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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

Zhengxin Wang and Robert G. Roeder
Proceedings of the National Academy of Sciences of the United States of America
Vol. 92, No. 15 (Jul. 18, 1995), pp. 7026-7030
Stable URL: http://www.jstor.org/stable/2367787
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
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
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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.

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