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Architectural Mediator subunits are differentially essential for global transcription in yeast (ChIP-seq)

ABSTRACT: Mediator is a modular complex required for RNA polymerase II transcription in vivo. We show that Mediator destabilization via depletion of the main complex scaffold Med14 or the head module scaffold Med17 is lethal and results in global transcriptional downregulation, though Med17 destruction has a markedly greater negative effect. Depletion of Med14 or Med17 impairs pre-initiation complex (PIC) formation and/or stability to similar degrees, suggesting that the differential transcriptional effects of head module destabilization and overall dissociation of the complex are not due to different extents of defective PIC formation. Co-depletion of Med14 and Med17 reduced transcription and TFIIB promoter occupancy to similar degrees as Med17 loss alone, suggesting that the independent head module can weakly stimulate transcription in vivo, though not at a level that maintains viability. Collectively, our data suggest that the head is the major functional module of Mediator with respect to PIC function in vivo.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE145494 | GEO | 2020/03/05

REPOSITORIES: GEO

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Connection of core and and tail Mediator modules restrains transcription from TFIID-dependent promoters [nsRNA-seq]

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2021-07-30 | GSE169747 | GEO

Connection of core and and tail Mediator modules restrains transcription from TFIID-dependent promoters [ChEC-seq]

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Connection of core and tail Mediator modules restrains transcription from TFIID-dependent promoters [ChIP-Seq]

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2021-07-30 | GSE171981 | GEO

Connection of core and and tail Mediator modules restrains transcription from TFIID-dependent promoters [ChEC-seq Med16-AID]

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Project description:Mediator, a transcriptional co-activator complex, is recruited to enhancers by DNA-binding activators via its tail module, and it interacts with RNA polymerase (Pol) II as part of the preinitiation complex (PIC) via its head module. Although Mediator has been described as a general transcription factor, it is unclear if it is essential for Pol II transcription and/or is a required component of the PIC in vivo. We comprehensively analyze this issue by measuring Pol II transcription upon rapid depletion of individual or multiple Mediator subunits from the nucleus. Depletion of individual subunits, even those essential for cell growth, causes a general but only modest decrease in Pol II transcription. Transcriptional effects are stronger on SAGA-dependent genes as opposed to TFIID-dependent genes. Thus, Mediator modules that associate either with the enhancer or with the core promoter confer partial transcriptional activity. Furthermore, Pol II transcription can occur when Mediator is not detected at core promoters. In contrast, simultaneous depletion of all Mediator modules causes a drastic decrease in Pol II transcription that is roughly comparable to the effect observed upon anchor-away-mediated depletion of Pol II or TBP. These results provide strong evidence that Mediator is essential for Pol II transcription in vivo, but that it is not a required component of the PIC.

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Project description: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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Architectural Mediator subunits are differentially essential for global transcription in yeast (RNA-seq/4tU-seq ; Med14-AID, Med17-AID)

Project description:This project aims to understand the function of different mediator subunits (Med14 and Med17) in transcription in S. cerevisiae. Thus we analyzed total and newly synthesized RNA levels in conditional Med14 and Med17 depletion strains. For this purpose we used an auxin inducible degron system system to specifically induce the degradation Mediator subunits by addition of auxin into the culture medium. We measured transcript levels after 30 min auxin or DMSO (control) treatment induction of degradation of Med14 or Med17 by the addition of auxin (30 min) or with the carrier DMSO (control) followed by a 6 min labelling of newly synthesized RNA with 4-thiouracil (4tU). In parallel wiltype S.pombe cells were labelled with 4tU for 6min during midlog growth phase. Prior to RNA extraction (Ribopure Yeast Kit, Ambion) our labelled S.cerevisiae cells of interest were mixed with labelled S.pombe cells as a spike to allow normalization against an exogenous reference (ratio 3 S .cerevisiae for 1 S.pombe cell. From the total RNA we purified the 4tU labelled fraction of RNAs containing 4tU. Both the total RNA and the purified newly synthesized RNAs will then be subject to RNA-sequencing after ribosomal RNA depletion. In summary, we will provide 16 samples for this project containing RNA from both S.cerevisiae and S.pombe. The sample read counts were normalized with size factors computed by the median-of-ratios method proposed by Anders and Huber (Anders et al. 2010) on S. pombe genes to make these counts comparable between samples.

2020-03-04 | GSE146300 | GEO

The Cdk8 kinase module regulates Mediator-RNA polymerase II interaction

Project description:The Cdk8 kinase module (CKM) is a dissociable part of the coactivator complex Mediator that regulates RNA polymerase II (Pol II transcription. The CKM has negative and positive functions in gene transcription that remain poorly understood at the mechanistic level. Here, we prepare recombinant CKM from the yeast Saccharomyces cerevisiae and show that it binds core Mediator (cMed) to sterically inhibit cMed binding to the Pol II preinitiation complex (PIC) in vitro. We further show that the Cdk8 kinase activity of CKM counteracts CKM-cMed interaction,thereby releasing CKM and enabling Mediator to bind the PIC. Finally, we report that the kinase activity of Cdk8 is required for gene activation during heat shock in vivo, but not under steady state growth conditions. These results converge with previous literature on a model for CKM function. In this model, CKM negatively regulates Mediator function at upstream activating sequences by preventing Mediator binding to the PIC at the promoter. During gene activation, Cdk8 kinase activity may release Mediator and allow its binding to the PIC, thereby stimulating transcription initiation and accounting for the positive function of CKM.

2021-06-16 | GSE161140 | GEO

Architectural Mediator subunits are differentially essential for global transcription in yeast (RNA-seq/4tU-seq ; Med14-Med17-doubleAID)

Project description:This project aims to understand the function of Mediator and the interplay in transcription in S. cerevisiae. Thus we analyzed total and newly synthesized RNA levels in a conditional Med14 and Med17 depletion strain. For this purpose we used an auxin inducible degron system system to specifically induce the degradation Med14 and Med17 by addition of auxin into the culture medium. We measured transcript levels after 30 min auxin or DMSO (control) treatment induction of degradation of Med14 and Med17 by the addition of auxin (30 min) or with the carrier DMSO (control) followed by a 6 min labelling of newly synthesized RNA with 4-thiouracil (4tU). In parallel wiltype S.pombe cells were labelled with 4tU for 6min during midlog growth phase. Prior to RNA extraction (Ribopure Yeast Kit, Ambion) our labelled S.cerevisiae cells of interest were mixed with labelled S.pombe cells as a spike to allow normalization against an exogenous reference (ratio 3 S .cerevisiae for 1 S.pombe cell. From the total RNA we purified the 4tU labelled fraction of RNAs containing 4tU. Both the total RNA and the purified newly synthesized RNAs will then be subject to RNA-sequencing after ribosomal RNA depletion. In summary, we will provide 8 samples for this project containing RNA from both S.cerevisiae and S.pombe. The sample read counts were normalized with size factors computed by the median-of-ratios method proposed by Anders and Huber (Anders et al. 2010) on S. pombe genes to make these counts comparable between samples.

2020-03-04 | GSE146321 | GEO

Mediator is essential for small nuclear and nucleolar RNA transcription in yeast

Project description:Eukaryotic RNA polymerase II (RNAPII) transcribes mRNA genes and non-protein coding RNAs (ncRNAs) including small nuclear and nucleolar RNAs (sn/snoRNAs). In metazoans, RNAPII transcription of sn/snoRNAs is facilitated by a number of specialized complexes, but no such complexes have been discovered in yeast. It has been proposed that yeast sn/snoRNA promoters use the same factors as mRNA promoters, but the extent to which regulators of mRNA genes function at yeast sn/snoRNA genes is unclear. Here, we investigated a potential role for the Mediator complex, essential for mRNA gene transcription, in the transcription of sn/snoRNA genes. We found that the Mediator maps to most sn/snoRNA gene regulatory regions and that rapid depletion of the essential structural subunit Med14 strongly reduces RNAPII and TFIIB occupancy as well as nascent transcription of sn/snoRNA genes. Deletion of Med3 and Med15, subunits of the activator-interacting Mediator tail module, does not affect Mediator recruitment to or RNAPII and TFIIB occupancy of sn/snoRNA genes. Our analyses suggest that Mediator promotes PIC formation and transcription at sn/snoRNA genes, expanding the role of this critical regulator beyond its known functions in mRNA gene transcription and demonstrating further mechanistic similarity between the transcription of mRNA and sn/snoRNA genes.

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