Hepatitis B Virus (HBV) DNA polymerase (P) protein consisting of terminal protein (TP), spacer, reverse transcriptase (RT), and RNase H, plays critical roles in viral assembly and replication. RNase H domain is required for HBV DNA replication, however critical motif or amino acid residues in the RNase H domain for the HBV replication has not been extrensively demonstrated yet. In the present study, several chimeras of P protein by substituting Duck hepatitis B virus (DHBV) sequences were constructed. Accordingly, we tested a series of P protein chimeras in which several substitution mutants were disigned to contain various amino acids of DHBV P protein. It is found that amino acid residues from 800 to 826 (800SRPLLRLPFQPTTGRTSLYAVSPSVPS826) in C -terminus of the RNase H domain are required to complete HBV replication. HBV P protein mutants in which single amino acid residue was substituted were examined for the rescue of HBV replication. Among these mutants tested, L806T mutant P protein have a defect in pgRNA encapsidation and viral DNA synthesis, demonstrating that leucine at position 806 is critical for HBV replication.
