Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Saccharomyces cerevisiae RNA polymerase III transcription factor (TF)IIIB has been assembled from three components. An assembly pathway of these polypeptides, which specifies their interactions, has been determined. The TATA-binding protein, TBP, and the TFIIB-related BRF1 gene product BRF, together reconstitute the transcription factor activity and TFIIC-dependent DNA-binding activity of the B' component of TFIIIB. BRF alone weakly binds to a TFIIIC-tRNA gene complex; TBP greatly stabilizes this interaction. B" transcription factor activity is recovered with its previously identified 90 kd polypeptide from SDS-polyacrylamide gels. Incorporation of the 90 kd B" protein into the transcription complex requires TBP. The heparin-resistant TFIIIB-DNA complex retains all three of its constituent proteins, TBP, BRF, and B".
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PMID:The role of the TATA-binding protein in the assembly and function of the multisubunit yeast RNA polymerase III transcription factor, TFIIIB. 145 36

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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PMID: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. 762 63

The tumour suppressor protein RB restricts cellular growth. This may involve inhibiting the synthesis of tRNA and 5S rRNA by RNA polymerase (pol) III. We have shown previously that RB can repress pol III transcription when overexpressed either in vitro or in vivo. We also demonstrated that pol III activity is elevated substantially in primary fibroblasts from RB-deficient mice. Here we address the molecular mechanism of this regulation. RB is shown to repress all types of pol III promoter. It can do this even if added after transcription complex assembly. Functional assays demonstrate that RB targets specifically the general pol III factor TFIIIB. A physical interaction between TFIIIB and RB is indicated by fractionation, pull-down and immunoprecipitation data. We show that TFIIIB activity is elevated in primary fibroblasts from RB-deficient mice. TFIIIB is a multisubunit complex that includes the TATA-binding protein (TBP) and a TFIIB-related factor called BRF. We show that RB itself contains regions of homology to both TBP and BRF and propose a model in which RB disrupts TFIIIB by mimicking these two components.
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PMID:Mechanistic analysis of RNA polymerase III regulation by the retinoblastoma protein. 915 32

Transcription by RNA polymerase III involves recruitment of the polymerase by template-bound accessory factors, followed by initiation, elongation, and termination steps. An immunopurification approach has been used to demonstrate that human RNA Pol III is composed of 16 subunits, some of which are apparently modified in HeLa cells. Partial denaturing conditions and sucrose gradient sedimentation at high salt result in the dissociation of a subcomplex that includes hRPC32, hRPC39, and hRPC62. Cognate cDNAs were isolated and shown to encode three subunits that are specific to RNA Pol III and homologous to three yeast subunits. The human RNA Pol III core lacking the subcomplex functions in transcription elongation and termination following nonspecific initiation on a tailed template, but fails to show promoter-dependent transcription initiation in conjunction with accessory factors. The capability for specific transcription initiation can be restored either by the natural subcomplex or by a stable subcomplex composed of recombinant hRPC32, hRPC39, and hRPC62 polypeptides. One component (hRPC39) of this subcomplex interacts physically with both hTBP and hTFIIIB90, two subunits of human RNA Pol III transcription initiation factor IIIB. These data strongly suggest that the hRPC32-hRPC39-hRPC62 subcomplex directs RNA Pol III binding to the TFIIIB-DNA complex via the interactions between TFIIIB and hRPC39.
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PMID:Three human RNA polymerase III-specific subunits form a subcomplex with a selective function in specific transcription initiation. 917 75

The RNA polymerase III factor TFIIIB forms a stable complex with DNA and can promote multiple rounds of initiation by polymerase. TFIIIB is composed of three subunits, the TATA binding protein (TBP), TFIIB-related factor (BRF), and B". Chemical footprinting, as well as mutagenesis of TBP, BRF, and promoter DNA, was used to probe the architecture of TFIIIB subunits bound to DNA. BRF bound to TBP-DNA through the nonconserved C-terminal region and required 15 bp downstream of the TATA box and as little as 1 bp upstream of the TATA box for stable complex formation. In contrast, formation of complete TFIIIB complexes required 15 bp both upstream and downstream of the TATA box. Hydroxyl radical footprinting of TFIIIB complexes and modeling the results to the TBP-DNA structure suggest that BRF and B" surround TBP on both faces of the TBP-DNA complex and provide an explanation for the exceptional stability of this complex. Competition for binding to TBP by BRF and either TFIIB or TFIIA suggests that BRF binds on the opposite face of the TBP-DNA complex from TFIIB and that the binding sites for TFIIA and BRF overlap. The positions of TBP mutations which are defective in binding BRF suggest that BRF binds to the top and N-terminal leg of TBP. One mutation on the N-terminal leg of TBP specifically affects the binding of the B" subunit.
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PMID:Architecture of protein and DNA contacts within the TFIIIB-DNA complex. 948 85

RNA polymerase III transcription is down-regulated when F9 embryonal carcinoma cells differentiate into parietal endoderm. This reflects a decrease in the activity of TFIIIB, a multisubunit complex that is required for all class III gene expression. Two essential components of TFIIIB are the TATA-binding protein (TBP) and an associated polypeptide called BRF that is specific to this complex. The abundance of both TBP and BRF decreases during F9 cell differentiation. Whereas the amount of TBP assembled into TFIIIB is down-regulated, this is not the case for all TBP-containing complexes. BRF levels show a more dramatic decline that appears sufficient to account for the overall change in transcriptional activity. Developmental regulation of a specific class of genes may therefore be achieved through changes in the availability of a TBP-associated factor.
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PMID:Regulation of a TATA-binding protein-associated factor during cellular differentiation. 964 84

Brf is the TFIIB-related component of Saccharomyces cerevisiae RNA polymerase III transcription initiation factor IIIB (TFIIIB). An extensive set of Brf fragments has been examined for the abilities to assemble the TFIIIB-DNA complex and recruit RNA polymerase III to accurately initiate transcription. The principal TFIIIB-assembly function of Brf was found to be contributed by a C-proximal segment spanning amino acids 435 to 545, while the principal transcription-directing function was contributed by a segment of its N-proximal, TFIIB-homologous half. The diverse activities of Brf were also reconstituted from combined fragments. The fragments spanning amino acids 1 to 282 and 284 to 596 were found to assemble into TFIIIB-DNA and TFIIIC-TFIIIB-DNA complexes that were very stable, transcriptionally highly active, and indistinguishable (by in vitro footprinting) from complexes formed with intact Brf. The proximities of the individual halves of split Brf to DNA were extensively mapped by photochemical cross-linking of the TFIIIB-DNA complex. We also identified sites of interaction of Brf fragments with TATA-binding protein (TBP), taking advantage of a recently completed mutational analysis of the TBP surface. The constraints established by these analyses specify a global model of the functional segments of Brf and how they fit into the structure of the TFIIIB-DNA complex.
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PMID:Functional and structural organization of Brf, the TFIIB-related component of the RNA polymerase III transcription initiation complex. 971 Jun 42

We have identified a putative gene within the Caenorhabditis elegans genome which has the potential to encode a protein homologous to BRF, an RNA polymerase III general transcription factor. The predicted protein shares very similar overall structure with human and yeast BRF. In particular, its N-terminal half comprises a zinc-ribbon motif and a TR domain which is also present in the cyclin box. The C. elegans protein is more similar to human BRF than to the yeast BRF proteins, as would be expected from an evolutionary standpoint. Alignment of the C. elegans protein with the four known BRF proteins reveals two blocks conserved between all five sequences within the diverged C-terminal region. Profile searches using these regions suggest that they may contain evolutionarily conserved motifs. These comparisons provide insight into the structure and function of an important transcription factor.
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PMID:Identification of a putative BRF homologue in the genome of Caenorhabditis elegans. 977 76

We have investigated the molecular basis of the requirement for protein kinase CK2 in nuclear transcription in Saccharomyces cerevisiae. In vivo and in vitro analysis has demonstrated that CK2 is required for efficient transcription of the tRNA and 55 rRNA genes by RNA polymerase III. This suggests that a component of the pol III transcription machinery is regulated by CK2. We tested this possibility by a biochemical complementation approach in which components of the pol III transcription machinery from wild type cells were tested for their ability to rescue transcription in extract from a conditionally CK2-deficient mutant. We found that pol III transcription initiation factor IIIB (TFIIIB) fully restores transcription in CK2-deficient extract. Further in vitro studies revealed that TFIIIB must be phosphorylated to be active, that a single subunit of wild type TFIIIB, the TATA binding protein (TBP), is efficiently phosphorylated by CK2, and that recombinant TBP and a limiting amount of CK2 rescues transcription in CK2-deficient extract. We conclude that TBP is the physiological target of CK2 among the components of the pol III transcription machinery. The implications of this result are discussed in the context of previous data concerning the regulation of TFIIIB.
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PMID:A review of progress towards elucidating the role of protein kinase CK2 in polymerase III transcription: regulation of the TATA binding protein. 1009 3

The yeast TFIIIB transcription factor is composed of three components, TBP, TFIIIB90 or B", and TFIIIB70 or BRF. TFIIIB70 is a pivotal component since it interacts with TBP, TFIIIC and RNA polymerase III (pol III). In order to better understand the role of TFIIIB70, we mutagenized extensively three evolutionary conserved motifs of its pol III-specific C-terminal extension. Conditional mutations lying in conserved regions II and III were obtained, some of which altered the interaction with the C34 subunit of pol III and were co-lethal with rpc34 mutations. Two conditional mutations in region II impaired the interaction with TBP and were suppressed by its overexpression. The pattern of suppression of the strongest mutation by overexpression of various mutant TBP, suggested a contact between TBP-R220 and TFIIIB70-D464 residues in vivo. As expected, this TFIIIB70 mutation impaired the assembly of TFIIIB. TFIIIC.DNA complexes and affected in vitro transcription of the SUP4 tRNA gene. Our results underscore the important role of region II of TFIIIB70 in pre-initiation as well as transcription complex assembly via C34 and TBP binding.
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PMID:Mutagenesis of yeast TFIIIB70 reveals C-terminal residues critical for interaction with TBP and C34. 1032 59


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