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.
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.
Saxena
Ashish
A
Genetics Program, Stony Brook University, Stony Brook, NY 11794, USA.
Ma
Beicong
B
Schramm
Laura
L
Hernandez
Nouria
N
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012320:RNA Polymerase III / Q000235:genetics*; D012342:RNA, Small Nuclear / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D035381:TATA-Binding Protein Associated Factors; D035181:TATA-Box Binding Protein / Q000235:genetics; D035581:Transcription Factor TFIIB / Q000235:genetics; D035361:Transcription Factor TFIIIB / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation
C427472:BDP1 protein, human; C090956:BRF1 protein, S cerevisiae; C441028:BRF1 protein, human; C416185:BRF2 protein, human; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012342:RNA, Small Nuclear; D011993:Recombinant Fusion Proteins; C106703:SNAPC protein complex, human; C116351:SNAPC4 protein, human; D029701:Saccharomyces cerevisiae Proteins; D035381:TATA-Binding Protein Associated Factors; D035181:TATA-Box Binding Protein; D035581:Transcription Factor TFIIB; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors; C405486:U6 small nuclear RNA; D012320:RNA Polymerase III