Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The central RNA polymerase III (Pol III) transcription factor TFIIIB is composed of the TATA-binding protein (TBP), Brf, a protein related to TFIIB, and the product of the newly cloned TFC5 gene. TFIIIB assembles autonomously on the upstream promoter of the yeast U6 snRNA (SNR6) gene in vitro, through the interaction of its TBP subunit with a consensus TATA box located at base pair -30. As both the DNA-binding domain of TBP and the U6 TATA box are nearly twofold symmetrical, we have examined how the binding polarity of TFIIIB is determined. We find that TFIIIB can bind to the U6 promoter in both directions, that TBP is unable to discern the natural polarity of the TATA element and that, as a consequence, the U6 TATA box is functionally symmetrical. A modest preference for TFIIIB binding in the natural direction of the U6 promoter is instead dictated by flanking DNA. Because the assembly of TFIIIB on the yeast U6 gene in vivo occurs via a TFIIIC-dependent mechanism, we investigated the influence of TFIIIC on the binding polarity of TFIIIB. TFIIIC places TFIIIB on the promoter in one direction only; thus, it is TFIIIC that primarily specifies the direction of transcription. Experiments using TFIIIB reconstituted with the altered DNA specificity mutant TBPm3 demonstrate that in the TFIIIB-U6 promoter complex, the carboxy-terminal repeat of TBP contacts the upstream half of the TATA box. This orientation of yeast TBP in Pol III promoter-bound TFIIIB is the same as in Pol II promoter-bound TFIID and in TBP-DNA complexes that have been analyzed by X-ray crystallography.
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PMID:The symmetry of the yeast U6 RNA gene's TATA box and the orientation of the TATA-binding protein in yeast TFIIIB. 749 93

TFC5, the unique and essential gene encoding the B" component of the Saccharomyces cerevisiae RNA polymerase III transcription factor (TF)IIIB has been cloned. It encodes a 594-amino acid protein (67,688 Da). Escherichia coli-produced B" has been used to reconstitute entirely recombinant TFIIIB that is fully functional for TFIIIC-directed, as well as TATA box-dependent, DNA binding and transcription. The DNase I footprints of entirely recombinant TFIIIB, composed of B", the 67-kDa Brf, and TATA box-binding protein, and TFIIIB reconstituted with natural B" are indistinguishable. A truncated form of B" lacking 39 N-terminal and 107 C-terminal amino acids is also functional for transcription.
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PMID:Cloning, expression, and function of TFC5, the gene encoding the B" component of the Saccharomyces cerevisiae RNA polymerase III transcription factor TFIIIB. 756 18

TFIIIB, the central transcription initiation factor of the eukaryotic nuclear RNA polymerase (pol) III is composed of three subunits: the TATA-binding protein; Brf, the TFIIB-related subunit; and B", the Saccharomyces cerevisiae, TFC5 gene product. The orientation of the B" subunit within the TFIIIB-DNA complex has been analyzed at two promoters by two approaches that involve site-specific photochemical protein-DNA cross-linking: a collection of B" internal and external deletion proteins has been surveyed for those deletions that alter the interaction of B" with DNA or change the orientation of B" relative to DNA; a method for regionally mapping cross-links between specific DNA sites and (32)P-end-labeled protein has also been applied. The results map an N-proximal segment of B" to the upstream end of the TFIIIB-DNA complex and amino acids 299-315 to the principal DNA-contact site, approximately 8 base pairs upstream of the TATA box. The analysis also indicates that a segment comprising amino acids 316-434 loops away from DNA, and locates the C-proximal 170 amino acids of B" downstream of the TATA box. Examination of two-cross-link products formed by DNA with adjacent and nearby photoactive nucleotides supports the conclusion that Brf and B" share an extended interface along the length of the TFIIIB-DNA complex.
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PMID:Alignment of the B" subunit of RNA polymerase III transcription factor IIIB in its promoter complex. 1049 45

Transcription factor IIIB (TFIIIB) is directly involved in transcription initiation by RNA polymerase III in eukaryotes. Yeast contain a single TFIIIB activity that is comprised of the TATA-binding protein (TBP), TFIIB-related factor 1 (BRF1), and TFIIIB", whereas two distinct TFIIIB activities, TFIIIB-alpha and TFIIIB-beta, have been described in human cells. Human TFIIIB-beta is required for transcription of genes with internal promoter elements, and contains TBP, a TFIIIB" homologue (TFIIIB150), and a BRF1 homologue (TFIIIB90), whereas TFIIIB-alpha is required for transcription of genes with promoter elements upstream of the initiation site. Here we describe the identification, cloning, and characterization of TFIIIB50, a novel homologue of TFIIB and TFIIIB90. TFIIIB50 and tightly associated factors, along with TBP and TFIIIB150, reconstitute human TFIIIB-alpha activity. Thus, higher eukaryotes, in contrast to the yeast Saccharomyces cerevisiae, have evolved two distinct TFIIB-related factors that mediate promoter selectivity by RNA polymerase III.
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PMID:A stable complex of a novel transcription factor IIB- related factor, human TFIIIB50, and associated proteins mediate selective transcription by RNA polymerase III of genes with upstream promoter elements. 1112 Oct 26