scholarly journals Kin28 depletion increases association of TFIID subunits Taf1 and Taf4 with promoters in Saccharomyces cerevisiae

2019 ◽  
Author(s):  
Elisabeth R. Knoll ◽  
Z. Iris Zhu ◽  
Debasish Sarkar ◽  
David Landsman ◽  
Randall H. Morse
Keyword(s):  
Transcription Factors ◽  
Rna Polymerase Ii ◽  
Mediator Complex ◽  
Gene Promoters ◽  
Initiation Complex ◽  
Pol Ii ◽  
Promoter Escape ◽  
General Transcription Factors ◽  
Promoter Occupancy ◽  
Encoding Genes

AbstractIn eukaryotes, transcription of mRNA-encoding genes by RNA polymerase II (Pol II) begins with assembly of the pre-initiation complex (PIC), comprising Pol II and the general transcription factors. Although the pathway of PIC assembly is well established, the mechanism of assembly and the dynamics of PIC components are not fully understood. For example, only recently has it been shown in yeast that the Mediator complex, which assists in pre-initiation complex formation at promoters of essentially all genes transcribed by Pol II, normally occupies promoters only transiently. This was inferred from studies showing that inhibiting Pol II promoter escape by depleting or inactivating Kin28 resulted in increased promoter occupancy by Mediator, as measured by chromatin immunoprecipitation (ChIP). Here we show that two subunits of TFIID, Taf1 and Taf4, similarly show increased occupancy as measured by ChIP upon depletion or inactivation of Kin28. In contrast, TBP occupancy is unaffected by depletion of Kin28, thus revealing an uncoupling of Taf and TBP occupancy during the transcription cycle. Increased Taf1 occupancy upon Kin28 depletion is suppressed by depletion of TBP, while depletion of TBP in the presence of Kin28 has little effect on Taf1 occupancy. Taf1 occupancy relative to TBP is higher at TFIID-dominated promoters and promoters having consensus TATA elements than at SAGA-dominated promoters and promoters lacking consensus TATA elements, consistent with prior work, and the increase in Taf occupancy upon depletion of Kin28 is more pronounced at TFIID-dominated promoters. Our results support the suggestion, based on recent structural studies, that TFIID may not remain bound to gene promoters through the transcription initiation cycle.Author SummaryTranscription of mRNA-encoding genes by RNA polymerase II (Pol II) begins when the pre-initiation complex, a large complex comprising Pol II and several general transcription factors, including the TATA-binding protein (TBP)-containing TFIID complex, assembles at gene promoters. Although the major steps in the pathway of PIC assembly have been identified, the mechanism of assembly in vivo and the dynamics of PIC components are not fully understood. In this work we have used a yeast strain that is engineered to allow inhibition of promoter escape by Pol II by administration of a chemical, in order to “freeze” the assembled PIC and thus determine whether this condition increases the promoter occupancy of TBP and two TBP-associated factors (Tafs) that are components of TFIID. This approach was used recently to demonstrate that the Mediator complex, which facilitates PIC assembly, normally binds only transiently to gene promoters. We find that Tafs, like Mediator, show increased occupancy when Pol II promoter escape is inhibited, whereas TBP binding is constant. These results imply that binding of TBP and Tafs is uncoupled during the transcription cycle, and that Taf occupancy is at least partially interrupted upon Pol II promoter escape.

scholarly journals Kin28 depletion increases association of TFIID subunits Taf1 and Taf4 with promoters in Saccharomyces cerevisiae

2020 ◽  
Vol 48 (8) ◽  
pp. 4244-4255 ◽  
Author(s):  
Elisabeth R Knoll ◽  
Z Iris Zhu ◽  
Debasish Sarkar ◽  
David Landsman ◽  
Randall H Morse
Keyword(s):  
Rna Polymerase Ii ◽  
Transcription Initiation ◽  
Mediator Complex ◽  
Gene Promoters ◽  
Structural Studies ◽  
Initiation Complex ◽  
Pol Ii ◽  
Promoter Escape ◽  
General Transcription Factors ◽  
Encoding Genes

Abstract Transcription of eukaryotic mRNA-encoding genes by RNA polymerase II (Pol II) begins with assembly of the pre-initiation complex (PIC), comprising Pol II and the general transcription factors. Although the pathway of PIC assembly is well established, the mechanism of assembly and the dynamics of PIC components are not fully understood. For example, only recently has it been shown that in yeast, the Mediator complex normally occupies promoters only transiently, but shows increased association when Pol II promoter escape is inhibited. Here we show that two subunits of TFIID, Taf1 and Taf4, similarly show increased occupancy as measured by ChIP upon depletion or inactivation of Kin28. In contrast, TBP occupancy is unaffected by depletion of Kin28, thus revealing an uncoupling of Taf and TBP occupancy during the transcription cycle. Increased Taf1 occupancy upon Kin28 depletion is suppressed by depletion of TBP, while depletion of TBP in the presence of Kin28 has little effect on Taf1 occupancy. The increase in Taf occupancy upon depletion of Kin28 is more pronounced at TFIID-dominated promoters compared to SAGA-dominated promoters. Our results support the suggestion, based on recent structural studies, that TFIID may not remain bound to gene promoters through the transcription initiation cycle.

scholarly journals Role of the pre-initiation complex in Mediator recruitment and dynamics

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Elisabeth R Knoll ◽  
Z Iris Zhu ◽  
Debasish Sarkar ◽  
David Landsman ◽  
Randall H Morse
Keyword(s):  
Rna Polymerase Ii ◽  
Gene Activation ◽  
Mediator Complex ◽  
Gene Promoters ◽  
Initiation Complex ◽  
Yeast Saccharomyces Cerevisiae ◽  
Pol Ii ◽  
Genome Wide ◽  
Cooperative Assembly

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.

scholarly journals Role of the pre-initiation complex in Mediator recruitment and dynamics

2017 ◽  
Author(s):  
Elisabeth R. Knoll ◽  
Z. Iris Zhu ◽  
David Landsman ◽  
Randall H. Morse
Keyword(s):  
Rna Polymerase Ii ◽  
Gene Activation ◽  
Mediator Complex ◽  
Gene Promoters ◽  
Initiation Complex ◽  
Eukaryotic Transcription ◽  
Pol Ii ◽  
Genome Wide ◽  
Complex Functions

AbstractThe Mediator complex functions in eukaryotic transcription by stimulating 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 med2Δ med3Δ med15Δ yeast are viable and that Mediator lacking Med2-Med3-Med15 is associated with active promoters genome-wide. 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.

scholarly journals Structure of human Mediator-RNA polymerase II transcription pre-initiation complex

2021 ◽  
Author(s):  
Srinivasan Rengachari ◽  
Sandra Schilbach ◽  
Shintaro Aibara ◽  
Christian Dienemann ◽  
Patrick Cramer
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcription Initiation ◽  
Complex Structure ◽  
Proximal Part ◽  
Initiation Complex ◽  
Protein Coding ◽  
Pol Ii ◽  
Promoter Escape ◽  
General Transcription Factors

Mediator is a conserved coactivator that enables regulated transcription initiation from eukaryotic protein-coding genes1-3. Mediator is recruited by transcriptional activators and binds the pre-initiation complex (PIC) to stimulate RNA polymerase II (Pol II) phosphorylation and promoter escape1-6. Here we prepare a 20-subunit recombinant human Mediator, reconstitute a 50-subunit Mediator-PIC complex, and resolve the complex structure by cryo-EM at an overall resolution of 4.5 Å. Mediator binds with its head module to the Pol II stalk and the general transcription factors TFIIB and TFIIE, resembling the Mediator-PIC interactions in the corresponding yeast complex7-9. One end of Mediator contains the metazoan-specific subunits MED27-MED30, which associate with exposed regions in MED14 and MED17 to form the proximal part of the tail module that binds activators. The opposite end of Mediator positions the flexibly linked CDK-activating kinase (CAK) of the general transcription factor TFIIH near the C-terminal repeat domain (CTD) of Pol II. The Mediator shoulder domain holds the CAK subunit CDK7, whereas the hook domain contacts a CDK7 element that flanks the kinase active site. The shoulder and hook reside in the Mediator head and middle modules, respectively, which can move relative to each other and may induce an active conformation of CDK7 to allosterically stimulate CTD phosphorylation and Pol II escape from the promoter.

Interaction of the TFIIB zinc ribbon with RNA polymerase II

2008 ◽  
Vol 36 (4) ◽  
pp. 595-598 ◽  
Author(s):  
Laura M. Elsby ◽  
Stefan G.E. Roberts
Keyword(s):  
Transcription Factor ◽  
Transcription Factors ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Structural Models ◽  
Initiation Complex ◽  
General Transcription Factors ◽  
Transcription Factor Iib ◽  
General Transcription Factor ◽  
Zinc Ribbon

Transcription by RNA polymerase II requires the assembly of the general transcription factors at the promoter to form a pre-initiation complex. The general transcription factor TF (transcription factor) IIB plays a central role in the assembly of the pre-initiation complex, providing a bridge between promoter-bound TFIID and RNA polymerase II/TFIIF. We have characterized a series of TFIIB mutants in their ability to support transcription and recruit RNA polymerase II to the promoter. Our analyses identify several residues within the TFIIB zinc ribbon that are required for RNA polymerase II assembly. Using the structural models of TFIIB, we describe the interface between the TFIIB zinc ribbon region and RNA polymerase II.

scholarly journals The General Transcription Factors IIA, IIB, IIF, and IIE Are Required for RNA Polymerase II Transcription from the Human U1 Small Nuclear RNA Promoter

1999 ◽  
Vol 19 (3) ◽  
pp. 2130-2141 ◽  
Author(s):  
T. C. Kuhlman ◽  
H. Cho ◽  
D. Reinberg ◽  
N. Hernandez
Keyword(s):  
Transcription Factors ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcription Initiation ◽  
Small Nuclear Rna ◽  
Initiation Complex ◽  
General Transcription Factors ◽  
Nuclear Rna ◽  
Transcription Initiation Complex ◽  
Rna Polymerase Ii Transcription

ABSTRACT RNA polymerase II transcribes the mRNA-encoding genes and the majority of the small nuclear RNA (snRNA) genes. The formation of a minimal functional transcription initiation complex on a TATA-box-containing mRNA promoter has been well characterized and involves the ordered assembly of a number of general transcription factors (GTFs), all of which have been either cloned or purified to near homogeneity. In the human RNA polymerase II snRNA promoters, a single element, the proximal sequence element (PSE), is sufficient to direct basal levels of transcription in vitro. The PSE is recognized by the basal transcription complex SNAPc. SNAPc, which is not required for transcription from mRNA-type RNA polymerase II promoters such as the adenovirus type 2 major late (Ad2ML) promoter, is thought to recruit TATA binding protein (TBP) and nucleate the assembly of the snRNA transcription initiation complex, but little is known about which GTFs other than TBP are required. Here we show that the GTFs IIA, IIB, IIF, and IIE are required for efficient RNA polymerase II transcription from snRNA promoters. Thus, although the factors that recognize the core elements of RNA polymerase II mRNA and snRNA-type promoters differ, they mediate the recruitment of many common GTFs.

scholarly journals Structure of the human Mediator-bound transcription preinitiation complex

Science ◽  
2021 ◽  
pp. eabg3074
Author(s):  
R. Abdella ◽  
A. Talyzina ◽  
S. Chen ◽  
C. J. Inouye ◽  
R. Tjian ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Rna Polymerase Ii ◽  
Active Site ◽  
Binding Sites ◽  
Preinitiation Complex ◽  
Eukaryotic Transcription ◽  
Pol Ii ◽  
General Transcription Factors ◽  
Cryo Electron Microscopy ◽  
Multiple Contacts

Eukaryotic transcription requires the assembly of a multi-subunit preinitiation complex (PIC) comprised of RNA polymerase II (Pol II) and the general transcription factors. The co-activator Mediator is recruited by transcription factors, facilitates the assembly of the PIC, and stimulates phosphorylation of the Pol II C-terminal domain (CTD) by the TFIIH subunit CDK7. Here, we present the cryo-electron microscopy structure of the human Mediator-bound PIC at sub-4 Å. Transcription factor binding sites within Mediator are primarily flexibly tethered to the tail module. CDK7 is stabilized by multiple contacts with Mediator. Two binding sites exist for the Pol II CTD, one between the head and middle modules of Mediator and the other in the active site of CDK7, providing structural evidence for Pol II CTD phosphorylation within the Mediator-bound PIC.

scholarly journals Molecular Genetics of the RNA Polymerase II General Transcriptional Machinery

1998 ◽  
Vol 62 (2) ◽  
pp. 465-503 ◽  
Author(s):  
Michael Hampsey
Keyword(s):  
Transcription Factors ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Regulatory Elements ◽  
Transcriptional Repressors ◽  
Rna Pol Ii ◽  
Pol Ii ◽  
The Core ◽  
General Transcription Factors ◽  
Transcriptional Machinery

SUMMARY Transcription initiation by RNA polymerase II (RNA pol II) requires interaction between cis-acting promoter elements and trans-acting factors. The eukaryotic promoter consists of core elements, which include the TATA box and other DNA sequences that define transcription start sites, and regulatory elements, which either enhance or repress transcription in a gene-specific manner. The core promoter is the site for assembly of the transcription preinitiation complex, which includes RNA pol II and the general transcription fctors TBP, TFIIB, TFIIE, TFIIF, and TFIIH. Regulatory elements bind gene-specific factors, which affect the rate of transcription by interacting, either directly or indirectly, with components of the general transcriptional machinery. A third class of transcription factors, termed coactivators, is not required for basal transcription in vitro but often mediates activation by a broad spectrum of activators. Accordingly, coactivators are neither gene-specific nor general transcription factors, although gene-specific coactivators have been described in metazoan systems. Transcriptional repressors include both gene-specific and general factors. Similar to coactivators, general transcriptional repressors affect the expression of a broad spectrum of genes yet do not repress all genes. General repressors either act through the core transcriptional machinery or are histone related and presumably affect chromatin function. This review focuses on the global effectors of RNA polymerase II transcription in yeast, including the general transcription factors, the coactivators, and the general repressors. Emphasis is placed on the role that yeast genetics has played in identifying these factors and their associated functions.

scholarly journals Disruption of cardiac Med1 inhibits RNA polymerase II promoter occupancy and promotes chromatin remodeling

2019 ◽  
Vol 316 (2) ◽  
pp. H314-H325 ◽  
Author(s):  
Duane D. Hall ◽  
Kathryn M. Spitler ◽  
Chad E. Grueter
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Chromatin Immunoprecipitation ◽  
Chromatin Accessibility ◽  
Gene Promoters ◽  
Specific Expression ◽  
Pol Ii ◽  
Transcriptional Start Sites

The Mediator coactivator complex directs gene-specific expression by binding distal enhancer-bound transcription factors through its Med1 subunit while bridging to RNA polymerase II (Pol II) at gene promoters. In addition, Mediator scaffolds epigenetic modifying enzymes that determine local DNA accessibility. Previously, we found that deletion of Med1 in cardiomyocytes deregulates more than 5,000 genes and promotes acute heart failure. Therefore, we hypothesized that Med1 deficiency disrupts enhancer-promoter coupling. Using chromatin immunoprecipitation-coupled deep sequencing (ChIP-seq; n = 3/ChIP assay), we found that the Pol II pausing index is increased in Med1 knockout versus floxed control mouse hearts primarily due to a decrease in Pol II occupancy at the majority of transcriptional start sites without a corresponding increase in elongating species. Parallel ChIP-seq assays reveal that Med1-dependent gene expression correlates strongly with histone H3 K27 acetylation, which is indicative of open and active chromatin at transcriptional start sites, whereas H3 K27 trimethylated levels, representing condensed and repressed DNA, are broadly increased and inversely correlate with absolute expression levels. Furthermore, Med1 deletion leads to dynamic changes in acetyl-K27 associated superenhancer regions and their enriched transcription factor-binding motifs that are consistent with altered gene expression. Our findings suggest that Med1 is important in establishing enhancer-promoter coupling in the heart and supports the proposed role of Mediator in establishing preinitiation complex formation. We also found that Med1 determines chromatin accessibility within genes and enhancer regions and propose that the composition of transcription factors associated with superenhancer changes to direct gene-specific expression. NEW & NOTEWORTHY Based on our previous findings that transcriptional homeostasis and cardiac function are disturbed by cardiomyocyte deletion of the Mediator coactivator Med1 subunit, we investigated potential underlying changes in RNA polymerase II localization and global chromatin accessibility. Using chromatin immunoprecipitation sequencing, we found that disrupted transcription arises from a deficit in RNA polymerase II recruitment to gene promoters. Furthermore, active versus repressive chromatin marks are redistributed within gene loci and at enhancer regions correlated with gene expression changes.

scholarly journals Architectural Mediator subunits are differentially essential for global transcription in yeast

2020 ◽  
Author(s):  
Jason P. Tourigny ◽  
Kenny Schumacher ◽  
Didier Devys ◽  
Gabriel E. Zentner
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Structural Integrity ◽  
Functional Module ◽  
Mediator Complex ◽  
Initiation Complex ◽  
Negative Effect ◽  
Promoter Occupancy ◽  
Rna Polymerase Ii Transcription

SummaryThe modular Mediator complex is a coactivator of RNA polymerase II transcription. We show that depletion of the main complex scaffold Med14 or the head module scaffold Med17 is lethal and results in global transcriptional downregulation in yeast, though Med17 removal has a markedly greater negative effect. Depletion of Med14 or Med17 impairs pre-initiation complex (PIC) assembly similarly, suggesting that the differential transcriptional effects observed are not due to differing extents of defective PIC formation. Co-depletion of Med14 and Med17 reduced transcription and TFIIB promoter occupancy similarly to Med17 ablation alone, suggesting that the independent head module can weakly stimulate transcription in vivo, though not to a level that maintains viability. We suggest that, while the structural integrity of complete Mediator and the head module are both important for PIC assembly, the head module additionally promotes optimal PIC function and is thus the key functional module of Mediator in this regard.

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