title: Purification and properties of rat liver nuclear proteins that interact with the hepatitis B virus enhancer 1.
abstract: The hepatitis B virus enhancer 1 element plays a fundamental role in the liver-specific regulation of hepatitis B virus gene expression. A central region of enhancer 1, the enhancer core domain, contains at least four cis-acting sequence motifs that are essential for enhancer 1 activity. In this study, we have investigated an essential motif within the core domain previously defined as footprint V (FPV). Transient transfection analyses demonstrate that FPV is capable of independently functioning in a liver-specific manner to activate transcription. Therefore, to further examine the liver-specific properties of FPV-mediated enhancer 1 activity, we have carried out the biochemical purification and characterization of FPV binding activity from rat liver nuclei. This study has conclusively identified hepatocyte nuclear factor 3beta (HNF-3beta), a liver-enriched member of the HNF-3/forkhead gene family, as the predominant purified protein that interacts with the FPV motif. Moreover, a cellular protein(s) that copurified with HNF-3beta specifically interacts with a novel sequence motif that partially overlaps FPV. Since this novel motif contains a palindromic sequence, we have tentatively referred to the protein(s) that binds to this site as palindrome-binding factor (PBF). Additional evidence indicates that HNF-3beta and PBF cooperatively interact with enhancer 1. Therefore, this study supports the hypothesis that FPV-mediated enhancer activity involves a cooperative interplay between HNF-3beta and at least one other enhancer 1-binding protein, PBF.
authors.affiliation: Department of Microbiology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Kosovsky
authors.forename: B
authors.initials: B
authors.lastname: Huan
authors.forename: A
authors.initials: A
authors.lastname: Siddiqui
mesh_terms: D051698:Activating Transcription Factor 2; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002846:Chromatography, Affinity; D002874:Chromosome Mapping; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004742:Enhancer Elements, Genetic; D005260:Female; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D006515:Hepatitis B virus / Q000235:genetics*; D051542:Hepatocyte Nuclear Factor 3-beta; D008099:Liver / Q000737:chemistry*; D008156:Luciferases; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000302:isolation & purification* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D051698:Activating Transcription Factor 2; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C496504:Foxa2 protein, rat; D009687:Nuclear Proteins; D014157:Transcription Factors; D051542:Hepatocyte Nuclear Factor 3-beta; D008156:Luciferases; D003850:Deoxyribonuclease I