title: Hepatitis B virus regulatory HBx protein binding to DDB1 is required but is not sufficient for maximal HBV replication.
abstract: Robust hepatitis B virus (HBV) replication is stimulated by the regulatory HBx protein. HBx binds the cellular protein DDB1; however, the importance of this interaction for HBV replication remains unknown. We tested whether HBx binding to DDB1 was required for HBV replication using a plasmid based replication assay in HepG2 cells. Three DDB1 binding-deficient HBx point mutants (HBx(69), HBx(90/91), HBx(R96E)) failed to restore wildtype levels of replication from an HBx-deficient plasmid, which established the importance of the HBx-DDB1 interaction for maximal HBV replication. Analysis of overlapping HBx truncation mutants revealed that both the HBx-DDB1 binding domain and the carboxyl region are required for maximal HBV replication both in vitro and in vivo, suggesting the HBx-DDB1 interaction recruits regulatory functions critical for replication. Finally we demonstrate that HBx localizes to the Cul4A-DDB1 complex, and discuss the possible implications for models of HBV replication.
authors.affiliation: Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Hodgson
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Hyser
authors.forename: Victor V
authors.initials: VV
authors.lastname: Keasler
authors.forename: Yong
authors.initials: Y
authors.lastname: Cang
authors.forename: Betty L
authors.initials: BL
authors.lastname: Slagle
mesh_terms: D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D056945:Hep G2 Cells; D006509:Hepatitis B / Q000378:metabolism* / Q000821:virology; D006515:Hepatitis B virus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D006801:Humans; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins; D014779:Virus Replication
chemical_list: C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein