Abstract
Transcription factor TFIIIB plays a central role in transcription initiation by RNA polymerase III on genes encoding tRNA, 5S rRNA, and other small structural RNAs. We report the purification of a human TFIIIB-derived complex containing only the TATA-binding polypeptide (TBP) and a 90-kDa subunit (TFIIIB90) and the isolation of a cDNA clone encoding the 90-kDa subunit. The N-terminal half of TFIIIB90 exhibits sequence similarity to the yeast TFIIIB70 (BRF) and the class II transcription factor TFIIB and interacts weakly with TBP. The C-terminal half of TFIIIB90 contains a high-mobility-group protein 2 (HMG2)-related domain and interacts strongly with TBP. Recombinant TFIIIB90 plus recombinant human TBP substitute for human TFIIIB in a complementation assay for transcription of 5S, tRNA, and VA1 RNA genes, and both the TFIIB-related domain and the HMG2-related domain are required for this activity. TFIIIB90 is also required for transcription of human 7SK and U6 RNA genes by RNA polymerase III, but apparently within a complex distinct from the TBP/TFIIIB90 complex.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Base Sequence
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Biological Evolution
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Cloning, Molecular
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Conserved Sequence
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DNA, Complementary / genetics
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DNA-Binding Proteins / metabolism
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Genetic Complementation Test
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High Mobility Group Proteins / genetics
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Humans
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Molecular Sequence Data
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Protein Binding
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Protein Conformation
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RNA, Small Nuclear / biosynthesis
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Recombinant Proteins / biosynthesis
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Sequence Homology, Amino Acid
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TATA-Binding Protein Associated Factors*
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TATA-Box Binding Protein
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Transcription Factor TFIIB
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Transcription Factor TFIIIB
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Transcription Factors / biosynthesis
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Transcription Factors / genetics*
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Transcription Factors / isolation & purification
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Transcription Factors / metabolism
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Transcription, Genetic*
Substances
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BRF1 protein, human
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DNA, Complementary
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DNA-Binding Proteins
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High Mobility Group Proteins
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RNA, Small Nuclear
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Recombinant Proteins
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TATA-Binding Protein Associated Factors
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TATA-Box Binding Protein
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Transcription Factor TFIIB
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Transcription Factor TFIIIB
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Transcription Factors