HAT1 signaling confers to assembly and epigenetic regulation of HBV cccDNA minichromosome

Rationale: Hepatitis B virus (HBV) is a leading cause of liver diseases.HBV covalently closed circular DNA (cccDNA) is a critical obstacle of complete elimination by anti-HBV therapy.HBV cccDNA accumulates in nucleus as a chromatin-like cccDNA minichromosome assembled by histones and non-histones.However, the underlying mechanism of modulation of cccDNA minichromosome in hepatocytes is poorly understood.Methods: A human liver-chimeric mouse model was established.The cccDNA-ChIP, Southern blot analysis, confocal assays, RIP assays and RNA pull-down assays, et al. were performed to assess the mechanism of assembly and epigenetic regulation of cccDNA minichromosome in human liver-chimeric mouse model, human primary hepatocytes (PHH), dHepaRG, HepG2-NTCP cell lines and clinical liver tissues.Results: Importantly, the expression levels of HAT1, CAF-1 and lncRNA HULC were significantly elevated in the liver from HBV-infected human liver-chimeric mice.Strikingly, the depletion of HAT1 reduced HBV replication and cccDNA accumulation, and impaired the assembly of histone H3/H4 and the deposition of HBx and p300 onto cccDNA to form cccDNA minichromosome in the cells.Mechanically, chromatin assembly factor-1 (CAF-1) was involved in the events.Interestingly, HAT1 modified the acetylation of histone H3K27/H4K5/H4K12 on cccDNA minichromosome.Moreover, lncRNA HULC-scaffold HAT1/HULC/HBc complex was responsible for the modification on cccDNA minichromosome.Additionally, HBV activated HAT1 through HBx-co-activated transcriptional factor Sp1 in a positive feedback manner.Conclusion: HAT1 signaling contributes to assembly and epigenetic regulation of HBV cccDNA minichromosome.