title: Characterization of the hepatitis B virus EnhI enhancer and X promoter complex.
abstract: The hepatitis B virus EnhI enhancer element overlaps the promoter of the X gene. By performing methylation interference experiments, four protein factor binding sites clustered in a 120-bp region were found to control the EnhI enhancer and X promoter activities. Deletion mapping experiments indicated that the two upstream protein factor binding sites constituted a basal enhancer module. This module, likely bound by a liver-specific factor and a ubiquitous factor, could activate the herpes simplex virus thymidine kinase gene promoter by 5- or 10-fold, depending on the orientation, in Huh7 cells, a liver-derived cell line, but not in other cell types tested. The two downstream protein factor binding sites interact with the upstream basal enhancer module in an orientation- and distance-dependent manner to increase the enhancer activity by another 10-fold. In addition, at least one of the two downstream protein factor binding sites is also essential for the X promoter activity.
authors.affiliation: Department of Microbiology, University of Southern California, Los Angeles 90033-1054.
authors.forename: W T
authors.initials: WT
authors.lastname: Guo
authors.forename: K D
authors.initials: KD
authors.lastname: Bell
authors.forename: J H
authors.initials: JH
authors.lastname: Ou
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D002467:Cell Nucleus / Q000502:physiology; D002872:Chromosome Deletion; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D015870:Gene Expression; D005814:Genes, Viral; D013006:Growth Hormone / Q000235:genetics; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D008113:Liver Neoplasms; D008969:Molecular Sequence Data; D010957:Plasmids; D011401:Promoter Regions, Genetic; D018139:Simplexvirus / Q000201:enzymology / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D013006:Growth Hormone; D013937:Thymidine Kinase