Article: article from journal or magazin.
Structure-function analysis of the human TFIIB-related factor II protein reveals an essential role for the C-terminal domain in RNA polymerase III transcription.
Molecular and Cellular Biology
The transcription factors TFIIB, Brf1, and Brf2 share related N-terminal zinc ribbon and core domains. TFIIB bridges RNA polymerase II (Pol II) with the promoter-bound preinitiation complex, whereas Brf1 and Brf2 are involved, as part of activities also containing TBP and Bdp1 and referred to here as Brf1-TFIIIB and Brf2-TFIIIB, in the recruitment of Pol III. Brf1-TFIIIB recruits Pol III to type 1 and 2 promoters and Brf2-TFIIIB to type 3 promoters such as the human U6 promoter. Brf1 and Brf2 both have a C-terminal extension absent in TFIIB, but their C-terminal extensions are unrelated. In yeast Brf1, the C-terminal extension interacts with the TBP/TATA box complex and contributes to the recruitment of Bdp1. Here we have tested truncated Brf2, as well as Brf2/TFIIB chimeric proteins for U6 transcription and for assembly of U6 preinitiation complexes. Our results characterize functions of various human Brf2 domains and reveal that the C-terminal domain is required for efficient association of the protein with U6 promoter-bound TBP and SNAP(c), a type 3 promoter-specific transcription factor, and for efficient recruitment of Bdp1. This in turn suggests that the C-terminal extensions in Brf1 and Brf2 are crucial to specific recruitment of Pol III over Pol II.
Amino Acid Sequence, Animals, Cell Line, DNA-Binding Proteins/genetics, Humans, Molecular Sequence Data, Nuclear Proteins/genetics, Promoter Regions, Genetic, Protein Binding, Protein Structure, Tertiary, RNA Polymerase III/genetics, RNA, Small Nuclear/genetics, Recombinant Fusion Proteins/genetics, Saccharomyces cerevisiae Proteins, TATA-Binding Protein Associated Factors, TATA-Box Binding Protein/genetics, Transcription Factor TFIIB/genetics, Transcription Factor TFIIIB/genetics, Transcription Factors/genetics, Transcriptional Activation
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