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

One model for the timing of cytokinesis is based on findings that p34(cdc2) can phosphorylate myosin regulatory light chain (LC20) on inhibitory sites (serines 1 and 2) in vitro (Satterwhite, L.L., M.H. Lohka, K.L. Wilson, T.Y. Scherson, L.J. Cisek, J.L. Corden, and T.D. Pollard. 1992. J. Cell Biol. 118:595-605), and this inhibition is proposed to delay cytokinesis until p34(cdc2) activity falls at anaphase. We have characterized previously several kinase activities associated with the isolated cortical cytoskeleton of dividing sea urchin embryos (Walker, G.R., C.B. Shuster, and D.R. Burgess. 1997. J. Cell Sci. 110:1373-1386). Among these kinases and substrates is p34(cdc2) and LC20. In comparison with whole cell activity, cortical H1 kinase activity is delayed, with maximum levels in cortices prepared from late anaphase/telophase embryos. To determine whether cortical-associated p34(cdc2) influences cortical myosin II activity during cytokinesis, we labeled eggs in vivo with [(32)P]orthophosphate, prepared cortices, and mapped LC20 phosphorylation through the first cell division. We found no evidence of serine 1,2 phosphorylation at any time during mitosis on LC20 from cortically associated myosin. Instead, we observed a sharp rise in serine 19 phosphorylation during anaphase and telophase, consistent with an activating phosphorylation by myosin light chain kinase. However, serine 1,2 phosphorylation was detected on light chains from detergent-soluble myosin II. Furthermore, cells arrested in mitosis by microinjection of nondegradable cyclin B could be induced to form cleavage furrows if the spindle poles were physically placed in close proximity to the cortex. These results suggest that factors independent of myosin II inactivation, such as the delivery of the cleavage stimulus to the cortex, determine the timing of cytokinesis.
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PMID:Parameters that specify the timing of cytokinesis. 1047 53

Cdc6p and the origin recognition complex (ORC) are essential for assembly of a pre-replicative complex (preRC) at origins of replication, before the initiation of DNA synthesis. In the absence of Cdc6p, cells fail to initiate DNA replication and undergo a "reductional" mitosis, in which the unreplicated chromosomes are randomly segregated to the spindle poles. We show here that the cells harboring a mutation in the essential Cdc6p Walker A-box arrest in late mitosis, probably at anaphase. This cell cycle block requires either the three Cdc28p phosphorylation sites within the N terminus of Cdc6p or a short region (aa 8-17) that contains a Cy (Cyclin) interaction sequence. These same two Cdc6p mutants that allow a reductional mitosis are defective in binding Cdc28p kinase. In addition to Cdc6p, ORC also binds to cyclin-dependent kinases (CDKs). Interestingly, Sic1p, a CDK inhibitor protein, blocked the S phase-specific Cdc28p-Clb5p kinase from interacting with ORC, but did not prevent the G(1)-specific Cdc28p-Cln2p kinase-ORC interaction. We suggest that ORC, Cdc6p, and Sic1p bind to different CDKs in a cell cycle-dependent manner to temporally regulate events that (i) allow preRC formation after mitosis, (ii) prevent mitosis before DNA replication can occur, and (iii) promote initiation of DNA replication.
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PMID:Binding of cyclin-dependent kinases to ORC and Cdc6p regulates the chromosome replication cycle. 1157 76

The six conserved MCM proteins are essential for normal DNA replication. They share a central core of homology that contains sequences related to DNA-dependent and AAA(+) ATPases. It has been suggested that the MCMs form a replicative helicase because a hexameric subcomplex formed by MCM4, -6, and -7 proteins has in vitro DNA helicase activity. To test whether ATPase and helicase activities are required for MCM protein function in vivo, we mutated conserved residues in the Walker A and Walker B motifs of MCM4, -6, and -7 and determined that equivalent mutations in these three proteins have different in vivo effects in fission yeast. Some mutations reported to abolish the in vitro helicase activity of the mouse MCM4/6/7 subcomplex do not affect the in vivo function of fission yeast MCM complex. Mutations of consensus CDK sites in Mcm4p and Mcm7p also have no phenotypic consequences. Co-immunoprecipitation analyses and in situ chromatin-binding experiments were used to study the ability of the mutant Mcm4ps to associate with the other MCMs, localize to the nucleus, and bind to chromatin. We conclude that the role of ATP binding and hydrolysis is different for different MCM subunits.
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PMID:Different phenotypes in vivo are associated with ATPase motif mutations in Schizosaccharomyces pombe minichromosome maintenance proteins. 1197 89

The cyclin-dependent kinase inhibitor p27Kip1 is a key regulator of the G1/S transition, and an inverse relationship between p27Kip1 protein expression and proliferation index has been reported in malignant lymphomas. However, a subset of aggressive B-cell lymphomas demonstrates high p27Kip1 expression despite a high proliferation index. The aim of this study was to determine potential mechanisms by which lymphoma cells abrogate the growth inhibitory effect of high p27Kip1. The effect of transforming growth factor-beta (TGF-beta) and serum stimulation on p27Kip1 expression and cyclin E/cdk2 activity was investigated in four lymphoma cell lines, Jurkat, CEM-6, OCI-Ly1 and Nalm-6. Reactive lymphocytes responded to growth inhibitory TGF-beta by inducing p27Kip1 expression, with subsequent accumulation of cells in G0/G1. In contrast, TGF-beta did not alter the level of p27Kip1 in Jurkat, CEM-6 and OCI-Ly1 cells with no change in cyclin E/cdk2-kinase activity. Serum stimulation also did not result in a significant change in p27Kip1 expression. Western blot analysis of subcellular fractions demonstrated cytoplasmic p27Kip1, corroborated by immunocytochemistry in a subset of the lymphoma cells. Sequestration of p27Kip1 by cyclin D3 was observed in the nuclear and cytoplasmic fractions of Nalm-6, OCI-Ly-1 and NCEB cells. These results indicate that multiple mechanisms contribute to the abrogation of growth regulation by unscheduled high p27Kip1 protein expression including deficient response to TGF-beta and serum, sequestration by cyclin D3 and cytoplasmic displacement.
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PMID:Growth regulation by p27Kip1 is abrogated by multiple mechanisms in aggressive malignant lymphomas. 1278 Jul 88

Eupolyphaga sinensis Walker is not only used as a food to enhance immunity, but is used as a traditional Chinese medicine and is known as the "preferred drug to regulate blood flow". Previous studies have reported its potential biological activities including anticoagulation, antithrombotic, liver protective effect and antitumor effects. Our results indicated that E. sinensis Walker 70% ethanol extract exhibited anti-tumor effects on S180 (murine sarcoma cell line) cells implanted mice. It effectively inhibited K562 (human chronic myeloid leukemia cell line) cells proliferation and induced G(2)-M phase arrest accompanying through up-regulation of cyclin B1, cdc2 and down-regulation of cyclin D1, cyclin E1, cdc25c and p53. In addition, it inhibited EGF secretion and EGFR kinase activity. Western blotting analysis indicated that it also inhibited the phosphorylation EGFR and activation of its downstream signaling molecules AKT and ERK. These results suggested that the antitumor mechanism of E. sinensis Walker involved altering the cell cycle and inhibiting EGFR phosphorylation in the EGFR signaling pathway.
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PMID:Eupolyphaga sinensis Walker inhibits human chronic myeloid leukemia cell K562 growth by inducing G2-M phase cell cycle arrest and targeting EGFR signaling pathway and in S180 tumor-bearing mice. 2481 61