Hepatitis B Virus Protein Priming Reaction

The hepatitis B virus (HBV) protein priming reaction is a unique and essential step in the viral replication cycle. It refers to the initiation of viral DNA synthesis by the HBV polymerase, which uses itself as a primer—a process termed "protein priming." In this mechanism, the initiating nucleotide becomes covalently linked to a specific tyrosine residue on the viral polymerase, enabling reverse transcription of pregenomic RNA (pgRNA) into DNA. The HBV polymerase (also called HP or Pol) is multifunctional and catalyzes reverse transcription. Protein priming begins when HP binds specifically to an RNA signal on pgRNA known as epsilon (ε or Hε), which serves as an obligatory template for initiation. The first deoxynucleotide is covalently attached via a phosphotyrosyl bond to a conserved tyrosine residue in the terminal protein (TP) domain of HP—Y63 in human HBV. This reaction requires both proper recognition of ε and correct folding/conformation of HP, often facilitated by host chaperone proteins. Initiating minus-strand DNA synthesis from pgRNA during viral replication. Ensures that only correctly packaged pgRNA templates are used through strict dependence on ε recognition.

Inhibition of HBV polymerase activity by disrupting protein-RNA interaction, polymerase conformation, or active site chemistry.