title: Kaposi's sarcoma-associated herpesvirus LANA-1 interacts with the short variant of BRD4 and releases cells from a BRD4- and BRD2/RING3-induced G1 cell cycle arrest.
abstract: The Kaposi's sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen 1 (LANA-1) is required for the replication of episomal viral genomes. Regions in its N-terminal and C-terminal domains mediate the interaction with host cell chromatin. Several cellular nuclear proteins, e.g., BRD2/RING3, histones H2A and H2B, MeCP2, DEK, and HP1alpha, have been suggested to mediate this interaction. In this work, we identify the double-bromodomain proteins BRD4 and BRD3/ORFX as additional LANA-1 interaction partners. The carboxy-terminal region of the short variant of BRD4 (BRD4S) containing the highly conserved extraterminal domain directly interacts with an element in the LANA-1 carboxy-terminal domain. We show that ectopically expressed BRD4S and BRD2/RING3 delay progression into the S phase of the cell cycle in epithelial and B-cell lines and increase cyclin E promoter activity. LANA-1 partly releases epithelial and B cells from a BRD4S- and BRD2/RING3-induced G1 cell cycle arrest and also promotes S-phase entry in the presence of BRD4S and BRD2/RING3. This is accompanied by a reduction in BRD4S-mediated cyclin E promoter activity. Our data are in keeping with the notion that the direct interaction of KSHV LANA-1 with BRD4 and other BRD proteins could play a role in the G1/S phase-promoting functions of KSHV LANA-1. Further, our data support a model in which the LANA-1 C terminus contributes to a functional attachment to acetylated histones H3 and H4 via BRD4 and BRD2, in addition to the recently demonstrated direct interaction (A. J. Barbera, J. V. Chodaparambil, B. Kelley-Clarke, V. Joukov, J. C. Walter, K. Luger, and K. M. Kaye, Science 311:856-861, 2006) of the LANA-1 N terminus with histones H2A and H2B.
authors.affiliation: Institut für Virologie, Medizinische Hochschule Hannover, Carl-Neuberg Str. 1, 30625 Hannover, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Ottinger
authors.forename: Thomas
authors.initials: T
authors.lastname: Christalla
authors.forename: Kavita
authors.initials: K
authors.lastname: Nathan
authors.forename: Melanie M
authors.initials: MM
authors.lastname: Brinkmann
authors.forename: Abel
authors.initials: A
authors.lastname: Viejo-Borbolla
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Schulz
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins; D002460:Cell Line; D000090266:Chromobox Protein Homolog 5; D019927:Cyclin E / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D016193:G1 Phase / Q000502:physiology*; D014644:Genetic Variation; D006367:HeLa Cells; D019288:Herpesvirus 8, Human / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity* / Q000502:physiology; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D015514:Oncogene Proteins, Fusion / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016196:S Phase / Q000502:physiology; D014157:Transcription Factors; D015533:Transcriptional Activation; D000092468:Bromodomain Containing Proteins
chemical_list: D000956:Antigens, Viral; D018797:Cell Cycle Proteins; D000090266:Chromobox Protein Homolog 5; D019927:Cyclin E; D017931:DNA Primers; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; D014157:Transcription Factors; C098415:BRD2 protein, human; D000092468:Bromodomain Containing Proteins; C441289:BRD4 protein, human; C000715594:CBX5 protein, human; C109540:latency-associated nuclear antigen