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)

TBP (TATA-binding protein)-associated factors (TAF(II)s) are components of large multiprotein complexes such as TFIID, TFTC, STAGA, PCAF/GCN5, and SAGA, which play a key role in the regulation of gene expression by RNA polymerase II. The structures of TFIID and TFTC have been determined at 3.5-nanometer resolution by electron microscopy and digital image analysis of single particles. Human TFIID resembles a macromolecular clamp that contains four globular domains organized around a solvent-accessible groove of a size suitable to bind DNA. TFTC is larger and contains five domains, four of which are similar to TFIID.
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PMID:Three-dimensional structures of the TAFII-containing complexes TFIID and TFTC. 1059 45

Transcription in human papillomaviruses (HPVs) is mainly regulated by cellular transcription factors and virus-encoded E2 proteins that act as sequence-specific DNA-binding proteins. Although the functions of E2 as a transcriptional activator and a repressor have been well documented, the role of cellular factors involved in E2-mediated regulation of the HPV promoters and the mechanism by which E2 modulates viral gene expression remain unclear. Using reconstituted cell-free transcription systems, we found that cellular enhancer-binding factors and general cofactors, such as TAF(II)s, TFIIA, Mediator, and PC4, are not required for E2-mediated repression. Unlike other transcriptional repressors that function through recruitment of histone deacetylase or corepressor complexes, HPV E2 is able to directly target components of the general transcription machinery to exert its repressor activity on the natural HPV E6 promoter. Interestingly, preincubation of TATA binding protein (TBP) or TFIID with HPV template is not sufficient to overcome E2-mediated repression, which can be alleviated only via formation of a minimal TBP (or TFIID)-TFIIB-RNA polymerase II-TFIIF preinitiation complex. Our data therefore indicate that E2 does not simply work by displacing TBP or TFIID from binding to the adjacent TATA box. Instead, E2 appears to function as an active repressor that directly inhibits HPV transcription at steps after TATA recognition by TBP or TFIID.
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PMID:Alleviation of human papillomavirus E2-mediated transcriptional repression via formation of a TATA binding protein (or TFIID)-TFIIB-RNA polymerase II-TFIIF preinitiation complex. 1059 14

TFIID is a multiprotein complex composed of the TATA binding protein (TBP) and TBP-associated factors (TAF(II)s). The binding of TFIID to the promoter is the first step of RNA polymerase II preinitiation complex assembly on protein-coding genes. Yeast (y) and human (h) TFIID complexes contain 10 to 13 TAF(II)s. Biochemical studies suggested that the Drosophila (d) TFIID complexes contain only eight TAF(II)s, leaving a number of yeast and human TAF(II)s (e.g., hTAF(II)55, hTAF(II)30, and hTAF(II)18) without known Drosophila homologues. We demonstrate that Drosophila has not one but two hTAF(II)30 homologues, dTAF(II)16 and dTAF(II)24, which are encoded by two adjacent genes. These two genes are localized in a head-to-head orientation, and their 5' extremities overlap. We show that these novel dTAF(II)s are expressed and that they are both associated with TBP and other bona fide dTAF(II)s in dTFIID complexes. dTAF(II)24, but not dTAF(II)16, was also found to be associated with the histone acetyltransferase (HAT) dGCN5. Thus, dTAF(II)16 and dTAF(II)24 are functional homologues of hTAF(II)30, and this is the first demonstration that a TAF(II)-GCN5-HAT complex exists in Drosophila. The two dTAF(II)s are differentially expressed during embryogenesis and can be detected in both nuclei and cytoplasm of the cells. These results together indicate that dTAF(II)16 and dTAF(II)24 may have similar but not identical functions.
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PMID:Two novel Drosophila TAF(II)s have homology with human TAF(II)30 and are differentially regulated during development. 1066 41

TATA box binding protein (TBP)-promoter interaction nucleates assembly of the RNA polymerase II transcription initiation complex. Transcription factor IIA (TFIIA) stabilizes the TBP-promoter complex whereas the N-terminal domain of the largest TAF(II) inhibits TBP-promoter interaction. We have mapped the interaction sites on TBP of Drosophila TAF(II)230 and yeast TFIIA (comprising two subunits, TOA1 and TOA2), using nuclear magnetic resonance (NMR), and also report structural evidence that subdomain II of the TAF(II)230 N-terminal inhibitory domain and TFIIA have overlapping binding sites on the convex surface of TBP. Together with previous mutational and biochemical data, our NMR results indicate that subdomain II augments subdomain I-mediated inhibition of TBP function by blocking TBP-TFIIA interaction.
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PMID:TFIIA-TAF regulatory interplay: NMR evidence for overlapping binding sites on TBP. 1069 76

The RNA polymerase II general transcription factor TFIID is a complex containing the TATA-binding protein (TBP) and associated factors (TAFs). We have used a mutant allele of the gene encoding yeast TAF(II)68/61p to analyze its function in vivo. We provide biochemical and genetic evidence that the C-terminal alpha-helix of TAF(II)68/61p is required for its direct interaction with TBP, the stable incorporation of TBP into the TFIID complex, the integrity of the TFIID complex, and the transcription of most genes in vivo. This is the first evidence that a yeast TAF(II) other than TAF(II)145/130 interacts with TBP, and the implications of this on the interpretation of data obtained studying TAF(II) mutants in vivo are discussed. We have identified a high copy suppressor of the TAF68/61 mutation, TSG2, that has sequence similarity to a region of the SAGA subunit Ada1. We demonstrate that it directly interacts with TAF(II)68/61p in vitro, is a component of TFIID, is required for the stability of the complex in vivo, and is necessary for the transcription of many yeast genes. On the basis of these functions, we propose that Tsg2/TAF(II)48p is the histone 2A-like dimerization partner for the histone 2B-like TAF(II)68/61p in the yeast TFIID complex.
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PMID:Identification of a yeast transcription factor IID subunit, TSG2/TAF48. 1075 5

The transcription factors TFIID and SAGA are multi-subunit complexes involved in transcription by RNA polymerase II. TFIID and SAGA contain common TATA-binding protein (TBP)-associated factor (TAF(II)) subunits and each complex contains a subunit with histone acetyltransferase activity. These observations have raised questions about whether the functions of the two complexes in vivo are unique or overlapping. Here we use genome-wide expression analysis to investigate how expression of the yeast genome depends on both shared and unique subunits of these two complexes. We find that expression of most genes requires one or more of the common TAF(II) subunits, indicating that the functions of TFIID and SAGA are widely required for gene expression. Among the subunits shared by TFIID and SAGA are three histone-like TAF(II)s, which have been proposed to form a sub-complex and mediate a common function in global transcription. Unexpectedly, we find that the histone-like TAF(II)s have distinct roles in expression of the yeast genome. Most importantly, we show that the histone acetylase components of TFIID and SAGA (TAF(II)145 and Gcn5) are functionally redundant, indicating that expression of a large fraction of yeast genes can be regulated through the action of either complex.
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PMID:Redundant roles for the TFIID and SAGA complexes in global transcription. 1086 29

Human SL1 is a general transcription initiation factor (GTF) essential for RNA polymerase I to start rRNA synthesis at class I promoters. It is comprised of the TATA box-binding protein (TBP) and three TBP-associated factors (TAF(I)48, TAF(I)63 and TAF(I)110). We have determined that the human genes TAF1A, TAF1B and TAF1C, encoding these three TAF(I) polypeptides, are localized at lq42, 2p25 and 16q24, respectively. All three genes are present as single copies in the human genome and map to different chromosomes, as shown by somatic cell hybrid panel and radiation hybrid panel analysis and FISH. Two of these genes, TAF1C and TAF1B, are transcribed into multiple RNAs, as determined through Northern analysis of mRNA from various human organs and cell lines. If translated into different polypeptides, this could result in production of variant isoforms of SL1 with different activation potentials.
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PMID:Genomic localization of the human genes TAF1A, TAF1B and TAF1C, encoding TAF(I)48, TAF(I)63 and TAF(I)110 subunits of class I general transcription initiation factor SL1. 1089 55

The TATA box-binding protein (TBP) and TBP-associated factors (TAF(II)s) compose the general transcription factor TFIID. The TAF(II) subunits mediate activated transcription by RNA polymerase II by interacting directly with site-specific transcriptional regulators. TAF(II)s also participate in promoter recognition by contacting core promoter elements in the context of TFIID. To further dissect the contribution of individual TAF(II) subunits to mammalian TFIID function, we employed a vaccinia virus-based protein expression system to study protein-protein interactions and complex assembly. We identified the domains of human (h) TAF(II)130 required for TAF(II)-TAF(II) interactions and formation of a complex with hTBP, hTAF(II)100, and hTAF(II)250. Functional analysis of partial TFIID complexes formed in vivo indicated that hTAF(II)130 was required for transcriptional activation by Sp1 in vitro. DNase I footprinting experiments demonstrated that purified hTBP/hTAF(II)250 complex reconstituted with or without additional TAF(II)s was significantly reduced for TATA box binding (as much as 9-fold) compared with free hTBP. By contrast, hTAF(II)130 stabilized binding of hTBP to the TATA box, whereas hTAF(II)100 had little effect. Thus, our biochemical analysis supports the notion that TAF(II)s possess distinct functions to regulate the activity of TFIID.
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PMID:Assembly of partial TFIID complexes in mammalian cells reveals distinct activities associated with individual TATA box-binding protein-associated factors. 1089 37

Mammalian rRNA genes are preceded by a terminator element that is recognized by the transcription termination factor TTF-I. In exploring the functional significance of the promoter-proximal terminator, we found that TTF-I associates with the p300/CBP-associated factor PCAF, suggesting that TTF-I may target histone acetyltransferase to the rDNA promoter. We demonstrate that PCAF acetylates TAF(I)68, the second largest subunit of the TATA box-binding protein (TBP)-containing factor TIF-IB/SL1, and acetylation enhances binding of TAF(I)68 to the rDNA promoter. Moreover, PCAF stimulates RNA polymerase I (Pol I) transcription in a reconstituted in vitro system. Consistent with acetylation of TIF-IB/SL1 being required for rDNA transcription, the NAD(+)-dependent histone deacetylase mSir2a deacetylates TAF(I)68 and represses Pol I transcription. The results demonstrate that acetylation of the basal Pol I transcription machinery has functional consequences and suggest that reversible acetylation of TIF-IB/SL1 may be an effective means to regulate rDNA transcription in response to external signals.
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PMID:Acetylation of TAF(I)68, a subunit of TIF-IB/SL1, activates RNA polymerase I transcription. 1125 Sep 1

Preinitiation complex assembly is nucleated by the binding of TFIID to the promoters of protein coding genes transcribed by RNA polymerase II. TFIID is comprised of the TATA-binding protein (TBP) and TBP-associated factors (TAF(II)s). We investigated the transcription properties of TBP and TFIID on chromatin templates. On naked templates both TBP and purified TFIID are able to initiate basal transcription. However, on chromatin templates only TBP mediates transcription initiation in a heat-treated extract, whereas TFIID does not. Moreover, TBP-mediated chromatin transcription is blocked in a nontreated extract. These observations suggest that a chromatin-targeted repressor is present in crude extracts and that chromatin per se is not refractory to transcription mediated by TBP. As TBP can function through TAF(II)-independent and TAF(II)-dependent pathways, the repression of TBP-mediated basal transcription may be an additional level to the control of Pol II transcription initiation on chromatin.
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PMID:Chromatin is permissive to TATA-binding protein (TBP)-mediated transcription initiation. 1127 78


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