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 basal transcription factor IIE (TFIIE) is thought to be one of the last factors to be assembled into a preinitiation complex (PIC) at eukaryotic promoters after RNA polymerase II and TFIIF have been incorporated. It was shown that a primary function of TFIIE is to recruit and cooperate with TFIIH in promoter melting. Here, we show that the large subunit of TFIIE (E56) can directly stimulate TBP binding to the promoter in the absence of other basal factors. The zinc-finger domain of E56, required for transcriptional activity, is critical for this function. In addition, the small subunit of TFIIE (E34) directly contacts DNA and TFIIA and thus providing a second mechanism for TFIIE to help binding of a TBP/IIA complex to the promoter, the first critical step in the PIC assembly. These studies suggest an alternative PIC assembly pathway in which TFIIE affects both TBP and TFIIH functions during initiation of RNA synthesis.
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PMID:An interplay between TATA box-binding protein and transcription factors IIE and IIA modulates DNA binding and transcription. 961 79

TFIID is a multiprotein complex comprised of the TATA-binding protein (TBP) and an array of TBP-associated factors (TAFIIs). Whereas TBP is sufficient for basal transcription in conjunction with other general transcription factors and RNA polymerase II, TAFIIs are additionally required for activator-dependent transcription in mammalian cell-free transcription systems. However, recent in vivo studies carried out in yeast suggest that TAFIIs are not globally required for activator function. The discrepancy between in vivo yeast studies and in vitro mammalian cell-free systems remains to be resolved. In this study, we describe a mammalian cell-free transcription system reconstituted with only recombinant proteins and epitope-tagged multiprotein complexes. Transcriptional activation can be recapitulated in this highly purified in vitro transcription system in the absence of TAFIIs. This TBP-mediated activation is not induced by human mediator, another transcriptional coactivator complex potentially implicated in activator response. In contrast, general transcription factors TFIIH and TFIIA play a significant role in TBP-mediated activation, which can be detected in vitro with Gal4 fusion proteins containing various transcriptional activation domains. Our data, therefore, suggest that TFIIH and TFIIA can mediate activator function in the absence of TAFIIs.
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PMID:TAFII-independent activation mediated by human TBP in the presence of the positive cofactor PC4. 968 14

Nuclear receptors for steroid/thyroid hormones, vitamin A,D and fat-soluble ligands form a gene superfamily of ligand-inducible transcription factors, which plays an important roles in a wide spectrum of biological events by regulating expression of a set of target genes. Two domains (A/B and E) of nuclear receptors are demonstrated to activate transcription, designated AF-1 (A/B) and AF-2 (E), respectively. Homo- and hetero-dimers of nuclear receptors bind target enhancer elements in the target gene promoters. The target enhancer elements are referred as hormone response elements (HRE), and composed of two hexamer core motifs. The orientations and spaces between two core motifs play critical roles in discreminating the recognition of HREs among the members of nuclear receptor. DNA-bound nuclear receptors controls transcription in a ligand-binding dependent way in co-operation with a multiprotein complex containing RNA polymerase II and a series of auxiliary factors, TFIIA,B,D, E,F and H. During process of ligand-induced transactivation by nuclear receptors, nuclear co-factors interacting with the AF-1 and AF-2 seem to be involved. Several transcriptional co-activators and co-repressors have been recently identified, and their function is currently under investigation.
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PMID:[Transcriptional control by steroid receptor]. 970 40

The transcriptional activity of an in vitro assembled human interferon-beta gene enhanceosome is highly synergistic. This synergy requires five distinct transcriptional activator proteins (ATF2/c-JUN, interferon regulatory factor 1, and p50/p65 of NF-kappaB), the high mobility group protein HMG I(Y), and the correct alignment of protein-binding sites on the face of the DNA double helix. Here, we investigate the mechanisms of enhanceosome-dependent transcriptional synergy during preinitiation complex assembly in vitro. We show that the stereospecific assembly of the enhanceosome is critical for the efficient recruitment of TFIIB into a template-committed TFIID-TFIIA-USA (upstream stimulatory activity complex) and for the subsequent recruitment of the RNA polymerase II holoenzyme complex. In addition, we provide evidence that recruitment of the holoenzyme by the enhanceosome is due, at least in part, to interactions between the enhanceosome and the transcriptional coactivator CREB, cAMP responsive element binding protein (CBP). These studies reveal a unique role of enhanceosomes in the cooperative assembly of the transcription machinery on the human interferon-beta promoter.
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PMID:Efficient recruitment of TFIIB and CBP-RNA polymerase II holoenzyme by an interferon-beta enhanceosome in vitro. 977 Apr 62

TATA-binding protein-associated factors (TAFIIs) within TFIID control differential gene transcription through interactions with both activators and core promoter elements. In particular, TAFII150 contributes to initiator-dependent transcription through an unknown mechanism. Here, we address whether TAFIIs within TFIID are sufficient, in conjunction with highly purified general transcription factors (GTFs), for differential core promoter-dependent transcription by RNA polymerase II and whether additional cofactors are required. We identify the human homologue of Drosophila TAFII150 through cognate cDNA cloning and show that it is a tightly associated component of human TFIID. More importantly, we demonstrate that the human TAFII150-containing TFIID complex is not sufficient, in the context of all purified GTFs and RNA polymerase II, to mediate transcription synergism between TATA and initiator elements and initiator-directed transcription from a TAFII-dependent TATA-less promoter. Therefore, TAFII-promoter interactions are not sufficient for the productive core promoter-selective functions of TFIID. Consistent with this finding, we have partially purified novel cofactor activities (TICs) that potentiate the TAFII-mediated synergism between TATA and initiator elements (TIC-1) and TAFII-dependent transcription from TATA-less promoters (TIC-2 and -3). Furthermore, we demonstrate an essential function for TFIIA in TIC- and TAFII-dependent basal transcription from a TATA-less promoter. Our results reveal a parallel between the basal transcription activity of TAFIIs through core promoter elements and TAFII-dependent activator function.
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PMID:Novel cofactors and TFIIA mediate functional core promoter selectivity by the human TAFII150-containing TFIID complex. 977 72

Assembly and activity of yeast RNA polymerase II (Pol II) preinitiation complexes (PIC) was investigated with an immobilized promoter assay and extracts made from wild-type cells and from cells containing conditional mutations in components of the Pol II machinery. We describe the following findings: (1) In one step, TFIID and TFIIA assemble at the promoter independently of holoenzyme. In another step, holoenzyme is recruited to the promoter. Mutations in the CTD of Pol II, Srb2, Srb4, and Srb5, and two mutations in TFIIB disrupt recruitment of all holoenzyme components tested without affecting TFIID and TFIIA recruitment. These results indicate that the stepwise assembly pathway is blocked after TFIID/TFIIA binding. (2) Both the Gal4-AH and Gal4-VP16 activators stimulate formation of active PICs by increasing the extent of PIC formation. The Gal4-AH activator stimulated PIC formation by enhancing the binding of TFIID and TFIIA, whereas Gal4-VP16 could enhance the recruitment of TFIID, TFIIA, and holoenzyme. (3) Extracts deficient in TFIIA activity showed reduced assembly of all PIC components. These and other results suggest that TFIIA acts at an early step by enhancing the stable recruitment of TFIID. (4) An extract containing the TFIIB mutant E62G, had no defect in PIC formation, but had a severe defect in transcription. Similarly, mutation of the TATA box reduced PIC formation only two- to fourfold, but severely compromised transcription. These results demonstate an involvement of TFIIB and the TATA box in one or more steps after recruitment of factors to the promoter.
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PMID:Intermediates in formation and activity of the RNA polymerase II preinitiation complex: holoenzyme recruitment and a postrecruitment role for the TATA box and TFIIB. 988 99

TFIIA has initially been identified as a component of transcription initiation complex of RNA polymerase II. Its role in transcription has been controversial. In this paper, we report the characterization and functional analysis of both the Arabidopsis TFIIA large and small subunits. Sequence analysis revealed that Arabidopsis TFIIA is structurally more related to animal than to yeast counterparts. Arabidopsis has at least two genes for the large subunit and one for the small subunit. Both types of genes are constitutively transcribed in various plant organs. The proteins encoded by the cDNA interact each other in yeast 2-hybrid system. Only the N-terminal part of the large subunit is necessary for the interaction with the small subunit. Recombinant Arabidopsis TFIIA polypeptides bind to TBP-DNA complex in gel shift assays. The large subunit of TFIIA can stimulate transcription in yeast and in plant cells when fused to a DNA-binding domain binding to cis sequences upstream of a minimal promoter. This trans-activating activity is localized to a 35 amino acid segment within the evolutionarily unconserved central region.
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PMID:Characterization and functional analysis of Arabidopsis TFIIA reveal that the evolutionarily unconserved region of the large subunit has a transcription activation domain. 1009 79

Adenovirus E1B 55,000-molecular-weight protein (55K) binds to host cell p53, stabilizing it, greatly increasing its affinity for its cognate DNA-binding site, and converting it from a regulated activator to a constitutive repressor. Here we analyzed the mechanism of repression by the p53-E1B 55K complex. E1B 55K repression requires that 55K be tethered to the promoter by binding directly to DNA-bound p53. Transcription from an assembled, p53-activated preinitiation complex was not repressed by the subsequent addition of E1B 55K, suggesting that either sites of 55K interaction with p53 or targets of 55K in the preinitiation complex are blocked. Specific E1B 55K repression was observed in reactions lacking TFIIA and with recombinant TATA-binding protein in place of TFIID, conditions under which p53 does not activate transcription. Thus, E1B 55K does not simply inhibit a p53-specific activation mechanism but rather blocks basal transcription. As a consequence, E1B 55K may repress transcription from any promoter with an associated p53-binding site, no matter what other activators associate with the promoter. E1B 55K did not repress basal transcription in reactions with recombinant and highly purified general transcription factors and RNA polymerase II but rather required a corepressor that copurifies with the polymerase.
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PMID:Corepressor required for adenovirus E1B 55,000-molecular-weight protein repression of basal transcription. 1020 64

TFIID is a general transcription factor required for the assembly of the transcription machinery on most eukaryotic promoters transcribed by RNA polymerase II. Although the TATA-binding subunit (TBP) of TFIID is able to support core promoter and activator-dependent transcription under some circumstances, the roles of TBP-associated factors (TAF(II)s) in TFIID-mediated activation remain unclear. To define the evolutionarily conserved function of TFIID and to elucidate the roles of TAF(II)s in gene activation, we have cloned the mouse TAF(II)55 subunit of TFIID and further isolated mouse TFIID from a murine FM3A-derived cell line that constitutively expresses FLAG-tagged mouse TAF(II)55. Both mouse and human TFIIDs are capable of mediating transcriptional activation by Gal4 fusions containing different activation domains in a highly purified human cell-free transcription system devoid of TFIIA and Mediator. Although TAF(II)-independent activation by Gal4-VP16 can also be observed in this highly purified human transcription system with either mouse or yeast TBP, TAF(II)s are strictly required for estrogen receptor-mediated activation independently of the core promoter sequence. In addition, TAF(II)s are necessary for transcription from a preassembled chromatin template. These findings clearly demonstrate an essential role of TAF(II)s as a transcriptional coactivator for estrogen receptor and in chromatin transcription.
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PMID:Isolation of mouse TFIID and functional characterization of TBP and TFIID in mediating estrogen receptor and chromatin transcription. 1043 27

Vitamin A and D play an important role in many biological processes including cell differentiation, proliferation and bone metabolism. These effects are believed to be mediated by specific nuclear receptors such as retinoic acid receptors (RARs) or vitamin D receptor (VDR), that regulate the transcription of a particular set of target genes. Hetero-dimers of RAR or VDR to retinoid X receptors (RXRs) bind target enhancer elements in their gene promoters. The target enhancer elements are referred as RA response elements (RAREs) or vitamin D response elements (VDREs), and composed of two hexamer core motife. DNA-bound RAR/VDR control transcription in a ligand-binding dependent way in co-operation with a multiprotein complex containing RNA polymerase II and a series of auxiliary factors, TFIIA, B, D, E, F and H. During process of ligand-induced transactivation by nuclear receptors, nuclear coactivators interacting with the AF-2 including ligand binding domain (LBD) seems to be involved. Several transcriptional coactivators and corepressors have been recently identified, and their function is currently under investigation.
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PMID:[Gene structure and transcriptional regulation of vitamin A, D binding proteins and nuclear receptors]. 1054 Aug 75


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