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Cao M, Qiu B, Zhou T, Zhang J. Control strategies for the timing of intracellular events. Phys Rev E 2020; 100:062401. [PMID: 31962487 DOI: 10.1103/physreve.100.062401] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Indexed: 11/07/2022]
Abstract
While the timing of intracellular events is essential for many cellular processes, gene expression inside a single cell can exhibit substantial cell-to-cell variability, raising the question of how cells ensure precision in event timing despite such stochasticity. We address this question by analyzing a biologically reasonable model of gene expression in the context of first passage time (FPT), focusing on two experimentally measurable statistics: mean FPT (MFPT) and timing variability (TV). We show that (1) transcriptional burst size (BS) and burst frequency (BF) can minimize the TV; (2) translational BS monotonically reduces the MFPT to a nonzero low bound; (3) the timescale of promoter kinetics can minimize both the MFPT and the TV, depending on the ratio of the on-switching rate over the off-switching rate; and (4) positive feedback regulation of any form can all minimize the TV, whereas negative feedback regulation of transcriptional BF or BS always enhances the TV. These control strategies can have broad implications for diverse cellular processes relying on precise temporal triggering of events.
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Affiliation(s)
- Mengfang Cao
- Key Laboratory of Computational Mathematics, Guangdong Province, School of Mathematics, Sun Yat-Sen University, Guangzhou, 510275, People's Republic of China
| | - Baohua Qiu
- Key Laboratory of Computational Mathematics, Guangdong Province, School of Mathematics, Sun Yat-Sen University, Guangzhou, 510275, People's Republic of China
| | - Tianshou Zhou
- Key Laboratory of Computational Mathematics, Guangdong Province, School of Mathematics, Sun Yat-Sen University, Guangzhou, 510275, People's Republic of China
| | - Jiajun Zhang
- Key Laboratory of Computational Mathematics, Guangdong Province, School of Mathematics, Sun Yat-Sen University, Guangzhou, 510275, People's Republic of China
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2
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Mediator, known as a coactivator, can act in transcription initiation in an activator-independent manner in vivo. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:687-696. [DOI: 10.1016/j.bbagrm.2018.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 06/28/2018] [Accepted: 07/04/2018] [Indexed: 01/20/2023]
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3
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Scholes C, DePace AH, Sánchez Á. Combinatorial Gene Regulation through Kinetic Control of the Transcription Cycle. Cell Syst 2016; 4:97-108.e9. [PMID: 28041762 DOI: 10.1016/j.cels.2016.11.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 08/09/2016] [Accepted: 11/23/2016] [Indexed: 11/20/2022]
Abstract
Cells decide when, where, and to what level to express their genes by "computing" information from transcription factors (TFs) binding to regulatory DNA. How is the information contained in multiple TF-binding sites integrated to dictate the rate of transcription? The dominant conceptual and quantitative model is that TFs combinatorially recruit one another and RNA polymerase to the promoter by direct physical interactions. Here, we develop a quantitative framework to explore kinetic control, an alternative model in which combinatorial gene regulation can result from TFs working on different kinetic steps of the transcription cycle. Kinetic control can generate a wide range of analog and Boolean computations without requiring the input TFs to be simultaneously bound to regulatory DNA. We propose experiments that will illuminate the role of kinetic control in transcription and discuss implications for deciphering the cis-regulatory "code."
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Affiliation(s)
- Clarissa Scholes
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
| | - Álvaro Sánchez
- The Rowland Institute at Harvard, Harvard University, Cambridge, MA 02142, USA.
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4
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Lacombe T, Poh SL, Barbey R, Kuras L. Mediator is an intrinsic component of the basal RNA polymerase II machinery in vivo. Nucleic Acids Res 2013; 41:9651-62. [PMID: 23963697 PMCID: PMC3834807 DOI: 10.1093/nar/gkt701] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Mediator is a prominent multisubunit coactivator that functions as a bridge between gene-specific activators and the basal RNA polymerase (Pol) II initiation machinery. Here, we study the poorly documented role of Mediator in basal, or activator-independent, transcription in vivo. We show that Mediator is still present at the promoter when the Pol II machinery is recruited in the absence of an activator, in this case through a direct fusion between a basal transcription factor and a heterologous DNA binding protein bound to the promoter. Moreover, transcription resulting from activator-independent recruitment of the Pol II machinery is impaired by inactivation of the essential Mediator subunit Med17 due to the loss of Pol II from the promoter. Our results strongly support that Mediator is an integral component of the minimal machinery essential in vivo for stable Pol II association with the promoter.
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Affiliation(s)
- Thierry Lacombe
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, affiliated with Université Paris-Sud, Gif-sur-Yvette 91198, France
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5
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Transcriptional regulation in Saccharomyces cerevisiae: transcription factor regulation and function, mechanisms of initiation, and roles of activators and coactivators. Genetics 2012; 189:705-36. [PMID: 22084422 DOI: 10.1534/genetics.111.127019] [Citation(s) in RCA: 239] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Here we review recent advances in understanding the regulation of mRNA synthesis in Saccharomyces cerevisiae. Many fundamental gene regulatory mechanisms have been conserved in all eukaryotes, and budding yeast has been at the forefront in the discovery and dissection of these conserved mechanisms. Topics covered include upstream activation sequence and promoter structure, transcription factor classification, and examples of regulated transcription factor activity. We also examine advances in understanding the RNA polymerase II transcription machinery, conserved coactivator complexes, transcription activation domains, and the cooperation of these factors in gene regulatory mechanisms.
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6
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Transcriptional activators and activation mechanisms. Protein Cell 2011; 2:879-88. [PMID: 22180087 DOI: 10.1007/s13238-011-1101-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 08/22/2011] [Indexed: 10/14/2022] Open
Abstract
Transcriptional activators are required to turn on the expression of genes in a eukaryotic cell. Activators bound to the enhancer can facilitate either the recruitment of RNA polymerase II to the promoter or its elongation. This article examines a few selected issues in understanding activator functions and activation mechanisms.
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7
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Deng W, Roberts SGE. TFIIB and the regulation of transcription by RNA polymerase II. Chromosoma 2007; 116:417-29. [PMID: 17593382 DOI: 10.1007/s00412-007-0113-9] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Revised: 05/21/2007] [Accepted: 05/21/2007] [Indexed: 02/01/2023]
Abstract
Accurate transcription of a gene by RNA polymerase II requires the assembly of a group of general transcription factors at the promoter. The general transcription factor TFIIB plays a central role in preinitiation complex assembly, providing a bridge between promoter-bound TFIID and RNA polymerase II. TFIIB makes extensive contact with the core promoter via two independent DNA-recognition modules. In addition to interacting with other general transcription factors, TFIIB directly modulates the catalytic center of RNA polymerase II in the transcription complex. Moreover, TFIIB has been proposed as a target of transcriptional activator proteins that act to stimulate preinitiation complex assembly. In this review, we will discuss our current understanding of these activities of TFIIB.
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Affiliation(s)
- Wensheng Deng
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
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8
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Judelson HS, Narayan R, Fong AMVA, Tani S, Kim KS. Performance of a tetracycline-responsive transactivator system for regulating transgenes in the oomycete Phytophthora infestans. Curr Genet 2007; 51:297-307. [PMID: 17377792 DOI: 10.1007/s00294-007-0125-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 02/23/2007] [Accepted: 02/24/2007] [Indexed: 11/27/2022]
Abstract
The oomycete genus Phytophthora includes many important plant pathogens for which extensive genome data exist, but lacking is an inducible expression system to study contributions of their genes to growth and pathogenicity. Here the adaptation of the reverse tetracycline transactivator (rtTA) system to P. infestans is described. Vectors were developed containing rtTA expressed from an oomycete promoter, and beta-glucuronidase (GUS) controlled by TetR binding sites fused to a minimal oomycete promoter. Transformants were obtained in which GUS was expressed in a dose-dependent manner by the rtTA inducer doxycycline, indicating that the gene switch functions in P. infestans. However, toxicity of rtTA hindered the isolation of transformants if expressed on the same plasmid as the nptII selection marker. Better results were obtained by cotransforming those genes on separate plasmids, with 92% of transformants acquiring both DNAs although only 4% expressed rtTA at detectable levels. Low levels of reporter activity were measured in such transformants, suggesting that rtTA activated transcription weakly. Also, significant variation in the sensitivity of isolates to doxycycline and tetracycline was observed. These results are useful both in terms of developing tools for functional genomics and understanding the fate of DNA during Phytophthora transformation.
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Affiliation(s)
- Howard S Judelson
- Department of Plant Pathology, University of California, Riverside, CA 92521, USA.
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9
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Elsby LM, O'Donnell AJM, Green LM, Sharrocks AD, Roberts SGE. Assembly of transcription factor IIB at a promoter in vivo requires contact with RNA polymerase II. EMBO Rep 2006; 7:898-903. [PMID: 16878124 PMCID: PMC1559668 DOI: 10.1038/sj.embor.7400767] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Revised: 06/29/2006] [Accepted: 06/30/2006] [Indexed: 01/19/2023] Open
Abstract
The general transcription factor TFIIB has a central role in the assembly of the preinitiation complex at the promoter, providing a platform for the entry of RNA polymerase II/TFIIF. We used an RNA interference (RNAi)-based system in which TFIIB expression is ablated in vivo and replaced with a TFIIB derivative that contains a silent mutation and is refractory to the RNAi. Using this approach, we found that transcriptionally defective TFIIB amino-terminal mutants showed distinct effects on the basis of their ability to compete with wild-type TFIIB in vivo. Moreover, analysis of the TFIIB mutant derivatives by chromatin immunoprecipitation showed that promoter occupancy by TFIIB is dependent on the association with RNA polymerase II. Together, our results support a mode of preinitiation complex assembly in which TFIIB/RNA polymerase II recruitment to the promoter occurs in vivo.
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Affiliation(s)
- Laura M Elsby
- Faculty of Life Sciences, The Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Amanda J M O'Donnell
- Faculty of Life Sciences, The Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Laura M Green
- Faculty of Life Sciences, The Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Andrew D Sharrocks
- Faculty of Life Sciences, The Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Stefan G E Roberts
- Faculty of Life Sciences, The Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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10
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Imoberdorf RM, Topalidou I, Strubin M. A role for gcn5-mediated global histone acetylation in transcriptional regulation. Mol Cell Biol 2006; 26:1610-6. [PMID: 16478983 PMCID: PMC1430249 DOI: 10.1128/mcb.26.5.1610-1616.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcriptional activators often require histone acetyltransferases (HATs) for full activity. The common explanation is that activators directly recruit HATs to gene promoters to locally hyperacetylate histones and thereby facilitate transcription complex formation. However, in addition to being targeted to specific loci, HATs such as Gcn5 also modify histones genome-wide. Here we provide evidence for a role of this global HAT activity in regulated transcription. We show that activation by direct recruitment of the transcriptional machinery neither recruits Gcn5 nor induces changes in histone acetylation yet can strongly depend on Gcn5 at promoters showing a high basal state of Gcn5-mediated histone acetylation. We also show that Gcn5 dependency varies among core promoters and is influenced by the strength of interaction used to recruit the machinery and by the affinity of the latter for the core promoter. These data support a role for global Gcn5 HAT activity in modulating transcription independently of its known coactivator function.
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Affiliation(s)
- Rachel Maria Imoberdorf
- Department of Microbiology and Molecular Medicine, University Medical Centre (C.M.U.), Rue Michel-Servet 1, 1211 Geneva 4, Switzerland
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11
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Schmid M, Arib G, Laemmli C, Nishikawa J, Durussel T, Laemmli UK. Nup-PI: the nucleopore-promoter interaction of genes in yeast. Mol Cell 2006; 21:379-91. [PMID: 16455493 DOI: 10.1016/j.molcel.2005.12.012] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2005] [Revised: 11/18/2005] [Accepted: 12/07/2005] [Indexed: 10/25/2022]
Abstract
Our previous work identified the inner basket of the NPC as a physical activation/protection station for force-tethered, epigenetically silenced genes. Here we show that a specific nucleopore-to-gene-promoter interaction (Nup-PI) is an early physiological event of gene activation. Nup-PI was discovered with chromatin endogenous cleavage (ChEC) experiments that mapped in vivo the genomic interaction sites of the nucleoporin Nup2p fused to microccocal nuclease (Nup2-MN). Strong Nup-PI, cleavage by Nup2-MN, is observed at the promoters of the GAL genes and at HXK1 upon activation of these genes with galactose. Nup-PI at the GAL locus requires Gal4p and the UASg and TATA box elements but not SAGA and active transcription. The physical, activation-dependent interaction of the GAL locus with the NPC basket was confirmed by imaging. Chromosome-wide ChEC studies indicated that Nup-PI occurs at numerous genes. The data identify the NPC basket as a new, integral participant in gene expression.
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Affiliation(s)
- Manfred Schmid
- Departments of Biochemistry and Molecular Biology, NCCR Frontiers in Genetics, University of Geneva, 30 Quai Ernest-Ansermet, CH1211-Geneva 4, Switzerland
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12
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Cheng JX, Gandolfi M, Ptashne M. Activation of the Gal1 Gene of Yeast by Pairs of 'Non-Classical' Activators. Curr Biol 2004; 14:1675-9. [PMID: 15380071 DOI: 10.1016/j.cub.2004.09.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2004] [Revised: 08/09/2004] [Accepted: 08/09/2004] [Indexed: 10/26/2022]
Abstract
Eukaryotic transcriptional activators work by recruiting to DNA the transcriptional machinery, including protein complexes required for chromatin modification, transcription initiation, and elongation. Which of these complexes must be directly recruited to trigger transcription? We test various "non-classical" transcription activators (comprising a component of the transcriptional machinery fused to a DNA binding domain) for their abilities to activate transcription of a chromosomally integrated reporter in yeast. Among these newly constructed fusion proteins, none efficiently activated transcription when working on its own. However, in several instances transcription was activated by a pair of such fusion proteins tethered to adjacent sites on DNA. In each of these cases, one fusion protein bore a component of the SAGA complex, and the other bore a component of the Mediator complex. Transcription was also activated by certain tripartite fusion proteins comprising a Mediator and a SAGA component fused to a DNA binding domain. The results are consistent with the finding that the classical activator Gal4, working at the GAL1 promoter, activates transcription by (at least in part) independently recruiting SAGA and Mediator.
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Affiliation(s)
- Jason X Cheng
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA
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13
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Albrecht RA, Kim SK, Zhang Y, Zhao Y, O'Callaghan DJ. The equine herpesvirus 1 EICP27 protein enhances gene expression via an interaction with TATA box-binding protein. Virology 2004; 324:311-26. [PMID: 15207618 DOI: 10.1016/j.virol.2004.03.040] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Revised: 03/11/2004] [Accepted: 03/24/2004] [Indexed: 11/25/2022]
Abstract
The mechanism(s) by which the early EICP27 gene product cooperates with other equine herpesvirus 1 (EHV-1) regulatory proteins to achieve maximal promoter activity remains unknown. Transient transfection assays revealed that deletion of residues 93-140 of the 470-aa EICP27 protein substantially diminished its activation of the immediate-early (IE) promoter, whereas deletion of residues 140-470 that contain a zinc-finger motif abolished this activity. Fluorescence microscopy of cells expressing the full-length EICP27 protein or portions of this protein revealed that an arginine-rich sequence spanning residues 178-185 mediates nuclear entry. Experiments employing the mammalian Gal4 two-plasmid system revealed that the EICP27 protein does not possess an independent trans-activation domain (TAD). Protein-protein interaction assays using purified proteins revealed that residues 124-220 of the EICP27 protein mediate its direct interaction with TATA box-binding protein (TBP). Partial deletion of this TBP-binding domain attenuated the ability of the EICP27 protein to stimulate the IE and early EICP0 promoters by 68% and 71%, respectively, indicating the importance of this protein-protein interaction.
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Affiliation(s)
- Randy A Albrecht
- Center for Molecular and Tumor Virology and Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA
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14
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Hori RT, Xu S, Hu X, Pyo S. TFIIB-facilitated recruitment of preinitiation complexes by a TAF-independent mechanism. Nucleic Acids Res 2004; 32:3856-63. [PMID: 15272087 PMCID: PMC506799 DOI: 10.1093/nar/gkh711] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Gene activators contain activation domains that are thought to recruit limiting components of the transcription machinery to a core promoter. VP16, a viral gene activator, has served as a model for studying the mechanistic aspects of transcriptional activation from yeast to human. The VP16 activation domain can be divided into two modules--an N-terminal subdomain (VPN) and a C-terminal subdomain (VPC). This study demonstrates that VPC stimulates core promoters that are either independent or dependent on TAFs (TATA-box Binding Protein-Associated Factors). In contrast, VPN only activates the TAF-independent core promoter and this activity increases in a synergistic fashion when VPN is dimerized (VPN2). Compared to one copy of VPN (VPN1), VPN2 also displays a highly cooperative increase in binding hTFIIB. The increased TFIIB binding correlates with VPN2's increased ability to recruit a complex containing TFIID, TFIIA and TFIIB. However, VPN1 and VPN2 do not increase the assembly of a complex containing only TFIID and TFIIA. The VPN subdomain also facilitates assembly of a complex containing TBP:TFIIA:TFIIB, which lacks TAFs, and provides a mechanism that could function at TAF-independent promoters. Taken together, these results suggest the interaction between VPN and TFIIB potentially initiate a network of contacts allowing the activator to indirectly tether TFIID or TBP to DNA.
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Affiliation(s)
- Roderick T Hori
- Department of Molecular Sciences, University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, TN 38163, USA.
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15
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Albrecht RA, Jang HK, Kim SK, O'Callaghan DJ. Direct interaction of TFIIB and the IE protein of equine herpesvirus 1 is required for maximal trans-activation function. Virology 2004; 316:302-12. [PMID: 14644612 DOI: 10.1016/j.virol.2003.08.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recently, we reported that the immediate-early (IE) protein of equine herpesvirus 1 (EHV-1) associates with transcription factor TFIIB [J. Virol. 75 (2001), 10219]. In the current study, the IE protein purified as a glutathione-S-transferase (GST) fusion protein was shown to interact directly with purified TFIIB in GST-pulldown assays. A panel of TFIIB mutants employed in protein-binding assays revealed that residues 125 to 174 within the first direct repeat of TFIIB mediate its interaction with the IE protein. This interaction is physiologically relevant as transient transfection assays demonstrated that (1). exogenous native TFIIB did not perturb IE protein function, and (2). ectopic expression of a TFIIB mutant that lacked the IE protein interactive domain significantly diminished the ability of the IE protein to trans-activate EHV-1 promoters. These results suggest that an interaction of the IE protein with TFIIB is an important aspect of the regulatory role of the IE protein in the trans-activation of EHV-1 promoters.
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Affiliation(s)
- Randy A Albrecht
- Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA
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16
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Matangkasombut O, Auty R, Buratowski S. Structure and Function of the TFIID Complex. ADVANCES IN PROTEIN CHEMISTRY 2004; 67:67-92. [PMID: 14969724 DOI: 10.1016/s0065-3233(04)67003-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Oranart Matangkasombut
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA
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17
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Leupin O, Bontron S, Strubin M. Hepatitis B virus X protein and simian virus 5 V protein exhibit similar UV-DDB1 binding properties to mediate distinct activities. J Virol 2003; 77:6274-83. [PMID: 12743284 PMCID: PMC154990 DOI: 10.1128/jvi.77.11.6274-6283.2003] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The UV-damaged DNA-binding activity protein (UV-DDB) consists of two subunits, DDB1 and DDB2, and functions in DNA repair and cell cycle regulation. The DDB1 subunit is a target for the hepatitis B virus X protein (HBx). Binding of HBx to DDB1 interferes with cell growth and viability in culture and has been implicated in the establishment of viral infection. DDB1 also interacts with the V proteins encoded by several paramyxoviruses including simian virus 5 (SV5), which prevent interferon signaling by targeting either STAT1 or STAT2 proteins for proteolysis. The role of V binding to DDB1, however, remains unclear. Here we show that the V protein of SV5 (SV5-V) and HBx exhibit strikingly similar DDB1 binding properties. Thus, SV5-V and HBx bind to DDB1 in a mutually exclusive manner, and SV5-V shares with HBx the ability to enhance the steady-state levels of DDB1 and to inhibit its association with DDB2. Yet only HBx induces cell death, and SV5-V can prevent HBx from doing so by blocking its interaction with DDB1. Binding of SV5-V to DDB1 may serve another function, since SV5-V shows a decreased ability to induce STAT1 degradation in cells expressing reduced amounts of DDB1. These findings demonstrate that HBx performs a unique function through its association with DDB1 for which SV5-V cannot substitute and suggest that SV5-V and HBx have evolved to bind DDB1 to achieve distinct functions, both by a mechanism that does not involve DDB2.
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Affiliation(s)
- Olivier Leupin
- Department of Genetics and Microbiology, University Medical Centre (C.M.U.), 1211 Geneva 4, Switzerland
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18
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Zeng X, Zhang D, Dorsey M, Ma J. Hypomutable regions of yeast TFIIB in a unigenic evolution test represent structural domains. Gene 2003; 309:49-56. [PMID: 12727357 DOI: 10.1016/s0378-1119(03)00492-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
As genome sequences of many organisms - including humans - are being decoded, there is a great need for genetic tools to analyze newly discovered genes/proteins. A 'unigenic evolution' approach has been previously proposed for dissecting protein domains, which is based on the assumption that functionally important regions of a protein may tolerate missense mutations less well than other regions. We describe a unigenic evolution analysis of general transcription factor IIB (TFIIB) - a protein that is well characterized both structurally and functionally - to better understand the molecular basis of this genetic approach. The overall distribution profile of hypomutable regions within yeast TFIIB correlates extremely well with the known compact structural domains, suggesting that the unigenic evolution approach can help reveal structural properties of a protein. We further show that a small region located immediately carboxyl-terminal to the zinc ribbon motif is functionally important despite its strong hypermutability. Our study further demonstrates the usefulness of the unigenic evolution approach in dissecting protein domains, but suggests that the mutability of different regions of a protein in such a test is determined primarily by their structural properties.
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Affiliation(s)
- Xiao Zeng
- Division of Developmental Biology, Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
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19
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Kobayashi A, Miyake T, Kawaichi M, Kokubo T. Mutations in the histone fold domain of the TAF12 gene show synthetic lethality with the TAF1 gene lacking the TAF N-terminal domain (TAND) by different mechanisms from those in the SPT15 gene encoding the TATA box-binding protein (TBP). Nucleic Acids Res 2003; 31:1261-74. [PMID: 12582246 PMCID: PMC150217 DOI: 10.1093/nar/gkg180] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The general transcription factor TFIID, composed of the TATA box-binding protein (TBP) and 14 TBP-associated factors (TAFs), is important for both basal and regulated transcription by RNA polymerase II. Although it is well known that the TAF N-terminal domain (TAND) at the amino-terminus of the TAF1 protein binds to TBP and thereby inhibits TBP function in vitro, the physiological role of this domain remains obscure. In our previous study, we screened for mutations that cause lethality when co-expressed with the TAF1 gene lacking TAND (taf1-DeltaTAND) and identified two DeltaTAND synthetic lethal (nsl) mutations as those in the SPT15 gene encoding TBP. In this study we isolated another nsl mutation in the same screen and identified it to be a mutation in the histone fold domain (HFD) of the TAF12 gene. Several other HFD mutations of this gene also exhibit nsl phenotypes, and all of them are more or less impaired in transcriptional activation in vivo. Interestingly, a set of genes affected in the taf1-DeltaTAND mutant is similarly affected in the taf12 HFD mutants but not in the nsl mutants of TBP. Therefore, we discovered that the nsl mutations of these two genes cause lethality in the taf1-DeltaTAND mutant by different mechanisms.
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Affiliation(s)
- Akiko Kobayashi
- Division of Gene Function in Animals, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan
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20
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Deckert J, Struhl K. Targeted recruitment of Rpd3 histone deacetylase represses transcription by inhibiting recruitment of Swi/Snf, SAGA, and TATA binding protein. Mol Cell Biol 2002; 22:6458-70. [PMID: 12192044 PMCID: PMC135627 DOI: 10.1128/mcb.22.18.6458-6470.2002] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Certain DNA-binding repressors inhibit transcription by recruiting Rpd3 histone deacetylase complexes to promoters and generating domains of histone deacetylation that extend over a limited number of nucleosomes. Here, we show that the degree of Rpd3-dependent repression depends on the activator and the level of activation, not the extent of histone deacetylation. In all cases tested, activator binding is unaffected by histone deacetylation. In contrast, Rpd3-dependent repression is associated with decreased occupancy by TATA binding protein (TBP), the Swi/Snf nucleosome-remodeling complex, and the SAGA histone acetylase complex. Transcriptional repression is bypassed by direct recruitment of TBP and several TBP-associated factors, but not by natural activation domains or direct recruitment of polymerase II holoenzyme components. These results suggest that the domain of localized histone deacetylation generated by recruitment of Rpd3 mediates repression by inhibiting recruitment of chromatin-modifying activities and TBP.
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Affiliation(s)
- Jutta Deckert
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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21
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Zhang DY, Carson DJ, Ma J. The role of TFIIB-RNA polymerase II interaction in start site selection in yeast cells. Nucleic Acids Res 2002; 30:3078-85. [PMID: 12136090 PMCID: PMC135743 DOI: 10.1093/nar/gkf422] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2002] [Revised: 05/20/2002] [Accepted: 05/20/2002] [Indexed: 11/14/2022] Open
Abstract
Previous studies have established a critical role of both TFIIB and RNA polymerase II (RNAPII) in start site selection in the yeast Saccharomyces cerevisiae. However, it remains unclear how the TFIIB-RNAPII interaction impacts on this process since such an interaction can potentially influence both preinitiation complex (PIC) stability and conformation. In this study, we further investigate the role of TFIIB in start site selection by characterizing our newly generated TFIIB mutants, two of which exhibit a novel upstream shift of start sites in vivo. We took advantage of an artificial recruitment system in which an RNAPII holoenzyme component is covalently linked to a DNA-binding domain for more direct and stable recruitment. We show that TFIIB mutations can exert their effects on start site selection in such an artificial recruitment system even though it has a relaxed requirement for TFIIB. We further show that these TFIIB mutants have normal affinity for RNAPII and do not alter the promoter melting/scanning step. Finally, we show that overexpressing the genetically isolated TFIIB mutant E62K, which has a reduced affinity for RNAPII, can correct its start site selection defect. We discuss a model in which the TFIIB-RNAPII interaction controls the start site selection process by influencing the conformation of PIC prior to or during PIC assembly, as opposed to PIC stability.
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Affiliation(s)
- Dong-Yi Zhang
- Division of Developmental Biology, Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
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22
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Yaghmai R, Cutting GR. Optimized regulation of gene expression using artificial transcription factors. Mol Ther 2002; 5:685-94. [PMID: 12027552 DOI: 10.1006/mthe.2002.0610] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A major focus in the basic science of gene therapy is the study of factors involved in target-specific regulation of gene expression. Optimization of artificial or "designer" transcription factors capable of specific regulation of target genes is a prerequisite to developing practical applications in human subjects. In this paper, we present a systematic and combinatorial approach to optimize engineered transcription factors using designed zinc-finger proteins fused to transcriptional effector domains derived from the naturally occurring activators (VP16 or P65) or repressor (KRAB) proteins. We also demonstrate effective targeting of artificial transcription factors to regulate gene expression from three different constitutive viral promoters (SV40, CMV, RSV). Achieving a desired level of gene expression from a targeted region depended on several variables, including target site affinities for various DNA-binding domains, the nature of the activator domain, the particular cell type used, and the position of the target site with respect to the core promoter. Hence, several aspects of the artificial transcription factors should be simultaneously evaluated to ensure the optimum level of gene expression from a given target site in a given cell type. Our observations and our optimization approach have substantial implications for designing safe and effective artificial transcription factors for cell-based and therapeutic uses.
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Affiliation(s)
- Reza Yaghmai
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins Hospital, 600 North Wolfe St., Blalock 1008, Baltimore, Maryland 21287-4922, USA.
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23
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Traven A, Staresincić L, Arnerić M, Sopta M. The yeast protein Xtc1 functions as a direct transcriptional repressor. Nucleic Acids Res 2002; 30:2358-64. [PMID: 12034822 PMCID: PMC117208 DOI: 10.1093/nar/30.11.2358] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The yeast protein Xtc1 was identified as a protein that binds directly and specifically to the activation domains of acidic activators such as E2F-1, Gal4 and VP16. Additionally, it was shown to co-purify with the RNA polymerase II holoenzyme complex and it was suggested that Xtc1 functions as a regulator of transcription that modulates the response of RNA polymerase II to transcriptional activators. We have further analyzed the transcription function of Xtc1 and show that its fusion to a heterologous DNA binding domain can repress transcription of a reporter gene in vivo in an Srb10/11-dependent manner. We suggest that the presence of Xtc1 in the RNA polymerase II holoenzyme could help to recruit an Srb10-active form of the holoenzyme to target promoters. This same protein has also been implicated in mitochondrial DNA recombination, maintenance and repair. Determination of the subcellular localization using a GFP-Xtc1 fusion shows that it localizes to both the nucleus and the mitochondria in vivo, which is consistent with Xtc1 having a function in both cellular compartments.
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Affiliation(s)
- Ana Traven
- Department of Molecular Genetics, Ruder BokoviM Institute, BijeniQka 54, 10000 Zagreb, Croatia
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24
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Mitsuzawa H, Ishihama A. Identification of histone H4-like TAF in Schizosaccharomyces pombe as a protein that interacts with WD repeat-containing TAF. Nucleic Acids Res 2002; 30:1952-8. [PMID: 11972332 PMCID: PMC113851 DOI: 10.1093/nar/30.9.1952] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The general transcription factor TFIID consists of the TATA-binding protein (TBP) and multiple TBP-associated factors (TAFs). We previously identified two distinct WD repeat-containing TAFs, spTAF72 and spTAF73, in the fission yeast Schizosaccharomyces pombe. Here we report the identification of another S.pombe TAF, spTAF50, which is the S.pombe homolog of histone H4-like TAFs such as human TAF80, Drosophila TAF60 and Saccharomyces cerevisiae TAF60. spTAF50 was identified in a two-hybrid screen as a protein that interacts with the C-terminal WD repeat-containing region of spTAF72. Gene disruption revealed that spTAF50 is essential for cell viability. In vitro, spTAF50 bound to spTAF72 but less efficiently to spTAF73. In S.pombe cells, spTAF50 was detected as a protein with an apparent molecular mass of approximately 50 kDa. Immunoprecipitation experiments demonstrated that spTAF50 is present in both the TFIID and SAGA-like complexes as in the case of spTAF72. These results indicate that the C-terminal region of spTAF72, which largely consists of WD repeats, interacts with spTAF50 in the TFIID and SAGA-like complexes, suggesting a role for the WD repeat domain in the interaction between TAFs.
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Affiliation(s)
- Hiroshi Mitsuzawa
- Department of Molecular Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
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25
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Mencía M, Moqtaderi Z, Geisberg JV, Kuras L, Struhl K. Activator-specific recruitment of TFIID and regulation of ribosomal protein genes in yeast. Mol Cell 2002; 9:823-33. [PMID: 11983173 DOI: 10.1016/s1097-2765(02)00490-2] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In yeast, TFIID strongly associates with nearly all ribosomal protein (RP) promoters, but a TAF-independent form of TBP preferentially associates with other active promoters. RP promoters are regulated in response to growth stimuli, in most cases by a Rap1-containing activator. This Rap1-dependent activator is necessary and sufficient for TFIID recruitment, whereas other activators do not efficiently recruit TFIID. TAFs are recruited to RP promoters even when TBP and other general transcription factors are not associated, suggesting that TFIID recruitment involves a direct activator-TAF interaction. Most RP promoters lack canonical TATA elements, and they are preferentially activated by the Rap1-containing activator. These results demonstrate activator-specific recruitment of TFIID in vivo, and they suggest that TFIID recruitment is important for coordinate expression of RP genes.
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Affiliation(s)
- Mario Mencía
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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26
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Lin-Marq N, Bontron S, Leupin O, Strubin M. Hepatitis B virus X protein interferes with cell viability through interaction with the p127-kDa UV-damaged DNA-binding protein. Virology 2001; 287:266-74. [PMID: 11531405 DOI: 10.1006/viro.2001.1036] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The hepatitis B virus X protein (HBx) is essential for establishing natural viral infection and has been implicated in the development of liver cancer associated with chronic infection. The basis for HBx function in either process is not understood. In cell culture, HBx exhibits pleiotropic activities affecting transcription, DNA repair, cell growth, and apoptotic cell death. Numerous cellular proteins including the p127-kDa subunit of UV-damaged DNA-binding activity have been reported to interact with HBx but the functional significance of these interactions remains unclear. Here we show that the binding of HBx to p127 interferes with cell viability. Mutational analysis reveals that HBx contacts p127 via a region to which no function has been assigned previously. An HBx variant bearing a single-charge reversal substitution within this region loses p127 binding and concomitant cytotoxicity. This mutant regains activity when directly fused to p127. These studies confirm that p127 is an important cellular target of HBx, and they indicate that HBx does not exert its effect by sequestering p127, and thereby preventing its normal function, but instead by conferring to p127 a deleterious activity.
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Affiliation(s)
- N Lin-Marq
- Department of Genetics and Microbiology, University Medical Centre, Rue Michel-Servet 1, Geneva 4, 1211, Switzerland
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27
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Chen BS, Sun ZW, Hampsey M. A Gal4-sigma 54 hybrid protein that functions as a potent activator of RNA polymerase II transcription in yeast. J Biol Chem 2001; 276:23881-7. [PMID: 11313364 DOI: 10.1074/jbc.m102893200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bacterial final sigma(54) protein associates with core RNA polymerase to form a holoenzyme complex that renders cognate promoters enhancer-dependent. Although unusual in bacteria, enhancer-dependent transcription is the paradigm in eukaryotes. Here we report that a fragment of Escherichia coli final sigma(54) encompassing amino acid residues 29-177 functions as a potent transcriptional activator in yeast when fused to a Gal4 DNA binding domain. Activation by Gal4-final sigma(54) is TATA-dependent and requires the SAGA coactivator complex, suggesting that Gal4-final sigma(54) functions by a normal mechanism of transcriptional activation. Surprisingly, deletion of the AHC1 gene, which encodes a polypeptide unique to the ADA coactivator complex, stimulates Gal4-final sigma(54)-mediated activation and enhances the toxicity of Gal4-final sigma(54). Accordingly, the SAGA and ADA complexes, both of which include Gcn5 as their histone acetyltransferase subunit, exert opposite effects on transcriptional activation by Gal4-final sigma(54). Gal4-final sigma(54) activation and toxicity are also dependent upon specific final sigma(54) residues that are required for activator-responsive promoter melting by final sigma(54) in bacteria, implying that activation is a consequence of final sigma(54)-specific features rather than a structurally fortuitous polypeptide fragment. As such, Gal4-final sigma(54) represents a novel tool with the potential to provide insight into the mechanism by which natural activators function in eukaryotic cells.
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Affiliation(s)
- B S Chen
- Department of Biochemistry, Division of Nucleic Acids Enzymology, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854-5635, USA
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28
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Abstract
The past decade has seen an explosive increase in information about regulation of eukaryotic gene transcription, especially for protein-coding genes. The most striking advances in our knowledge of transcriptional regulation involve the chromatin template, the large complexes recruited by transcriptional activators that regulate chromatin structure and the transcription apparatus, the holoenzyme forms of RNA polymerase II involved in initiation and elongation, and the mechanisms that link mRNA processing with its synthesis. We describe here the major advances in these areas, with particular emphasis on the modular complexes associated with RNA polymerase II that are targeted by activators and other regulators of mRNA biosynthesis.
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Affiliation(s)
- T I Lee
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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29
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Kraemer SM, Ranallo RT, Ogg RC, Stargell LA. TFIIA interacts with TFIID via association with TATA-binding protein and TAF40. Mol Cell Biol 2001; 21:1737-46. [PMID: 11238911 PMCID: PMC86722 DOI: 10.1128/mcb.21.5.1737-1746.2001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
TFIIA and TATA-binding protein (TBP) associate directly at the TATA element of genes transcribed by RNA polymerase II. In vivo, TBP is complexed with approximately 14 TBP-associated factors (TAFs) to form the general transcription factor TFIID. How TFIIA and TFIID communicate is not well understood. We show that in addition to making direct contacts with TBP, yeast TAF40 interacts directly and specifically with TFIIA. Mutational analyses of the Toa2 subunit of TFIIA indicate that loss of functional interaction between TFIIA and TAF40 results in conditional growth phenotypes and defects in transcription. These results demonstrate that the TFIIA-TAF40 interaction is important in vivo and indicate a functional role for TAF40 as a bridging factor between TFIIA and TFIID.
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Affiliation(s)
- S M Kraemer
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA
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30
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Hernández-Hernández A, Ferrús A. Prodos is a conserved transcriptional regulator that interacts with dTAF(II)16 in Drosophila melanogaster. Mol Cell Biol 2001; 21:614-23. [PMID: 11134347 PMCID: PMC86631 DOI: 10.1128/mcb.21.2.614-623.2001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2000] [Accepted: 10/16/2000] [Indexed: 11/20/2022] Open
Abstract
The transcription factor TFIID is a multiprotein complex that includes the TATA box binding protein (TBP) and a number of associated factors, TAF(II). Prodos (PDS) is a conserved protein that exhibits a histone fold domain (HFD). In yeast two-hybrid tests using PDS as bait, we cloned the Drosophila TAF(II), dTAF(II)16, as a specific PDS target. dTAF(II)16 is closely related to human TAF(II)30 and to another recently discovered Drosophila TAF, dTAF(II)24. PDS and dTAF(II)24 do not interact, however, thus establishing a functional difference between these dTAFs. The PDS-dTAF(II)16 interaction is mediated by the HFD motif in PDS and the N terminus in dTAF(II)16, as indicated by yeast two-hybrid assays with protein fragments. Luciferase-reported transcription tests in transfected cells show that PDS or an HFD-containing fragment activates transcription only with the help of dTAF(II)16 and TBP. Consistent with this, the eye phenotype of flies expressing a sev-Ras1 construct is modulated by PDS and dTAF(II)16 in a gene dosage-dependent manner. Finally, we show that PDS function is required for cell viability in somatic mosaics. These findings indicate that PDS is a novel transcriptional coactivator that associates with a member of the general transcription factor TFIID.
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31
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Xie Y, Sun L, Kodadek T. TATA-binding protein and the Gal4 transactivator do not bind to promoters cooperatively. J Biol Chem 2000; 275:40797-803. [PMID: 11006288 DOI: 10.1074/jbc.m007019200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The yeast Gal4 protein, like many activators, binds TATA-binding protein (TBP) directly in vitro. It has been speculated that this protein-protein interaction is important for Gal4p-mediated activation of transcription, but little work has been done to test specific models involving this interaction. In this study, the effect of Gal4p on TBP-TATA binding is addressed. Specifically, it is asked if the Gal4p-TBP interaction can support cooperative binding of the two factors to promoters. It is easy to see how such an event could stimulate transcription, particularly from promoters with a non-consensus TATA box. In vitro, however, a derivative of Gal4p (Gal4-(1-93+768-881)) containing the DNA-binding, dimerization, and activation domains does not bind to promoter DNA cooperatively with either recombinant, purified TBP, or with protein from a yeast crude extract. In vivo, reporter gene experiments using promoters with differing TBP affinities reveal no major Gal4p-mediated stimulation of TBP function from weak TATA boxes, as would be predicted if the proteins bind cooperatively. Furthermore, native Gal4p and a potent Gal4p-based artificial activator lacking a TBP-binding activation domain support similar ratios of transcription from a series of promoters identical except for mutations in the TATA box. It is concluded that Gal4p and TBP do not bind cooperatively to promoters and that this mechanism does not contribute substantially to Gal4p-mediated transcriptional activation.
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Affiliation(s)
- Y Xie
- Departments of Internal Medicine and Biochemistry, Ryburn Center for Molecular Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8573, USA
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32
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Dorris DR, Struhl K. Artificial recruitment of TFIID, but not RNA polymerase II holoenzyme, activates transcription in mammalian cells. Mol Cell Biol 2000; 20:4350-8. [PMID: 10825198 PMCID: PMC85802 DOI: 10.1128/mcb.20.12.4350-4358.2000] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In yeast cells, transcriptional activation occurs when the RNA polymerase II (Pol II) machinery is artificially recruited to a promoter by fusing individual components of this machinery to a DNA-binding domain. Here, we show that artificial recruitment of components of the TFIID complex can activate transcription in mammalian cells. Surprisingly, artificial recruitment of TATA-binding protein (TBP) activates transiently transfected and chromosomally integrated promoters with equal efficiency, whereas artificial recruitment of TBP-associated factors activates only chromosomal reporters. In contrast, artificial recruitment of various components of the mammalian Pol II holoenzyme does not confer transcriptional activation, nor does it result in synergistic activation in combination with natural activation domains. In the one case examined in more detail, the Srb7 fusion failed to activate despite being associated with the Pol II holoenzyme and being directly recruited to the promoter. Interestingly, some acidic activation domains are less effective when the promoter is chromosomally integrated rather than transiently transfected, whereas the Sp1 glutamine-rich activation domain is more effective on integrated reporters. Thus, yeast and mammalian cells differ with respect to transcriptional activation by artificial recruitment of the Pol II holoenzyme.
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Affiliation(s)
- D R Dorris
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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33
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Zhang DY, Dorsey MJ, Voth WP, Carson DJ, Zeng X, Stillman DJ, Ma J. Intramolecular interaction of yeast TFIIB in transcription control. Nucleic Acids Res 2000; 28:1913-20. [PMID: 10756191 PMCID: PMC103289 DOI: 10.1093/nar/28.9.1913] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The general transcription factor TFIIB is a key component in the eukaryotic RNA polymerase II (RNAPII) transcriptional machinery. We have previously shown that a yeast TFIIB mutant (called YR1m4) with four amino acid residues in a species-specific region changed to corresponding human residues affects the expression of genes activated by different activators in vivo. We report here that YR1m4 can interact with several affected activators in vitro. In addition, YR1m4 and other mutants with amino acid alterations within the same region can interact with TATA-binding protein (TBP) and RNAPII normally. However, YR1m4 is defective in supporting activator-independent transcription in assays con-ducted both in vitro and in vivo. We further demonstrate that the interaction between the C-terminal core domain and the N-terminal region is weakened in YR1m4 and other related TFIIB mutants. These results suggest that the intramolecular interaction property of yeast TFIIB plays an important role in transcription regulation in cells.
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Affiliation(s)
- D Y Zhang
- Division of Developmental Biology, Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
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34
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Stargell LA, Moqtaderi Z, Dorris DR, Ogg RC, Struhl K. TFIIA has activator-dependent and core promoter functions in vivo. J Biol Chem 2000; 275:12374-80. [PMID: 10777519 DOI: 10.1074/jbc.275.17.12374] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The physiological role of TFIIA was investigated by analyzing transcription in a yeast strain that contains a TATA-binding protein (TBP) mutant (N2-1) defective for interacting with TFIIA. In cells containing N2-1, transcription from a set of artificial his3 promoters dependent on different activators is generally reduced by a similar extent, indicating that TFIIA function is largely nonselective for activators. In addition, TATA element utilization, a core promoter function, is altered at his3 promoters dependent on weak activators. Genomic expression analysis reveals that 3% of the genes are preferentially affected by a factor of 4 or more. Chimeras of affected promoters indicate that the sensitivity to the TFIIA-TBP interaction can map either to the upstream or core promoter region. Unlike wild-type TBP or TFIIA, the N2-1 derivative does not activate transcription when artificially recruited to the promoter via a heterologous DNA binding domain, indicating that TFIIA is important for transcription even in the absence of an activation domain. Taken together, these results suggest that TFIIA plays an important role in both activator-dependent and core promoter functions in vivo. Further, they suggest that TFIIA function may not be strictly related to the recruitment of TBP to promoters but may also involve a step after TBP recruitment.
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Affiliation(s)
- L A Stargell
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523, USA
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35
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Hawkes NA, Evans R, Roberts SG. The conformation of the transcription factor TFIIB modulates the response to transcriptional activators in vivo. Curr Biol 2000; 10:273-6. [PMID: 10712906 DOI: 10.1016/s0960-9822(00)00363-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The general transcription factor TFIIB plays a crucial role in the assembly of the transcriptional preinitiation complex and has also been proposed as a target of transcriptional activator proteins (reviewed in [1]). TFIIB is composed of two domains which are engaged in an intramolecular interaction that is disrupted upon interaction with the activation domain of the Herpesvirus VP16 protein in vitro [2] [3]. The significance of this event for transcriptional activation is not known, however. The amino-terminal intramolecular interaction domain is the most conserved region of TFIIB and plays a role in transcription start-site selection [4] [5] [6]. In addition, we have shown previously that the integrity of this region is required for transcriptional activation in vivo [4]. Here, we have defined a charge cluster at the amino terminus of TFIIB that is required for transcriptional activation in vivo. We found that this domain determines the affinity of the TFIIB intramolecular interaction and the ability of TFIIB to interact with a transcriptional activation domain, but not with components of the holoenzyme. Our results suggest that the intramolecular interaction in TFIIB regulates transcriptional activation in vivo.
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Affiliation(s)
- N A Hawkes
- Division of Gene Expression, Department of Biochemistry, Wellcome Trust Biocentre, University of Dundee, Dundee, DD1 5EH, UK
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36
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Pan S, Czarnecka-Verner E, Gurley WB. Role of the TATA binding protein-transcription factor IIB interaction in supporting basal and activated transcription in plant cells. THE PLANT CELL 2000; 12:125-36. [PMID: 10634912 PMCID: PMC140219 DOI: 10.1105/tpc.12.1.125] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/1999] [Accepted: 11/03/1999] [Indexed: 05/20/2023]
Abstract
The TATA binding protein (TBP) and transcription factor IIB (TFIIB) play crucial roles in transcription of class II genes. The requirement for TBP-TFIIB interactions was evaluated in maize cells by introducing mutations into the Arabidopsis TBP (AtTBP2) within the C-terminal stirrup. Protein binding experiments indicated that amino acid residues E-144 and E-146 of AtTBP2 are both essential for TFIIB binding in vitro. Activation domains derived from herpes simplex viral protein VP16, the Drosophila fushi tarazu glutamine-rich domain (ftzQ), and yeast Gal4 were tested in transient assays. TBP-TFIIB interactions were dispensable for basal transcription but were required for activated transcription. In general, activated transcription was more severely inhibited by TBP mutation E-146R than by mutation E-144R. However, these TBP mutations had little effect on activity of the full-length cauliflower mosaic virus 35S and maize ubiquitin promoters, thus demonstrating that strong TBP-TFIIB contacts are not always required for transcription driven by complex promoters.
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Affiliation(s)
- S Pan
- Department of Microbiology and Cell Science, Program of Plant Molecular and Cellular Biology, University of Florida, Building 981, P.O. Box 110700, Gainesville, Florida 32611-0700, USA
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37
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Bertolotti A, Bell B, Tora L. The N-terminal domain of human TAFII68 displays transactivation and oncogenic properties. Oncogene 1999; 18:8000-10. [PMID: 10637511 DOI: 10.1038/sj.onc.1203207] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In Ewing tumor, the (11;22) chromosomal translocation produces a chimeric molecule composed of the amino-terminal domain of EWS fused to the carboxyl-terminal DNA-binding domain of FLI-1. Previously, we have identified a novel protein TAFII68, which is highly similar to EWS and another closely related protein TLS (also called FUS). We demonstrate that the N-terminus of TAFII68 efficiently stimulates transcription when fused to two different DNA binding domains and that overexpression of TAFII68-FLI-1 chimeras in NIH3T3 cells leads to oncogenic transformation. We have also investigated the molecular mechanisms which could account for the transcriptional activation and the oncogenic transformation potential of the N-termini of TAFII68 and EWS. Thus, we have tested whether the artificial recruitment of components of the preinitiation complex (PIC) or a histone acetyltransferase (HAT) could bypass the requirement for the activation domains of either EWS or TAFII68. Recruitment of individual components of the transcription machinery or the GCN5 HAT is not sufficient to promote activation from FLI-1 responsive genes either in transfection experiments or in oncogenic transformation assays. These results suggest that the TAFII68 or EWS activation domains enhance a step after PIC formation in the transcriptional activation process.
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Affiliation(s)
- A Bertolotti
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, BP 163 - 67404 Illkirch Cedex, CU de Strasbourg, France
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38
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Majello B, Napolitano G, Giordano A, Lania L. Transcriptional regulation by targeted recruitment of cyclin-dependent CDK9 kinase in vivo. Oncogene 1999; 18:4598-605. [PMID: 10467404 DOI: 10.1038/sj.onc.1202822] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The CDK9 kinase in association with Cyclin T is a component of the transcription positive-acting complex pTEFb which facilitates the transition from abortive to productive transcription elongation by phosphorylating the carboxyl-terminal domain of RNA polymerase II. The Cyclin T1/CDK9 complex is implicated in Tat transactivation, and it has been suggested that Tat functions by recruiting this complex to RNAPII through cooperative binding to RNA. Here, we demonstrate that targeted recruitment of Cyclin T1/CDK9 kinase complex to specific promoters, through fusion to a DNA-binding domain of either Cyclin T1 or CDK9 kinase, stimulates transcription in vivo. Transcriptional enhancement was dependent on active CDK9, as a catalytically inactive form had no transcriptional effect. We determined that, unlike conventional activators, DNA-bound CDK9 does not activate enhancerless TATA-promoters unless TBP is overexpressed, suggesting that CDK9 acts in vivo at a step subsequent to TFIID recruitment DNA-bound. Finally, we determined that CDK9-mediated transcriptional activation is mediated by preferentially stimulating productive transcription elongation.
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Affiliation(s)
- B Majello
- Department of Genetics, Molecular and General Biology, University of Naples 'Federico II' and International Institute of Genetics and Biophysics, CNR, Naples, Italy
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39
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Struhl K, Kadosh D, Keaveney M, Kuras L, Moqtaderi Z. Activation and repression mechanisms in yeast. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 1999; 63:413-21. [PMID: 10384306 DOI: 10.1101/sqb.1998.63.413] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- K Struhl
- Department Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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40
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Dove SL, Hochschild A. Use of artificial activators to define a role for protein-protein and protein-DNA contacts in transcriptional activation. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 1999; 63:173-80. [PMID: 10384281 DOI: 10.1101/sqb.1998.63.173] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- S L Dove
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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41
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Kuras L, Struhl K. Binding of TBP to promoters in vivo is stimulated by activators and requires Pol II holoenzyme. Nature 1999; 399:609-13. [PMID: 10376605 DOI: 10.1038/21239] [Citation(s) in RCA: 390] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In eukaryotes, transcriptional activators have been proposed to function by recruiting the RNA polymerase II (Pol II) machinery, by altering the conformation of this machinery, or by affecting steps after initiation, but the evidence is not definitive. Genomic footprinting of yeast TATA-box elements reveals activator-dependent alterations of chromatin structure and activator-independent protection, but little is known about the association of specific components of the Pol II machinery with promoters in vivo. Here we analyse TATA-box-binding-protein (TBP) occupancy of 30 yeast promoters in vivo. We find that TBP association with promoters is stimulated by activators and inhibited by the Cyc8-Tup1 repressor, and that transcriptional activity correlates strongly with the degree of TBP occupancy. In a small subset of promoters, TBP occupancy is higher than expected when gene activity is low, and the activator-dependent increase is modest. TBP association depends on the Pol II holoenzyme component Srb4, but not on the Kin28 subunit of the transcription factor TFIIH, even though both proteins are generally required for transcription. Thus in yeast cells, TBP association with promoters occurs in concert with the Pol II holoenzyme, activator-dependent recruitment of the Pol II machinery occurs at the vast majority of promoters, and Kin28 acts after the initial recruitment.
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Affiliation(s)
- L Kuras
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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42
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Krapp A, Strubin M. B-Cell coactivator OBF-1 exhibits unusual transcriptional properties and functions in a DNA-bound Oct-1-dependent fashion. Mol Cell Biol 1999; 19:4247-54. [PMID: 10330165 PMCID: PMC104384 DOI: 10.1128/mcb.19.6.4247] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Eukaryotic transcriptional activators generally comprise both a DNA-binding domain that recognizes specific cis-regulatory elements in the target genes and an activation domain which is essential for transcriptional stimulation. Activation domains typically behave as structurally and functionally autonomous modules that retain their intrinsic activities when directed to a promoter by a variety of heterologous DNA-binding domains. Here we report that OBF-1, a B-cell-specific coactivator for transcription factor Oct-1, challenges this traditional view in that it contains an atypical activation domain that exhibits two unexpected functional properties when tested in the yeast Saccharomyces cerevisiae. First, OBF-1 by itself has essentially no intrinsic activation potential, yet it strongly synergizes with other activation domains such as VP16 and Gal4. Second, OBF-1 exerts its effect in association with DNA-bound Oct-1 but is inactive when attached to a heterologous DNA-binding domain. These findings suggest that activation by OBF-1 is not obtained by simple recruitment of the coactivator to the promoter but requires interaction with DNA-bound Oct-1 to stimulate a step distinct from those regulated by classical activation domains.
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Affiliation(s)
- A Krapp
- Department of Genetics and Microbiology, University Medical Centre, 1211 Geneva 4, Switzerland
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43
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Ranallo RT, Struhl K, Stargell LA. A TATA-binding protein mutant defective for TFIID complex formation in vivo. Mol Cell Biol 1999; 19:3951-7. [PMID: 10330135 PMCID: PMC104354 DOI: 10.1128/mcb.19.6.3951] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Using an intragenic complementation screen, we have identified a temperature-sensitive TATA-binding protein (TBP) mutant (K151L, K156Y) that is defective for interaction with certain yeast TBP-associated factors (TAFs) at the restrictive temperature. The K151L,K156Y mutant appears to be functional for RNA polymerase I (Pol I) and Pol III transcription, and it is capable of supporting Gal4-activated and Gcn4-activated transcription by Pol II. However, transcription from certain TATA-containing and TATA-less Pol II promoters is reduced at the restrictive temperature. Immunoprecipitation analysis of extracts prepared after culturing cells at the restrictive temperature for 1 h indicates that the K151L,K156Y derivative is severely compromised in its ability to interact with TAF130, TAF90, TAF68/61, and TAF25 while remaining functional for interaction with TAF60 and TAF30. Thus, a TBP mutant that is compromised in its ability to form TFIID can support the response to Gcn4 but is defective for transcription from specific promoters in vivo.
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Affiliation(s)
- R T Ranallo
- Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA
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44
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Zhang Z, Murphy A, Hu JC, Kodadek T. Genetic selection of short peptides that support protein oligomerization in vivo. Curr Biol 1999; 9:417-20. [PMID: 10226028 DOI: 10.1016/s0960-9822(99)80188-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
An important goal in protein engineering is to control associations between designed proteins. This is most often done by fusing known, naturally occurring oligomerization modules, such as leucine zippers [1] [2] [3], to the proteins of interest [4] [5] [6]. It is of considerable interest to design or discover new oligomerization domains that have novel binding specificities [7] [8] [9] [10] [11] in order to expand the 'toolbox' of the protein engineer and also to eliminate associations of the designed proteins with endogenous factors. We report here a simple genetic selection scheme through which to search libraries for peptides that are able to mediate homodimerization or higher-order self-oligomerization of a protein in vivo. We found several peptides that support oligomerization of the lambda repressor DNA-binding domain in Escherichia coli cells, some of them as efficiently as the endogenous dimerization domain or the GCN4 leucine zipper. Many are very small, comprising as few as six residues. This study strongly supports the notion that peptide sequence space is rich in small peptides, which might be useful in protein engineering and other applications.
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Affiliation(s)
- Z Zhang
- Department of Chemistry and Biochemistry, University of Texas at Austin, Austin 78712, USA
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45
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Gaudreau L, Keaveney M, Nevado J, Zaman Z, Bryant GO, Struhl K, Ptashne M. Transcriptional activation by artificial recruitment in yeast is influenced by promoter architecture and downstream sequences. Proc Natl Acad Sci U S A 1999; 96:2668-73. [PMID: 10077568 PMCID: PMC15826 DOI: 10.1073/pnas.96.6.2668] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The idea that recruitment of the transcriptional machinery to a promoter suffices for gene activation is based partly on the results of "artificial recruitment" experiments performed in vivo. Artificial recruitment can be effected by a "nonclassical" activator comprising a DNA-binding domain fused to a component of the transcriptional machinery. Here we show that activation by artificial recruitment in yeast can be sensitive to any of three factors: position of the activator-binding elements, sequence of the promoter, and coding sequences downstream of the promoter. In contrast, classical activators worked efficiently at all promoters tested. In all cases the "artificial recruitment" fusions synergized well with classical activators. A classical activator evidently differs from a nonclassical activator in that the former can touch multiple sites on the transcriptional machinery, and we propose that that difference accounts for the broader spectrum of activity of the typical classical activator. A similar conclusion is reached from studies in mammalian cells in the accompanying paper [Nevado, J., Gaudreau, L., Adam, M. & Ptashne, M. (1999) Proc. Natl. Acad. Sci. USA 96, 2674-2677].
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Affiliation(s)
- L Gaudreau
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA
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46
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Huh JR, Park JM, Kim M, Carlson BA, Hatfield DL, Lee BJ. Recruitment of TBP or TFIIB to a promoter proximal position leads to stimulation of RNA polymerase II transcription without activator proteins both in vivo and in vitro. Biochem Biophys Res Commun 1999; 256:45-51. [PMID: 10066420 DOI: 10.1006/bbrc.1999.0280] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Eukaryotic transcriptional activators may function, at least in part, to facilitate the assembly of the RNA polymerase II (pol II) preinitiation complex at the core promoter region through their interaction with a subset of components of the basal transcription machinery. Previous studies have shown that artificial tethering of TATA-binding protein (TBP) to the promoter region is sufficient to stimulate pol II transcription in yeast. To test whether this phenomenon is a general one in eukaryotic pol II transcription, the DNA-binding domain of yeast GAL4 was fused to either Xenopus laevis TBP or TFIIB in order to enable these factors to be efficiently positioned near the transcription start site in a GAL4-binding site-dependent manner. We found that GAL4-xTBP as well as GAL4-xTFIIB directed an increased level of transcription without involvement of the transcriptional activator, suggesting that incorporation of these basal factors into a preinitiation complex (PIC) is a major rate-limiting step accelerated by activator proteins in metazoans. These results show that transcription activation by artificial recruitment of basal transcription machinery can be observed in general among eukaryotic transcription both in vivo and in vitro. Furthermore, failure of recovery of transcription by adding GAL4-xTFIIB after depletion of endogenous TBP with TATA oligo competitor suggests that recruitment of TBP cannot be bypassed for Pol II transcription.
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Affiliation(s)
- J R Huh
- Institute for Molecular Biology and Genetics, Seoul National University, Seoul, 151-742, Korea
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47
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Barberis A, Gaudreau L. Recruitment of the RNA polymerase II holoenzyme and its implications in gene regulation. Biol Chem 1998; 379:1397-405. [PMID: 9894806 DOI: 10.1515/bchm.1998.379.12.1397] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In yeast cells, interaction between a DNA-bound protein and a single component of the RNA polymerase II (poIII) holoenzyme is sufficient to recruit the latter to a promoter and thereby activate gene transcription. Here we review results which have suggested such a simple mechanism for how genes can be turned on. The series of experiments which eventually led to this model was originally instigated by studying gene expression in a yeast strain which carries a point mutation in Gal11, a component of the poIII holoenzyme. In cells containing this mutant protein termed Gall11P, a derivative of the transcriptional activator Gal4 devoid of any classical activating region is turned into a strong activator. This activating function acquired by an otherwise silent DNA-binding protein is solely due to a novel and fortuitous interaction between Gal11P and a fragment of the Gal4 dimerization region generated by the P mutation. The simplest explanation for these results is that tethering Gal11 to DNA recruits the poIII holoenzyme and, consequently, activates gene transcription. Transcription factors that are believed not to be integral part of the poIII holoenzyme but are nevertheless required for this instance of gene activation, e.g. the TATA-binding TFIID complex, may bind DNA cooperatively with the holoenzyme when recruited to a promoter, thus forming a complete poIII preinitiation complex. One prediction of this model is that recruitment of the entire poIII transcription complex and consequent gene activation can be achieved by tethering different components to DNA. Indeed, fusion of a DNA-binding domain to a variety of poIII holoenzyme components and TFIID subunits leads to activation of genes bearing the recognition site for the DNA-binding protein. These results imply that accessory factors, which are required to remove or modify nucleosomes do not need to be directly contacted by activators, but can rather be engaged in the activation process when the poIII complex is recruited to DNA. In fact, recruitment of the poIII holoenzyme suffices to remodel nucleosomes at the PHO5 promoter and presumably at many other promoters. Other events in the process of gene expression following recruitment of the transcription complex, e.g. initiation, promoter clearance, elongation and termination, could unravel as a consequence of the recruitment step and the formation of an active preinitiation complex on DNA. This view does not exclude the possibility that classical activators also act directly on chromatin remodeling and post-recruitment steps to regulate gene expression.
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Affiliation(s)
- A Barberis
- Institute of Molecular Biology, University of Zurich, Switzerland
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48
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Ford E, Strubin M, Hernandez N. The Oct-1 POU domain activates snRNA gene transcription by contacting a region in the SNAPc largest subunit that bears sequence similarities to the Oct-1 coactivator OBF-1. Genes Dev 1998; 12:3528-40. [PMID: 9832505 PMCID: PMC317248 DOI: 10.1101/gad.12.22.3528] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/1998] [Accepted: 09/29/1998] [Indexed: 11/24/2022]
Abstract
The RNA polymerases II and III snRNA gene promoters contain an octamer sequence as part of the enhancer and a proximal sequence element (PSE) as part of the core promoter. The octamer and the PSE bind the POU domain activator Oct-1 and the basal transcription factor SNAPc, respectively. Oct-1, but not Oct-1 with a single E7R mutation within the POU domain, binds cooperatively with SNAPc and, in effect, recruits SNAPc to the PSE. Here, we show that SNAPc recruitment is mediated by an interaction between the Oct-1 POU domain and a small region of the largest subunit of SNAPc, SNAP190. This SNAP190 region is strikingly similar to a region in the B-cell-specific Oct-1 coactivator, OBF-1, that is required for interaction with octamer-bound Oct-1 POU domain. The Oct-1 POU domain-SNAP190 interaction is a direct protein-protein contact as determined by the isolation of a switched specificity SNAP190 mutant that interacts with Oct-1 POU E7R but not with wild-type Oct-1 POU. We also show that this direct protein-protein contact results in activation of transcription. Thus, we have identified an activation target of a human activator, Oct-1, within its cognate basal transcription complex.
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Affiliation(s)
- E Ford
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724 USA
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49
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Song CS, Jung MH, Kim SC, Hassan T, Roy AK, Chatterjee B. Tissue-specific and androgen-repressible regulation of the rat dehydroepiandrosterone sulfotransferase gene promoter. J Biol Chem 1998; 273:21856-66. [PMID: 9705324 DOI: 10.1074/jbc.273.34.21856] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dehydroepiandrosterone sulfotransferase (Std) catalyzes sulfonation of androgenic steroids and certain aromatic procarcinogens. In rats, this enzyme is selectively expressed in the liver, and its expression is strongly repressed by androgens. DNase I footprinting and electrophoretic mobility shift analyses revealed two hepatocyte nuclear factor-1 (HNF1), three CCAAT/enhancer-binding protein (C/EBP), and one consensus palindromic thyroid hormone response elements within the first 215 base pairs (bp) of the promoter sequence of rat Std. This promoter is normally inactive in fibroblast-derived NIH 3T3 cells. However, overexpression of HNF1 and C/EBP resulted in synergistic activation of the Std promoter in this cell type, indicating essential roles of these two trans-regulators in liver-selective expression of the rat Std gene. On the other hand, point mutations at any one of five cis elements proximal to the -215 bp region markedly reduced reporter gene expression, suggesting that all of these sites are important for overall promoter function. Androgenic repression of the Std gene in rat liver can be recapitulated in androgen receptor (AR)-negative HepG2 hepatoma cells after cotransfection with an AR expression plasmid. Functional assay of a nested set of 5'-deleted promoters mapped the negative androgen response region between positions -235 and -310. Antibody supershift and oligonucleotide competition identified three OCT-1 and two C/EBP elements between bp -231 and -292. An additional OCT-1 site was found to overlap with a C/EBP element at the -262/-252 position. Mutational inactivation of any one of five cis elements within the -231/-292 region abolished negative androgen response. However, none of these cis elements showed DNase I protection by recombinant AR in footprinting assay, suggesting the absence of a direct AR-DNA interaction. Thus, these studies on rat Std promoter function indicate that (i) HNF1 and C/EBP are responsible for liver specificity of the rat Std gene; (ii) androgenic repression of the gene requires the presence of all of the OCT-1 and C/EBP elements between positions -231 and -292; and (iii) AR may exert its negative regulatory effect indirectly through transcriptional interference of OCT-1 and C/EBP rather than through a direct DNA-AR interaction.
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Affiliation(s)
- C S Song
- Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284-7762, USA
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50
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Majello B, Napolitano G, De Luca P, Lania L. Recruitment of human TBP selectively activates RNA polymerase II TATA-dependent promoters. J Biol Chem 1998; 273:16509-16. [PMID: 9632719 DOI: 10.1074/jbc.273.26.16509] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An increasing body of evidence suggests that eukaryotic activators stimulate polymerase II transcription by facilitating the assembly of the functional basal machinery at the promoter. Here we describe experiments that provide added support for the idea that recruitment of TATA-binding protein (TBP) is a rate-limiting step for transcription activation in mammalian cells. We found that, in human cell lines, recruitment of TBP to a promoter, as a GAL4-TBP fusion protein, can provide a substantial activation of transcription. Activation mediated by the hTBP, tethered to promoter DNA, is strictly dependent upon the presence of a functional TATA element, and it directs faithful transcription initiation. Interestingly, GAL4-hTBP activation was not observed from initiator (Inr) -dependent TATA-less promoters. These results suggest that TBP binding to DNA is not a rate-limiting step for the initial stages of TFIID recruitment to initiator-dependent TATA-less promoters. Finally, we provide evidence that synergy between GAL4-hTBP and defined transcription domains is restricted to activators, such as VP16 and Tat, which are likely to function at steps subsequent to the TFIID recruitment. These findings strengthen the idea that recruitment of TBP represents an important mechanism of activation of TATA-dependent promoters, and on the other hand, they suggest that TBP-DNA interactions are largely dispensable for specific transcription of initiator dependent TATA-less promoters.
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Affiliation(s)
- B Majello
- Department of Genetics, Molecular and General Biology, University of Naples "Federico II," via Mezzocannone 8, 80134 Naples, Italy
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