Project description:Temporal coordination of developmental programs is necessary for normal ontogeny, but the mechanism by which this is accomplished is poorly understood. We have previously shown that two components of the Mediator CDK8 module, CENTER CITY (CCT/MED12) and GRAND CENTRAL (GCT/MED13), are required for timing of pattern formation during embryogenesis in Arabidopsis. Here, we performed global gene expression analyses of wild-type, cct-1, and gct-2 seedlings (above-ground portions only) to help analyze their post-embryonic phenotypes. Our results suggest that MED12 and MED13 act as global regulators of developmental timing by fine-tuning expression of temporal regulatory genes.
Project description:Temporal coordination of developmental programs is necessary for normal ontogeny, but the mechanism by which this is accomplished is poorly understood. We have previously shown that two components of the Mediator CDK8 module, CENTER CITY (CCT/MED12) and GRAND CENTRAL (GCT/MED13), are required for timing of pattern formation during embryogenesis in Arabidopsis. Here, we performed global gene expression analyses of wild-type, cct-1, and gct-2 seedlings (above-ground portions only) to help analyze their post-embryonic phenotypes. Our results suggest that MED12 and MED13 act as global regulators of developmental timing by fine-tuning expression of temporal regulatory genes. Seeds of wild-type Col-0, cct-1, and gct-2 were sown in Fafard #2 soil. Seedlings (above-ground portions only) were harvested when the first two leaf primordia were 1 mm in length, which was at day 7 for wild-type seedlings and day 9 for the two mutants. 75-100 seedlings were used for each of three biological replicates.
Project description:The transition of pluripotent stem cells (PSCs) from primed to naïve states constitutes a prototypical example of cellular plasticity. The naïve state can be stabilized by defined chemical cocktails that block extracellular signals, notably including the MEK pathway. However, little is known regarding the underlying transcriptional mechanisms. Here, we report that the transcriptional landscape of the naïve state can be mimicked in mouse and human PSCs by stimulating transcriptional enhancers. This is attained by inhibiting the CDK8 and CDK19 kinases, which are negative regulators of Mediator, a critical component of enhancer function. Mechanistically, CDK8/19i triggers a global increase in the recruitment of RNA Pol II at promoters and enhancers, hyperactivating enhancers and their target genes. Lastly, the emergence of naïve pluripotency in the pre-implantation epiblast coincides with a marked reduction in CDK8/19 activity, and CDK8/19i blocks its subsequent developmental progression. These findings suggest that naïve pluripotency during development includes hyperactivation of enhancers and can be captured in vitro, either by blunting extracellular signaling, or by stimulating enhancer-driven transcription. These principles may apply to other cellular transitions.
Project description:Mediator is regarded a general co-activator of RNA-Polymerase II dependent transcription but not much is known about its function and regulation in mouse pluripotent embryonic stem cells (mESC). One means of controlling Mediator function is provided by binding of the Cdk8 module (Med12, Cdk8, Ccnc and Med13) to Mediator. Here we report that the Cdk8 module subunit Med12 operates together with PRC1 to silence developmental key genes in the pluripotent state. At the molecular level, PRC1 is required to assemble ncRNA containing Med12-Mediator complexes at promoters of repressed genes. In the course of cellular differentiation the H2A-ubiquitin binding protein Zrf1 abrogates PRC1-Med12 binding and facilitates the recruitment of Cdk8 into Mediator. Remodeling of the Mediator-associated protein complex converts Mediator into a transcriptional enhancer that mediates ncRNA-dependent activation of Polycomb target genes
Project description:Expression profiling following depletion of Mediator Cdk8 module subunits Cdk8, Cyclin C (CycC), Med12 and Med13 72 hours after dsRNA treatment of Drosophila melanogaster S2 cells. Results provide insight into the role of individual Cdk8 module subunits in regulation of transcription. 22 samples. 2 Cdk8 dsRNA, 4 CycC dsRNA, 4 Med12 dsRNA, 4 Med13 dsRNA, 8 control samples including 4 Luciferase (Luc) dsRNA and 4 GFP dsRNA
Project description:Expression profiling following depletion of Mediator Cdk8 module subunits Cdk8, Cyclin C (CycC), Med12 and Med13 72 hours after dsRNA treatment of Drosophila melanogaster S2 cells. Results provide insight into the role of individual Cdk8 module subunits in regulation of transcription.
Project description:In nature, plants are often exposed to recurring adverse environmental conditions. Acclimation to high temperature stress entails transcriptional responses that are mediated by heat-shock transcription factors (HSFs), and they are primed to better withstand subsequent stress events. This heat stress (HS)-induced transcriptional memory results in more efficient re-induction of transcription upon recurring HS. However, the mechanisms by which HSFs recruit and enact the transcriptional machinery remain unclear. Here, we identified two subunits of the kinase module of the Mediator transcriptional co-regulator complex, CDK8 and MED12, as regulators of HS memory in Arabidopsis thaliana. Enhanced re-induction of gene expression after recurrent HS and physiological HS memory, as well as H3K4 methylation are compromised in cdk8 and med12 mutants. HSFA2 interacts with CDK8 during and after HS and recruits it to memory gene loci, where CDK8 binds in the promoter but also the gene body, together with core Mediator and RNA polymerase II (Pol II). Our data suggest that CDK8 resolves stalled Pol II complexes or promotes efficient recycling for subsequent cycles of transcription. As HSFA2, CDK8 is largely dispensable for the initial induction of gene expression after HS and thus promotes transcriptional memory independently of HS-dependent primary gene induction. Our findings provide a model for the complex role of the Mediator kinase module during transcriptional memory in multicellular eukaryotes through interaction with transcription factors, chromatin modifications and promotion of Pol II productivity.
Project description:The L-Mediator is a general co-activator of RNA Polymerase II transcription and is formed by the reversible association of the S-Mediator and the kinase module harbouring Cdk8. We describe the Cdk11-Lcp1 complex and show that its inactivation alter the global expression profiles in a very similar way than mutations of the kinase module. Cdk11 is broadly distributed onto chromatin and phosphorylate the Med27 and Med4 Mediator subunits on conserved residues. The inactivation of either Cdk11 or the mutation of its target residues on the Mediator leads to a strongly decreased association of the kinase module and the S-Mediator. The results show that Cdk11-Lcp1 regulates that assembly of the L-Mediator complex. Total RNA was isolated from two biological replicates for all conditions, and each biological replicate was hybridized in duplicate on Agilent arrays (dye-swap).