Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The C-terminal domain (CTD) of the largest subunit of RNA polymerase II plays critical roles in the initiation, elongation and processing of primary transcripts. These activities are at least partially regulated by the phosphorylation of the CTD by three cyclin-dependent protein kinases (CDKs), namely CDK7, CDK8 and CDK9. In this study, we systematically compared the phosphorylation of different recombinant CTD substrates by recombinant CDK7/CycH/MAT1, CDK8/CycC and CDK9/CycT1 kinases. We showed that CDK7, CDK8 and CDK9 produce different patterns of phosphorylation of the CTD. CDK7/CycH/MAT1 generates mostly hyperphosphorylated full-length and truncated CTD peptides, while CDK8/CycC and CDK9/CycT1 generate predominantly hypophosphorylated peptides. Total activity towards different parts of the CTD also differs between the three kinases; however, these differences did not correlate with their ability to hyperphosphorylate the substrates. The last 10 repeats of the CTD can act as a suppressor of the activity of the kinases in the context of longer peptides. Our results indicate that the three kinases possess different biochemical properties that could reflect their actions in vivo.
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PMID:Three cyclin-dependent kinases preferentially phosphorylate different parts of the C-terminal domain of the large subunit of RNA polymerase II. 1500 12

Mediator exists in a free form containing the Med12, Med13, CDK8, and CycC subunits (the Srb8-11 module) and a smaller form, which lacks these four subunits and associates with RNA polymerase II (Pol II), forming a holoenzyme. We use chromatin immunoprecipitation (ChIP) and DNA microarrays to investigate genome-wide localization of Mediator and the Srb8-11 module in fission yeast. Mediator and the Srb8-11 module display similar binding patterns, and interactions with promoters and upstream activating sequences correlate with increased transcription activity. Unexpectedly, Mediator also interacts with the downstream coding region of many genes. These interactions display a negative bias for positions closer to the 5' ends of open reading frames (ORFs) and appear functionally important, because downregulation of transcription in a temperature-sensitive med17 mutant strain correlates with increased Mediator occupancy in the coding region. We propose that Mediator coordinates transcription initiation with transcriptional events in the coding region of eukaryotic genes.
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PMID:Genome-wide occupancy profile of mediator and the Srb8-11 module reveals interactions with coding regions. 1663 Aug 87

CDK8 (cyclin-dependent kinase 8), along with CycC, Med12, and Med13, form a repressive module (the Cdk8 module) that prevents RNA polymerase II (pol II) interactions with Mediator. Here, we report that the ability of the Cdk8 module to prevent pol II interactions is independent of the Cdk8-dependent kinase activity. We use electron microscopy and single-particle reconstruction to demonstrate that the Cdk8 module forms a distinct structural entity that binds to the head and middle region of Mediator, thereby sterically blocking interactions with pol II.
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PMID:The cyclin-dependent kinase 8 module sterically blocks Mediator interactions with RNA polymerase II. 1704 18

Mediator (MED) is a conserved multisubunit complex bridging transcriptional activators and repressors to the general RNA polymerase II initiation machinery. In yeast, MED is organized in three core modules and a separable 'Cdk8 module' consisting of the cyclin-dependent kinase Cdk8, its partner CycC, Med12 and Med13. This regulatory module, specifically required for cellular adaptation to environmental cues, is thought to act through the Cdk8 kinase activity. Here we have investigated the functions of the four Cdk8 module subunits in the metazoan model Drosophila. Physical interactions detected among the four fly subunits provide support for a structurally conserved Cdk8 module. We analyzed the in vivo functions of this module using null mutants for Cdk8, CycC, Med12 and Med13. Each gene is required for the viability of the organism but not of the cell. Cdk8-CycC and Med12-Med13 act as pairs, which share some functions but also have distinct roles in developmental gene regulation. These data reveal functional attributes of the Cdk8 module, apart from its regulated kinase activity, that may contribute to the diversification of genetic programs.
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PMID:Distinct roles for Mediator Cdk8 module subunits in Drosophila development. 1729 Feb 21

The multisubunit Mediator (MED) complex bridges DNA-bound transcriptional regulators to the RNA polymerase II (PolII) initiation machinery. In yeast, the 25 MED subunits are distributed within three core subcomplexes and a separable kinase module composed of Med12, Med13 and the Cdk8-CycC pair thought to control the reversible interaction between MED and PolII by phosphorylating repeated heptapeptides within the Rpb1 carboxyl-terminal domain (CTD). Here, MED conservation has been investigated across the eukaryotic kingdom. Saccharomyces cerevisiae Med2, Med3/Pgd1 and Med5/Nut1 subunits are apparent homologs of metazoan Med29/Intersex, Med27/Crsp34 and Med24/Trap100, respectively, and these and other 30 identified human MED subunits have detectable counterparts in the amoeba Dictyostelium discoideum, indicating that none is specific to metazoans. Indeed, animal/fungal subunits are also conserved in plants, green and red algae, entamoebids, oomycetes, diatoms, apicomplexans, ciliates and the 'deep-branching' protists Trichomonas vaginalis and Giardia lamblia. Surprisingly, although lacking CTD heptads, T. vaginalis displays 44 MED subunit homologs, including several CycC, Med12 and Med13 paralogs. Such observations have allowed the identification of a conserved 17-subunit framework around which peripheral subunits may be assembled, and support a very ancient eukaryotic origin for a large, four-module MED. The implications of this comprehensive work for MED structure-function relationships are discussed.
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PMID:Comparative genomics supports a deep evolutionary origin for the large, four-module transcriptional mediator complex. 1851 35

The multiprotein transcriptional Mediator complex provides a key link between RNA polymerase II and upstream transcriptional activator proteins. Previous work has established that the multidrug resistance transcription factors Pdr1 and Pdr3 interact with the Mediator component Med15/Gal11 to drive normal levels of expression of the ATP-binding cassette transporter-encoding gene PDR5 in Saccharomyces cerevisiae. PDR5 transcription is induced upon loss of the mitochondrial genome (rho(0) cells) and here we provide evidence that this rho(0) induction is Med15 independent. A search through other known Mediator components determined that Med12/Srb8, a member of the CDK8 Mediator submodule, is required for rho(0) activation of PDR5 transcription. The CDK8 submodule contains the cyclin C homologue (CycC/Srb11), cyclin-dependent kinase Cdk8/Srb10, and the large Med13/Srb9 protein. Loss of these other proteins did not lead to the same block in PDR5 induction. Chromatin immunoprecipitation analyses demonstrated that Med15 is associated with the PDR5 promoter in both rho(+) and rho(0), whereas Med12 recruitment to this target promoter is highly responsive to loss of the mitochondrial genome. Coimmunoprecipitation experiments revealed that association of Pdr3 with Med12 can only be detected in rho(0) cells. These experiments uncover the unique importance of Med12 in activated transcription of PDR5 seen in rho(0) cells.
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PMID:Differential roles of transcriptional mediator subunits in regulation of multidrug resistance gene expression in Saccharomyces cerevisiae. 2050 76

The multiprotein Mediator complex is required for the regulated transcription of nearly all RNA polymerase II-dependent genes. Mediator contains the Cdk8 regulatory subcomplex, which directs periodic transcription and influences cell cycle progression in fission yeast. Here we investigate the role of CycC, the cognate cyclin partner of Cdk8, in cell cycle control. Previous reports suggested that CycC interacts with other cellular Cdks, but a fusion of CycC to Cdk8 reported here did not cause any obvious cell cycle phenotypes. We find that Cdk8 and CycC interactions are stabilized within the Mediator complex and the activity of Cdk8-CycC is regulated by other Mediator components. Analysis of a mutant yeast strain reveals that CycC, together with Cdk8, primarily affects M-phase progression but mutations that release Cdk8 from CycC control also affect timing of entry into S phase.
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PMID:Cyclin C influences the timing of mitosis in fission yeast. 2851 43