IFN-α confers epigenetic regulation of HBV cccDNA minichromosome by modulating GCN5-mediated succinylation of histone H3K79 to clear HBV cccDNA

Abstract

Background Hepatitis 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. Results Succinylation 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. Conclusions IFN-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.

Systematic Analysis of Lysine Succinylation in Vero cells infected with Small Ruminant Morbillivirus

“…Increasing evidence indicates that histone acylation modifications have important roles in virus infection. Yuan Y et al first reported that histone succinylation might promote HBV replication (69). Interestingly, significantly expression of histone succinylated protein was not found in this study which indicates that histone succinylation might have little effect on SRMV infection.…”

Histone succinylation and its function on the nucleosome

“…Furthermore, the inhibition of KAT2A succinylation reduces H3K79 succinylation, thereby restricting HBV replication. These phenomena were verified in the reduction of cccDNA expression in cells expressing siKAT2A 58 . In addition, KAT2A‐mediated succinylation of histone H3K79 was found to contribute to epigenetic regulation of cccDNA microchromosomes.…”

Recent Advances in Hepatitis B Treatment

“…They have improved pharmacokinetics and allowed for a longer half-life, enabling a weekly administration [ 66 ]. PEG-IFN-α is administered subcutaneously and has direct antiviral as well as immunomodulatory activity [ 67 , 68 , 69 , 70 ]. One year of PEG-IFN-α treatment in HbeAg-positive patients led to HbeAg seroconversion in 29–32% of the patients and sustainable reduced HbsAg levels in 3–7% of the patients, 24 weeks after the end of the treatment, highlighting the effectiveness of PEG-IFN-α against HBV [ 2 , 71 ].…”