Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The eukaryotic cell division cycle is coordinated by cyclin-dependent kinases (CDKs), represented by a single major serine/threonine kinase in yeasts (Cdc2/CDC28) and a family of kinases (CDK1 to CDK8) in human cells. Previously, two cdc2 homologs, cdc2MsA and cdc2MsB, have been identified in alfalfa (Medicago sativa). By isolating cDNAs using a cdc2MsA probe, we demonstrate here that at least four additional cdc2 homologous genes are expressed in the tetraploid alfalfa. Proteins encoded by the new cdc2MsC to cdc2MsF cDNAs share the characteristic functional domains of CDKs with the conserved and plant-specific sequence elements. Transcripts from cdc2MsA, cdc2MsB, cdc2MsC, and cdc2MsE genes are synthesized throughout the cell cycle, whereas the amounts of cdc2MsD and cdc2MsF mRNAs peak during G2-to-M phases. The translation of Cdc2MsA/B, Cdc2MsD, and Cdc2MsF proteins follows the pattern of transcript accumulation. The multiplicity of kinase complexes with cell cycle phase-dependent activities was revealed by in vitro phosphorylation experiments. Proteins bound to p13suc1-Sepharose or immunoprecipitated with Cdc2MsA/B antibodies from cells at G1-to-S and G2-to-M phase boundaries showed elevated kinase activities. the Cdc2MsF antibodies separated a G2-to-M phase-related kinase complex. Detection of histone H1 phosphorylation activities in fractions immunoprecipitated with antimitotic cyclin (CyclinMs2) antibodies from G2-to-M phase cells indicates the complex formation between this cyclin and a kinase partner in alfalfa. The observed fluctuation of transcript levels, amounts, and activities of kinases in different cell cycle phases reflects a multilevel regulatory system during cell cycle progression in plants.
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PMID:Cell cycle phase specificity of putative cyclin-dependent kinase variants in synchronized alfalfa cells. 906 53

Cyclin C, a putative G1 cyclin, was originally isolated through its ability to complement a Saccharomyces cerevisiae strain lacking the G1 cyclin gene CLN1-3. Unlike cyclins D1 and E, the other two G1 cyclins obtained by the same approach and subsequently shown to play important roles during the G1/S transition, there is thus far no evidence to support the hypothesis that cyclin C is indeed critical for the promotion of cell cycle progression. In BAF-B03 cells, an interleukin 3 (IL-3)-dependent murine pro-B-cell line, cyclin C gene mRNA was induced at the G1/S phase upon IL-3 stimulation and reached a maximal level in the S phase. Enforced expression of exogenous cyclin C in this cell line failed to alter its growth properties. In the present study, we examined whether cyclin C is capable of cooperating with the cytokine-responsive immediate-early gene products c-Myc and c-Fos in the promotion of cell proliferation. We found that cyclin C is able to cooperate functionally with c-Myc, but not c-Fos, to induce both BAF-B03 cell proliferation in a cytokine-independent fashion and the formation of cell clusters. Furthermore, cyclin C was primarily responsible for the induction of cdc2 gene expression. Our data define a novel role for cyclin C in the regulation of both the G1/S and G2/M phases of the cell cycle, and this effect appears to be independent of the activity of CDK8 in the control of transcription.
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PMID:A critical role for cyclin C in promotion of the hematopoietic cell cycle by cooperation with c-Myc. 958 84

Phosphorylation of the yeast transcription factor GAL4 at S699 is required for efficient galactose-inducible transcription. We demonstrate that this site is a substrate for the RNA polymerase holoenzyme-associated CDK SRB10. S699 phosphorylation requires SRB10 in vivo, and this site is phosphorylated by purified SRB10/ SRB11 CDK/cyclin in vitro. RNA Pol II holoenzymes purified from WT yeast phosphorylate GAL4 at sites observed in vivo whereas holoenzymes from srb10 yeast are incapable of phosphorylating GAL4 at S699. Mutations at GAL4 S699 and srb10 are epistatic for GAL induction, demonstrating that SRB10 regulates GAL4 activity through this phosphorylation in vivo. These results demonstrate a function for the SRB10/ CDK8 holoenzyme-associated CDK that involves regulation of transactivators by phosphorylation during transcriptional activation.
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PMID:GAL4 is regulated by the RNA polymerase II holoenzyme-associated cyclin-dependent protein kinase SRB10/CDK8. 1036 Jan 83

A number of mammalian multiprotein complexes containing homologs of Saccharomyces cerevisiae Mediator subunits have been described recently. High-molecular-mass complexes (1 to 2 MDa) sharing several subunits but apparently differing in others include the TRAP/SMCC, NAT, DRIP, ARC, and human Mediator complexes. Smaller multiprotein complexes (approximately 500 to 700 kDa), including the murine Mediator, CRSP, and PC2, have also been described that contain subsets of subunits of the larger complexes. To evaluate whether these different multiprotein complexes exist in vivo in a single form or in multiple different forms, HeLa cell nuclear extract was directly resolved over a Superose 6 gel filtration column. Immunoblotting of column fractions using antisera specific for several Mediator subunits revealed one major size class of high-molecular-mass (approximately 2-MDa) complexes containing multiple mammalian Mediator subunits. No peak was apparent at approximately 500 to 700 kDa, indicating that either the smaller complexes reported are much less abundant than the higher-molecular-mass complexes or they are subcomplexes generated by dissociation of larger complexes during purification. Quantitative immunoblotting indicated that there are about 3 x 10(5) to 6 x 10(5) molecules of hSur2 Mediator subunit per HeLa cell, i.e., the same order of magnitude as RNA polymerase II and general transcription factors. Immunoprecipitation of the approximately 2-MDa fraction with anti-Cdk8 antibody indicated that at least two classes of Mediator complexes occur, one containing CDK8 and cyclin C and one lacking this CDK-cyclin pair. The approximately 2-MDa complexes stimulated activated transcription in vitro, whereas a 150-kDa fraction containing a subset of Mediator subunits inhibited activated transcription.
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PMID:Characterization of mediator complexes from HeLa cell nuclear extract. 1141 38

The suc1/Cks proteins are well-conserved regulatory components of cyclin-dependent kinases 1 and 2 (CDK1/2). These small molecular mass proteins form a stable complex with CDK1/2 and are essential for normal regulation of CDKs during the cell division cycle and for degradation of p27(kip1). Despite the high degree of homology between the nine known CDKs, only CDK1, CDK2 and, to a lesser extent, CDK3 are able to bind to the suc1/Cks proteins. No additional suc1/Cks-related proteins interacting with other CDKs have been reported. We have purified, from starfish oocytes, a 15 kDa protein, p15(CDK-BP), which cross-reacts with anti-Cks antibodies (L. Azzi, L. Meijer, A.C. Ostvold, J. Lew, J.H. Wang, J. Biol. Chem. 269 (1994)). Following microsequencing of internal peptides and generation of corresponding oligonucleotides we cloned two cDNAs encoding two closely related proteins, p15A and p15B. The predicted protein sequences display distant but distinct homology with the Suc1/Cks proteins, including the genuine starfish Cks homologue protein, p9(CksMg). P15 transcripts are essentially expressed in oocytes. Recombinant p15B or native p15(CDK-BP) bind a 34 kDa protein cross-reacting with anti-PSTAIRE antibodies, a feature characteristic of CDK-related proteins. In addition p15B interacts tightly with CDK4, CDK6, CDK8 and the yeast CDC28-related kinase Pho85, but not with CDK1, CDK2 or CDK7. P15 does not appear to alter the catalytic activity of the bound kinases.
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PMID:Molecular cloning and characterisation of p15(CDK-BP), a novel CDK-binding protein. 1200 96

We have established a uniform procedure for the expression and purification of the cyclin-dependent kinases CDK7/CycH/MAT1, CDK8/CycC and CDK9/CycT1. We attach a His(6)-tag to one of the subunits of each complex and then co-express it together with the other subunits in Spodoptera frugiperda insect cells. The CDK complexes are subsequently purified by Ni(2+)-NTA and Mono S chromatography. This approach generates large amounts of active recombinant kinases that are devoid of contaminating kinase activities. Importantly, the properties of these recombinant kinases are similar to their natural counterparts (Pinhero et al. 2004, Eur J Biochem 271:1004-14). Our protocol provides a novel systematic approach for the purification of these three (and possibly other) recombinant CDKs.
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PMID:A uniform procedure for the purification of CDK7/CycH/MAT1, CDK8/CycC and CDK9/CycT1. 1532 39

The p53 transcriptional network orchestrates alternative stress responses such as cell-cycle arrest and apoptosis. Here we investigate the mechanism of differential expression of p21, a key mediator of p53-dependent cell-cycle arrest. We demonstrate that the transcriptional activity of the p21 promoter varies greatly in response to distinct p53-activating stimuli. Chromatin immunoprecipitation analysis of the p21 locus indicates that histone acetyltransferases, general transcription factors, and Mediator subunits are assembled into alternative transcriptional complexes of different activity. Interestingly, core Mediator subunits MED1 and MED17 are recruited to the p21 locus regardless of the p53-activating stimuli utilized. In contrast, three subunits of the CDK module of Mediator (CDK8, MED12, and cyclin C) are exclusively recruited during conditions of strong p21 transcriptional activation. Furthermore, increased binding of CDK8 to p53 target genes correlates positively with transcriptional strength. RNAi experiments demonstrate that CDK8 functions as a coactivator within the p53 transcriptional program.
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PMID:CDK8 is a stimulus-specific positive coregulator of p53 target genes. 1761 95

Mediator is an essential transcriptional cofactor of RNA polymerase II (Pol II) in eukaryotes. This cofactor is a large complex containing up to 30 subunits and consisting of four modules: head, middle, tail, and CDK/Cyclin. Generally, Mediator connects transcriptional regulators, cofactors, chromatin regulators, and chromatin remodellers, with the pre-initiation complex to provide a platform for the assembly of these factors. Many previous studies have revealed that CDK8, a subunit of the CDK/Cyclin module, is one of the key subunits mediating the pivotal roles of Mediator in transcriptional regulation. In addition to CDK8, CDK11 is conserved among vertebrates as a Mediator subunit and closely resembles CDK8. While the role of CDK8 has been studied extensively, little is known of the role of CDK11 in Mediator. We purified human CDK11 (hCDK11)-containing protein complexes from an epitope-tagged hCDK11-expressing HeLa cell line and found that hCDK11 could independently form Mediator complexes devoid of human CDK8 (hCDK8). To investigate the in vivo transcriptional activity of the complex, we employed a luciferase assay. Although hCDK11 has nearly 80% amino acid sequence identity to hCDK8, siRNA-knockdown study revealed that hCDK8 and hCDK11 possess opposing functions in viral activator VP16-dependent transcriptional regulation.
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PMID:Human mediator kinase subunit CDK11 plays a negative role in viral activator VP16-dependent transcriptional regulation. 1865 50

Mediator is a large complex containing up to 30 subunits that consist of four modules each: head, middle, tail and CDK/Cyclin. Recent studies have shown that CDK8, a subunit of the CDK/Cyclin module, is one of the key subunits of Mediator that mediates its pivotal roles in transcriptional regulation. In addition to CDK8, CDK19 was identified in human Mediator with a great deal of similarity to CDK8 but was conserved only in vertebrates. Previously, we reported that human CDK19 could form the Mediator complexes independent of CDK8. To further investigate the in vivo transcriptional activities of the complexes, we used a luciferase assay in combined with siRNA-mediated knockdown to show that CDK8 and CDK19 possess opposing functions in viral activator VP16-dependent transcriptional regulation. CDK8 supported transcriptional activation, whereas CDK19, however, counteracted it. In this study, we further characterized CDK19. We used microarrays to identify target genes for each CDK, and we selected six genes: two target genes of CDK8, two target genes of CDK19 and two genes that were targets for both. Surprisingly, it turned out that both CDKs bound to all six target genes, regardless of their effects in transcription upon binding, suggesting Mediator as a context-specific transcriptional regulator.
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PMID:Identification of target genes for the CDK subunits of the Mediator complex. 2211 96

The Mediator complex consists of more than 20 subunits. This is composed of four modules: head, middle, tail and CDK/Cyclin. Importantly, Mediator complex is known to play pivotal roles in transcriptional regulation, but its molecular mechanisms are still elusive. Many studies, including our own, have revealed that CDK8, a kinase subunit of the CDK/Cyclin module, is one of the key subunits involved in these roles. Additionally, we previously demonstrated that a novel CDK component, CDK19, played similar roles. It is assumed that various factors that directly affect transcriptional regulation target these two CDKs; thus, we conducted yeast two-hybrid screenings to isolate the CDK19-interacting proteins. From a screening of 40 million colonies, we obtained 287 clones that provided positive results encoded mRNAs, and it turned out that 59 clones of them encoded nuclear proteins. We checked the reading frames of the candidate clones and obtained three positive clones, all of which encoded the transcriptional cofactors, Brahma-related gene 1, B-cell CLL/lymphoma 6 and suppressor of zeste 12 homolog. Intriguingly, these three cofactors are also related to chromatin regulation. Further studies demonstrated that those could bind not only to CDK19 but also to CDK8. These results help elucidate the functional mechanism for the mutual regulations between transcription and chromatin.
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PMID:Mediator CDK subunits are platforms for interactions with various chromatin regulatory complexes. 2266 59


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