Structure and function of a human transcription factor TFIIIB subunit that is evolutionarily conserved and contains both TFIIB- and high-mobility-group protein 2-related domains.

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.
Mesh Terms:
Amino Acid Sequence, Base Sequence, Cloning, Molecular, Conserved Sequence, DNA, Complementary, DNA-Binding Proteins, Evolution, Genetic Complementation Test, High Mobility Group Proteins, Humans, Molecular Sequence Data, Protein Binding, Protein Conformation, RNA, Small Nuclear, Recombinant Proteins, Sequence Homology, Amino Acid, TATA-Binding Protein Associated Factors, TATA-Box Binding Protein, Transcription Factor TFIIB, Transcription Factor TFIIIB, Transcription Factors, Transcription, Genetic
Proc. Natl. Acad. Sci. U.S.A.
Date: Jul. 18, 1995
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