOBEC3A and Inhibit HBV Replication

Abstract

Background: Hepatitis B e antigen (HBeAg) precursor proteins, which share an identical encoding PreC/C open reading frame (PreC/C-ORF) of hepatitis B virus (HBV) core, can inhibit viral replication in vitro. The apolipoprotein B mRNA (messenger ribonucleic acid) editing enzyme catalytic polypeptide 3A (APOBEC3A) can inhibit HBV replication by interacting with the HBV core protein. The aim of the study was to explore whether the HBeAg precursor proteins can regulate HBV replication by interacting with APOBEC3A. Methods: Plasmids harboring the coding sequence of HBeAg precursor proteins (P25 and P22) and APOBEC3A were individually or co-transfected into human hepatoma and embryonic kidney cells. P25, P22, and APOBEC3A expressions were quantified by Western blotting. The co-localization and interaction of P25, P22, and APOBEC3A were determined by confocal microscopy and co-immunoprecipitation (Co-IP). We constructed serial precursor proteins of HBeAg deletion mutants for further Co-IP analysis. Enzyme-linked immunosorbent assay (ELISA) was employed to evaluate the levels of HBeAg and HBsAg. HBV replication intermediates from the transfected cells were detected by Southern blotting. Results: P25, P22, and APOBEC3A proteins were successfully expressed in transfected cells, and both P25 and P22 protein co-localization with APOBEC3A protein in the cytoplass. Co-IP with APOBEC3A was mediated by the central region of the HBeAg precursor (amino acids 107–178). The levels of HBsAg were significantly lower in cells co-transfected with HBV e-, P22/P25, and APOBEC3A, than in cells co-transfected with HBV e-, APOBEC3A, or in cells co-transfected with HBV e-, P22/P25. The levels of HBeAg were lower in cells co-transfected with HBV e-, P22/P25, and APOBEC3A, than in cells co-transfected with HBV e-, P22/P25. Compare with cells transfected with HBV e-, APOBEC3A, or in cells co-transfected with HBV e-, P25/P22, HBV replication intermediates were lower in the cells co-transfected with HBV e-, P25, APOBEC3A, and significantly lower in the cells with HBV e-, P22, APOBEC3A. Conclusions: HBV replication can be inhibited by the interaction of P25/P22 with APOBEC3A protein in the cytoplasm.