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Crawford T, Siebler L, Sulkowska A, Nowack B, Jiang L, Pan Y, Lämke J, Kappel C, Bäurle I. The Mediator kinase module enhances polymerase activity to regulate transcriptional memory after heat stress in Arabidopsis. EMBO J 2024; 43:437-461. [PMID: 38228917 PMCID: PMC10897291 DOI: 10.1038/s44318-023-00024-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 12/12/2023] [Accepted: 12/14/2023] [Indexed: 01/18/2024] Open
Abstract
Plants are often exposed to recurring adverse environmental conditions in the wild. Acclimation to high temperatures entails transcriptional responses, which prime plants to better withstand subsequent stress events. Heat stress (HS)-induced transcriptional memory results in more efficient re-induction of transcription upon recurrence of heat stress. Here, we identified CDK8 and MED12, two subunits of the kinase module of the transcription co-regulator complex, Mediator, as promoters of heat stress memory and associated histone modifications in Arabidopsis. CDK8 is recruited to heat-stress memory genes by HEAT SHOCK TRANSCRIPTION FACTOR A2 (HSFA2). Like HSFA2, CDK8 is largely dispensable for the initial gene induction upon HS, and its function in transcriptional memory is thus independent of primary gene activation. In addition to the promoter and transcriptional start region of target genes, CDK8 also binds their 3'-region, where it may promote elongation, termination, or rapid re-initiation of RNA polymerase II (Pol II) complexes during transcriptional memory bursts. Our work presents a complex role for the Mediator kinase module during transcriptional memory in multicellular eukaryotes, through interactions with transcription factors, chromatin modifications, and promotion of Pol II efficiency.
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Affiliation(s)
- Tim Crawford
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Lara Siebler
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | | | - Bryan Nowack
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Li Jiang
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Yufeng Pan
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Jörn Lämke
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Christian Kappel
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Isabel Bäurle
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam, Germany.
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2
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Miyasaka S, Kitada R, Kokubo T. Taf1 N-terminal domain 2 (TAND2) of TFIID promotes formation of stable and mobile unstable TBP-TATA complexes. Gene 2023; 889:147800. [PMID: 37716588 DOI: 10.1016/j.gene.2023.147800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 09/05/2023] [Accepted: 09/12/2023] [Indexed: 09/18/2023]
Abstract
In eukaryotes, TATA-binding protein (TBP) occupancy of the core promoter globally correlates with transcriptional activity of class II genes. Elucidating how TBP is delivered to the TATA box or TATA-like element is crucial to understand the mechanisms of transcriptional regulation. A previous study demonstrated that the inhibitory DNA binding (IDB) surface of human TBP plays an indispensable role during the two-step formation of the TBP-TATA complex, first assuming an unstable and unbent intermediate conformation, and subsequently converting slowly to a stable and bent conformation. The DNA binding property of TBP is altered by physical contact of this surface with TBP regulators. In the present study, we examined whether the interaction between Taf1 N-terminal domain 2 (TAND2) and the IDB surface affected DNA binding property of yeast TBP by exploiting TAND2-fused TBP derivatives. TAND2 promoted formation of two distinct types of TBP-TATA complexes, which we arbitrarily designated as complex I and II. While complex I was stable and similar to the well-characterized original TBP-TATA complex, complex II was unstable and moved along DNA. Removal of TAND2 from TBP after complex formation revealed that continuous contact of TAND2 with the IDB surface was required for formation of complex II but not complex I. Further, TFIIA could be incorporated into the complex of TAND2-fused TBP and the TATA box, which was dependent on the amino-terminal non-conserved region of TBP, implying that this region could facilitate the exchange between TAND2 and TFIIA on the IDB surface. Collectively, these findings provide novel insights into the mechanism by which TBP is relieved from the interaction with TAND to bind the TATA box or TATA-like element within promoter-bound TFIID.
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Affiliation(s)
- Shinji Miyasaka
- Molecular and Cellular Biology Laboratory, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Ryota Kitada
- Molecular and Cellular Biology Laboratory, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Tetsuro Kokubo
- Molecular and Cellular Biology Laboratory, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa, Japan.
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3
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Singh S, Sahu RK, Sugathan A, Tomar RS. The H2A N-terminal tail is required to alleviate copper-induced stress in Saccharomyces cerevisiae. FEMS Yeast Res 2021; 21:6459723. [PMID: 34894216 DOI: 10.1093/femsyr/foab061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Accepted: 12/09/2021] [Indexed: 11/13/2022] Open
Abstract
Histone tail residues drive many biological processes by regulating genome-wide transcription. Functions of histone H3 and H4 tail residues in stress-responsive gene transcriptional programs have been extensively studied. The H2A tail residues have been shown to regulate DNA damage repair and oxidative stress response, but the involvement of N-terminal tail of H2A (H2ANtT) in proteostasis regulation is unknown. The unfolded protein response pathway (UPR) is an essential mechanism adopted by cells to prevent protein toxicity in response to ER stress. The disturbance in ER can occur by various factors such as heat stress, redox imbalance, exposure to xenobiotics and metals. Copper is utilized as a cofactor by cellular enzymes, but excessive copper affects ER homeostasis. We found that cells lacking 1-20 residues of H2ANtT are intolerant to copper stress, owing to the accumulation of misfolded proteins in the mutant cells. H2A 1-20 truncation also reduces the physiological UPR, and copper exposure further aggravates this effect. Furthermore, the expression of a spliced version of HAC1 mRNA in H2A∆(1-20) cells, encoding the downstream transcription factor of UPR signalling, rescues their growth under copper stress. Altogether these results provide evidence that H2ANtT reduces copper-induced ER stress by regulating UPR signalling.
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Affiliation(s)
- Sakshi Singh
- Laboratory of Chromatin Biology, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Rd, Bhauri, Madhya Pradesh 462066, India
| | - Rakesh Kumar Sahu
- Laboratory of Chromatin Biology, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Rd, Bhauri, Madhya Pradesh 462066, India
| | - Anaswara Sugathan
- Laboratory of Chromatin Biology, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Rd, Bhauri, Madhya Pradesh 462066, India
| | - Raghuvir Singh Tomar
- Laboratory of Chromatin Biology, Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Rd, Bhauri, Madhya Pradesh 462066, India
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4
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The N-Terminal Tail of Histone H3 Regulates Copper Homeostasis in Saccharomyces cerevisiae. Mol Cell Biol 2021; 41:MCB.00210-20. [PMID: 33257505 DOI: 10.1128/mcb.00210-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 11/22/2020] [Indexed: 11/20/2022] Open
Abstract
Copper homeostasis is crucial for various cellular processes. The balance between nutritional and toxic copper levels is maintained through the regulation of its uptake, distribution, and detoxification via antagonistic actions of two transcription factors, Ace1 and Mac1. Ace1 responds to toxic copper levels by transcriptionally regulating detoxification genes CUP1 and CRS5 Cup1 metallothionein confers protection against toxic copper levels. CUP1 gene regulation is a multifactorial event requiring Ace1, TATA-binding protein (TBP), chromatin remodeler, acetyltransferase (Spt10), and histones. However, the role of histone H3 residues has not been fully elucidated. To investigate the role of the H3 tail in CUP1 transcriptional regulation, we screened the library of histone mutants in copper stress. We identified mutations in H3 (K23Q, K27R, K36Q, Δ5-16, Δ13-16, Δ13-28, Δ25-28, Δ28-31, and Δ29-32) that reduce CUP1 expression. We detected reduced Ace1 occupancy across the CUP1 promoter in K23Q, K36Q, Δ5-16, Δ13-28, Δ25-28, and Δ28-31 mutations correlating with the reduced CUP1 transcription. The majority of these mutations affect TBP occupancy at the CUP1 promoter, augmenting the CUP1 transcription defect. Additionally, some mutants displayed cytosolic protein aggregation upon copper stress. Altogether, our data establish previously unidentified residues of the H3 N-terminal tail and their modifications in CUP1 regulation.
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5
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Quintero-Cadena P, Lenstra TL, Sternberg PW. RNA Pol II Length and Disorder Enable Cooperative Scaling of Transcriptional Bursting. Mol Cell 2020; 79:207-220.e8. [DOI: 10.1016/j.molcel.2020.05.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 04/09/2020] [Accepted: 05/19/2020] [Indexed: 12/15/2022]
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6
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Knoll ER, Zhu ZI, Sarkar D, Landsman D, Morse RH. Role of the pre-initiation complex in Mediator recruitment and dynamics. eLife 2018; 7:39633. [PMID: 30540252 PMCID: PMC6322861 DOI: 10.7554/elife.39633] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 12/12/2018] [Indexed: 12/19/2022] Open
Abstract
The Mediator complex stimulates the cooperative assembly of a pre-initiation complex (PIC) and recruitment of RNA Polymerase II (Pol II) for gene activation. The core Mediator complex is organized into head, middle, and tail modules, and in budding yeast (Saccharomyces cerevisiae), Mediator recruitment has generally been ascribed to sequence-specific activators engaging the tail module triad of Med2-Med3-Med15 at upstream activating sequences (UASs). We show that yeast lacking Med2-Med3-Med15 are viable and that Mediator and PolII are recruited to promoters genome-wide in these cells, albeit at reduced levels. To test whether Mediator might alternatively be recruited via interactions with the PIC, we examined Mediator association genome-wide after depleting PIC components. We found that depletion of Taf1, Rpb3, and TBP profoundly affected Mediator association at active gene promoters, with TBP being critical for transit of Mediator from UAS to promoter, while Pol II and Taf1 stabilize Mediator association at proximal promoters.
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Affiliation(s)
- Elisabeth R Knoll
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, United States
| | - Z Iris Zhu
- Computational Biology Branch, National Center for Biotechnology Information, National Library of Medicine, Bethesda, United States
| | - Debasish Sarkar
- Wadsworth Center, New York State Department of Health, Albany, United States
| | - David Landsman
- Computational Biology Branch, National Center for Biotechnology Information, National Library of Medicine, Bethesda, United States
| | - Randall H Morse
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, United States.,Wadsworth Center, New York State Department of Health, Albany, United States
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7
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Thornlow BP, Hough J, Roger JM, Gong H, Lowe TM, Corbett-Detig RB. Transfer RNA genes experience exceptionally elevated mutation rates. Proc Natl Acad Sci U S A 2018; 115:8996-9001. [PMID: 30127029 PMCID: PMC6130373 DOI: 10.1073/pnas.1801240115] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Transfer RNAs (tRNAs) are a central component for the biological synthesis of proteins, and they are among the most highly conserved and frequently transcribed genes in all living things. Despite their clear significance for fundamental cellular processes, the forces governing tRNA evolution are poorly understood. We present evidence that transcription-associated mutagenesis and strong purifying selection are key determinants of patterns of sequence variation within and surrounding tRNA genes in humans and diverse model organisms. Remarkably, the mutation rate at broadly expressed cytosolic tRNA loci is likely between 7 and 10 times greater than the nuclear genome average. Furthermore, evolutionary analyses provide strong evidence that tRNA genes, but not their flanking sequences, experience strong purifying selection acting against this elevated mutation rate. We also find a strong correlation between tRNA expression levels and the mutation rates in their immediate flanking regions, suggesting a simple method for estimating individual tRNA gene activity. Collectively, this study illuminates the extreme competing forces in tRNA gene evolution and indicates that mutations at tRNA loci contribute disproportionately to mutational load and have unexplored fitness consequences in human populations.
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Affiliation(s)
- Bryan P Thornlow
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064
| | - Josh Hough
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064
| | - Jacquelyn M Roger
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064
| | - Henry Gong
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064
| | - Todd M Lowe
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064;
- Genomics Institute, University of California, Santa Cruz, CA 95064
| | - Russell B Corbett-Detig
- Department of Biomolecular Engineering, University of California, Santa Cruz, CA 95064;
- Genomics Institute, University of California, Santa Cruz, CA 95064
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8
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TOR Facilitates the Targeting of the 19S Proteasome Subcomplex To Enhance Transcription Complex Assembly at the Promoters of the Ribosomal Protein Genes. Mol Cell Biol 2018; 38:MCB.00469-17. [PMID: 29712756 DOI: 10.1128/mcb.00469-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Accepted: 04/23/2018] [Indexed: 12/12/2022] Open
Abstract
TOR (target of rapamycin) has been previously implicated in transcriptional stimulation of the ribosomal protein (RP) genes via enhanced recruitment of NuA4 (nucleosome acetyltransferase of H4) to the promoters. However, it is not clearly understood how TOR enhances NuA4 recruitment to the promoters of the RP genes. Here we show that TOR facilitates the recruitment of the 19S proteasome subcomplex to the activator to enhance the targeting of NuA4 to the promoters of the RP genes. NuA4, in turn, promotes the recruitment of TFIID (transcription factor IID, composed of TATA box-binding protein [TBP] and a set of TBP-associated factors [TAFs]) and RNA polymerase II to the promoters of the RP genes to enhance transcriptional initiation. Therefore, our results demonstrate that TOR facilitates the recruitment of the 19S proteasome subcomplex to the promoters of the RP genes to promote the targeting of NuA4 for enhanced preinitiation complex (PIC) formation and consequently transcriptional initiation, hence illuminating TOR regulation of RP gene activation. Further, our results reveal that TOR differentially regulates PIC formation (and hence transcription) at the non-RP genes, thus demonstrating a complex regulation of gene activation by TOR.
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9
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Abstract
Alterations in the regulation of gene expression are frequently associated with developmental diseases or cancer. Transcription activation is a key phenomenon in the regulation of gene expression. In all eukaryotes, mediator of RNA polymerase II transcription (Mediator), a large complex with modular organization, is generally required for transcription by RNA polymerase II, and it regulates various steps of this process. The main function of Mediator is to transduce signals from the transcription activators bound to enhancer regions to the transcription machinery, which is assembled at promoters as the preinitiation complex (PIC) to control transcription initiation. Recent functional studies of Mediator with the use of structural biology approaches and functional genomics have revealed new insights into Mediator activity and its regulation during transcription initiation, including how Mediator is recruited to transcription regulatory regions and how it interacts and cooperates with PIC components to assist in PIC assembly. Novel roles of Mediator in the control of gene expression have also been revealed by showing its connection to the nuclear pore and linking Mediator to the regulation of gene positioning in the nuclear space. Clear links between Mediator subunits and disease have also encouraged studies to explore targeting of this complex as a potential therapeutic approach in cancer and fungal infections.
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Affiliation(s)
- Julie Soutourina
- Institute for Integrative Biology of the Cell (I2BC), Institute of Life Sciences Frédéric Joliot, Commissariat à l'énergie Atomique et aux énergies alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), University Paris Sud, University Paris Saclay, F-91198 Gif-sur-Yvette, France
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10
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Watanabe K, Kokubo T. SAGA mediates transcription from the TATA-like element independently of Taf1p/TFIID but dependent on core promoter structures in Saccharomyces cerevisiae. PLoS One 2017; 12:e0188435. [PMID: 29176831 PMCID: PMC5703507 DOI: 10.1371/journal.pone.0188435] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 11/07/2017] [Indexed: 11/21/2022] Open
Abstract
In Saccharomyces cerevisiae, core promoters of class II genes contain a TATA element, either a TATA box (TATA[A/T]A[A/T][A/G]) or TATA-like element (1 or 2 bp mismatched version of the TATA box). The TATA element directs the assembly of the preinitiation complex (PIC) to ensure accurate transcriptional initiation. It has been proposed the PIC is assembled by two distinct pathways in which TBP is delivered by TFIID or SAGA, leading to the widely accepted model that these complexes mediate transcription mainly from TATA-like element- or TATA box-containing promoters, respectively. Although both complexes are involved in transcription of nearly all class II genes, it remains unclear how efficiently SAGA mediates transcription from TATA-like element-containing promoters independently of TFIID. We found that transcription from the TATA box-containing AGP1 promoter was greatly stimulated in a Spt3p-dependent manner after inactivation of Taf1p/TFIID. Thus, this promoter provides a novel experimental system in which to evaluate SAGA-mediated transcription from TATA-like element(s). We quantitatively measured transcription from various TATA-like elements in the Taf1p-dependent CYC1 promoter and Taf1p-independent AGP1 promoter. The results revealed that SAGA could mediate transcription from at least some TATA-like elements independently of Taf1p/TFIID, and that Taf1p-dependence or -independence is highly robust with respect to variation of the TATA sequence. Furthermore, chimeric promoter mapping revealed that Taf1p-dependence or independence was conferred by the upstream activating sequence (UAS), whereas Spt3p-dependent transcriptional stimulation after inactivation of Taf1p/TFIID was specific to the AGP1 promoter and dependent on core promoter regions other than the TATA box. These results suggest that TFIID and/or SAGA are regulated in two steps: the UAS first specifies TFIID or SAGA as the predominant factor on a given promoter, and then the core promoter structure guides the pertinent factor to conduct transcription in an appropriate manner.
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Affiliation(s)
- Kiyoshi Watanabe
- Molecular and Cellular Biology Laboratory, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Tetsuro Kokubo
- Molecular and Cellular Biology Laboratory, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Kanagawa, Japan
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11
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Morris LP, Conley AB, Degtyareva N, Jordan IK, Doetsch PW. Genome-wide map of Apn1 binding sites under oxidative stress in Saccharomyces cerevisiae. Yeast 2017; 34:447-458. [PMID: 28752642 DOI: 10.1002/yea.3247] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Accepted: 07/19/2017] [Indexed: 12/18/2022] Open
Abstract
The DNA is cells is continuously exposed to reactive oxygen species resulting in toxic and mutagenic DNA damage. Although the repair of oxidative DNA damage occurs primarily through the base excision repair (BER) pathway, the nucleotide excision repair (NER) pathway processes some of the same lesions. In addition, damage tolerance mechanisms, such as recombination and translesion synthesis, enable cells to tolerate oxidative DNA damage, especially when BER and NER capacities are exceeded. Thus, disruption of BER alone or disruption of BER and NER in Saccharomyces cerevisiae leads to increased mutations as well as large-scale genomic rearrangements. Previous studies demonstrated that a particular region of chromosome II is susceptible to chronic oxidative stress-induced chromosomal rearrangements, suggesting the existence of DNA damage and/or DNA repair hotspots. Here we investigated the relationship between oxidative damage and genomic instability utilizing chromatin immunoprecipitation combined with DNA microarray technology to profile DNA repair sites along yeast chromosomes under different oxidative stress conditions. We targeted the major yeast AP endonuclease Apn1 as a representative BER protein. Our results indicate that Apn1 target sequences are enriched for cytosine and guanine nucleotides. We predict that BER protects these sites in the genome because guanines and cytosines are thought to be especially susceptible to oxidative attack, thereby preventing large-scale genome destabilization from chronic accumulation of DNA damage. Information from our studies should provide insight into how regional deployment of oxidative DNA damage management systems along chromosomes protects against large-scale rearrangements. Copyright © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- Lydia P Morris
- Program in Genetics and Molecular Biology, Emory University Atlanta, GA, 30322, USA.,Department of Biochemistry, Emory University Atlanta, GA, 30322, USA.,WebbWrites, LLC, Durham, NC, USA
| | - Andrew B Conley
- School of Biology, Georgia Institute of Technology Atlanta, GA, 30332, USA.,Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | | | - I King Jordan
- School of Biology, Georgia Institute of Technology Atlanta, GA, 30332, USA
| | - Paul W Doetsch
- Program in Genetics and Molecular Biology, Emory University Atlanta, GA, 30322, USA.,Department of Biochemistry, Emory University Atlanta, GA, 30322, USA.,Department of Hematology and Medical Oncology, Emory University Atlanta, GA, 30322, USA.,Winship Cancer Institute, Emory University Atlanta, GA, 30322, USA
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12
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Eychenne T, Werner M, Soutourina J. Toward understanding of the mechanisms of Mediator function in vivo: Focus on the preinitiation complex assembly. Transcription 2017; 8:328-342. [PMID: 28841352 DOI: 10.1080/21541264.2017.1329000] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Mediator is a multisubunit complex conserved in eukaryotes that plays an essential coregulator role in RNA polymerase (Pol) II transcription. Despite intensive studies of the Mediator complex, the molecular mechanisms of its function in vivo remain to be fully defined. In this review, we will discuss the different aspects of Mediator function starting with its interactions with specific transcription factors, its recruitment to chromatin and how, as a coregulator, it contributes to the assembly of transcription machinery components within the preinitiation complex (PIC) in vivo and beyond the PIC formation.
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Affiliation(s)
- Thomas Eychenne
- a Institute for Integrative Biology of the Cell (I2BC), Institute of Life Sciences Frédéric Joliot, CEA, CNRS , Univ. Paris Sud, University Paris Saclay , Gif-sur-Yvette , France.,b Institut Pasteur, (Epi)genomics of Animal Development Unit , Development and Stem Cell Biology Department, CNRS UMR3778 , Paris , France
| | - Michel Werner
- a Institute for Integrative Biology of the Cell (I2BC), Institute of Life Sciences Frédéric Joliot, CEA, CNRS , Univ. Paris Sud, University Paris Saclay , Gif-sur-Yvette , France
| | - Julie Soutourina
- a Institute for Integrative Biology of the Cell (I2BC), Institute of Life Sciences Frédéric Joliot, CEA, CNRS , Univ. Paris Sud, University Paris Saclay , Gif-sur-Yvette , France
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13
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Petrenko N, Jin Y, Wong KH, Struhl K. Evidence that Mediator is essential for Pol II transcription, but is not a required component of the preinitiation complex in vivo. eLife 2017; 6. [PMID: 28699889 PMCID: PMC5529107 DOI: 10.7554/elife.28447] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Accepted: 07/09/2017] [Indexed: 12/27/2022] Open
Abstract
The Mediator complex has been described as a general transcription factor, but it is unclear if it is essential for Pol II transcription and/or is a required component of the preinitiation complex (PIC) in vivo. Here, we show that depletion of individual subunits, even those essential for cell growth, causes a general but only modest decrease in transcription. In contrast, simultaneous depletion of all Mediator modules causes a drastic decrease in transcription. Depletion of head or middle subunits, but not tail subunits, causes a downstream shift in the Pol II occupancy profile, suggesting that Mediator at the core promoter inhibits promoter escape. Interestingly, a functional PIC and Pol II transcription can occur when Mediator is not detected at core promoters. These results provide strong evidence that Mediator is essential for Pol II transcription and stimulates PIC formation, but it is not a required component of the PIC in vivo. DOI:http://dx.doi.org/10.7554/eLife.28447.001
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Affiliation(s)
- Natalia Petrenko
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School Boston, Boston, United States
| | - Yi Jin
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School Boston, Boston, United States
| | - Koon Ho Wong
- Faculty of Health Sciences, University of Macau, Macau, China
| | - Kevin Struhl
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School Boston, Boston, United States
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14
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Petrenko N, Jin Y, Wong KH, Struhl K. Mediator Undergoes a Compositional Change during Transcriptional Activation. Mol Cell 2016; 64:443-454. [PMID: 27773675 DOI: 10.1016/j.molcel.2016.09.015] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 08/01/2016] [Accepted: 09/09/2016] [Indexed: 10/20/2022]
Abstract
Mediator is a transcriptional co-activator recruited to enhancers by DNA-binding activators, and it also interacts with RNA polymerase (Pol) II as part of the preinitiation complex (PIC). We demonstrate that a single Mediator complex associates with the enhancer and core promoter in vivo, indicating that it can physically bridge these transcriptional elements. However, the Mediator kinase module associates strongly with the enhancer, but not with the core promoter, and it dissociates from the enhancer upon depletion of the TFIIH kinase. Severing the kinase module from Mediator by removing the connecting subunit Med13 does not affect Mediator association at the core promoter but increases occupancy at enhancers. Thus, Mediator undergoes a compositional change in which the kinase module, recruited via Mediator to the enhancer, dissociates from Mediator to permit association with Pol II and the PIC. As such, Mediator acts as a dynamic bridge between the enhancer and core promoter.
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Affiliation(s)
- Natalia Petrenko
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Yi Jin
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Koon Ho Wong
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Faculty of Health Sciences, University of Macau, Macau SAR, China.
| | - Kevin Struhl
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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15
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Eyboulet F, Wydau-Dematteis S, Eychenne T, Alibert O, Neil H, Boschiero C, Nevers MC, Volland H, Cornu D, Redeker V, Werner M, Soutourina J. Mediator independently orchestrates multiple steps of preinitiation complex assembly in vivo. Nucleic Acids Res 2015; 43:9214-31. [PMID: 26240385 PMCID: PMC4627066 DOI: 10.1093/nar/gkv782] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 07/21/2015] [Indexed: 12/20/2022] Open
Abstract
Mediator is a large multiprotein complex conserved in all eukaryotes, which has a crucial coregulator function in transcription by RNA polymerase II (Pol II). However, the molecular mechanisms of its action in vivo remain to be understood. Med17 is an essential and central component of the Mediator head module. In this work, we utilised our large collection of conditional temperature-sensitive med17 mutants to investigate Mediator's role in coordinating preinitiation complex (PIC) formation in vivo at the genome level after a transfer to a non-permissive temperature for 45 minutes. The effect of a yeast mutation proposed to be equivalent to the human Med17-L371P responsible for infantile cerebral atrophy was also analyzed. The ChIP-seq results demonstrate that med17 mutations differentially affected the global presence of several PIC components including Mediator, TBP, TFIIH modules and Pol II. Our data show that Mediator stabilizes TFIIK kinase and TFIIH core modules independently, suggesting that the recruitment or the stability of TFIIH modules is regulated independently on yeast genome. We demonstrate that Mediator selectively contributes to TBP recruitment or stabilization to chromatin. This study provides an extensive genome-wide view of Mediator's role in PIC formation, suggesting that Mediator coordinates multiple steps of a PIC assembly pathway.
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Affiliation(s)
- Fanny Eyboulet
- Institute for Integrative Biology of the Cell (I2BC), Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA, CNRS, Université Paris Sud, F-91191 Gif-sur-Yvette cedex, France
| | - Sandra Wydau-Dematteis
- Institute for Integrative Biology of the Cell (I2BC), Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA, CNRS, Université Paris Sud, F-91191 Gif-sur-Yvette cedex, France
| | - Thomas Eychenne
- Institute for Integrative Biology of the Cell (I2BC), Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA, CNRS, Université Paris Sud, F-91191 Gif-sur-Yvette cedex, France
| | | | - Helen Neil
- Institute for Integrative Biology of the Cell (I2BC), Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA, CNRS, Université Paris Sud, F-91191 Gif-sur-Yvette cedex, France
| | - Claire Boschiero
- Institute for Integrative Biology of the Cell (I2BC), Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA, CNRS, Université Paris Sud, F-91191 Gif-sur-Yvette cedex, France
| | - Marie-Claire Nevers
- CEA, iBiTec-S, Service de Pharmacologie et d'Immunoanalyse, F-91191 Gif sur Yvette cedex, France
| | - Hervé Volland
- CEA, iBiTec-S, Service de Pharmacologie et d'Immunoanalyse, F-91191 Gif sur Yvette cedex, France
| | - David Cornu
- CNRS, Centre de Recherche de Gif, SICaPS, F-91198 Gif-sur-Yvette cedex, France
| | - Virginie Redeker
- CNRS, Centre de Recherche de Gif, SICaPS, F-91198 Gif-sur-Yvette cedex, France
| | - Michel Werner
- Institute for Integrative Biology of the Cell (I2BC), Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA, CNRS, Université Paris Sud, F-91191 Gif-sur-Yvette cedex, France
| | - Julie Soutourina
- Institute for Integrative Biology of the Cell (I2BC), Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA, CNRS, Université Paris Sud, F-91191 Gif-sur-Yvette cedex, France
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16
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Raabe CA, Brosius J. Does every transcript originate from a gene? Ann N Y Acad Sci 2015; 1341:136-48. [PMID: 25847549 DOI: 10.1111/nyas.12741] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 02/05/2015] [Accepted: 02/11/2015] [Indexed: 12/20/2022]
Abstract
Outdated gene definitions favored regions corresponding to mature messenger RNAs, in particular, the open reading frame. In eukaryotes, the intergenic space was widely regarded nonfunctional and devoid of RNA transcription. Original concepts were based on the assumption that RNA expression was restricted to known protein-coding genes and a few so-called structural RNA genes, such as ribosomal RNAs or transfer RNAs. With the discovery of introns and, more recently, sensitive techniques for monitoring genome-wide transcription, this view had to be substantially modified. Tiling microarrays and RNA deep sequencing revealed myriads of transcripts, which cover almost entire genomes. The tremendous complexity of non-protein-coding RNA transcription has to be integrated into novel gene definitions. Despite an ever-growing list of functional RNAs, questions concerning the mass of identified transcripts are under dispute. Here, we examined genome-wide transcription from various angles, including evolutionary considerations, and suggest, in analogy to novel alternative splice variants that do not persist, that the vast majority of transcripts represent raw material for potential, albeit rare, exaptation events.
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Affiliation(s)
- Carsten A Raabe
- Institute of Experimental Pathology, ZMBE, University of Münster, Münster, Germany
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17
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Genome-wide targeting of the epigenetic regulatory protein CTCF to gene promoters by the transcription factor TFII-I. Proc Natl Acad Sci U S A 2015; 112:E677-86. [PMID: 25646466 DOI: 10.1073/pnas.1416674112] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
CCCTC-binding factor (CTCF) is a key regulator of nuclear chromatin structure and gene regulation. The impact of CTCF on transcriptional output is highly varied, ranging from repression to transcriptional pausing and transactivation. The multifunctional nature of CTCF may be directed solely through remodeling chromatin architecture. However, another hypothesis is that the multifunctional nature of CTCF is mediated, in part, through differential association with protein partners having unique functions. Consistent with this hypothesis, our mass spectrometry analyses of CTCF interacting partners reveal a previously undefined association with the transcription factor general transcription factor II-I (TFII-I). Biochemical fractionation of CTCF indicates that a distinct CTCF complex incorporating TFII-I is assembled on DNA. Unexpectedly, we found that the interaction between CTCF and TFII-I is essential for directing CTCF to the promoter proximal regulatory regions of target genes across the genome, particularly at genes involved in metabolism. At genes coregulated by CTCF and TFII-I, we find knockdown of TFII-I results in diminished CTCF binding, lack of cyclin-dependent kinase 8 (CDK8) recruitment, and an attenuation of RNA polymerase II phosphorylation at serine 5. Phenotypically, knockdown of TFII-I alters the cellular response to metabolic stress. Our data indicate that TFII-I directs CTCF binding to target genes, and in turn the two proteins cooperate to recruit CDK8 and enhance transcription initiation.
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18
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Mutations on the DNA binding surface of TBP discriminate between yeast TATA and TATA-less gene transcription. Mol Cell Biol 2014; 34:2929-43. [PMID: 24865972 DOI: 10.1128/mcb.01685-13] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Most RNA polymerase (Pol) II promoters lack a TATA element, yet nearly all Pol II transcription requires TATA binding protein (TBP). While the TBP-TATA interaction is critical for transcription at TATA-containing promoters, it has been unclear whether TBP sequence-specific DNA contacts are required for transcription at TATA-less genes. Transcription factor IID (TFIID), the TBP-containing coactivator that functions at most TATA-less genes, recognizes short sequence-specific promoter elements in metazoans, but analogous promoter elements have not been identified in Saccharomyces cerevisiae. We generated a set of mutations in the yeast TBP DNA binding surface and found that most support growth of yeast. Both in vivo and in vitro, many of these mutations are specifically defective for transcription of two TATA-containing genes with only minor defects in transcription of two TATA-less, TFIID-dependent genes. TBP binds several TATA-less promoters with apparent high affinity, but our results suggest that this binding is not important for transcription activity. Our results are consistent with the model that sequence-specific TBP-DNA contacts are not important at yeast TATA-less genes and suggest that other general transcription factors or coactivator subunits are responsible for recognition of TATA-less promoters. Our results also explain why yeast TBP derivatives defective for TATA binding appear defective in activated transcription.
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19
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Wong KH, Jin Y, Struhl K. TFIIH phosphorylation of the Pol II CTD stimulates mediator dissociation from the preinitiation complex and promoter escape. Mol Cell 2014; 54:601-12. [PMID: 24746699 DOI: 10.1016/j.molcel.2014.03.024] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 02/19/2014] [Accepted: 03/07/2014] [Indexed: 11/30/2022]
Abstract
The transition between transcriptional initiation and elongation by RNA polymerase (Pol) II is associated with phosphorylation of its C-terminal tail (CTD). Depletion of Kin28, the TFIIH subunit that phosphorylates the CTD, does not affect elongation but causes Pol II occupancy profiles to shift upstream in a FACT-independent manner indicative of a defect in promoter escape. Stronger defects in promoter escape are linked to stronger effects on preinitiation complex formation and transcription, suggesting that impairment in promoter escape results in premature dissociation of general factors and Pol II near the promoter. Kin28 has a stronger effect on genes whose transcription is dependent on SAGA as opposed to TFIID. Strikingly, Kin28 depletion causes a dramatic increase in Mediator at the core promoter. These observations suggest that TFIIH phosphorylation of the CTD causes Mediator dissociation, thereby permitting rapid promoter escape of Pol II from the preinitiation complex.
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Affiliation(s)
- Koon Ho Wong
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Faculty of Health Sciences, University of Macau, Macau SAR, China
| | - Yi Jin
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
| | - Kevin Struhl
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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20
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Ansari SA, Paul E, Sommer S, Lieleg C, He Q, Daly AZ, Rode KA, Barber WT, Ellis LC, LaPorta E, Orzechowski AM, Taylor E, Reeb T, Wong J, Korber P, Morse RH. Mediator, TATA-binding protein, and RNA polymerase II contribute to low histone occupancy at active gene promoters in yeast. J Biol Chem 2014; 289:14981-95. [PMID: 24727477 DOI: 10.1074/jbc.m113.529354] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Transcription by RNA polymerase II (Pol II) in eukaryotes requires the Mediator complex, and often involves chromatin remodeling and histone eviction at active promoters. Here we address the role of Mediator in recruitment of the Swi/Snf chromatin remodeling complex and its role, along with components of the preinitiation complex (PIC), in histone eviction at inducible and constitutively active promoters in the budding yeast Saccharomyces cerevisiae. We show that recruitment of the Swi/Snf chromatin remodeling complex to the induced CHA1 promoter, as well as its association with several constitutively active promoters, depends on the Mediator complex but is independent of Mediator at the induced MET2 and MET6 genes. Although transcriptional activation and histone eviction at CHA1 depends on Swi/Snf, Swi/Snf recruitment is not sufficient for histone eviction at the induced CHA1 promoter. Loss of Swi/Snf activity does not affect histone occupancy of several constitutively active promoters; in contrast, higher histone occupancy is seen at these promoters in Mediator and PIC component mutants. We propose that an initial activator-dependent, nucleosome remodeling step allows PIC components to outcompete histones for occupancy of promoter sequences. We also observe reduced promoter association of Mediator and TATA-binding protein in a Pol II (rpb1-1) mutant, indicating mutually cooperative binding of these components of the transcription machinery and indicating that it is the PIC as a whole whose binding results in stable histone eviction.
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Affiliation(s)
- Suraiya A Ansari
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Emily Paul
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Sebastian Sommer
- the Adolf-Butenandt-Institut, Universität München, 80336 Munich, Germany
| | - Corinna Lieleg
- the Adolf-Butenandt-Institut, Universität München, 80336 Munich, Germany
| | - Qiye He
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, the Department of Biomedical Science, University at Albany School of Public Health, Albany, New York 12201-0509, and
| | - Alexandre Z Daly
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Kara A Rode
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Wesley T Barber
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Laura C Ellis
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Erika LaPorta
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, the Department of Biomedical Science, University at Albany School of Public Health, Albany, New York 12201-0509, and
| | - Amanda M Orzechowski
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Emily Taylor
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Tanner Reeb
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Jason Wong
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509
| | - Philipp Korber
- the Adolf-Butenandt-Institut, Universität München, 80336 Munich, Germany
| | - Randall H Morse
- From the Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, the Department of Biomedical Science, University at Albany School of Public Health, Albany, New York 12201-0509, and
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21
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Farzadfard F, Perli SD, Lu TK. Tunable and multifunctional eukaryotic transcription factors based on CRISPR/Cas. ACS Synth Biol 2013; 2:604-13. [PMID: 23977949 PMCID: PMC3805333 DOI: 10.1021/sb400081r] [Citation(s) in RCA: 270] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
![]()
Transcriptional regulation is central
to the complex behavior of
natural biological systems and synthetic gene circuits. Platforms
for the scalable, tunable, and simple modulation of transcription
would enable new abilities to study natural systems and implement
artificial capabilities in living cells. Previous approaches to synthetic
transcriptional regulation have relied on engineering DNA-binding
proteins, which necessitate multistep processes for construction and
optimization of function. Here, we show that the CRISPR/Cas system
of Streptococcus pyogenes can be programmed
to direct both activation and repression to natural and artificial
eukaryotic promoters through the simple engineering of guide RNAs
with base-pairing complementarity to target DNA sites. We demonstrate
that the activity of CRISPR-based transcription factors (crisprTFs)
can be tuned by directing multiple crisprTFs to different positions
in natural promoters and by arraying multiple crisprTF-binding sites
in the context of synthetic promoters in yeast and human cells. Furthermore,
externally controllable regulatory modules can be engineered by layering
gRNAs with small molecule-responsive proteins. Additionally, single
nucleotide substitutions within promoters are sufficient to render
them orthogonal with respect to the same gRNA-guided crisprTF. We
envision that CRISPR-based eukaryotic gene regulation will enable
the facile construction of scalable synthetic gene circuits and open
up new approaches for mapping natural gene networks and their effects
on complex cellular phenotypes.
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Affiliation(s)
- Fahim Farzadfard
- Department of Electrical Engineering & Computer Science and Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- MIT Synthetic Biology Center, 500 Technology Square, Cambridge, Massachusetts 02139, United States
- MIT Microbiology
Program, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Samuel D. Perli
- Department of Electrical Engineering & Computer Science and Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- MIT Synthetic Biology Center, 500 Technology Square, Cambridge, Massachusetts 02139, United States
| | - Timothy K. Lu
- Department of Electrical Engineering & Computer Science and Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- MIT Synthetic Biology Center, 500 Technology Square, Cambridge, Massachusetts 02139, United States
- MIT Microbiology
Program, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
- Biophysics Program, Harvard University, Cambridge, Massachusetts 02139, United States
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22
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Abstract
The Mediator complex is a multi-subunit assembly that appears to be required for regulating expression of most RNA polymerase II (pol II) transcripts, which include protein-coding and most non-coding RNA genes. Mediator and pol II function within the pre-initiation complex (PIC), which consists of Mediator, pol II, TFIIA, TFIIB, TFIID, TFIIE, TFIIF and TFIIH and is approximately 4.0 MDa in size. Mediator serves as a central scaffold within the PIC and helps regulate pol II activity in ways that remain poorly understood. Mediator is also generally targeted by sequence-specific, DNA-binding transcription factors (TFs) that work to control gene expression programs in response to developmental or environmental cues. At a basic level, Mediator functions by relaying signals from TFs directly to the pol II enzyme, thereby facilitating TF-dependent regulation of gene expression. Thus, Mediator is essential for converting biological inputs (communicated by TFs) to physiological responses (via changes in gene expression). In this review, we summarize an expansive body of research on the Mediator complex, with an emphasis on yeast and mammalian complexes. We focus on the basics that underlie Mediator function, such as its structure and subunit composition, and describe its broad regulatory influence on gene expression, ranging from chromatin architecture to transcription initiation and elongation, to mRNA processing. We also describe factors that influence Mediator structure and activity, including TFs, non-coding RNAs and the CDK8 module.
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Affiliation(s)
- Zachary C Poss
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, CO , USA
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23
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Ansari SA, Morse RH. Mechanisms of Mediator complex action in transcriptional activation. Cell Mol Life Sci 2013; 70:2743-56. [PMID: 23361037 PMCID: PMC11113466 DOI: 10.1007/s00018-013-1265-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 01/07/2013] [Accepted: 01/09/2013] [Indexed: 12/14/2022]
Abstract
Mediator is a large multisubunit complex that plays a central role in the regulation of RNA Pol II transcribed genes. Conserved in overall structure and function among eukaryotes, Mediator comprises 25-30 protein subunits that reside in four distinct modules, termed head, middle, tail, and CDK8/kinase. Different subunits of Mediator contact other transcriptional regulators including activators, co-activators, general transcription factors, subunits of RNA Pol II, and specifically modified histones, leading to the regulated expression of target genes. This review is focused on the interactions of specific Mediator subunits with diverse transcription regulators and how those interactions contribute to Mediator function in transcriptional activation.
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Affiliation(s)
- Suraiya A. Ansari
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY 12201–0509 USA
| | - Randall H. Morse
- Laboratory of Molecular Genetics, Wadsworth Center, New York State Department of Health, Albany, NY 12201–0509 USA
- Department of Biomedical Science, University at Albany School of Public Health, Albany, NY USA
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24
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Mechanisms of antisense transcription initiation from the 3' end of the GAL10 coding sequence in vivo. Mol Cell Biol 2013; 33:3549-67. [PMID: 23836882 DOI: 10.1128/mcb.01715-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In spite of the important regulatory functions of antisense transcripts in gene expression, it remains unknown how antisense transcription is initiated. Recent studies implicated RNA polymerase II in initiation of antisense transcription. However, how RNA polymerase II is targeted to initiate antisense transcription has not been elucidated. Here, we have analyzed the association of RNA polymerase II with the antisense initiation site at the 3' end of the GAL10 coding sequence in dextrose-containing growth medium that induces antisense transcription. We find that RNA polymerase II is targeted to the antisense initiation site at GAL10 by Reb1p activator as well as general transcription factors (e.g., TFIID, TFIIB, and Mediator) for antisense transcription initiation. Intriguingly, while GAL10 antisense transcription is dependent on TFIID, its sense transcription does not require TFIID. Further, the Gal4p activator that promotes GAL10 sense transcription is dispensable for antisense transcription. Moreover, the proteasome that facilitates GAL10 sense transcription does not control its antisense transcription. Taken together, our results reveal that GAL10 sense and antisense transcriptions are regulated differently and shed much light on the mechanisms of antisense transcription initiation.
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25
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Affiliation(s)
- Arnold J Berk
- Department of Microbiology, Immunology and Molecular Genetics, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA.
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26
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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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27
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Moyle-Heyrman G, Viswanathan R, Widom J, Auble DT. Two-step mechanism for modifier of transcription 1 (Mot1) enzyme-catalyzed displacement of TATA-binding protein (TBP) from DNA. J Biol Chem 2012; 287:9002-12. [PMID: 22298788 DOI: 10.1074/jbc.m111.333484] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The TATA box binding protein (TBP) is a central component of the transcription preinitiation complex, and its occupancy at a promoter is correlated with transcription levels. The TBP-promoter DNA complex contains sharply bent DNA and its interaction lifetime is limited by the ATP-dependent TBP displacement activity of the Snf2/Swi2 ATPase Mot1. Several mechanisms for Mot1 action have been proposed, but how it catalyzes TBP removal from DNA is unknown. To better understand the Mot1 mechanism, native gel electrophoresis and FRET were used to determine how Mot1 affects the trajectory of DNA in the TBP-DNA complex. Strikingly, in the absence of ATP, Mot1 acts to unbend DNA, whereas TBP remains closely associated with the DNA in a stable Mot1-TBP-DNA ternary complex. Interestingly, and in contrast to full-length Mot1, the isolated Mot1 ATPase domain binds DNA, and its affinity for DNA is nucleotide-dependent, suggesting parallels between the Mot1 mechanism and DNA translocation-based mechanisms of chromatin remodeling enzymes. Based on these findings, a model is presented for Mot1 that links a DNA conformational change with ATP-induced DNA translocation.
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28
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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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29
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Distinct role of Mediator tail module in regulation of SAGA-dependent, TATA-containing genes in yeast. EMBO J 2011; 31:44-57. [PMID: 21971086 DOI: 10.1038/emboj.2011.362] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 09/07/2011] [Indexed: 11/08/2022] Open
Abstract
The evolutionarily conserved Mediator complex is required for transcription of nearly all RNA Pol II-dependent promoters, with the tail module serving to recruit Mediator to active promoters in current models. However, transcriptional dependence on tail module subunits varies in a gene-specific manner, and the generality of the tail module requirement for transcriptional activation has not been explored. Here, we show that tail module subunits function redundantly to recruit Mediator to promoters in yeast, and transcriptome analysis shows stronger effects on genome-wide expression in a double-tail subunit deletion mutant than in single-subunit deletion mutants. Unexpectedly, TATA-containing and SAGA-dependent genes were much more affected by impairment of tail module function than were TFIID-dependent genes. Consistent with this finding, Mediator and preinitiation complex association with SAGA-dependent promoters is substantially reduced in gal11/med15Δ med3Δ yeast, whereas association of TBP, Pol II, and other Mediator modules with TFIID-dependent genes is largely independent of the tail module. Thus, we have identified a connection between the Mediator tail module and the division of promoter dependence between TFIID and SAGA.
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30
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Viswanathan R, Auble DT. One small step for Mot1; one giant leap for other Swi2/Snf2 enzymes? BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1809:488-96. [PMID: 21658482 DOI: 10.1016/j.bbagrm.2011.05.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 05/14/2011] [Accepted: 05/20/2011] [Indexed: 12/13/2022]
Abstract
The TATA-binding protein (TBP) is a major target for transcriptional regulation. Mot1, a Swi2/Snf2-related ATPase, dissociates TBP from DNA in an ATP dependent process. The experimental advantages of this relatively simple reaction have been exploited to learn more about how Swi2/Snf2 ATPases function biochemically. However, many unanswered questions remain and fundamental aspects of the Mot1 mechanism are still under debate. Here, we review the available data and integrate the results with structural and biochemical studies of related enzymes to derive a model for Mot1's catalytic action consistent with the broad literature on enzymes in this family. We propose that the Mot1 ATPase domain is tethered to TBP by a flexible, spring-like linker of alpha helical hairpins. The linker juxtaposes the ATPase domain such that it can engage duplex DNA on one side of the TBP-DNA complex. This allows the ATPase to employ short-range, nonprocessive ATP-driven DNA tracking to pull or push TBP off its DNA site. DNA translocation is a conserved property of ATPases in the broader enzyme family. As such, the model explains how a structurally and functionally conserved ATPase domain has been put to use in a very different context than other enzymes in the Swi2/Snf2 family. This article is part of a Special Issue entitled:Snf2/Swi2 ATPase structure and function.
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Affiliation(s)
- Ramya Viswanathan
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, VA 22908, USA
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Mao C, Brown CR, Falkovskaia E, Dong S, Hrabeta-Robinson E, Wenger L, Boeger H. Quantitative analysis of the transcription control mechanism. Mol Syst Biol 2011; 6:431. [PMID: 21081924 PMCID: PMC3010110 DOI: 10.1038/msb.2010.83] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 09/27/2010] [Indexed: 01/01/2023] Open
Abstract
Activated PHO5 promoter chromatin at steady state represents a statistical ensemble of distinct structures. The extent of promoter nucleosome loss depends on the strength of the transcriptional activator of PHO5, indicative of continuous disassembly and reassembly of nucleosomes at the induced promoter. PHO5 promoter nucleosome loss and expression are exponentially related, pointing at two or more steps of the expression process that are activator controlled. The intrinsic noise profile of PHO5 expression permits quantitative distinction between alternative regulatory architectures. The assumption of two activator-controlled steps, promoter nucleosome removal and assembly of the transcription machinery, is necessary and sufficient to account for the quantitative relationship between PHO5 expression, intrinsic noise, and promoter nucleosome loss.
The search for factors that interact with transcriptional activators has provided clues to the possible mechanisms of transcriptional regulation. However, the promiscuity of activator interactions has supported alternative regulatory hypotheses whose relative likelihood could not be assessed. A possible solution to the problem is suggested by recent theoretical work showing that the regulatory architecture of the gene expression process is reflected in the magnitude and frequency spectrum of steady-state fluctuations in gene expression (intrinsic noise). In this study, we analyzed promoter chromatin structure and the magnitude of intrinsic noise over a wide range of expression values for the PHO5 gene of yeast. We show that the relationship between gene expression and promoter nucleosome loss is exponential rather than linear, suggesting activator control of at least two steps of the expression process. Interpretation of our data with regard to a stochastic model of chromatin remodeling and gene expression allowed us to quantitatively distinguish between competing regulatory hypotheses, demonstrating the value of noise measurements for analysis of the gene regulatory mechanism. We show that the assumption of two activator-controlled steps, nucleosome removal and assembly of the transcription machinery, is necessary and sufficient to account for the quantitative relationship between our experimental observables. Gene transcription requires a sequence of promoter state transitions, including chromatin remodeling, assembly of the transcription machinery, and clearance of the promoter by RNA polymerase. The rate-limiting steps in this sequence are regulated by transcriptional activators that bind at specific promoter elements. As the transition kinetics of individual promoters cannot be observed, the identity of the activator-controlled steps has remained a matter of speculation. In this study, we investigated promoter chromatin structure, and the intrinsic noise of expression over a wide range of expression values for the PHO5 gene of yeast. Interpretation of our results with regard to a stochastic model of promoter chromatin remodeling and gene expression suggests that the regulatory architecture of the gene expression process is measurably reflected in its intrinsic noise profile. Our chromatin structure and noise analyses indicate that the activator of PHO5 transcription stimulates the rates of promoter nucleosome disassembly, and assembly of the transcription machinery after nucleosome removal, but no other rates of the expression process.
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Affiliation(s)
- Changhui Mao
- Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA
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32
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Ohyama Y, Kasahara K, Kokubo T. Saccharomyces cerevisiae Ssd1p promotes CLN2 expression by binding to the 5′-untranslated region of CLN2 mRNA. Genes Cells 2010; 15:1169-88. [DOI: 10.1111/j.1365-2443.2010.01452.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Sugihara F, Kasahara K, Kokubo T. Highly redundant function of multiple AT-rich sequences as core promoter elements in the TATA-less RPS5 promoter of Saccharomyces cerevisiae. Nucleic Acids Res 2010; 39:59-75. [PMID: 20805245 PMCID: PMC3017598 DOI: 10.1093/nar/gkq741] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In eukaryotes, protein-coding genes are transcribed by RNA polymerase II (pol II) together with general transcription factors (GTFs). TFIID, the largest GTF composed of TATA element-binding protein (TBP) and 14 TBP-associated factors (TAFs), plays a critical role in transcription from TATA-less promoters. In metazoans, several core promoter elements other than the TATA element are thought to be recognition sites for TFIID. However, it is unclear whether functionally homologous elements also exist in TATA-less promoters in Saccharomyces cerevisiae. Here, we identify the cis-elements required to support normal levels of transcription and accurate initiation from sites within the TATA-less and TFIID-dependent RPS5 core promoter. Systematic mutational analyses show that multiple AT-rich sequences are required for these activities and appear to function as recognition sites for TFIID. A single copy of these sequences can support accurate initiation from the endogenous promoter, indicating that they carry highly redundant functions. These results show a novel architecture of yeast TATA-less promoters and support a model in which pol II scans DNA downstream from a recruited site, while searching for appropriate initiation site(s).
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Affiliation(s)
- Fuminori Sugihara
- Division of Molecular and Cellular Biology, Graduate School of Nanobioscience, Yokohama City University, Yokohama, Kanagawa, Japan
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Ecevit O, Khan MA, Goss DJ. Kinetic analysis of the interaction of b/HLH/Z transcription factors Myc, Max, and Mad with cognate DNA. Biochemistry 2010; 49:2627-35. [PMID: 20170194 PMCID: PMC2852888 DOI: 10.1021/bi901913a] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Myc, Mad, and Max proteins belong to the basic helix-loop-helix leucine zipper family of transcription factors. They bind to a specific hexanucleotide element of DNA, the E-box (CACGTG). To be biologically active, Myc and Mad require dimerization with Max. For the route of complex assembly of these dimers, there are two proposed pathways. In the monomer pathway, two monomers bind DNA sequentially and assemble their dimerization interface while bound to DNA. In the dimer pathway, two monomers form a dimer first prior to association with DNA. The monomer pathway is kinetically favored. In this report, stopped-flow polarization was utilized to determine the rates and temperature dependence of all of the individual steps for both assembly pathways. Myc.Max dimerization had a rate constant approximately 5- and approximately 2-fold higher than those of Max.Max and Mad.Max dimerization, respectively. The protein dimerization rates as well as the dimer-DNA rates were found to be independent of concentration, suggesting conformational changes were rate-limiting. The Arrhenius activation energies for the dimerization of Myc, Mad, and Max with Max were 20.4 +/- 0.8, 29 +/- 0.6, and 40 +/- 0.2 kJ/mol, respectively. Further, rate constants for Max.Max homodimer DNA binding are significantly higher than for Myc.Max and Mad.Max heterodimers binding to DNA. Monomer-DNA binding showed a faster rate than dimer-DNA binding. These studies show the rate-limiting step for the dimer pathway is the formation of protein dimers, and this reaction is slower than formation of protein dimers on the DNA interface, kinetically favoring the monomer pathway.
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Affiliation(s)
- Ozgur Ecevit
- Department of Chemistry and Biochemistry, Hunter College and Graduate Center of the City University of New York, New York, NY 10065
| | - Mateen A Khan
- Department of Chemistry and Biochemistry, Hunter College and Graduate Center of the City University of New York, New York, NY 10065
| | - Dixie J Goss
- Department of Chemistry and Biochemistry, Hunter College and Graduate Center of the City University of New York, New York, NY 10065
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35
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Donner AJ, Ebmeier CC, Taatjes DJ, Espinosa JM. CDK8 is a positive regulator of transcriptional elongation within the serum response network. Nat Struct Mol Biol 2010; 17:194-201. [PMID: 20098423 PMCID: PMC2920286 DOI: 10.1038/nsmb.1752] [Citation(s) in RCA: 272] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2009] [Accepted: 11/25/2009] [Indexed: 01/13/2023]
Abstract
The Mediator complex allows communication between transcription factors and RNA polymerase II (RNAPII). CDK8, the kinase found in some variants of Mediator, has been characterized mostly as a transcriptional repressor. Recently, CDK8 was demonstrated to be a potent oncoprotein. Here we show that CDK8 is a positive regulator of genes within the serum response network, including several members of the AP-1 and EGR family of oncogenic transcription factors. Mechanistic studies demonstrate that CDK8 is not required for RNAPII recruitment or promoter escape. Instead, CDK8 depletion leads to the appearance of slower elongation complexes carrying hypophosphorylated RNAPII. CDK8-Mediator regulates precise steps in the assembly of the RNAPII elongation complex, including the recruitment of P-TEFb and BRD4. Furthermore, CDK8-Mediator specifically interacts with P-TEFb. Thus, we uncovered a novel role for CDK8 in transcriptional regulation that may contribute to its oncogenic effects.
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Affiliation(s)
- Aaron J Donner
- Howard Hughes Medical Institute, The University of Colorado at Boulder, Boulder, Colorado, USA
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36
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Jedidi I, Zhang F, Qiu H, Stahl SJ, Palmer I, Kaufman JD, Nadaud PS, Mukherjee S, Wingfield PT, Jaroniec CP, Hinnebusch AG. Activator Gcn4 employs multiple segments of Med15/Gal11, including the KIX domain, to recruit mediator to target genes in vivo. J Biol Chem 2010; 285:2438-55. [PMID: 19940160 PMCID: PMC2807301 DOI: 10.1074/jbc.m109.071589] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Revised: 11/10/2009] [Indexed: 11/06/2022] Open
Abstract
Mediator is a multisubunit coactivator required for initiation by RNA polymerase II. The Mediator tail subdomain, containing Med15/Gal11, is a target of the activator Gcn4 in vivo, critical for recruitment of native Mediator or the Mediator tail subdomain present in sin4Delta cells. Although several Gal11 segments were previously shown to bind Gcn4 in vitro, the importance of these interactions for recruitment of Mediator and transcriptional activation by Gcn4 in cells was unknown. We show that interaction of Gcn4 with the Mediator tail in vitro and recruitment of this subcomplex and intact Mediator to the ARG1 promoter in vivo involve additive contributions from three different segments in the N terminus of Gal11. These include the KIX domain, which is a critical target of other activators, and a region that shares a conserved motif (B-box) with mammalian coactivator SRC-1, and we establish that B-box is a critical determinant of Mediator recruitment by Gcn4. We further demonstrate that Gcn4 binds to the Gal11 KIX domain directly and, by NMR chemical shift analysis combined with mutational studies, we identify the likely binding site for Gcn4 on the KIX surface. Gcn4 is distinctive in relying on comparable contributions from multiple segments of Gal11 for efficient recruitment of Mediator in vivo.
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Affiliation(s)
- Iness Jedidi
- From the Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, and
| | - Fan Zhang
- From the Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, and
| | - Hongfang Qiu
- From the Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, and
| | - Stephen J. Stahl
- the Protein Expression Laboratory, NIAMS, National Institutes of Health, Bethesda, Maryland 20892 and
| | - Ira Palmer
- the Protein Expression Laboratory, NIAMS, National Institutes of Health, Bethesda, Maryland 20892 and
| | - Joshua D. Kaufman
- the Protein Expression Laboratory, NIAMS, National Institutes of Health, Bethesda, Maryland 20892 and
| | - Philippe S. Nadaud
- the Department of Chemistry, The Ohio State University, Columbus, Ohio 43210
| | - Sujoy Mukherjee
- the Department of Chemistry, The Ohio State University, Columbus, Ohio 43210
| | - Paul T. Wingfield
- the Protein Expression Laboratory, NIAMS, National Institutes of Health, Bethesda, Maryland 20892 and
| | | | - Alan G. Hinnebusch
- From the Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, and
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37
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Sikorski TW, Buratowski S. The basal initiation machinery: beyond the general transcription factors. Curr Opin Cell Biol 2009; 21:344-51. [PMID: 19411170 DOI: 10.1016/j.ceb.2009.03.006] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 03/26/2009] [Accepted: 03/29/2009] [Indexed: 01/19/2023]
Abstract
In vitro experiments led to a simple model in which basal transcription factors sequentially assembled with RNA Polymerase II to generate a preinitiation complex (PIC). Emerging evidence indicates that PIC composition is not universal, but promoter-dependent. Active promoters are occupied by a mixed population of complexes, including regulatory factors such as NC2, Mot1, Mediator, and TFIIS. Recent studies are expanding our understanding of the roles of these factors, demonstrating that their functions are both broader and more context dependent than previously realized.
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Affiliation(s)
- Timothy W Sikorski
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, United States
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38
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Sprouse RO, Wells MN, Auble DT. TATA-binding protein variants that bypass the requirement for Mot1 in vivo. J Biol Chem 2009; 284:4525-35. [PMID: 19098311 PMCID: PMC2640957 DOI: 10.1074/jbc.m808951200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 12/18/2008] [Indexed: 12/27/2022] Open
Abstract
Mot1 is an essential TATA-binding protein (TBP)-associated factor and Snf2/Swi2 ATPase that both represses and activates transcription. Biochemical and structural results support a model in which ATP binding and hydrolysis induce a conformational change in Mot1 that drives local translocation along DNA, thus removing TBP. Although this activity explains transcriptional repression, it does not as easily explain Mot1-mediated transcriptional activation, and several different models have been proposed to explain how Mot1 activates transcription. To better understand the function of Mot1 in yeast cells in vivo, particularly with regard to gene activation, TBP mutants were identified that bypass the requirement for Mot1 in vivo. Although TBP has been extensively mutated and analyzed previously, this screen uncovered two novel TBP variants that are unique in their ability to bypass the requirement for Mot1. Surprisingly, in vitro analyses reveal that rather than having acquired an improved biochemical activity, one of the TBPs was defective for interaction with polymerase II preinitiation complex (PIC) components and other regulators of TBP function. The other mutant was defective for DNA binding in vitro yet was still recruited to chromatin in vivo. These results suggest that Mot1-mediated dissociation of TBP (or TBP-containing complexes) from chromatin can explain the Mot1 activation mechanism at some promoters. The results also suggest that PICs can be dynamically unstable and that appropriate PIC instability is critical for the regulation of transcription in vivo.
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Affiliation(s)
- Rebekka O Sprouse
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, Virginia 22908, USA
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39
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Arnett DR, Jennings JL, Tabb DL, Link AJ, Weil PA. A proteomics analysis of yeast Mot1p protein-protein associations: insights into mechanism. Mol Cell Proteomics 2008; 7:2090-106. [PMID: 18596064 DOI: 10.1074/mcp.m800221-mcp200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Yeast Mot1p, a member of the Snf2 ATPase family of proteins, is a transcriptional regulator that has the unusual ability to both repress and activate mRNA gene transcription. To identify interactions with other proteins that may assist Mot1p in its regulatory processes, Mot1p was purified from replicate yeast cell extracts, and Mot1p-associated proteins were identified by coupled multidimensional liquid chromatography and tandem mass spectrometry. Using this approach we generated a catalog of Mot1p-interacting proteins. Mot1p interacts with a range of transcriptional co-regulators as well as proteins involved in chromatin remodeling. We propose that interaction with such a wide range of proteins may be one mechanism through which Mot1p subserves its roles as a transcriptional activator and repressor.
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Affiliation(s)
- Diana R Arnett
- Department of Molecular Physiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0615, USA
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40
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Aparicio O, Geisberg JV, Struhl K. Chromatin immunoprecipitation for determining the association of proteins with specific genomic sequences in vivo. ACTA ACUST UNITED AC 2008; Chapter 17:Unit 17.7. [PMID: 18228445 DOI: 10.1002/0471143030.cb1707s23] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Chromatin immunoprecipitation (ChIP) is a powerful and widely applied technique for detecting the association of individual proteins with specific genomic regions in vivo. Live cells are treated with formaldehyde to generate protein-protein and protein- DNA cross-links between molecules in close proximity on the chromatin template in vivo. DNA sequences that cross-link with a given protein are selectively enriched and reversal of the formaldehyde cross-link permits recovery and quantitative analysis of the immunoprecipitated DNA. As formaldehyde inactivates cellular enzymes essentially immediately upon addition to cells, ChIP provides snapshots of protein-protein and protein- DNA interactions at a particular time point, and hence is useful for kinetic analysis of events occurring on chromosomal sequences in vivo. In addition, ChIP can be combined with microarray technology to identify the location of specific proteins on a genome-wide basis. This unit describes the ChIP protocol for Saccharomyces cerevisiae; however, it is also applicable to other organisms.
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Affiliation(s)
- Oscar Aparicio
- University of Southern California, Los Angeles, California, USA
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41
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Aparicio O, Geisberg JV, Sekinger E, Yang A, Moqtaderi Z, Struhl K. Chromatin immunoprecipitation for determining the association of proteins with specific genomic sequences in vivo. ACTA ACUST UNITED AC 2008; Chapter 21:Unit 21.3. [PMID: 18265358 DOI: 10.1002/0471142727.mb2103s69] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Chromatin immunoprecipitation (ChIP) is a powerful and widely applied technique for detecting the association of individual proteins with specific genomic regions in vivo. Live cells are treated with formaldehyde to generate protein-protein and protein-DNA cross-links between molecules that are in close proximity on the chromatin template in vivo. DNA sequences that cross-link with a given protein are selectively enriched, and reversal of the formaldehyde cross-linking permits recovery and quantitative analysis of the immunoprecipitated DNA. As formaldehyde inactivates cellular enzymes essentially immediately upon addition to cells, ChIP provides snapshots of protein-protein and protein-DNA interactions at a particular time point, and hence is useful for kinetic analysis of events occurring on chromosomal sequences in vivo. In addition, ChIP can be combined with microarray technology to identify the location of specific proteins on a genome-wide basis. in this unit describes the ChIP procedure for Saccharomyces cerevisiae; describes the corresponding steps for mammalian cells.
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Affiliation(s)
- Oscar Aparicio
- University of Southern California, Los Angeles, California, USA
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42
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Wade JT, Struhl K. The transition from transcriptional initiation to elongation. Curr Opin Genet Dev 2008; 18:130-6. [PMID: 18282700 DOI: 10.1016/j.gde.2007.12.008] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 12/20/2007] [Indexed: 11/26/2022]
Abstract
Transcription is the first step in gene expression, and its regulation underlies multicellular development and the response to environmental changes. Most studies of transcriptional regulation have focused on the recruitment of RNA polymerase to promoters. However, recent work has shown that, for many promoters, post-recruitment steps in transcriptional initiation are likely to be rate limiting. The rate at which RNA polymerase transitions from transcriptional initiation to elongation varies dramatically between promoters and between organisms and is the target of multiple regulatory proteins that can function to both repress and activate transcription.
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Affiliation(s)
- Joseph T Wade
- Wadsworth Center, New York State Department of Health, Albany, NY 12208, United States.
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43
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Kasahara K, Ki S, Aoyama K, Takahashi H, Kokubo T. Saccharomyces cerevisiae HMO1 interacts with TFIID and participates in start site selection by RNA polymerase II. Nucleic Acids Res 2008; 36:1343-57. [PMID: 18187511 PMCID: PMC2275077 DOI: 10.1093/nar/gkm1068] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Saccharomyces cerevisiae HMO1, a high mobility group B (HMGB) protein, associates with the rRNA locus and with the promoters of many ribosomal protein genes (RPGs). Here, the Sos recruitment system was used to show that HMO1 interacts with TBP and the N-terminal domain (TAND) of TAF1, which are integral components of TFIID. Biochemical studies revealed that HMO1 copurifies with TFIID and directly interacts with TBP but not with TAND. Deletion of HMO1 (Δhmo1) causes a severe cold-sensitive growth defect and decreases transcription of some TAND-dependent genes. Δhmo1 also affects TFIID occupancy at some RPG promoters in a promoter-specific manner. Interestingly, over-expression of HMO1 delays colony formation of taf1 mutants lacking TAND (taf1ΔTAND), but not of the wild-type strain, indicating a functional link between HMO1 and TAND. Furthermore, Δhmo1 exhibits synthetic growth defects in some spt15 (TBP) and toa1 (TFIIA) mutants while it rescues growth defects of some sua7 (TFIIB) mutants. Importantly, Δhmo1 causes an upstream shift in transcriptional start sites of RPS5, RPS16A, RPL23B, RPL27B and RPL32, but not of RPS31, RPL10, TEF2 and ADH1, indicating that HMO1 may participate in start site selection of a subset of class II genes presumably via its interaction with TFIID.
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Affiliation(s)
- Koji Kasahara
- Division of Molecular and Cellular Biology, International Graduate School of Arts and Sciences, Yokohama City University, Yokohama, 230-0045, Japan
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44
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He Q, Battistella L, Morse RH. Mediator requirement downstream of chromatin remodeling during transcriptional activation of CHA1 in yeast. J Biol Chem 2007; 283:5276-86. [PMID: 18093974 DOI: 10.1074/jbc.m708266200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mediator complex is essential for transcription by RNA polymerase II in eukaryotes. Although chromatin remodeling is an integral part of transcriptional activation at many promoters, whether Mediator is required for this function has not been determined. Here we have used the yeast CHA1 gene to study the role of Mediator in chromatin remodeling and recruitment of the transcription machinery. We show by chromatin immunoprecipitation that Mediator subunits are recruited to the induced CHA1 promoter. Inactivation of Mediator at 37 degrees C in yeast harboring the srb4-138 (med17) ts mutation severely reduces CHA1 activation and prevents recruitment to the induced CHA1 promoter of Med18/Srb5, from the head module of Mediator, and Med14/Rgr1, which bridges the middle and tail modules. In contrast, recruitment of Med15/Gal11 from the tail module is unaffected in med17 ts yeast at 37 degrees C. Recruitment of TATA-binding protein (TBP) is severely compromised in the absence of functional Mediator, whereas Kin28 and polymerase II recruitment are reduced but to a lesser extent. Induced levels of histone H3K4me3 at the CHA1 promoter are not diminished by inactivation of Mediator, whereas recruitment of Paf1 and of Ser2- and Ser5-phosphorylated forms of Rbp1 are reduced but not eliminated. Loss of histone H3 from the induced CHA1 promoter is seen in wild type yeast but is greatly reduced by loss of intact Mediator. In contrast, Swi/Snf recruitment and nucleosome remodeling are unaffected by loss of Mediator function. Thus, Mediator is required for recruitment of the transcription machinery subsequent to chromatin remodeling during CHA1 induction.
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Affiliation(s)
- Qiye He
- Department of Biomedical Sciences, State University of New York at Albany School of Public Health, Albany, New York 12201-2002, USA
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45
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Abstract
Eukaryotes transcribe much of their genomes, but little is known about the fidelity of transcriptional initiation by RNA polymerase II in vivo. I suggest that 90% of Pol II initiation events in yeast represent transcriptional noise, and that the specificity of initiation is comparable to that of DNA-binding proteins and other biological processes. This emphasizes the need to develop criteria that distinguish transcriptional noise from transcription with a biological function.
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Affiliation(s)
- Kevin Struhl
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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46
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Kilgore JA, Hoose SA, Gustafson TL, Porter W, Kladde MP. Single-molecule and population probing of chromatin structure using DNA methyltransferases. Methods 2007; 41:320-32. [PMID: 17309843 PMCID: PMC2923433 DOI: 10.1016/j.ymeth.2006.08.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Accepted: 08/15/2006] [Indexed: 11/20/2022] Open
Abstract
Probing chromatin structure with DNA methyltransferases offers advantages over more commonly used nuclease-based and chromatin immunoprecipitation methods for detection of nucleosomes and non-histone protein-DNA interactions. Here, we describe two related methods in which the readout of MTase accessibility is obtained by assaying 5-methylcytosine in DNA through the PCR-based technique of bisulfite genomic sequencing. The methyltransferase accessibility protocol (MAP) determines the relative frequency at which the enzyme accesses each of its target sites over an entire population of PCR amplified product. While MAP yields much quantitative information about relative accessibility of a region of chromatin, a complementary single-molecule view of methyltransferase accessibility, termed MAP for individual templates (MAP-IT), is provided by analysis of cloned PCR products. Absolute rather than relative methylation frequencies in a region are obtained by summing the methylation status at each site over a cohort of clones. Moreover, as the integrity of individual molecules is maintained in MAP-IT, unique information about the distribution of multiple footprints along continuous regions is gleaned. In principle, the population MAP and single-molecule MAP-IT strategies can be used to analyze chromatin structure in a variety of model systems. Here, we describe the application of MAP in living Saccharomyces cerevisiae cells and MAP-IT in the analysis of a mammalian tumor suppressor gene in nuclei. This application of MAP-IT provides the first means to simultaneously determine CpG methylation of mammalian genes and their overlying chromatin structure in the same single DNA molecule.
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Affiliation(s)
- Jessica A. Kilgore
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA
| | - Scott A. Hoose
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA
| | - Tanya L. Gustafson
- Department of Veterinary Integrative Biosciences, Texas A&M University, 4458 TAMU, College Station, TX 77843-4458, USA
| | - Weston Porter
- Department of Veterinary Integrative Biosciences, Texas A&M University, 4458 TAMU, College Station, TX 77843-4458, USA
| | - Michael P. Kladde
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA
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47
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Uffenbeck SR, Krebs JE. The role of chromatin structure in regulating stress-induced transcription in Saccharomyces cerevisiae. Biochem Cell Biol 2007; 84:477-89. [PMID: 16936821 DOI: 10.1139/o06-079] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
All cells, whether free-living or part of a multicellular organism, must contend with a variety of environmental fluctuations that can be harmful or lethal to the cell. Cells exposed to different kinds of environmental stress rapidly alter gene transcription, resulting in the immediate downregulation of housekeeping genes, while crucial stress-responsive transcription is drastically increased. Common cis-acting elements within many stress-induced promoters, such as stress response elements and heat shock elements, allow for coordinated expression in response to many different stresses. However, specific promoter architectures, i.e., specific combinations of high- and low-affinity stress-responsive cis elements embedded in a particular chromatin environment, allow for unique expression patterns that are responsive to the individual type and degree of stress. The coordination of transcriptional stress responses and the role that chromatin structure plays in the regulation and kinetics of such responses is discussed. The interplay among global and gene-specific stress responses is illustrated using the constitutive and stress-induced transcriptional regulation of HSP82 as a model. This review also investigates evidence suggesting that stress-induced transcription is globally synchronized with the stress-induced repression of housekeeping gene via 2 distinct mechanisms of facilitating the binding of TATA-binding protein (TBP): TFIID and SAGA-mediated TBP binding.
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Affiliation(s)
- Shannon R Uffenbeck
- Department of Biological Sciences, University of AK Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA
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Reppas NB, Wade JT, Church GM, Struhl K. The transition between transcriptional initiation and elongation in E. coli is highly variable and often rate limiting. Mol Cell 2007; 24:747-757. [PMID: 17157257 DOI: 10.1016/j.molcel.2006.10.030] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 10/10/2006] [Accepted: 10/24/2006] [Indexed: 10/23/2022]
Abstract
We perform a genome-wide analysis of the transition between transcriptional initiation and elongation in Escherichia coli by determining the association of core RNA polymerase (RNAP) and the promoter-recognition factor sigma70 with respect to RNA transcripts. We identify 1286 sigma70-associated promoters, including many internal to known operons, and demonstrate that sigma70 is usually released very rapidly from elongating RNAP complexes. On average, RNAP density is higher at the promoter than in the coding sequence, although the ratio is highly variable among different transcribed regions. Strikingly, a significant fraction of RNAP-bound promoters is not associated with transcriptional activity, perhaps due to an intrinsic energetic barrier to promoter escape. Thus, the transition from transcriptional initiation to elongation is highly variable, often rate limiting, and in some cases is essentially blocked such that RNAP is effectively "poised" to transcribe only under the appropriate environmental conditions. The genomic pattern of RNAP density in E. coli differs from that in yeast and mammalian cells.
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Affiliation(s)
- Nikos B Reppas
- Harvard University Biophysics Program, Harvard Medical School, Boston, Massachusetts 02115; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Joseph T Wade
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - George M Church
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Kevin Struhl
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
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Garbett KA, Tripathi MK, Cencki B, Layer JH, Weil PA. Yeast TFIID serves as a coactivator for Rap1p by direct protein-protein interaction. Mol Cell Biol 2007; 27:297-311. [PMID: 17074814 PMCID: PMC1800639 DOI: 10.1128/mcb.01558-06] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2006] [Revised: 09/06/2006] [Accepted: 10/13/2006] [Indexed: 11/20/2022] Open
Abstract
In vivo studies have previously shown that Saccharomyces cerevisiae ribosomal protein (RP) gene expression is controlled by the transcription factor repressor activator protein 1 (Rap1p) in a TFIID-dependent fashion. Here we have tested the hypothesis that yeast TFIID serves as a coactivator for RP gene transcription by directly interacting with Rap1p. We have found that purified recombinant Rap1p specifically interacts with purified TFIID in pull-down assays, and we have mapped the domains of Rap1p and subunits of TFIID responsible. In vitro transcription of a UAS(RAP1) enhancer-driven reporter gene requires both Rap1p and TFIID and is independent of the Fhl1p-Ifh1p coregulator. UAS(RAP1) enhancer-driven transactivation in extracts depleted of both Rap1p and TFIID is efficiently rescued by addition of physiological amounts of these two purified factors but not TATA-binding protein. We conclude that Rap1p and TFIID directly interact and that this interaction contributes importantly to RP gene transcription.
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Affiliation(s)
- Krassimira A Garbett
- Department of Molecular Physiology and Biophysics, Vanderbilt University, School of Medicine, Nashville, TN 37232-0615, USA
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Abstract
In eukaryotes, the core promoter serves as a platform for the assembly of transcription preinitiation complex (PIC) that includes TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH, and RNA polymerase II (pol II), which function collectively to specify the transcription start site. PIC formation usually begins with TFIID binding to the TATA box, initiator, and/or downstream promoter element (DPE) found in most core promoters, followed by the entry of other general transcription factors (GTFs) and pol II through either a sequential assembly or a preassembled pol II holoenzyme pathway. Formation of this promoter-bound complex is sufficient for a basal level of transcription. However, for activator-dependent (or regulated) transcription, general cofactors are often required to transmit regulatory signals between gene-specific activators and the general transcription machinery. Three classes of general cofactors, including TBP-associated factors (TAFs), Mediator, and upstream stimulatory activity (USA)-derived positive cofactors (PC1/PARP-1, PC2, PC3/DNA topoisomerase I, and PC4) and negative cofactor 1 (NC1/HMGB1), normally function independently or in combination to fine-tune the promoter activity in a gene-specific or cell-type-specific manner. In addition, other cofactors, such as TAF1, BTAF1, and negative cofactor 2 (NC2), can also modulate TBP or TFIID binding to the core promoter. In general, these cofactors are capable of repressing basal transcription when activators are absent and stimulating transcription in the presence of activators. Here we review the roles of these cofactors and GTFs, as well as TBP-related factors (TRFs), TAF-containing complexes (TFTC, SAGA, SLIK/SALSA, STAGA, and PRC1) and TAF variants, in pol II-mediated transcription, with emphasis on the events occurring after the chromatin has been remodeled but prior to the formation of the first phosphodiester bond.
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Affiliation(s)
- Mary C Thomas
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4935, USA
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