Abstract
BackgroundHepatitis B virus covalently closed circular DNA (HBV cccDNA) is assembled by histones and non-histones into a chromatin-like cccDNA minichromosome in the nucleus. The cellular histone acetyltransferase GCN5, displaying succinyltransferase activity, is recruited onto cccDNA to modulate HBV transcription in cells. Clinically, IFN-α is able to repress cccDNA. However, the underlying mechanism of IFN-α in the depression of cccDNA mediated by GCN5 is poorly understood. Here, we explored the effect of IFN-α on GCN5-mediated succinylation in the epigenetic regulation of HBV cccDNA minichromosome.ResultsSuccinylation modification of the cccDNA minichromosome has been observed in HBV-infected human liver-chimeric mice and HBV-expressing cell lines. Moreover, histone H3K79 succinylation by GCN5 was identified in the system. Interestingly, the mutant of histone H3K79 efficiently blocked the replication of HBV, and interference with GCN5 resulted in decreased levels of HBV DNA, HBsAg, and HBeAg in the supernatant from de novo HBV-infected HepaRG cells. Consistently, the levels of histone H3K79 succinylation were significantly elevated in the livers of HBV-infected human liver-chimeric mice. The knockdown or overexpression of GCN5 or the mutant of GCN5 could affect the binding of GCN5 to cccDNA or H3K79 succinylation, leading to a change in cccDNA transcription activity. In addition, Southern blot analysis validated that siGCN5 decreased the levels of cccDNA in the cells, suggesting that GCN5-mediated succinylation of histone H3K79 contributes to the epigenetic regulation of cccDNA minichromosome. Strikingly, IFN-α effectively depressed histone H3K79 succinylation in HBV cccDNA minichromosome in de novo HepG2-NTCP and HBV-infected HepaRG cells.ConclusionsIFN-α epigenetically regulates the HBV cccDNA minichromosome by modulating GCN5-mediated succinylation of histone H3K79 to clear HBV cccDNA. Our findings provide new insights into the mechanism by which IFN-α modulate the epigenetic regulation of HBV cccDNA minichromosome.
Highlights
Chronic hepatitis B virus (HBV) infection is a leading cause of hepatitis, cirrhosis, and liver cancer, resulting in an estimated 650,000 deaths per year [1,2,3]
Histone H3K79 succinylation is anchored on the HBV closed circular DNA (cccDNA) minichromosome Similar to the nucleosome in host cells, HBV cccDNA is organized into a chromatin-like minichromosome by histones and non-histone proteins [27]
We validated the data in HBV-expressing HepaRG and HepG2-NTCP cells (Fig. 1b and c), suggesting that histone H3 succinylation is anchored on the HBV cccDNA minichromosome
Summary
Chronic hepatitis B virus (HBV) infection is a leading cause of hepatitis, cirrhosis, and liver cancer, resulting in an estimated 650,000 deaths per year [1,2,3]. The encapsidated rcDNA is imported into the nucleus, where it is converted into covalently closed circular DNA (cccDNA), which serves as the template for viral transcription and secures HBV persistence [7,8,9]. Cellular proteins, such as histone H3, H4, H2A, and H2B, are the main structural components assembled onto cccDNA to form the original cccDNA minichromosome [11, 12]. Hepatitis B virus covalently closed circular DNA (HBV cccDNA) is assembled by histones and nonhistones into a chromatin-like cccDNA minichromosome in the nucleus. The cellular histone acetyltransferase GCN5, displaying succinyltransferase activity, is recruited onto cccDNA to modulate HBV transcription in cells. We explored the effect of IFN-α on GCN5-mediated succinylation in the epigenetic regulation of HBV cccDNA minichromosome
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