Transcription Activation via Enhanced Preinitiation Complex Assembly in a Human Cell-Free System Lacking TAFIIs

Oelgeschläger, Thomas; Tao, Ye; Kang, Yun Kyoung; Roeder, Robert G.

doi:10.1016/s1097-2765(00)80092-1

Cited by 93 publications

(78 citation statements)

References 40 publications

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“…1, 3, 18, and 57). However, it is consistent with the more recent studies indicating (i) that TFIID-specific TAF II s may not be generally required for normal activator functions either in yeast cells (58,59) or in unfractionated HeLa nuclear extracts containing a more natural complement of nuclear proteins (57), whereas in some cases they may be involved in core promoter specific functions (60, 61 and references therein) and (ii) that components of SRB͞mediator complexes may be generally or specifically required for activator functions in various situations (reviewed in ref. 62).…”

Section: Discussionsupporting

confidence: 91%

Thyroid hormone receptor-associated proteins and general positive cofactors mediate thyroid hormone receptor function in the absence of the TATA box-binding protein-associated factors of TFIID

Fondell

Guermah

Malik

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

141

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Coactivators previously implicated in liganddependent activation functions by thyroid hormone receptor (TR) include p300 and CREB-binding protein (CBP), the steroid receptor coactivator-1 (SRC-1)-related family of proteins, and the multicomponent TR-associated protein (TRAP) complex. Here we show that two positive cofactors (PC2 and PC4) derived from the upstream stimulatory activity (USA) cofactor fraction act synergistically to mediate thyroid hormone (T 3 )-dependent activation either by TR or by a TR-TRAP complex in an in vitro system reconstituted with purified factors and DNA templates. Significantly, the TRAPmediated enhancement of activation by TR does not require the TATA box-binding protein-associated factors of TFIID. Furthermore, neither the pleiotropic coactivators CBP and p300 nor members of the SRC-1 family were detected in either the TR-TRAP complex or the other components of the in vitro assay system. These results show that activation by TR at the level of naked DNA templates is enhanced by cooperative functions of the TRAP coactivators and the general coactivators PC2 and PC4, and they further indicate a potential functional redundancy between TRAPs and TATA boxbinding protein-associated factors in TFIID. In conjunction with earlier studies on other nuclear receptor-interacting cofactors, the present study also suggests a multistep pathway, involving distinct sets of cofactors, for activation of hormone responsive genes.In eukaryotes activation of the transcription of specific genes by RNA polymerase II involves the concerted action of gene specific activators bound to cognate regulatory elements, general transcription initiation factors that form the preinitiation complex at common core promoter elements, and a number of transcriptional coactivators (reviewed in refs. 1 and 2). Broadly defined as factors necessary for activator function, but not for transcription from core promoter elements by the minimal basal factors, the coactivators fall into several nonmutually exclusive groups: (i) factors intimately associated with the general transcriptional machinery, including TFIIA and the TATA box-binding protein (TBP)-associated factor (TAF II ) In the case of nuclear hormone receptors (reviewed in ref. 8) a number of ligand-dependent receptor-interacting proteins have been identified and shown to be required for optimal receptor function in vivo (reviewed in refs. 9-11). The best characterized of these are the SRC-1 family of proteins (including SRC-1͞p160, TIF-2͞GRIP-1, ACTR͞PCIP͞ RAC3͞AIB1͞TRAM1; reviewed in refs. 9-11), the pleiotropic coactivator p300͞CBP (reviewed in ref . 7), and the interacting PCAF (12). By contrast, a distinct coactivator complex, comprised of 9-10 major thyroid hormone receptor (TR)-associated proteins (TRAPs), was recently identified and shown to markedly enhance activation by thyroid hormone receptor in a cell free system comprised of purified factors and naked DNA templates (13). A broader role for the TRAP complex in nuclear hormone receptor function was i...

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Section: Discussionsupporting

confidence: 91%

Thyroid hormone receptor-associated proteins and general positive cofactors mediate thyroid hormone receptor function in the absence of the TATA box-binding protein-associated factors of TFIID

Fondell

Guermah

Malik

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

141

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“…7). Consistent with these observations in vivo, TAF-independent activation was demonstrated in transcriptional experiments in vitro, using TFIID-depleted HeLa nuclear extracts, which could possess activator targets other than TAFs (8), or even with a highly purified cell-free transcription system (9,10). Furthermore, transcription activation is reconstituted by supplementing purified yeast holoenzyme with only TBP (11,12).…”

supporting

confidence: 68%

A role of transcriptional activators as antirepressors for the autoinhibitory activity of TATA box binding of transcription factor IID

Kotani

Banno

Ikura

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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. 2). An alternative model postulates that the holoenzyme enters the preinitiation complex as a preassembled unit (2, 3). Although the nature of the assembly pathway most relevant to the in vivo context remains unclear, access of TFIID to the core promoter is likely to be a critical step in any pathway, given that only TFIID binds to the promoter in a sequence-specific manner. In support of this view, in vitro recruitment experiments using immobilized promoters demonstrated that the holoenzyme is not recruited independently of TFIID and TFIIA (4).TFIID is a multimeric protein complex consisting of the TATA box-binding protein (TBP) and Ͼ10 distinct TBPassociated factors (TAFs), which are conserved from yeast to man (reviewed in ref. . Consistent with these observations in vivo, TAF-independent activation was demonstrated in transcriptional experiments in vitro, using TFIID-depleted HeLa nuclear extracts, which could possess activator targets other than TAFs (8), or even with a highly purified cell-free transcription system (9, 10). Furthermore, transcription activation is reconstituted by supplementing purified yeast holoenzyme with only TBP (11, 12). These observations suggest that activators contribute to activated transcription by interacting with multiple targets (e.g., basal factors, TAFs, SRB mediators, or other unknown cofactors).Although TAFs are well recognized as positive cofactors, in our view, at least certain TAFs are negative cofactors. Importantly, highly purified TFIID manifests lower transcriptional activity than TBP alone (13) and binds to the core promoter poorly (reviewed in ref. 14). This inhibitory activity for promoter binding in TFIID is suppressed by limited proteolysis of TFIID or by TFIIA (14,15). These results strongly suggest that this inhibitory activity could be intrinsic to TFIID and derived from TAF(s) and is sensitive to proteases. Consistent with this idea, Drosophila (d)TAF230, or the homologous yTAF145, inhibits TBP binding to the TATA box when these TAFs are mixed with TBP in vitro (16)(17)(18). Mutational analyses of dTAF230 indicate that the N-terminal 156 residues inhibit TATA box binding through direct interaction with TBP (19,20). This N-terminal domain (designated as TAND; TAF N-terminal domain), has been dissected into subdomain 1 (dTAND-1; residues 11-77) and subdomain 2 (dTAND-2; residues 82-156), which bind to the concave undersurface and the convex upper surface of TBP in This paper was submitted directly (Track II) to the PNAS office.

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“…5A clearly indicated that dMediator is the major binding target of the VP16 activator protein in nuclear extracts, whether TAFs provide a redundant, synergistic, or distinct function in transcriptional activation in the presence of dMediator is not known. Therefore, we compared the requirement of dMediator in Pol II transcription to that of TAFs, using immunodepletion studies similar to that carried out in the human system (30). We immunodepleted nuclear extract with an Ab against dMediator (anti-dSOH1), TFIID (anti-dTAF II 250), or ␤-galactosidase (control).…”

Section: Downloaded Frommentioning

confidence: 99%

Drosophila Mediator Complex Is Broadly Utilized by Diverse Gene-Specific Transcription Factors at Different Types of Core Promoters

Park

Gim

Kim

et al. 2001

Molecular and Cellular Biology

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To decipher the mechanistic roles of Mediator proteins in regulating developmental specific gene expression and compare them to those of TATA-binding protein (TBP)-associated factors (TAFs), we isolated and analyzed a multiprotein complex containing Drosophila Mediator (dMediator) homologs. dMediator interacts with several sequence-specific transcription factors and basal transcription machinery and is critical for activated transcription in response to diverse transcriptional activators. The requirement for dMediator did not depend on a specific core promoter organization. By contrast, TAFs are preferentially utilized by promoters having a specific core element organization. Therefore, Mediator proteins are suggested to act as a pivotal coactivator that integrates promoter-specific activation signals to the basal transcription machinery.Precise regulation of gene expression is fundamentally required for a broad spectrum of developmental processes in multicellular organisms. Although distinct sequence-specific transcription factors are primarily responsible for this regulation, transcriptional coactivator-corepressor proteins also add a significant secondary layer to the regulation of gene expression. A number of coactivator complexes have been identified in eukaryotes, and their functions in gene activation at specific promoters have been analyzed, primarily in vitro. However, the mechanism by which these transcriptional coactivators regulate gene expression in living organisms is not well understood.Among eukaryotic transcriptional coactivators, two classes of proteins, Mediator proteins and TATA-binding protein (TBP)-associated factors (TAFs), are central to the process of transcriptional regulation. These proteins were isolated as multiprotein complexes composed of more than 10 polypeptides and associate with the basal transcription machinery (RNA polymerase II [Pol II] and TBP, respectively). Both complexes interact with transcriptional activators and are required for transcriptional activation in reconstituted in vitro systems (3,8,40). These facts suggest that Mediator and TAF complexes function as coactivators by relaying transcriptional activation signals from DNA-bound activators to the basal transcription machinery. However, it has not been clearly determined whether Mediator and TAF complexes contribute redundantly or distinctly to the transcriptional activation process, nor have their mechanistic roles in Pol II transcription been clearly deciphered.Although both Mediator and TAF complexes were initially identified from in vitro assays, recent genetic analyses in yeast suggest that TAFs do not function as general coactivators under physiological conditions. First, the depletion of various TFIID-specific TAFs does not have a significant effect on transcriptional activation of most genes in yeast (12,28,41). Second, yeast TAF II 145/130 was shown to function as a core promoter selectivity factor rather than a general coactivator (36). These observations are in good agreement with earlier reports that ...

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Transcription Activation via Enhanced Preinitiation Complex Assembly in a Human Cell-Free System Lacking TAFIIs

Cited by 93 publications

References 40 publications

Thyroid hormone receptor-associated proteins and general positive cofactors mediate thyroid hormone receptor function in the absence of the TATA box-binding protein-associated factors of TFIID

Thyroid hormone receptor-associated proteins and general positive cofactors mediate thyroid hormone receptor function in the absence of the TATA box-binding protein-associated factors of TFIID

A role of transcriptional activators as antirepressors for the autoinhibitory activity of TATA box binding of transcription factor IID

Drosophila Mediator Complex Is Broadly Utilized by Diverse Gene-Specific Transcription Factors at Different Types of Core Promoters

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