title: The Ubiquitin Ligase Itch and Ubiquitination Regulate BFRF1-Mediated Nuclear Envelope Modification for Epstein-Barr Virus Maturation.
abstract: The cellular endosomal sorting complex required for transport (ESCRT) was recently found to mediate important morphogenesis processes at the nuclear envelope (NE). We previously showed that the Epstein-Barr virus (EBV) BFRF1 protein recruits the ESCRT-associated protein Alix to modulate NE structure and promote EBV nuclear egress. Here, we uncover new cellular factors and mechanisms involved in this process. BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. BFRF1 is ubiquitinated, and elimination of possible ubiquitination by either lysine mutations or fusion of a deubiquitinase hampers NE-derived vesicle formation and virus maturation. While it interacts with multiple Nedd4-like ubiquitin ligases, BFRF1 preferentially binds Itch ligase. We show that Itch associates with Alix and BFRF1 and is required for BFRF1-induced NE vesicle formation. Our data demonstrate that Itch, ubiquitin, and Alix control the BFRF1-mediated modulation of the NE and EBV maturation, uncovering novel regulatory mechanisms of nuclear egress of viral nucleocapsids.
  
  
  
  The nuclear envelope (NE) of eukaryotic cells not only serves as a transverse scaffold for cellular processes, but also as a natural barrier for most DNA viruses that assemble their nucleocapsids in the nucleus. Previously, we showed that the cellular endosomal sorting complex required for transport (ESCRT) machinery is required for the nuclear egress of EBV. Here, we further report the molecular interplay among viral BFRF1, the ESCRT adaptor Alix, and the ubiquitin ligase Itch. We found that BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. The lysine residues and the ubiquitination of BFRF1 regulate the formation of BFRF1-induced NE-derived vesicles and EBV maturation. During the process, a ubiquitin ligase, Itch, preferably associates with BFRF1 and is required for BFRF1-induced NE vesicle formation. Therefore, our data indicate that Itch, ubiquitin, and Alix control the BFRF1-mediated modulation of the NE, suggesting novel regulatory mechanisms for ESCRT-mediated NE modulation.
authors.affiliation: School of Nursing, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan.
authors.forename: Chung-Pei
authors.initials: CP
authors.lastname: Lee
authors.affiliation: School of Nursing, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Guan-Ting
authors.initials: GT
authors.lastname: Liu
authors.affiliation: Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Hsiu-Ni
authors.initials: HN
authors.lastname: Kung
authors.affiliation: Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Po-Ting
authors.initials: PT
authors.lastname: Liu
authors.affiliation: Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yen-Tzu
authors.initials: YT
authors.lastname: Liao
authors.affiliation: Graduate Institute of Medical Genomics and Proteomics, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Lu-Ping
authors.initials: LP
authors.lastname: Chow
authors.affiliation: Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Ling-Shih
authors.initials: LS
authors.lastname: Chang
authors.affiliation: Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yu-Hsin
authors.initials: YH
authors.lastname: Chang
authors.affiliation: Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Chou-Wei
authors.initials: CW
authors.lastname: Chang
authors.affiliation: Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Wen-Chi
authors.initials: WC
authors.lastname: Shu
authors.affiliation: Department of Biological Sciences, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Annie
authors.initials: A
authors.lastname: Angers
authors.affiliation: Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Farina
authors.affiliation: Institute of Cancer Research, National Health Research Institutes, Taipei, Taiwan.
authors.forename: Su-Fang
authors.identifier: 0000-0001-8706-2439
authors.initials: SF
authors.lastname: Lin
authors.affiliation: Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Ching-Hwa
authors.initials: CH
authors.lastname: Tsai
authors.affiliation: Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Fadila
authors.initials: F
authors.lastname: Bouamr
authors.affiliation: Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan mrc@ntu.edu.tw.
authors.forename: Mei-Ru
authors.initials: MR
authors.lastname: Chen
mesh_terms: D006367:HeLa Cells; D004854:Herpesvirus 4, Human / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*; D019065:Virus Assembly; D014779:Virus Replication
chemical_list: C406064:BFRF1 protein, Human herpesvirus 4; D008565:Membrane Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; C432966:ITCH protein, human; D044767:Ubiquitin-Protein Ligases