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)

Activation of the cdc2 kinase in the cell cycle occurs upon binding to a regulatory subunit called cyclin. Cyclin A associates with both Cdc2 and its homologue Cdk2. The two complexes appear in S phase but cyclin A/Cdk2 is activated earlier than cyclin A/Cdc2. Several regions in Cdc2 are involved in binding cyclins A and B. Phosphorylation of cyclin/Cdk complexes ensures that the kinase activity peaks at a specific time in the cell cycle. Phosphorylation of Thr161 in Cdc2 is required for strong cyclin binding and kinase activity in vitro; its dephosphorylation is necessary for cells to exit mitosis. We have identified a novel 'Activating factor' that stimulates binding between cyclin and Cdc2 by inducing phosphorylation of Cdc2 on Thr161. We propose that Thr161 is targeted by an additional cell cycle regulatory pathway.
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PMID:cdc2 protein kinase: structure-function relationships. 148 49

Treatment of human myeloid leukemia cells (HL-60, U-937, THP-1) with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with differentiation along the monocytic lineage. This induction by TPA is characterized in part by growth arrest and the appearance of differentiated monocytic phenotype. The present studies demonstrate that myeloid leukemia cells exit the cell cycle to G0-G1 between 24 and 36 h following TPA treatment. This G0-G1 arrest was accompanied by down-regulation of the cell cycle-regulatory genes cdc2, cyclin A, cyclin B, and cdc25. Similar findings were obtained for histones H1 and H4. Cell cycle progression of synchronized U-937 cells revealed low to undetectable mRNA levels for these genes in G1 and maximal transcription in G2-M phase. Results obtained from mRNA half-life studies demonstrate that the stability of cdc2, cyclin A, cyclin B, and cdc25 transcripts is similar in control and TPA-treated U-937 cells. Nuclear run-on assays demonstrated down-regulation of histone gene transcription, while there was no signal detectable for the cell cycle-regulatory genes. The present findings also demonstrate that long term culture of TPA-differentiated U-937 cells is associated with a decrease in G0-G1-arrested cells and an increase of cells in S and G2-M after 25 days. This reentry into the cell cycle was accompanied by loss of adherence, down-regulation of markers for the monocytic phenotype, and induction of the cell cycle-regulatory genes. This process of retrodifferentiation was completed after 36 days when patterns of cell cycle-regulatory and histone gene expression were identical to that in untreated U-937 cells.
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PMID:Differentiation and retrodifferentiation of human myeloid leukemia cells is associated with reversible induction of cell cycle-regulatory genes. 153 83

The mouse FT210 cell line is a temperature-sensitive cdc2 mutant. FT210 cells are found to arrest specifically in G2 phase and unlike many alleles of cdc2 and cdc28 mutants of yeasts, loss of p34cdc2 at the nonpermissive temperature has no apparent effect on cell cycle progression through the G1 and S phases of the division cycle. FT210 cells and the parent wild-type FM3A cell line each possess at least three distinct histone H1 kinases. H1 kinase activities in chromatography fractions were identified using a synthetic peptide substrate containing the consensus phosphorylation site of histone H1 and the kinase subunit compositions were determined immunochemically with antisera prepared against the "PSTAIR" peptide, the COOH-terminus of mammalian p34cdc2 and the human cyclins A and B1. The results show that p34cdc2 forms two separate complexes with cyclin A and with cyclin B1, both of which exhibit thermal lability at the non-permissive temperature in vitro and in vivo. A third H1 kinase with stable activity at the nonpermissive temperature is comprised of cyclin A and a cdc2-like 34-kD subunit, which is immunoreactive with anti-"PSTAIR" antiserum but is not recognized with antiserum specific for the COOH-terminus of p34cdc2. The cyclin A-associated kinases are active during S and G2 phases and earlier in the division cycle than the p34cdc2-cyclin B1 kinase. We show that mouse cells possess at least two cdc2-related gene products which form cell cycle regulated histone H1 kinases and we propose that the murine homolog of yeast p34cdc/CDC28 is essential only during the G2-to-M transition in FT210 cells.
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PMID:Requirement for p34cdc2 kinase is restricted to mitosis in the mammalian cdc2 mutant FT210. 153 42

Studies on the functional and structural properties of the cdc2 kinase, a key cell-cycle regulator, have been possible thanks to the availability of cdc2-specific immunoreagents. In an attempt to elucidate the biochemical regulation of the cdc2 kinase in more detail, we have raised a series of novel mouse monoclonal antibodies against human recombinant cdc2 protein. The five Mab reported here can be subclassified into two groups according to their interspecies cross-reactivity and distinct immunoprecipitation patterns. Thus, the target epitopes of Mab POH-1, POH-2 and POH-7 (group 1) appear to be limited to a few mammalian species and the fraction of cdc2 immunoprecipitable by these Mab from cellular extracts is considerably enhanced by denaturation. In contrast, the POH-3 and POH-8 (group 2) Mab recognize a denaturation-sensitive epitope on cdc2 which is present in all tested mammalian species. More importantly, each of the two groups of Mab immunoprecipitate forms of cdc2 associated with a characteristic set of cellular proteins, none of which appears to be cyclin A or cyclin B. None of the antibodies precipitated a histone-H1 or casein-kinase activity, although an activity which phosphorylated some of the coprecipitated proteins was coprecipitated with the group 2 Mab. These novel Mab did not interfere with the association of cdc2 with cyclin A in vitro and efficient immunoprecipitation of a panel of cdc2 mutant proteins suggests that the target epitopes may not involve amino acid residues essential for currently known cdc2 functions. The results of the present study provide evidence for the existence of additional forms of the cdc2 protein in exponentially growing human cells, distinct from both the monomeric and the cyclin-bound cdc2 identified so far.
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PMID:Distinct forms of human CDC2 identified by novel monoclonal antibodies. 162 47

Xenopus eggs contain two distinct cdc2 homologs of 34 and 32 kd. We show that the 32 kd cdc2 protein, like the 34 kd protein, is a kinase. However, unlike the 34 kd homolog, the 32 kd cdc2 kinase activity does not decrease dramatically at the end of mitosis. The 32 kd protein does not associate with mitotic cyclins B1 and B2 but does associate with cyclin A and a novel doublet of proteins of 54 kd that may regulate its activity. We also show that depletion of the 32 kd cdc2 homolog from a Xenopus extract blocks DNA replication, but does not inhibit entry into mitosis. By contrast, depletion of the 34 kd cdc2 homolog or absence of mitotic cyclins from an extract does not inhibit replication, but does block entry into mitosis. Our results indicate that in higher eukaryotes, DNA replication (G1-S) and mitosis (G2-M) may be controlled by distinctly different cdc2 proteins.
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PMID:Evidence that the G1-S and G2-M transitions are controlled by different cdc2 proteins in higher eukaryotes. 165 71

Cyclins are regulatory subunits which associate with kinases to form complexes that control many of the important steps in cell-cycle progression. The best characterized of the cyclin-containing complexes is the association of cyclin B with the p34cdc2 kinase. The p34cdc2/cyclin B complex is required for the G2 to M transition (see refs 1-4 for review), but the physiological role of other cyclin complexes is unclear. Human cyclin A binds independently to two kinases, associating with either p34cdc2 or a related protein, p33 (refs 5-7). In adenovirus-transformed cells, the viral E1A oncoprotein seems to associate with p33/cyclin A but not with p34cdc2/cyclin A (B. Faha, M.M., L-H.T. and E.H., manuscript submitted). To isolate the gene for p33, we have cloned several novel human cdc2-related genes. The protein product of one of these genes, cdk2 (cyclin-dependent kinase 2), shares 65% sequence identity with p34cdc2 (ref. 8) and 89% identity with the Xenopus Eg-1 gene product. Immunochemical characterization and partial proteolytic mapping show that the cdk2 gene product is the cyclin A-associated p33. Immunoprecipitations of the p33cdk2 protein suggest that it can act as a protein kinase in vitro. As p33cdk2 is bound to cyclin A and is targeted by the viral E1A protein, we suggest that the p33cdk2/cyclin A complex has a unique role in cell-cycle regulation of vertebrate cells.
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PMID:Isolation of the human cdk2 gene that encodes the cyclin A- and adenovirus E1A-associated p33 kinase. 165 4

THE cyclins were first identified by their cell-cycle-dependent synthesis and destruction and have a key role in the control of mitosis in Xenopus embryonic cell cycles. All higher eukaryotes have at least two types of cyclins, the A- and B-type, which can be distinguished by sequence motifs and the timing of their destruction in the cell cycle. The degradation of both cyclins is required for exit from mitosis, but the activation and destruction of cyclin A occur earlier in the cell cycle than with the B-type cyclins. This suggests that cyclin A has a distinct role in cell-cycle progression. We have used an antisense oligodeoxy-nucleotide directed against cyclin A to investigate this role. Ablation of cyclin A messenger RNA in cytostatic factor/metaphase-arrested extracts of Xenopus eggs, followed by in vitro progression into interphase, resulted in the premature appearance of cyclin B-cdc2-associated H1 kinase activity and premature entry into mitosis. Although cyclin A-ablated extracts could initiate DNA synthesis during interphase, S phase was not completed before entry into mitosis. The effects of cyclin A ablation were reversed by the addition of cyclin A mRNA or cyclin A protein to the extracts.
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PMID:Role for cyclin A in the dependence of mitosis on completion of DNA replication. 165 66

Maturation-promoting factor (MPF) activity has been demonstrated for the first time in fish oocytes. We purified MPF from a 100,000g supernatant of crushed, naturally spawned carp oocytes using four chromatography columns: Q-Sepharose Fast-Flow, p13suc1-affinity Sepharose, Mono S, and Superose 12. The final preparation was purified over 1000-fold with a recovery of about 1%. On Superose 12, MPF eluted as a single peak with an apparent molecular weight of 100 kDa. SDS-PAGE analysis of the active fractions after Superose 12 revealed the presence of four proteins of 33, 34, 46, and 48 kDa. A monoclonal antibody against the PSTAIR sequence of cdc2 kinase recognized the 33- and 34-kDa proteins for which the 46- and 48-kDa proteins are endogenous substrates. The 46- and 48-kDa proteins were recognized by a monoclonal antibody against Escherichia coli-produced goldfish cyclin B, but not by an anti-cyclin A antibody. When oocytes were matured in the presence of 32P, the labeling was seen with the 34-kDa protein, but not with the 33-kDa protein. The 34-kDa protein corresponded to the MPF activity, but the 33-kDa protein did not. These findings indicate that carp MPF is a complex of cdc2 kinase and cyclin B, and further that active MPF contains the phosphorylated form of cdc2 kinase.
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PMID:Purification and characterization of maturation-promoting factor in fish. 172 95

Functional clam cyclin A and B proteins have been produced using a baculovirus expression system. Both cyclin A and B can induce meiosis I and meiosis II in Xenopus in the absence of protein synthesis. Half-maximal induction occurs at 50 nM for cyclin A and 250 nM for cyclin B. Addition of 25 nM cyclin A to activated Xenopus egg extracts arrested in the cell cycle by treatment with RNase or emetine activates cdc2 kinase to the normal metaphase level and stimulates one oscillatory cell cycle. High levels of cyclin A cause marked hyperactivation of cdc2 kinase and a stable arrest at the metaphase point in the cell cycle. Kinetic studies demonstrate the concentration of cyclin A added does not affect the 10 min lag period required for kinase activation or the timing of maximal activity, but does control the rate of deactivation of cdc2 kinase during exit from mitosis. In addition, exogenous clam cyclin A inhibits the degradation of both A- and B-type endogenous Xenopus cyclins. These results define a system for investigating the biochemistry and regulation of cdc2 kinase activation by cyclin A.
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PMID:Activation of p34cdc2 kinase by cyclin A. 182 88

Previous work has established that destruction of cyclin B is necessary for exit from mitosis and entry into the next interphase. Sea urchin cyclin B lacking an N-terminal domain is stable, permanently activates cdc2 kinase, resulting in mitotic arrest, and permanently activates the destruction pathway acting on full length cyclin B. Here we have compared the properties of clam cyclins A and B lacking related N-terminal domains. Both cyclin A delta 60 and B delta 97 bind to cdc2 kinase, keep it hyperactivated and block the completion of mitosis. By adding purified delta cyclin proteins to a cell-free system at different cell cycle times, we find that when the cell-free system reaches the cyclin destruction point in the presence of either A delta 60 or B delta 97, the cyclin destruction pathway acting on full length cyclins fails to be turned off. However, the two cyclins differ dramatically in their ability to turn on cyclin destruction. When added to emetine-arrested interphase lysates devoid of endogenous cyclins, only cyclin B delta 97 activates the cyclin destruction system; cyclin A delta 60 does not. This functional difference between the two cyclin types, the first to be described, provides strong support for the idea that the two cyclins have different roles in the cell cycle and suggests that one specialized role of the cyclin B-cdc2 complex is to activate the cyclin destruction pathway and drive cells into interphase of the next cell cycle.
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PMID:Both cyclin A delta 60 and B delta 97 are stable and arrest cells in M-phase, but only cyclin B delta 97 turns on cyclin destruction. 183 59


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