scholarly journals Connection of core and tail Mediator modules restrains transcription from TFIID-dependent promoters

PLoS Genetics ◽  
2021 ◽  
Vol 17 (8) ◽  
pp. e1009529
Author(s):  
Moustafa M. Saleh ◽  
Célia Jeronimo ◽  
François Robert ◽  
Gabriel E. Zentner
Keyword(s):  
Transcriptional Activity ◽  
Tail Dependence ◽  
Saga Complex ◽  
Full Expression ◽  
Separation Results ◽  
Proper Balance ◽  
Coactivator Complex

The Mediator coactivator complex is divided into four modules: head, middle, tail, and kinase. Deletion of the architectural subunit Med16 separates core Mediator (cMed), comprising the head, middle, and scaffold (Med14), from the tail. However, the direct global effects of tail/cMed disconnection are unclear. We find that rapid depletion of Med16 downregulates genes that require the SAGA complex for full expression, consistent with their reported tail dependence, but also moderately overactivates TFIID-dependent genes in a manner partly dependent on the separated tail, which remains associated with upstream activating sequences. Suppression of TBP dynamics via removal of the Mot1 ATPase partially restores normal transcriptional activity to Med16-depleted cells, suggesting that cMed/tail separation results in an imbalance in the levels of PIC formation at SAGA-requiring and TFIID-dependent genes. We propose that the preferential regulation of SAGA-requiring genes by tailed Mediator helps maintain a proper balance of transcription between these genes and those more dependent on TFIID.

scholarly journals Connection of core and tail Mediator modules restrains transcription from TFIID-dependent promoters

2021 ◽  
Author(s):  
Moustafa M. Saleh ◽  
Célia Jeronimo ◽  
François Robert ◽  
Gabriel E. Zentner
Keyword(s):  
Transcriptional Activity ◽  
Tail Dependence ◽  
Saga Complex ◽  
Full Expression ◽  
Separation Results ◽  
Proper Balance ◽  
Coactivator Complex

AbstractThe Mediator coactivator complex is divided into four modules: head, middle, tail, and kinase. Deletion of the architectural subunit Med16 separates core Mediator (cMed), comprising the head, middle, and scaffold (Med14), from the tail. However, the direct global effects of tail/cMed disconnection are unclear. We find that rapid depletion of Med16 downregulates genes that require the SAGA complex for full expression, consistent with their reported tail dependence, but also moderately overactivates TFIID-dependent genes in a manner partly dependent on the separated tail, which remains associated with upstream activating sequences. Suppression of TBP dynamics via removal of the Mot1 ATPase partially restores normal transcriptional activity to Med16-depleted cells, suggesting that cMed/tail separation results in an imbalance in the levels of PIC formation at SAGA-requiring and TFIID-dependent genes. We suggest that the preferential regulation of SAGA-requiring genes by tailed Mediator helps maintain a proper balance of transcription between these genes and those more dependent on TFIID.

scholarly journals NRC-Interacting Factor 1 Is a Novel Cotransducer That Interacts with and Regulates the Activity of the Nuclear Hormone Receptor Coactivator NRC

2002 ◽  
Vol 22 (19) ◽  
pp. 6883-6894 ◽  
Author(s):  
Muktar A. Mahajan ◽  
Audrey Murray ◽  
Herbert H. Samuels
Keyword(s):  
Amino Acid ◽  
Transcriptional Activation ◽  
Transcriptional Activity ◽  
Hormone Receptors ◽  
Nuclear Protein ◽  
Zinc Fingers ◽  
Nuclear Hormone Receptor ◽  
Coactivator Complex

ABSTRACT We previously reported the cloning and characterization of a novel nuclear hormone receptor transcriptional coactivator, which we refer to as NRC. NRC is a 2,063-amino-acid nuclear protein which contains a potent N-terminal activation domain and several C-terminal modules which interact with CBP and ligand-bound nuclear hormone receptors as well as c-Fos and c-Jun. In this study we sought to clone and identify novel factors that interact with NRC to modulate its transcriptional activity. Here we describe the cloning and characterization of a novel protein we refer to as NIF-1 (NRC-interacting factor 1). NIF-1 was cloned from rat pituitary and human cell lines and was found to interact in vivo and in vitro with NRC. NIF-1 is a 1,342-amino-acid nuclear protein containing a number of conserved domains, including six Cys-2/His-2 zinc fingers, an N-terminal stretch of acidic amino acids, and a C-terminal leucine zipper-like motif. Zinc fingers 1 to 3 are potential DNA-binding BED finger domains recently proposed to play a role in altering local chromatin architecture. We mapped the interaction domains of NRC and NIF-1. Although NIF-1 does not directly interact with nuclear receptors, it markedly enhances ligand-dependent transcriptional activation by nuclear hormone receptors in vivo as well as activation by c-Fos and c-Jun. These results, and the finding that NIF-1 interacts with NRC in vivo, suggest that NIF-1 functions to regulate transcriptional activation through NRC. We suggest that NIF-1, and factors which associate with coactivators but not receptors, be referred to as cotransducers, which act in vivo either as part of a coactivator complex or downstream of a coactivator complex to modulate transcriptional activity. Our findings suggest that NIF-1 may be a functional component of an NRC complex and acts as a regulator or cotransducer of NRC function.

scholarly journals Structure of the human SAGA coactivator complex

2021 ◽  
Author(s):  
Dominik A. Herbst ◽  
Meagan N. Esbin ◽  
Robert K. Louder ◽  
Claire Dugast-Darzacq ◽  
Gina M. Dailey ◽  
...  
Keyword(s):  
Chromatin Modification ◽  
Structural Elements ◽  
Saga Complex ◽  
Functional Elements ◽  
The Core ◽  
Damage Repair ◽  
Disease Mutations ◽  
Core Module ◽  
Important Therapeutic Target ◽  
Coactivator Complex

AbstractThe SAGA complex is a regulatory hub involved in gene regulation, chromatin modification, DNA damage repair and signaling. While structures of yeast SAGA (ySAGA) have been reported, there are noteworthy functional and compositional differences for this complex in metazoans. Here we present the cryogenic-electron microscopy (cryo-EM) structure of human SAGA (hSAGA) and show how the arrangement of distinct structural elements results in a globally divergent organization from that of yeast, with a different interface tethering the core module to the TRRAP subunit, resulting in a dramatically altered geometry of functional elements and with the integration of a metazoan-specific splicing module. Our hSAGA structure reveals the presence of an inositol hexakisphosphate (InsP6) binding site in TRRAP and an unusual property of its pseudo-(Ψ)PIKK. Finally, we map human disease mutations, thus providing the needed framework for structure-guided drug design of this important therapeutic target for human developmental diseases and cancer.

scholarly journals Role of Metazoan Mediator Proteins in Interferon-Responsive Transcription

2003 ◽  
Vol 23 (2) ◽  
pp. 620-628 ◽  
Author(s):  
Joe F. Lau ◽  
Inna Nusinzon ◽  
Darya Burakov ◽  
Leonard P. Freedman ◽  
Curt M. Horvath
Keyword(s):  
Transcriptional Activation ◽  
Transcriptional Activity ◽  
Activation Function ◽  
Dominant Negative ◽  
Gene Promoters ◽  
A Subunit ◽  
Induced Signal ◽  
Necessary And Sufficient ◽  
Coactivator Complex

ABSTRACT The interferon (IFN)-induced signal transduction and transcription activation complex, ISGF3, is assembled from three proteins, STAT1, STAT2, and IRF9. Of these components, STAT2 provides a fundamental and essential transcriptional activation function for ISGF3. In the present study, we show that ISGF3-mediated transcription is dependent on STAT2 interactions with DRIP150, a subunit of the multimeric Mediator coactivator complex. Other Mediator subunits, DRIP77 and DRIP130, were found either to bind STAT2 without augmenting ISGF3 transcriptional activity or to enhance ISGF3 transcription without binding STAT2, but only DRIP150 both enhanced IFN-dependent transcription and coimmunoprecipitated with STAT2. Endogenous DRIP150 and STAT2 were able to interact in solution, and DNA affinity chromatography and chromatin immunoprecipitation assays demonstrated that DRIP150 binds to the mature, activated ISGF3-DNA complex and is recruited to target gene promoters in an IFN-dependent fashion. IFN-dependent recruitment of DRIP130 to an ISGF3 target promoter and SRB10-STAT2 coprecipitation suggest indirect association with a multisubunit Mediator complex. The site of STAT2 interaction was mapped to DRIP150 residues 188 to 566, which are necessary and sufficient for interaction with STAT2. Expression of this DRIP150 fragment, but not DRIP150 fragments outside the STAT2 interaction region, suppressed ISGF3-mediated transcriptional activity in a dominant-negative fashion, suggesting a direct functional role of this domain in mediating STAT2-DRIP150 interactions. These findings indicate that the IFN-activated ISGF3 transcription factor regulates transcription through contact with DRIP150 and implicate the Mediator coactivator complex in IFN-activated gene regulation.

scholarly journals The SAGA core module is critical during Drosophila oogenesis and is broadly recruited to promoters

2021 ◽  
Author(s):  
Jelly HM Soffers ◽  
Sergio Garcia-Moreno Alcantara ◽  
Xuanying Li ◽  
Wanqing Shao ◽  
Chrisopher Seidel ◽  
...  
Keyword(s):  
Gene Activation ◽  
Start Site ◽  
Saga Complex ◽  
Drosophila Oogenesis ◽  
The Core ◽  
Core Module ◽  
Entire Complex ◽  
Active Genes ◽  
Coactivator Complex

The Spt/Ada-Gcn5 Acetyltransferase (SAGA) coactivator complex has multiple modules with different enzymatic and non-enzymatic functions. How each module contributes to gene activation in specific biological contexts is not well understood. Here we analyzed the role of the non-enzymatic core module during Drosophila oogenesis. We show that depletion of several SAGA-specific subunits belonging to the core module blocked egg chamber development during mid-oogenesis stages, resulting in stronger phenotypes than those obtained after depletion of SAGA’s histone acetyltransferase module or deubiquitination module. These results, as well as additional genetic analyses pointing to an interaction with TBP, suggested a differential role of SAGA modules at different promoter types. However, SAGA subunits co-occupied all promoter types of active genes in ChIP-seq and ChIP-nexus experiments. Thus, the SAGA complex appears to occupy promoters in its entirety, consistent with the strong biochemical integrity of the complex. The high-resolution genomic binding profiles are congruent with SAGA recruitment by activators upstream of the start site, and retention on chromatin by interactions with modified histones downstream of the start site. The stronger genetic requirement of the core module during oogenesis may therefore be explained through its interaction with TBP or its role in recruiting the enzymatic modules to the promoter. We propose the handyman principle, which posits that a distinct genetic requirement for specific components may conceal the fact that the entire complex is physically present.

scholarly journals Analysis of Spt7 Function in the Saccharomyces cerevisiae SAGA Coactivator Complex

2002 ◽  
Vol 22 (15) ◽  
pp. 5367-5379 ◽  
Author(s):  
Pei-Yun Jenny Wu ◽  
Fred Winston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
The Other ◽  
Deletion Mutants ◽  
Saga Complex ◽  
Number Of Genes ◽  
Processed Form ◽  
Altered Form ◽  
And Function ◽  
Coactivator Complex

ABSTRACT The Saccharomyces cerevisiae SAGA complex is required for the normal transcription of a large number of genes. Complex integrity depends on three core subunits, Spt7, Spt20, and Ada1. We have investigated the role of Spt7 in the assembly and function of SAGA. Our results show that Spt7 is important in controlling the levels of the other core subunits and therefore of SAGA. In addition, partial SAGA complexes containing Spt7 can be assembled in the absence of both Spt20 and Ada1. Through biochemical and genetic analyses of a series of spt7 deletion mutants, we have identified a region of Spt7 required for interaction with the SAGA component Spt8. An adjacent Spt7 domain was found to be required for a processed form of Spt7 that is present in a previously identified altered form of SAGA called SLIK, SAGAalt, or SALSA. Analysis of an spt7 mutant with greatly reduced levels of SLIK/SAGAalt/SALSA suggests a subtle role for this complex in transcription that may be redundant with a subset of SAGA functions.

The Anti-Atherogenic Properties of Sesamin are Mediated via Improved Macrophage Cholesterol Efflux Through PPARγ1-LXRα and MAPK Signaling

2014 ◽  
Vol 84 (1-2) ◽  
pp. 79-91 ◽  
Author(s):  
Amin F. Majdalawieh ◽  
Hyo-Sung Ro
Keyword(s):  
Cholesterol Efflux ◽  
Transcriptional Activity ◽  
Molecular Mechanisms ◽  
Foam Cell ◽  
Mapk Signaling ◽  
Luciferase Reporter ◽  
Foam Cell Formation ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Macrophage Cholesterol Efflux

Background: Foam cell formation resulting from disrupted macrophage cholesterol efflux, which is triggered by PPARγ1 and LXRα, is a hallmark of atherosclerosis. Sesamin and sesame oil exert anti-atherogenic effects in vivo. However, the exact molecular mechanisms underlying such effects are not fully understood. Aim: This study examines the potential effects of sesamin (0, 25, 50, 75, 100 μM) on PPARγ1 and LXRα expression and transcriptional activity as well as macrophage cholesterol efflux. Methods: PPARγ1 and LXRα expression and transcriptional activity are assessed by luciferase reporter assays. Macrophage cholesterol efflux is evaluated by ApoAI-specific cholesterol efflux assays. Results: The 50 μM, 75 μM, and 100 μM concentrations of sesamin up-regulated the expression of PPARγ1 (p< 0.001, p < 0.001, p < 0.001, respectively) and LXRα (p = 0.002, p < 0.001, p < 0.001, respectively) in a concentration-dependent manner. Moreover, 75 μM and 100 μM concentrations of sesamin led to 5.2-fold (p < 0.001) and 6.0-fold (p<0.001) increases in PPAR transcriptional activity and 3.9-fold (p< 0.001) and 4.2-fold (p < 0.001) increases in LXR transcriptional activity, respectively, in a concentration- and time-dependent manner via MAPK signaling. Consistently, 50 μM, 75 μM, and 100 μM concentrations of sesamin improved macrophage cholesterol efflux by 2.7-fold (p < 0.001), 4.2-fold (p < 0.001), and 4.2-fold (p < 0.001), respectively, via MAPK signaling. Conclusion: Our findings shed light on the molecular mechanism(s) underlying sesamin’s anti-atherogenic effects, which seem to be due, at least in part, to its ability to up-regulate PPARγ1 and LXRα expression and transcriptional activity, improving macrophage cholesterol efflux. We anticipate that sesamin may be used as a therapeutic agent for treating atherosclerosis.

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