title: [Roles of full-length and truncated hepatitis B virus X protein and of interactions with the host-encoded damaged DNA binding protein 1 in HBV replication].
abstract: OBJECTIVE
  To investigate the roles of the hepatitis B virus (HBV)-encoded X protein (HBx), including the full-length and truncated isoforms, and in conjunction with the host-encoded damaged DNA binding protein 1 (DDB1) in HBV replication.
  
  
  METHODS
  Recominant expression plasmids carrying the wild-type HBV genome (pGEM-HBV1.2) or with deletion of the full-length HBx protein (pHBV-deltaX), or carrying the full-length HBx protein (pSI-X) or the HBx1to101 (pSI-X1to101) or HBx43to154 (pSI-X43to154) isoforms were constructed for transfection into HepG2 cells. The pcDNA6.2-GW/EmGFP-miR (DDB1-miRNA) vector was constructed for silencing of the DDB1 gene in co-transfected HepG2 cells. At 72 h after transfections, DDB1 silencing was confirmed by western blot analysis and real-time quantitive reverse transcription PCR, HBV DNA copies number was assessed by real time PCR, and levels of hepatitis B surface antigen (HbsAg) and hepatitis B e antigen (HbeAg) were determined by ELISA. Differences between groups was statistically analyzed by single-factor analysis of variance and the t-test.
  
  
  RESULTS
  Transfection with pHBV-deltaX led to reductions in DDB1 mRNA (to 52.74% of that in the wild-type pGEM-HBV1.2 transfected cells), HBV replication (to 55.49%), HBsAg level (48.05%), and HBeAg level (46.22%). Co-transfection with pSI-X or pSI-X43to154, but not with pSI-X1to101, restored the pHBV-deltaX-induced reductions in DDB1 mRNA, HBV replication, HBsAg and HBeAg to wild-type levels. The quantity of DDB1 mRNA was approximately parallel with the quantity of HBV DNA copies in all the HepG2 transfection groups.
  
  
  CONCLUSIONS
  The COOH-terminal amino acids of HBx are required for HBV replication in hepatocytes, possibly involving the host-encoded DDB1 protein.
authors.affiliation: Zhongshan Hospital, Fudan University, Shanghai 200032, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Yang
authors.forename: Song
authors.initials: S
authors.lastname: He
authors.forename: Na
authors.initials: N
authors.lastname: Luo
authors.forename: Li
authors.initials: L
authors.lastname: Luo
authors.forename: Hao
authors.initials: H
authors.lastname: Fan
authors.forename: Qian
authors.initials: Q
authors.lastname: Gong
mesh_terms: D004268:DNA-Binding Proteins / Q000378:metabolism*; D056945:Hep G2 Cells; D006514:Hepatitis B Surface Antigens / Q000378:metabolism; D006513:Hepatitis B e Antigens / Q000378:metabolism; D006515:Hepatitis B virus / Q000378:metabolism* / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D020033:Protein Isoforms / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014162:Transfection; D054334:Viral Regulatory and Accessory Proteins; D014779:Virus Replication
chemical_list: C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; D006514:Hepatitis B Surface Antigens; D006513:Hepatitis B e Antigens; D020033:Protein Isoforms; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein