cccDNA
Genome Replication and Regulation of Viral Gene ExpressionCharacterization of Hepatitis B Precore/Core-Related AntigensChronic hepatitis B virus (HBV) infection afflicts approximately 257 million people, who are at high risk of progressing to chronic liver diseases, including fibrosis, cirrhosis, and hepatocellular carcinoma. Current therapies rarely achieve cure of HBV infection due to the persistence of the HBV episome, the covalently closed circular DNA (cccDNA), in the nuclei of infected hepatocytes. Peripheral markers of cccDNA levels and...
Genome Replication and Regulation of Viral Gene ExpressionCharacterization of the Termini of Cytoplasmic Hepatitis B Virus Deproteinated Relaxed Circular DNAThe covalently closed circular DNA (cccDNA) is the persistent form of the hepatitis B virus (HBV) genome in viral infection and an undisputed antiviral target for an HBV cure. HBV cccDNA is converted from viral genomic relaxed circular DNA (rcDNA) through a complex process that involves removing the covalently bound viral polymerase from rcDNA, which produces a deproteinated-rcDNA (DP-rcDNA) intermediate for cccDNA formation. In this...
Virus-Cell InteractionsInterferon Alpha Induces Multiple Cellular Proteins That Coordinately Suppress Hepadnaviral Covalently Closed Circular DNA TranscriptionPegylated IFN-α is the only therapeutic regimen that can induce a functional cure of chronic hepatitis B in a small, but significant, fraction of treated patients. Understanding the mechanisms underlying the antiviral functions of IFN-α in hepadnaviral infection may reveal molecular targets for development of novel antiviral agents to improve the therapeutic efficacy of IFN-α. By a loss-of-function genetic screening of individual IFN-...
Virus-Cell InteractionsAn Alternatively Spliced Sirtuin 2 Isoform 5 Inhibits Hepatitis B Virus Replication from cccDNA by Repressing Epigenetic Modifications Made by Histone Lysine MethyltransferasesSirt2, a predominant cytoplasmic α-tubulin deacetylase, promotes the growth of hepatocellular carcinoma; indeed, HBV replication increases Sirt2 expression, and overexpression of Sirt2 is associated with hepatic fibrosis and epithelial-to-mesenchymal transition. Increased amounts of Sirt2 isoforms 1, 2, and 5 upon HBV replication might further upregulate HBV replication, leading to a vicious cycle of virus replication/disease...
MinireviewRevisiting Hepatitis B Virus: Challenges of Curative TherapiesWith a yearly death toll of 880,000, hepatitis B virus (HBV) remains a major health problem worldwide, despite an effective prophylactic vaccine and well-tolerated, effective antivirals. HBV causes chronic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. The viral genome persists in infected hepatocytes even after long-term antiviral therapy, and its integration, though no longer able to support viral replication,...
Genome Replication and Regulation of Viral Gene ExpressionCellular DNA Topoisomerases Are Required for the Synthesis of Hepatitis B Virus Covalently Closed Circular DNAPersistent HBV infection relies on stable maintenance and proper functioning of a nuclear episomal form of the viral genome called cccDNA, the most stable HBV replication intermediate. One of the major reasons for the failure of currently available antiviral therapeutics to cure chronic HBV infection is their inability to eradicate or inactivate cccDNA. We report here a chemical genetics approach to identify host cellular factors...
Virus-Cell InteractionsParvulin 14 and Parvulin 17 Bind to HBx and cccDNA and Upregulate Hepatitis B Virus Replication from cccDNA to Virion in an HBx-Dependent MannerThe HBx protein plays an essential regulatory role in HBV replication. We found that substrate-binding residues on the human parvulin peptidylprolyl cis/trans isomerase proteins Par14 and Par17 bound to conserved arginine-proline (RP) motifs on HBx in the cytoplasm, nucleus, and mitochondria. The HBx-Par14/Par17 interaction stabilized HBx; promoted its translocation to the nucleus and mitochondria; and stimulated...
Genome Replication and Regulation of Viral Gene ExpressionT5 Exonuclease Hydrolysis of Hepatitis B Virus Replicative Intermediates Allows Reliable Quantification and Fast Drug Efficacy Testing of Covalently Closed Circular DNA by PCRcccDNA elimination is a major goal in future curative regimens for chronic HBV patients. However, PCR-based assays for cccDNA quantification show a principally constrained specificity when high levels of input virus or replicative intermediates are present. Here, we characterized T5 exonuclease as a suitable enzyme for medium-throughput in vitro assays that preserves cccDNA but efficiently removes rcDNA prior to PCR-based...