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Mindel V, Brodsky S, Yung H, Manadre W, Barkai N. Revisiting the model for coactivator recruitment: Med15 can select its target sites independent of promoter-bound transcription factors. Nucleic Acids Res 2024:gkae718. [PMID: 39187372 DOI: 10.1093/nar/gkae718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Revised: 07/08/2024] [Accepted: 08/09/2024] [Indexed: 08/28/2024] Open
Abstract
Activation domains (ADs) within transcription factors (TFs) induce gene expression by recruiting coactivators such as the Mediator complex. Coactivators lack DNA binding domains (DBDs) and are assumed to passively follow their recruiting TFs. This is supported by direct AD-coactivator interactions seen in vitro but has not yet been tested in living cells. To examine that, we targeted two Med15-recruiting ADs to a range of budding yeast promoters through fusion with different DBDs. The DBD-AD fusions localized to hundreds of genomic sites but recruited Med15 and induced transcription in only a subset of bound promoters, characterized by a fuzzy-nucleosome architecture. Direct DBD-Med15 fusions shifted DBD localization towards fuzzy-nucleosome promoters, including promoters devoid of the endogenous Mediator. We propose that Med15, and perhaps other coactivators, possess inherent promoter preference and thus actively contribute to the selection of TF-induced genes.
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Affiliation(s)
- Vladimir Mindel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sagie Brodsky
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Hadas Yung
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Wajd Manadre
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Naama Barkai
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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Warfield L, Donczew R, Mahendrawada L, Hahn S. Yeast Mediator facilitates transcription initiation at most promoters via a Tail-independent mechanism. Mol Cell 2022; 82:4033-4048.e7. [PMID: 36208626 PMCID: PMC9637718 DOI: 10.1016/j.molcel.2022.09.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 05/12/2022] [Accepted: 09/13/2022] [Indexed: 11/06/2022]
Abstract
Mediator (MED) is a conserved factor with important roles in basal and activated transcription. Here, we investigate the genome-wide roles of yeast MED by rapid depletion of its activator-binding domain (Tail) and monitoring changes in nascent transcription. Rapid Tail depletion surprisingly reduces transcription from only a small subset of genes. At most of these Tail-dependent genes, in unperturbed conditions, MED is detected at both the UASs and promoters. In contrast, at most Tail-independent genes, we find MED primarily at promoters but not at the UASs. These results suggest that MED Tail and activator-mediated MED recruitment regulates only a small subset of genes. Furthermore, we define three classes of genes that differ in PIC assembly pathways and the requirements for MED Tail, SAGA, TFIID, and BET factors Bdf1/2. Our combined results have broad implications for the roles of MED, other coactivators, and mechanisms of transcriptional regulation at different gene classes.
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Affiliation(s)
- Linda Warfield
- Fred Hutchinson Cancer Center, 1100 Fairview Ave N, Mailstop A1-162, Seattle, WA 98109, USA
| | - Rafal Donczew
- Fred Hutchinson Cancer Center, 1100 Fairview Ave N, Mailstop A1-162, Seattle, WA 98109, USA
| | - Lakshmi Mahendrawada
- Fred Hutchinson Cancer Center, 1100 Fairview Ave N, Mailstop A1-162, Seattle, WA 98109, USA
| | - Steven Hahn
- Fred Hutchinson Cancer Center, 1100 Fairview Ave N, Mailstop A1-162, Seattle, WA 98109, USA.
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3
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Stampfel G, Kazmar T, Frank O, Wienerroither S, Reiter F, Stark A. Transcriptional regulators form diverse groups with context-dependent regulatory functions. Nature 2015; 528:147-51. [PMID: 26550828 DOI: 10.1038/nature15545] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 09/02/2015] [Indexed: 12/25/2022]
Abstract
One of the most important questions in biology is how transcription factors (TFs) and cofactors control enhancer function and thus gene expression. Enhancer activation usually requires combinations of several TFs, indicating that TFs function synergistically and combinatorially. However, while TF binding has been extensively studied, little is known about how combinations of TFs and cofactors control enhancer function once they are bound. It is typically unclear which TFs participate in combinatorial enhancer activation, whether different TFs form functionally distinct groups, or if certain TFs might substitute for each other in defined enhancer contexts. Here we assess the potential regulatory contributions of TFs and cofactors to combinatorial enhancer control with enhancer complementation assays. We recruited GAL4-DNA-binding-domain fusions of 812 Drosophila TFs and cofactors to 24 enhancer contexts and measured enhancer activities by 82,752 luciferase assays in S2 cells. Most factors were functional in at least one context, yet their contributions differed between contexts and varied from repression to activation (up to 289-fold) for individual factors. Based on functional similarities across contexts, we define 15 groups of TFs that differ in developmental functions and protein sequence features. Similar TFs can substitute for each other, enabling enhancer re-engineering by exchanging TF motifs, and TF-cofactor pairs cooperate during enhancer control and interact physically. Overall, we show that activators and repressors can have diverse regulatory functions that typically depend on the enhancer context. The systematic functional characterization of TFs and cofactors should further our understanding of combinatorial enhancer control and gene regulation.
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Affiliation(s)
- Gerald Stampfel
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Tomáš Kazmar
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Olga Frank
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Sebastian Wienerroither
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Franziska Reiter
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Alexander Stark
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Dr. Bohr-Gasse 7, 1030 Vienna, Austria
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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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Højfeldt JW, Van Dyke AR, Mapp AK. Transforming ligands into transcriptional regulators: building blocks for bifunctional molecules. Chem Soc Rev 2011; 40:4286-94. [PMID: 21701709 DOI: 10.1039/c1cs15050b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The human body is comprised of several hundred distinct cell types that all share a common genomic template. This diversity arises from regulated expression of individual genes. The first critical step in this process is transcription and is governed by a large number of transcription factors. Small molecules that can alter transcription hold tremendous utility as chemical probes and therapeutics. To fully realize their potential, however, artificial transcription factors must be able to orchestrate protein recruitment at gene promoters just like their natural counterparts. This tutorial review surveys the discovery of small ligands (drug-like molecules and short peptides) that bind transcriptional coregulatory proteins, and thus comprise one of the two essential characteristics of a transcription factor. By joining these ligands to DNA-targeting moieties, one can construct a bifunctional molecule that recruits its protein target to specific genes and controls gene transcription.
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Affiliation(s)
- Jonas W Højfeldt
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA
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Young ET, Tachibana C, Chang HWE, Dombek KM, Arms EM, Biddick R. Artificial recruitment of mediator by the DNA-binding domain of Adr1 overcomes glucose repression of ADH2 expression. Mol Cell Biol 2008; 28:2509-16. [PMID: 18250152 PMCID: PMC2293114 DOI: 10.1128/mcb.00658-07] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2007] [Revised: 10/17/2007] [Accepted: 01/28/2008] [Indexed: 01/16/2023] Open
Abstract
The transcription factor Adr1 activates numerous genes in nonfermentable carbon source metabolism. An unknown mechanism prevents Adr1 from stably binding to the promoters of these genes in glucose-grown cells. Glucose depletion leads to Snf1-dependent binding. Chromatin immunoprecipitation showed that the Adr1 DNA-binding domain could not be detected at the ADH2 promoter under conditions in which the binding of the full-length protein occurred. This suggested that an activation domain is required for stable binding, and coactivators may stabilize the interaction with the promoter. Artificial recruitment of Mediator tail subunits by fusion to the Adr1 DNA-binding domain overcame both the inhibition of promoter binding and glucose repression of ADH2 expression. In contrast, an Adr1 DNA-binding domain-Tbp fusion did not overcome glucose repression, although it was an efficient activator of ADH2 expression under derepressing conditions. When Mediator was artificially recruited, ADH2 expression was independent of SNF1, SAGA, and Swi/Snf, whereas ADH2 expression was dependent on these factors with wild-type Adr1. These results suggest that in the presence of glucose, the ADH2 promoter is accessible to Adr1 but that other interactions that occur when glucose is depleted do not take place. Artificial recruitment of Mediator appears to overcome this requirement and to allow stable binding and transcription under normally inhibitory conditions.
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Affiliation(s)
- Elton T Young
- Department of Biochemistry, Box 357350, University of Washington, Seattle, WA 98195-7350, USA.
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STAGA recruits Mediator to the MYC oncoprotein to stimulate transcription and cell proliferation. Mol Cell Biol 2007; 28:108-21. [PMID: 17967894 DOI: 10.1128/mcb.01402-07] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Activation of eukaryotic gene transcription involves the recruitment by DNA-binding activators of multiprotein histone acetyltransferase (HAT) and Mediator complexes. How these coactivator complexes functionally cooperate and the roles of the different subunits/modules remain unclear. Here we report physical interactions between the human HAT complex STAGA (SPT3-TAF9-GCN5-acetylase) and a "core" form of the Mediator complex during transcription activation by the MYC oncoprotein. Knockdown of the STAF65gamma component of STAGA in human cells prevents the stable association of TRRAP and GCN5 with the SPT3 and TAF9 subunits; impairs transcription of MYC-dependent genes, including MYC transactivation of the telomerase reverse transcriptase (TERT) promoter; and inhibits proliferation of MYC-dependent cells. STAF65gamma is required for SPT3/STAGA interaction with core Mediator and for MYC recruitment of SPT3, TAF9, and core Mediator components to the TERT promoter but is dispensable for MYC recruitment of TRRAP, GCN5, and p300 and for acetylation of nucleosomes and loading of TFIID and RNA polymerase II on the promoter. These results suggest a novel STAF65gamma-dependent function of STAGA-type complexes in cell proliferation and transcription activation by MYC postloading of TFIID and RNA polymerase II that involves direct recruitment of core Mediator.
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Reeves WM, Hahn S. Targets of the Gal4 transcription activator in functional transcription complexes. Mol Cell Biol 2005; 25:9092-102. [PMID: 16199885 PMCID: PMC1265783 DOI: 10.1128/mcb.25.20.9092-9102.2005] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Although biochemical and genetic methods have detected many activator-transcription factor interactions, the direct functional targets of most activators remain undetermined. For this study, photo-cross-linkers positioned within the Gal4 C-terminal acidic activating region were used to identify polypeptides in close physical proximity to Gal4 during transcription activation in vitro. Of six specifically cross-linked polypeptides, three (Tra1, Taf12, and Gal11) are subunits of four complexes (SAGA, Mediator, NuA4, and TFIID) known to play a role in gene regulation. These cross-linking targets had differential effects on activation. SAGA was critical for activation by Gal4, Gal11 contributed modestly to activation, and TFIID and NuA4 were not important for activation under our conditions. Tra1, Taf12, and Gal11 have also been identified as cross-linking targets of the Gcn4 acidic central activating region. Our results demonstrate that two unrelated acidic activators converge on the same set of functional targets.
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Affiliation(s)
- Wendy M Reeves
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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Fishburn J, Mohibullah N, Hahn S. Function of a eukaryotic transcription activator during the transcription cycle. Mol Cell 2005; 18:369-78. [PMID: 15866178 DOI: 10.1016/j.molcel.2005.03.029] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Revised: 03/19/2005] [Accepted: 03/24/2005] [Indexed: 11/15/2022]
Abstract
Site-specific photocrosslinkers positioned within the central transcription-activating region of yeast Gcn4 were used to identify, in an unbiased way, three polypeptides in direct physical proximity to the activator during the process of transcription activation. Crosslinking was specific and did not change during different steps of the transcription cycle. The crosslinking targets were identified as Tra1, Gal11, and Taf12, subunits of four complexes (SAGA, NuA4, Mediator, and TFIID) known to play a role in gene regulation. Using this crosslinking assay, an activating region mutant, and extracts depleted of individual complexes containing the crosslinking targets, we found that contact with Tra1/SAGA is critical for activation, Gal11 contact has a modest effect on activation, and contact with TFIID and NuA4 is of little or no importance for activation under our conditions. Thus, a single activating region contacts multiple factors, and each contact makes differential contributions to transcriptional activation.
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Affiliation(s)
- James Fishburn
- Howard Hughes Medical Institute, 1100 Fairview Ave North, Mailstop A1-162, Seattle, Washington 98109, USA
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Current awareness on yeast. Yeast 2005; 22:241-8. [PMID: 15762016 DOI: 10.1002/yea.1159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Larschan E, Winston F. The Saccharomyces cerevisiae Srb8-Srb11 complex functions with the SAGA complex during Gal4-activated transcription. Mol Cell Biol 2005; 25:114-23. [PMID: 15601835 PMCID: PMC538787 DOI: 10.1128/mcb.25.1.114-123.2005] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Saccharomyces cerevisiae SAGA (Spt-Ada-Gcn5-acetyltransferase) complex functions as a coactivator during Gal4-activated transcription. A functional interaction between the SAGA component Spt3 and TATA-binding protein (TBP) is important for TBP binding at Gal4-activated promoters. To better understand the role of SAGA and other factors in Gal4-activated transcription, we selected for suppressors that bypass the requirement for SAGA. We obtained eight complementation groups and identified the genes corresponding to three of the groups as NHP10, HDA1, and SRB9. In contrast to the srb9 suppressor mutation that we identified, an srb9Delta mutation causes a strong defect in Gal4-activated transcription. Our studies have focused on this requirement for Srb9. Srb9 is part of the Srb8-Srb11 complex, associated with the Mediator coactivator. Srb8-Srb11 contains the Srb10 kinase, whose activity is important for GAL1 transcription. Our data suggest that Srb8-Srb11, including Srb10 kinase activity, is directly involved in Gal4 activation. By chromatin immunoprecipitation studies, Srb9 is present at the GAL1 promoter upon induction and facilitates the recruitment or stable association of TBP. Furthermore, the association of Srb9 with the GAL1 upstream activation sequence requires SAGA and specifically Spt3. Finally, Srb9 association also requires TBP. These results suggest that Srb8-Srb11 associates with the GAL1 promoter subsequent to SAGA binding, and that the binding of TBP and Srb8-Srb11 is interdependent.
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Affiliation(s)
- Erica Larschan
- Department of Genetics, Harvard Medical School, 77 Ave. Louis Pasteur, Boston, MA 02115, USA
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