title: Multiprotein bridging factor 1 (MBF1) is an evolutionarily conserved transcriptional coactivator that connects a regulatory factor and TATA element-binding protein.
abstract: Multiprotein bridging factor 1 (MBF1) is a transcriptional cofactor that bridges between the TATA box-binding protein (TBP) and the Drosophila melanogaster nuclear hormone receptor FTZ-F1 or its silkworm counterpart BmFTZ-F1. A cDNA clone encoding MBF1 was isolated from the silkworm Bombyx mori whose sequence predicts a basic protein consisting of 146 amino acids. Bacterially expressed recombinant MBF1 is functional in interactions with TBP and a positive cofactor MBF2. The recombinant MBF1 also makes a direct contact with FTZ-F1 through the C-terminal region of the FTZ-F1 DNA-binding domain and stimulates the FTZ-F1 binding to its recognition site. The central region of MBF1 (residues 35-113) is essential for the binding of FTZ-F1, MBF2, and TBP. When the recombinant MBF1 was added to a HeLa cell nuclear extract in the presence of MBF2 and FTZ622 bearing the FTZ-F1 DNA-binding domain, it supported selective transcriptional activation of the fushi tarazu gene as natural MBF1 did. Mutations disrupting the binding of FTZ622 to DNA or MBF1, or a MBF2 mutation disrupting the binding to MBF1, all abolished the selective activation of transcription. These results suggest that tethering of the positive cofactor MBF2 to a FTZ-F1-binding site through FTZ-F1 and MBF1 is essential for the binding site-dependent activation of transcription. A homology search in the databases revealed that the deduced amino acid sequence of MBF1 is conserved across species from yeast to human.
authors.affiliation: Department of Genetics, Graduate University for Advanced Studies, Mishima, Shizuoka-ken 411, Japan.
authors.forename: K i
authors.initials: Ki
authors.lastname: Takemaru
authors.forename: F Q
authors.initials: FQ
authors.lastname: Li
authors.forename: H
authors.initials: H
authors.lastname: Ueda
authors.forename: S
authors.initials: S
authors.lastname: Hirose
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx; D002148:Calmodulin-Binding Proteins; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004268:DNA-Binding Proteins / Q000235:genetics*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster; D019143:Evolution, Molecular; D051717:Fushi Tarazu Transcription Factors; D006367:HeLa Cells; D018398:Homeodomain Proteins; D006801:Humans; D019476:Insect Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D054339:Steroidogenic Factor 1; D035181:TATA-Box Binding Protein; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D002148:Calmodulin-Binding Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C115911:EDF1 protein, human; C485470:Edf1 protein, mouse; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; D019476:Insect Proteins; C491465:MBF1 protein, Drosophila; C106951:MBF1 protein, S cerevisiae; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D054339:Steroidogenic Factor 1; D035181:TATA-Box Binding Protein; D015534:Trans-Activators; D014157:Transcription Factors; C497169:ftz protein, Drosophila; C499713:nuclear hormone receptor FTZ-F1, Bombyx mori; C499712:nuclear hormone receptor FTZ-F1, Drosophila