Binding of nuclear factors to functional domains of the duck hepatitis B virus enhancer

• DOI: 10.1128/jvi.67.10.6192-6200.1993
• Publication Date: 2020-01-06T16:29:36Z
• Authors: A Lilienbaum; B Crescenzo-Chaigne; A A Sall; J Pillot; E Elfassi
• Keywords: MESH: Thymidine Kinase; MESH: Cell Nucleus; 0301 basic medicine; Hepatitis B virus; [SDV]Life Sciences [q-bio]; Molecular Sequence Data; Restriction Mapping; MESH: Binding, Competitive; Genome, Viral; MESH: Base Sequence; Binding, Competitive; Thymidine Kinase; Hepatitis B Virus, Duck; MESH: Hepatitis B Virus, Duck; 03 medical and health sciences; MESH: Promoter Regions, Genetic; Animals; Deoxyribonuclease I; Humans; MESH: Animals; MESH: Tumor Cells, Cultured; Promoter Regions, Genetic; MESH: Restriction Mapping; Cells, Cultured; Cell Nucleus; MESH: Humans; MESH: Molecular Sequence Data; Binding Sites; Base Sequence; Nuclear Proteins; MESH: Transcription Factors; MESH: Deoxyribonuclease I; MESH: DNA, Viral; 3. Good health; [SDV] Life Sciences [q-bio]; MESH: Hepatitis B virus; Enhancer Elements, Genetic; MESH: Binding Sites; Oligodeoxyribonucleotides; DNA, Viral; MESH: Oligodeoxyribonucleotides; MESH: Enhancer Elements, Genetic; MESH: Genome, Viral; MESH: Nuclear Proteins; MESH: Cells, Cultured; Transcription Factors

We have analyzed the structures, relative organization, and activities of binding sites for nuclear factors in the duck hepatitis B virus (duck HBV) enhancer. DNase I footprinting analysis and mobility shift assays demonstrate that this enhancer of 192 bp contains at least three binding sites for transcription factors: one for hepatocyte-adipocyte C/EBP, a second for the liver-specific transactivator hepatocyte nuclear factor 1 HNF-1, and a third for a factor, called F3, which binds to a DNA sequence bearing some resemblance to that for the ubiquitous factor EF-C. Analysis of transcriptional activity reveals that oligonucleotides corresponding to the individual binding sites, inserted upstream from a heterologous promoter, display very weak enhancer activity, whereas the enhancer encompassing these three sites displays very high activity. Analysis of duck HBV enhancer mutants indicates that the deletion of any of these sites leads to a modification of transcriptional enhancer activity. The hepatocyte nuclear factor 1 binding site is crucial, since an internal deletion of 14 bp abolishes the activity. The C/EBP site can act as repressor, and the F3 site is required for full activity. Comparative analysis reveals that the nuclear factors are similar to those bound to the human HBV enhancer but that the organization of their binding sites in the duck HBV enhancer is different.