title: HBx relieves chromatin-mediated transcriptional repression of hepatitis B viral cccDNA involving SETDB1 histone methyltransferase.
abstract: OBJECTIVE
  Maintenance of the covalently closed circular HBV DNA (cccDNA) that serves as a template for HBV transcription is responsible for the failure of antiviral therapies. While studies in chronic hepatitis patients have shown that high viremia correlates with hyperacetylation of cccDNA-associated histones, the molecular mechanisms controlling cccDNA stability and transcriptional regulation are still poorly understood. This study aimed to decipher the role of chromatin and chromatin modifier proteins on HBV transcription.
  
  
  METHODS
  We analyzed the chromatin structure of actively transcribed or silenced cccDNA by infecting primary human hepatocytes and differentiated HepaRG cells with wild-type virus or virus deficient (HBVX-) for the expression of hepatitis B virus X protein (HBx), that is required for HBV expression.
  
  
  RESULTS
  In the absence of HBx, HBV cccDNA was transcriptionally silenced with the concomitant decrease of histone 3 (H3) acetylation and H3K4me3, increase of H3 di- and tri-methylation (H3K9me) and the recruitment of heterochromatin protein 1 factors (HP1) that correlate with condensed chromatin. SETDB1 was found to be the main histone methyltransferase responsible for the deposition of H3K9me3 and HBV repression. Finally, full transcriptional reactivation of HBVX- upon HBx re-expression correlated with an increase of histone acetylation and H3K4me3, and a concomitant decrease of HP1 binding and of H3K9me3 on the cccDNA.
  
  
  CONCLUSIONS
  Upon HBV infection, cellular mechanisms involving SETDB1-mediated H3K9me3 and HP1 induce silencing of HBV cccDNA transcription through modulation of chromatin structure. HBx is able to relieve this repression and allow the establishment of active chromatin.
authors.affiliation: Unité des Hépacivirus et Immunité Innée, Institut Pasteur, 28 rue du Dr. Roux, 75015 Paris, France; UMR CNRS 3569, 28 rue du Dr. Roux, 75015 Paris, France.
authors.forename: Lise
authors.initials: L
authors.lastname: Rivière
authors.affiliation: Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon, F-69000 Lyon, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Gerossier
authors.affiliation: Unité des Hépacivirus et Immunité Innée, Institut Pasteur, 28 rue du Dr. Roux, 75015 Paris, France; UMR CNRS 3569, 28 rue du Dr. Roux, 75015 Paris, France; Institute for Experimental Virology, Group Innate Immunity and Viral Evasion, 30625 Hannover, Germany(†).
authors.forename: Aurélie
authors.initials: A
authors.lastname: Ducroux
authors.affiliation: Laboratoire de Pathogenèse des Virus de l'Hépatite B, Département de Virologie, Institut Pasteur, 75015 Paris, France.
authors.forename: Sarah
authors.initials: S
authors.lastname: Dion
authors.affiliation: Laboratoire de Pathogenèse des Virus de l'Hépatite B, Département de Virologie, Institut Pasteur, 75015 Paris, France; Laboratory of Molecular Virology and Immunology, Institute Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China(†).
authors.forename: Qiang
authors.initials: Q
authors.lastname: Deng
authors.affiliation: Laboratoire de Pathogenèse des Virus de l'Hépatite B, Département de Virologie, Institut Pasteur, 75015 Paris, France.
authors.forename: Marie-Louise
authors.initials: ML
authors.lastname: Michel
authors.affiliation: Inserm Unit U785, University Paris-Sud, Paul Brousse Hospital, 12 Avenue Paul Vaillant Couturier, 94800 Villejuif, France.
authors.forename: Marie-Annick
authors.initials: MA
authors.lastname: Buendia
authors.affiliation: Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon, F-69000 Lyon, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Hantz
authors.affiliation: Unité des Hépacivirus et Immunité Innée, Institut Pasteur, 28 rue du Dr. Roux, 75015 Paris, France; UMR CNRS 3569, 28 rue du Dr. Roux, 75015 Paris, France. Electronic address: christine.neuveut@pasteur.fr.
authors.forename: Christine
authors.initials: C
authors.lastname: Neuveut
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D015139:Blotting, Southern; D002478:Cells, Cultured; D004270:DNA, Circular / Q000235:genetics* / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay; D006509:Hepatitis B / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D006515:Hepatitis B virus / Q000235:genetics* / Q000378:metabolism; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D011496:Protein Methyltransferases / Q000235:genetics* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004270:DNA, Circular; D004279:DNA, Viral; C110719:LAMTOR5 protein, human; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; C454062:SETDB1 protein, human
keywords: Epigenetic; HBV; HBx; HP1; SETDB1; cccDNA regulation