title: Viral reprogramming of the Daxx histone H3.3 chaperone during early Epstein-Barr virus infection.
abstract: Host chromatin assembly can function as a barrier to viral infection. Epstein-Barr virus (EBV) establishes latent infection as chromatin-assembled episomes in which all but a few viral genes are transcriptionally silent. The factors that control chromatin assembly and guide transcription regulation during the establishment of latency are not well understood. Here, we demonstrate that the EBV tegument protein BNRF1 binds the histone H3.3 chaperone Daxx to modulate histone mobility and chromatin assembly on the EBV genome during the early stages of primary infection. We demonstrate that BNRF1 substitutes for the repressive cochaperone ATRX to form a ternary complex of BNRF1-Daxx-H3.3-H4, using coimmunoprecipitation and size-exclusion chromatography with highly purified components. FRAP (fluorescence recovery after photobleaching) assays were used to demonstrate that BNRF1 promotes global mobilization of cellular histone H3.3. Mutation of putative nucleotide binding motifs on BNRF1 attenuates the displacement of ATRX from Daxx. We also show by immunofluorescence combined with fluorescence in situ hybridization that BNRF1 is important for the dissociation of ATRX and Daxx from nuclear bodies during de novo infection of primary B lymphocytes. Virion-delivered BNRF1 suppresses Daxx-ATRX-mediated H3.3 loading on viral chromatin as measured by chromatin immunoprecipitation assays and enhances viral gene expression during early infection. We propose that EBV tegument protein BNRF1 replaces ATRX to reprogram Daxx-mediated H3.3 loading, in turn generating chromatin suitable for latent gene expression.
  
  
  OBJECTIVE
  Epstein-Barr Virus (EBV) is a human herpesvirus that efficiently establishes latent infection in primary B lymphocytes. Cellular chromatin assembly plays an important role in regulating the establishment of EBV latency. We show that the EBV tegument protein BNRF1 functions to regulate chromatin assembly on the viral genome during early infection. BNRF1 alters the host cellular chromatin assembly to prevent antiviral repressive chromatin and establish chromatin structure permissive for viral gene expression and the establishment of latent infection.
authors.affiliation: The Wistar Institute, Philadelphia, Pennsylvania, USA Perelman School of Medicine, The University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Tsai
authors.affiliation: The Wistar Institute, Philadelphia, Pennsylvania, USA.
authors.forename: Lilian
authors.initials: L
authors.lastname: Chan
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Gibeault
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Kristen
authors.initials: K
authors.lastname: Conn
authors.affiliation: The Wistar Institute, Philadelphia, Pennsylvania, USA.
authors.forename: Jayaraju
authors.initials: J
authors.lastname: Dheekollu
authors.affiliation: The Wistar Institute, Philadelphia, Pennsylvania, USA Perelman School of Medicine, The University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: John
authors.initials: J
authors.lastname: Domsic
authors.affiliation: The Wistar Institute, Philadelphia, Pennsylvania, USA Perelman School of Medicine, The University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Ronen
authors.initials: R
authors.lastname: Marmorstein
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Luis M
authors.initials: LM
authors.lastname: Schang
authors.affiliation: The Wistar Institute, Philadelphia, Pennsylvania, USA lieberman@wistar.org.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Lieberman
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D001402:B-Lymphocytes / Q000821:virology; D001665:Binding Sites; D002478:Cells, Cultured; D002850:Chromatography, Gel; D056970:Co-Repressor Proteins; D004265:DNA Helicases / Q000037:antagonists & inhibitors*; D036681:Fluorescence Recovery After Photobleaching; D005455:Fluorescent Antibody Technique; D004854:Herpesvirus 4, Human / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D047468:Immunoprecipitation; D017404:In Situ Hybridization, Fluorescence; D018832:Molecular Chaperones; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D014759:Viral Envelope Proteins / Q000378:metabolism*; D017735:Virus Latency; D000075924:X-linked Nuclear Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D018832:Molecular Chaperones; D050505:Mutant Proteins; D009687:Nuclear Proteins; C062724:P140 protein, Epstein-barr virus; D014759:Viral Envelope Proteins; D004265:DNA Helicases; C092332:ATRX protein, human; D000075924:X-linked Nuclear Protein