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Phosphorylated MED1 Links Transcription Recycling and Cancer Growth

ABSTRACT: Mammalian RNA polymerase II (Pol II) initiation, elongation, termination and reinitiation are well studied, but how Pol II dynamically recycles after the transcription cycle remains unclear. By establishing in vitro and in vivo transcription recycling systems, we find that human Mediator 1 (MED1), when phosphorylated at the mammal-specific threonine 1032 by cyclin-dependent kinase 9, dynamically travels with Pol II throughout the transcribed genes to drive Pol II recycling. Mechanistically, MED1 phosphorylation leads to an increase of recycled Pol II via the molecular bridge of MED31, enhancing mRNA output during the transcription recycling process. Importantly, MED1 phosphorylation increases during prostate cancer progression to the lethal phase, and pharmacological inhibition of CDK9 decreases prostate tumor growth through decreasing MED1 phosphorylation and Pol II recycling. Our findings reveal essential mechanisms underlying Pol II recycling and suggest a neglected, yet fundamental Pol II transcription process for therapeutic intervention.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE127894 | GEO | 2022/04/20

REPOSITORIES: GEO

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Establishment of a novel in vitro transcription assay

Project description:RNA Polymerase II (Pol II) transcriptional recycling is an underappreciated mechanism for which the required factors and contributions to overall gene expression levels are poorly understood. We describe an in vitro methodology facilitating unbiased identification of putative RNA Pol II transcriptional recycling factors and quantitative measurement of transcriptional output from recycled transcriptional components. By combing our in vitro transcription assays with other experiments (e.g. in vivo dynamic ChIP-seq assays), we identified PAF1 complex components and phospho-MED1 as drivers for transcription recycling, revealing a new layer in controlling Pol II-dependent transcription. Our findings also point to RNA Pol II transcription recycling as a mechanism that functions aberrantly in disease states such as cancer, and indicate the potential to target factors such as PAF1 and phospho-MED1 that drive RNA Pol II recycling in cancer.

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In Vitro Transcription Recycling Assay Identifies PAF1 as a Driver of RNA Pol II Recycling

Project description:RNA Polymerase II transcriptional recycling is an underappreciated mechanism for which the required factors and contributions to overall gene expression levels are poorly understood. We describe an in vitro methodology facilitating unbiased identification of novel RNA Pol II transcriptional recycling factors and quantitative measurement of transcriptional output from recycled transcriptional components. Proof-of-principle experiments identified PAF1 complex components among recycling factors and detected defective transcriptional output from RNA Pol II recycling following PAF1 depletion. Dynamic ChIP-seq confirmed in vivo PAF1 complex cycling through gene bodies with RNA Pol II and recycling back to the transcription start sites, while PAF1 silencing triggered defective RNA Pol II recycling. Prostate tumors exhibited enhanced transcriptional recycling, which was attenuated by antibody-based PAF1 depletion. These findings identify RNA Pol II recycling as a potential target in cancer and demonstrate the assay’s applicability to characterize RNA Pol II recycling in cells and tissues from other disease states.

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The nuclear pore-associated TREX-2 complex employs the Mediator Med31 submodule as a docking site to regulate gene expression

Project description:Nuclear pore complexes (NPCs) influence gene expression besides their established function in nuclear transport. The TREX-2 complex localizes to the NPC basket and affects gene-NPC interactions, transcription and mRNA export. How TREX-2 regulates the gene expression machinery is unknown. Here, we show that TREX-2 interacts with the Mediator complex, an essential regulator of RNA Polymerase (Pol) II. Structural and biochemical studies identify a conserved region on TREX-2, which directly binds the Mediator Med31/Med7N submodule. TREX-2 regulates assembly of Mediator with its Cdk8 kinase and is required for recruitment and site-specific phosphorylation of Pol II. Transcriptome and phenotypic profiling confirm that TREX-2 and Med31 are functionally interdependent. TREX-2 additionally uses its Mediator-interacting surface to regulate mRNA export suggesting a mechanism for coupling transcription initiation and early steps of mRNA processing at the Mediator level. In sum, we provide insight into how NPC-associated adaptor complexes can access the core transcription machinery. RNAseq was performed from WT, sac3∆, cdk8∆ and Sac3 R288D mutant cells. For each strain triplicates were analyzed. WT strain was sac3∆ transformed with pRS315 SAC3 WT

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The nuclear pore-associated TREX-2 complex employs the Mediator Med31 submodule as a docking site to regulate gene expression

2015-08-27 | GSE67431 | GEO

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Project description:The Mediator co-activator 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. We previously found that deletion of Med1 in cardiomyocytes deregulates more than 5000 genes and promotes acute heart failure and hypothesize Med1 deficiency disrupts enhancer-promoter coupling. Using ChIP-seq, we find Pol-II pausing index is increased in Med1 knockout versus floxed control hearts primarily from decreased Pol-II occupancy at the majority of transcriptional start sites. Med1-dependent gene expression correlates strongly with histone H3 K27 acetylation while H3 K27 tri-methylated levels are increased and inversely correlate with absolute expression levels. Furthermore, Med1 deletion leads to dynamic changes in acetyl-K27 associated super-enhancer 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 by facilitating the recruitment of Pol-II to gene promoters, determining chromatin accessibility within genes and enhancer regions and altering transcription factor binding motifs that are likely important in directing gene-specific expression.

2019-10-30 | GSE118965 | GEO

Molecular determinants for enzalutamide-induced transcription in prostate cancer

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Activation of P-TEFb by androgen receptor-regulated enhancer RNAs in androgen deprivation conditions [ChIP-Seq]

Project description:Androgen receptor (AR) is required for castration resistant prostate cancer (CRPC) progression, but the function and disease relevance of AR-bound enhancers remain poorly understood. Here, we identify a group of AR-regulated enhancer RNAs (e.g. PSA eRNA) that are upregulated in CRPC cells, patient-derived xenografts (PDX) and patient tissues. PSA eRNA binds to CYCLIN T1, activates P-TEFb and promotes in cis and trans gene transcription by increasing serine-2 phosphorylation of RNA polymerase II (Pol II-Ser2p). To avoid the total Pol II changing by PSA eRNA. We measured the total Pol II using N20 and 8WG16 antibodies with or without PSA eRNA knocking down. To avoid the AR binding changes by PSA eRNA, we also measured the AR binding using AR N20 antibodies with or without PSA eRNA knocking down. Androgen receptor (AR) binding sites in human prostate cancer cell lines, C4-2, were studied using ChIP-seq. Total Pol II Ser-2p and AR binding sites in human prostate cancer cell lines C4-2 with or without PSA eRNA knockdown, were studied using ChIP-seq. ChIP enriched DNA were sequenced using Illumina HiSeq 2500and input DNA were sequenced using Illumina HiSeq 2000.

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