title: Hepatitis delta virus proteins repress hepatitis B virus enhancers and activate the alpha/beta interferon-inducible MxA gene.
abstract: Co-infection and superinfection of hepatitis B virus (HBV) with hepatitis delta virus (HDV) leads to suppression of HBV replication both in patients and in animal and cellular models. The mechanisms behind this inhibition have not previously been explored fully. HBV replication is governed by four promoters and two enhancers, Enh1 and Enh2. Repression of these enhancers has been reported to be one of the main mechanisms of HBV inhibition. Moreover, in a previous study, it has been demonstrated that alpha interferon (IFN-alpha)-inducible MxA protein inhibits HBV replication. HDV encodes two proteins, p24 and p27. p27 was shown to activate several heterologous promoters, including HBV promoters. In an attempt to analyse the mechanisms of HBV inhibition by HDV, the question was raised whether HDV proteins could act directly by repressing HBV enhancers, and/or indirectly by activating the MxA gene. This issue was addressed in a co-transfection model in Huh-7 cells, using p24- or p27-expressing plasmids along with Enh1, Enh2, HBV and MxA promoter-luciferase constructs. Enh1 and Enh2 were strongly repressed, by 60 and 80 % and 40 and 60 %, by p24 and p27, respectively. In addition, p27 was responsible for threefold activation of the MxA promoter and potentiation of IFN-alpha on this promoter. MxA mRNA quantification and a virus yield reduction assay confirmed these results. In conclusion, this study shows that HDV proteins inhibit HBV replication by trans-repressing its enhancers and by trans-activating the IFN-alpha-inducible MxA gene.
authors.affiliation: INSERM U845, Faculté de Médecine de Necker, Université Paris 5, France.|Service de Bactériologie, Virologie, Hygiène, Associé au Centre National de Référence des Hépatites B, C et Delta, Hôpital Avicenne, Assistance Publique des Hôpitaux de Paris, Université Paris 13, Faculté de Bobigny, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Williams
authors.affiliation: INSERM U845, Faculté de Médecine de Necker, Université Paris 5, France.|Service de Bactériologie, Virologie, Hygiène, Associé au Centre National de Référence des Hépatites B, C et Delta, Hôpital Avicenne, Assistance Publique des Hôpitaux de Paris, Université Paris 13, Faculté de Bobigny, France.
authors.forename: Ségolène
authors.initials: S
authors.lastname: Brichler
authors.affiliation: Service de Bactériologie, Virologie, Hygiène, Associé au Centre National de Référence des Hépatites B, C et Delta, Hôpital Avicenne, Assistance Publique des Hôpitaux de Paris, Université Paris 13, Faculté de Bobigny, France.
authors.forename: Nadjia
authors.initials: N
authors.lastname: Radjef
authors.affiliation: Laboratoire de Virologie, Hôpital Saint Vincent de Paul, Université Paris 5, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Lebon
authors.affiliation: Service de Virologie, UPRES EA 3610 Faculté de Médecine, Université Lille 2, Centre Hospitalier Régional et Universitaire de Lille, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Goffard
authors.affiliation: Service de Virologie, UPRES EA 3610 Faculté de Médecine, Université Lille 2, Centre Hospitalier Régional et Universitaire de Lille, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Hober
authors.affiliation: Laboratoire de Biochimie, Hôpital Avicenne, Assistance Publique des Hôpitaux de Paris, Université Paris 13, Faculté de Bobigny, France.
authors.forename: Remi
authors.initials: R
authors.lastname: Fagard
authors.affiliation: INSERM U845, Faculté de Médecine de Necker, Université Paris 5, France.
authors.forename: Dina
authors.initials: D
authors.lastname: Kremsdorf
authors.affiliation: INSERM U871, Lyon, France.|Service de Bactériologie, Virologie, Hygiène, Associé au Centre National de Référence des Hépatites B, C et Delta, Hôpital Avicenne, Assistance Publique des Hôpitaux de Paris, Université Paris 13, Faculté de Bobigny, France.
authors.forename: Paul
authors.initials: P
authors.lastname: Dény
authors.affiliation: INSERM U845, Faculté de Médecine de Necker, Université Paris 5, France.|Service de Bactériologie, Virologie, Hygiène, Associé au Centre National de Référence des Hépatites B, C et Delta, Hôpital Avicenne, Assistance Publique des Hôpitaux de Paris, Université Paris 13, Faculté de Bobigny, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Gordien
mesh_terms: D019677:Artificial Gene Fusion; D002460:Cell Line; D004742:Enhancer Elements, Genetic; D019204:GTP-Binding Proteins / Q000096:biosynthesis*; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D006515:Hepatitis B virus / Q000254:growth & development / Q000502:physiology*; D003698:Hepatitis Delta Virus / Q000254:growth & development / Q000502:physiology*; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D064547:Myxovirus Resistance Proteins; D011485:Protein Binding; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D014764:Viral Proteins; D008156:Luciferases; D019204:GTP-Binding Proteins