Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Cks1 protein is a component of the Cdc28 protein kinase in the budding yeast Saccharomyces cerevisiae. This paper reports the cloning of two homologs of the S. cerevisiae CKS1 gene from human cells. These homologs, CKShs1 and CKShs2, both encode proteins of 79 amino acids that share considerable homology at the amino acid level with the products of CKS1 from S. cerevisiae and suc1+ from the fission yeast Schizosaccharomyces pombe. Both human homologs are capable of rescuing a null mutation of the S. cerevisiae CKS1 gene when expressed from the S. cerevisiae GAL1 promoter. S. pombe suc1+ expressed from the GAL1 promoter is also capable of rescuing a S. cerevisiae cks1 null mutation. Ckshs1 or Ckshs2 protein linked to Sepharose beads can bind the Cdc28/Cdc2 protein kinase from both S. cerevisiae and human cells. The CKShs1 and CKShs2 mRNAs are expressed in different patterns through the cell cycle in HeLa cells, which may reflect specialized roles for the encoded proteins.
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PMID:Human cDNAs encoding homologs of the small p34Cdc28/Cdc2-associated protein of Saccharomyces cerevisiae and Schizosaccharomyces pombe. 222 11

The Saccharomyces cerevisiae gene CDC28 encodes a protein kinase required for cell cycle initiation. In an attempt to identify genes encoding proteins that interact with the Cdc28 protein kinase, high-copy plasmid suppressors of a temperature-sensitive cdc28 mutation were isolated. One such suppressor, CKS1, was found to encode an 18-kilodalton protein that shared a high degree of homology with the suc1+ protein (p13) of Schizosaccharomyces pombe (67% amino acid sequence identity). Disruption of the chromosomal CKS1 gene conferred a G1 arrest phenotype similar to that of cdc28 mutants. The presence of the 18-kilodalton Cks1 protein in yeast lysates was demonstrated by using Cks-1 specific antiserum. Furthermore, the Cks1 protein was shown to be physically associated with active forms of the Cdc28 protein kinase. These data suggest that Cks1 is an essential component of the Cdc28 protein kinase complex.
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PMID:The Saccharomyces cerevisiae CKS1 gene, a homolog of the Schizosaccharomyces pombe suc1+ gene, encodes a subunit of the Cdc28 protein kinase complex. 266 68

In the interest of identifying components of the Cdc28 protein kinase complex, dosage suppression analysis was performed on temperature-sensitive and dominant negative CDC28 mutations. Dosage suppression is based on a rationale in which elevated expression of wild-type genes can rescue mutations in a target gene as a result of interaction between the respective encoded proteins. Three sequences capable of rescuing a temperature sensitive cdc28 mutation were isolated from a library of wild-type genomic DNA segments in the high copy vector YEp13. Two of these, named CLN1 and CLN2 were found to encode closely related proteins with homology to cyclins. The third, CKS1, encodes an 18K (K = 10(3) Mr) protein that has been shown to be a component of the Cdc28 protein kinase complex and is a homolog of the suc1+ product of fission yeast. A number of dosage suppressors of the CDC28-dn1 dominant negative mutation have been isolated. The one analyzed to date encodes a truncated subunit of the mitochondrial enzyme succinyl-CoA synthetase. The basis for suppression in this case remains to be elucidated.
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PMID:Analysis of the Cdc28 protein kinase complex by dosage suppression. 269 37

Inhibition of DNA synthesis prevents mitotic entry through the action of the S-phase checkpoint. We have isolated S-phase arrest-defective (sad) mutants that show lethality in the presence of the DNA synthesis inhibitor hydroxyurea (HU). Several of these mutants show phenotypes consistent with inappropriate mitotic entry in the presence of unreplicated DNA, indicating a defect in the S-phase checkpoint. sad1 mutants are additionally defective for the G1 and G2 DNA damage checkpoints, and for DNA damage-induced transcription of RNR2 and RNR3. The transcriptional response to DNA damage requires activation of the Dun1 protein kinase. Activation of Dun1 in response to replication blocks or DNA damage is blocked in sad1 mutants. The HU sensitivity of sad1 mutants is suppressed by mutations in CKS1, a subunit of the p34CDC28 kinase, further establishing a link between cell cycle progression and lethality. sad1 mutants are allelic to rad53, a radiation-sensitive mutant. SAD1 encodes an essential protein kinase. The observation that SAD1 controls three distinct checkpoints suggests a common mechanism for cell cycle arrest at these points. Together, these observations implicate protein phosphorylation in the cellular response to DNA damage and replication blocks.
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PMID:The SAD1/RAD53 protein kinase controls multiple checkpoints and DNA damage-induced transcription in yeast. 795 5

Protein phosphorylation is believed to play a role in the regulation of ciliary motility in the protozoan Paramecium tetraurelia. Five protein kinases from Paramecium, activated by cyclic nucleotides or Ca2+, have been characterized previously. We report here the identification of a family of second-messenger-independent casein kinases in Paramecium. Casein kinase activity was enriched in the soluble fraction of cilia, but there was also significant activity tightly associated with axonemes. Three ciliary casein kinase activities (soluble CKS1 and CKS2, and axonemal CKA) were separated by chromatography and characterized. The native forms of all three were monomeric, with molecular masses of 28-45 kDa as judged by in-gel kinase assays and sizing by gel filtration. CKS2 was inhibited by heparin, but CKA was unaffected and CKS1 was stimulated. All three activities preferred acidic substrates such as casein and phosvitin, but they could be distinguished by their preference for other substrates. Antibodies against mammalian casein kinase I recognized CKS1 and CKS2 in immunoblots (43 kDa), but did not stain CKA. The antibodies to casein kinase I were used to probe other cellular fractions. A 65 kDa antigen (particulate casein kinase, CKP) was enriched in particulate fractions of whole cells. This 65 kDa protein was found in isolated cell cortices, but was not present in the infraciliary lattice. This report represents the first biochemical identification of a casein kinase I family in protozoa.
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PMID:Identification of a family of casein kinases in Paramecium: biochemical characterization and cellular localization. 828 70

The CKS1 gene of Saccharomyces cerevisiae encodes a small essential protein shown to interact genetically and physically with the Cdc28 protein kinase. To investigate the specific functions of the CKS1 gene product, conditional temperature-sensitive mutant alleles were generated. The mutations were found to impair the ability of cells to undergo both the G1/S-phase and G2/M-phase transitions of the cell cycle, as well as the ability to bud. Mutants were not defective, however, in their ability to activate Cdc28 kinase as assayed in vitro on the substrate histone H1. It is likely, therefore, that Cks1 mediates a more specialized function of the Cdc28 kinase such as its ability to form specific multimeric complexes or to localize properly in cellular compartments.
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PMID:The Cdk-associated protein Cks1 functions both in G1 and G2 in Saccharomyces cerevisiae. 849 79

We have analyzed five mutant alleles of two cyclin-dependent kinases from Arabidopsis thaliana, CDC2aAt and CDC2bAt, in Schizosaccharomyces pombe. Two of the five mutant alleles produced similar phenotypes for both cyclin-dependent kinases. The other three mutants caused phenotypes dependent on the particular cyclin-dependent kinase. Of all the mutant alleles, only two were found to possess a detectable kinase activity. Our mutational analysis lends further support for CDC2aAt being the true orthologue of the yeast cdc2. CDC2bAt, even though quite divergent from S. pombe cdc2, still retains the ability to interact with at least some essential cell cycle regulators, suggesting some functional homology with the yeast protein. Additionally, we demonstrated that the three amino acid deletion in the DL50 mutants results in the loss of the ability to interact with the suc1/CKS1 proteins.
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PMID:Mutational analysis of two Arabidopsis thaliana cyclin-dependent kinases in fission yeast. 1010 Jun 39

p13(suc1) (Cks) proteins have been implicated in the regulation of cyclin-dependent kinase (CDK) activity. However, the mechanism by which Cks influences the function of cyclin-CDK complexes has remained elusive. We show here that Cks1 is required for the protein kinase activity of budding yeast G(1) cyclin-CDK complexes. Cln2 and Cdc28 subunits coexpressed in baculovirus-infected insect cells fail to exhibit protein kinase activity towards multiple substrates in the absence of Cks1. Cks1 can both stabilize Cln2-Cdc28 complexes and activate intact complexes in vitro, suggesting that it plays multiple roles in the biogenesis of active G(1) cyclin-CDK complexes. In contrast, Cdc28 forms stable, active complexes with the B-type cyclins Clb4 and Clb5 regardless of whether Cks1 is present. The levels of Cln2-Cdc28 and Cln3-Cdc28 protein kinase activity are severely reduced in cks1-38 cell extracts. Moreover, phosphorylation of G(1) cyclins, which depends on Cdc28 activity, is reduced in cks1-38 cells. The role of Cks1 in promoting G(1) cyclin-CDK protein kinase activity both in vitro and in vivo provides a simple molecular rationale for the essential role of CKS1 in progression through G(1) phase in budding yeast.
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PMID:Cks1 is required for G(1) cyclin-cyclin-dependent kinase activity in budding yeast. 1091 69

The SUC1/CKS1 proteins associate with cyclin-dependent kinases (CDKs) and play an essential role in the regulation of the cell cycle. Recently, an Arabidopsis thaliana SUC1/CKS1 homologous gene, designated CKS1At, has been cloned. Here, overexpression of CKS1At in Arabidopsis is shown to reduce leaf size and root growth rates. Reduced root growth resulted primarily from an increase of the cell-cycle duration and a shortening of the meristem. Endoreduplication was unaffected. The increased cell-cycle duration was associated with an equal extension of both the G1 and G2 phases. This inhibition was due to the binding of CDK subunits with CDKs. The reduced growth rates in response to altered cell-cycle gene expression demonstrates a direct dependence of plant growth rates on cell-cycle regulation.
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PMID:CKS1At overexpression in Arabidopsis thaliana inhibits growth by reducing meristem size and inhibiting cell-cycle progression. 1131 29

The SUC1/CKS1 proteins interact with cyclin-dependent kinases (CDKs) and play an essential, but yet not entirely resolved, role in the regulation of the cell cycle. With the Arabidopsis thaliana CKS1At protein as bait in a two-hybrid screen, two novel Arabidopsis CDKs, Arath;CDKB1;2 and Arath;CDKB2;1, were isolated. A closely related homologue of Arath;CDKB2;1 was discovered in the databases and was nominated Arath;CDKB2;2. Transcript analysis of the five known Arath;CDKA and Arath;CDKB genes revealed that they all had the highest expression in flowers and cell suspensions. Differences in the expression patterns in roots, leaves and stems suggest unique roles for each CDK.
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PMID:Identification of novel cyclin-dependent kinases interacting with the CKS1 protein of Arabidopsis. 1143 58


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