SIRT3 restricts HBV transcription and replication via epigenetic regulation of cccDNA involving SUV39H1 and SETD1A histone methyltransferases

Ren JH¹, Hu JL^1,2, Cheng ST¹, Yu HB¹, Wong VKW³, Law BYK³, Yang YF⁴, Huang Y¹, Liu Y¹, Chen WX⁵, Cai XF¹, Tang H¹, Hu Y¹, Zhang WL¹, Liu X¹, Long QX¹, Zhou L⁶, Tao NN¹, Zhou HZ¹, Yang QX¹, Ren F¹, He L¹, Gong R¹, Huang AL^1,2, Chen J¹.

Hepatology. 2018 Apr 6. doi: 10.1002/hep.29912.

PMID:29624717   DOI:10.1002/hep.29912

Abstract

Hepatitis B virus (HBV) infection remains a major health problem worldwide. Maintenance of the covalently closed circular DNA (cccDNA) which serves as a template for HBV RNA transcription is responsible for the failure of eradicating chronic HBV during current antiviral therapy. cccDNA is assembled with cellular histone proteins into chromatin, but little is known about the regulation of HBV chromatin by histone posttranslational modifications. In this study, we identified SIRT3 as a host factor restricting HBV transcription and replication by screening seven members of Sirtuin family which is the class III histone deacetylase. Ectopic SIRT3 expression significantly reduced total HBV RNAs, 3.5-kb RNA as well as replicative intermediate DNA in HBV-infected HepG2-NTCP cells and PHH. In contrast, gene silencing of SIRT3 promoted HBV transcription and replication. Mechanistic study found nuclear SIRT3 was recruited to the HBV cccDNA, where it deacetylated histone 3 lysine 9 (H3K9). Importantly, occupancy of SIRT3 onto cccDNA could increase the recruitment of histone methyltransferase SUV39H1 to cccDNA and decrease recruitment of SETD1A, leading to a marked increase of H3K9me3 and a decrease of H3K4me3 on cccDNA. Moreover, SIRT3-mediated HBV cccDNA transcriptional repression involved decreased binding of host RNA polymerase II and transcription factor YY1 to cccDNA. Finally, viral protein HBx could relieve SIRT3-mediated cccDNA transcriptional repression by inhibiting both SIRT3 expression and its recruitment to cccDNA.