Integrated defective replication units of hepatitis B virus

Area of Science:

• Hepatology
• Molecular Virology
• Cell Biology

Background:

• Hepatitis B virus (HBV) poses a significant global health challenge.
• Understanding HBV replication is crucial for developing antiviral therapies.
• Previous studies showed HBV DNA constructs could be transcribed in transformed cells.

Purpose of the Study:

• To establish stable human hepatoma HepG2 cell lines constitutively transcribing HBV DNA units.
• To investigate if these integrated DNA units function as defective replication units.
• To analyze the transcriptional activity and replication of these defective units.

Main Methods:

• Generation of stable HepG2 transformants with integrated HBV DNA and neomycin resistance genes.
• Cotransfection of transformants with replication-competent HBV DNA.
• Analysis of viral RNA transcripts and reverse transcription products.
• Quantification of transcriptional start site usage.

Main Results:

• Stable HepG2 transformants constitutively transcribed integrated HBV DNA units.
• Transcripts from these units were reverse transcribed upon cotransfection with wild-type HBV DNA.
• Defective pregenomes were preferentially transcribed from viral pregenome starts (9:1 ratio).
• Integrated defective pregenomes were incorporated into the replicating pool upon wild-type HBV induction.

Conclusions:

• Integrated HBV DNA constructs can function as defective replication units in HepG2 cells.
• Transcriptional activity and replication of these units are regulated by wild-type HBV.
• This model system provides insights into HBV replication and potential therapeutic strategies.