title: Interactions of the transcription factors MIBP1 and RFX1 with the EP element of the hepatitis B virus enhancer.
abstract: We previously demonstrated that MIBP1 and RFX1 polypeptides associate in vivo to form a complex that binds to the MIF-1 element in the c-myc gene and the major histocompatibility complex class II X-box recognition sequence. We now show that the EP element, a key regulatory sequence within hepatitis B virus enhancer I, also associates with MIBP1 and RFX1. Using polyclonal antisera directed against either oligonucleotide-purified MIBP1 or a peptide derived from the major histocompatibility complex class II promoter-binding protein RFX1, we showed that MIBP1 and RFX1 are both present in the DNA-protein complexes at the EP site. In addition, while the EP element can act cooperatively with several adjacent elements to transactivate hepatitis B virus expression, we demonstrated that the EP site alone can repress transcription of simian virus 40 promoter in a position- and orientation-independent manner, suggesting a silencer function in hepatocarcinoma cells.
authors.affiliation: Laboratory of Biological Chemistry, National Cancer Institute, Bethesda, Maryland 20892, USA.
authors.forename: M
authors.initials: M
authors.lastname: Blake
authors.forename: J
authors.initials: J
authors.lastname: Niklinski
authors.forename: M
authors.initials: M
authors.lastname: Zajac-Kaye
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004273:DNA, Neoplasm / Q000302:isolation & purification / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005802:Genes, MHC Class II; D006515:Hepatitis B virus / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D000071701:Regulatory Factor X Transcription Factors; D000071716:Regulatory Factor X1; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; C000605537:RFX1 protein, human; D000071701:Regulatory Factor X Transcription Factors; D000071716:Regulatory Factor X1; D014157:Transcription Factors; C077171:HIVEP2 protein, human