Hepatitis B virus cccDNA is formed through distinct repair processes of each strand

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Hepatitis B virus (HBV) infection affects over a third of the global population, causing nearly a million deaths annually.
• The persistence of HBV covalently closed circular DNA (cccDNA) is the primary driver of chronic HBV infection.
• The precise molecular mechanisms underlying cccDNA formation from relaxed circular DNA (rcDNA) are not fully understood.

Purpose of the Study:

• To elucidate the molecular mechanisms of HBV cccDNA formation from rcDNA.
• To identify the specific human repair factors involved in the distinct repair pathways of HBV rcDNA minus and plus strands.

Main Methods:

• Utilized biochemical repair systems to analyze the repair of HBV rcDNA minus and plus-strand lesions.
• Investigated the requirement for specific human DNA repair factors, including proliferating cell nuclear antigen (PCNA), replication factor C (RFC) complex, DNA polymerase delta (POLδ), flap endonuclease 1 (FEN-1), and DNA ligase 1 (LIG1).

Main Results:

• Demonstrated that the repair of the HBV rcDNA plus strand requires PCNA, RFC, POLδ, FEN-1, and LIG1, resembling DNA lagging strand synthesis.
• Showed that only FEN-1 and LIG1 are necessary for the repair of the HBV rcDNA minus strand.
• Provided a detailed mechanistic understanding of rcDNA repair into cccDNA within biochemical systems.

Conclusions:

• The distinct requirements for human repair factors in minus and plus-strand DNA repair highlight a complex process in HBV cccDNA formation.
• These findings offer crucial insights into the molecular basis of HBV persistence and potential therapeutic targets for chronic hepatitis B.