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)

M phase-promoting factor (MPF) consists of a p34cdc2 (cdc2) kinase and cyclin B complex which in its active form promotes G2 to M transition. The role of MPF in G2 arrest following DNA damage, however, has remained largely uncharacterized. We have investigated whether nitrogen mustard (HN2) interfered with either the formation of MPF or its activation. For this purpose, we measured cdc2 kinase activity relative to cdc2 and cyclin B protein turnover and the phosphorylation status of cdc2. Studies were performed in two exceptional human lymphoma cell lines, which differed in HN2 sensitivity by 5-fold (CA46, 50% growth-inhibitory dose = 1.0 microM; JLP119, 50% growth-inhibitory dose = 0.2 microM) but exhibited virtually identical DNA interstrand and DNA-protein cross-link exposure. Following HN2 treatment, CA46 cells ceased to enter mitosis and exhibited a marked delay in G2 phase. Failure to enter mitosis paralleled inhibition of cdc2 kinase. Inhibition was not due to decreased levels of cdc2 or cyclin B protein; rather, G2 arrest correlated with the accumulation of both tyrosine-phosphorylated cdc2 and cyclin B. These findings implied that G2 arrest resulted from a down-regulation of the processes that activate MPF. We also found that JLP119 cells, within a few hours of mitosis at the time of drug treatment, evaded checkpoint control and continued cell division unabated by DNA damage. Furthermore, despite similar DNA cross-link exposure, JLP119 cells within the window of checkpoint control were more susceptible to S phase delay than CA46 cells. Altered cell cycle responses correlated with the greater susceptibility of JLP119 cells to the cytotoxic effects of HN2.
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PMID:Relationships between cdc2 kinase, DNA cross-linking, and cell cycle perturbations induced by nitrogen mustard. 153 88

The p107wee1 protein kinase plays a central role in regulating the cell cycle of fission yeast. It mediates transmission of signal(s) related to the nutritional status of the cell to the p34cdc2 protein kinase, which is an active component of the MPF complex driving cells into mitosis. p107wee1 is itself subject to control by the products of other genes such as nim1+/cdr1+, win1+, and perhaps wis1+ and other wis+ genes. At present, the relationships between these genes and their possible roles in the mitotic control are unclear and must await further analysis (Fig. 5). It is likely that some of the gene products are concerned with the sensing and/or transmission of nutritional signals. p107wee1 negatively regulates the activity of p34cdc2, probably by direct tyrosine phosphorylation, and also appears to regulate the activities of the cdc1+ and cdc27+ gene products. The effects of nitrogen starvation and of wee1 mutations on conditional lethal mutations at the cdc1, cdc2, and cdc27 loci, taken together, support the largely speculative model shown in Figure 5. During the normal cycle, the balance between phosphorylated and dephosphorylated p34cdc2 changes such that at the appropriate time, p34cdc2 is activated and the cell enters mitosis. We suggest that the cdc1+ and cdc27+ products may be regulated in a similar way. Such a mechanism would ensure coordinated activation of these and perhaps other proteins required for the G2/M transition. There are, of course, many uncertainties, and these must await elucidation by biochemical and genetic analysis.
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PMID:New elements in the mitotic control of the fission yeast Schizosaccharomyces pombe. 181 10

Receptor-mediated endocytosis is inhibited during mitosis in mammalian cells and earlier work on A431 cells suggested that one of the sites inhibited was the invagination of coated pits (Pypaert, M., J. M. Lucocq, and G. Warren. 1987. Eur. J. Cell Biol. 45: 23-29). To explore this inhibition further, we have reproduced it in broken HeLa cells. Mitotic or interphase cells were broken by freeze-thawing in liquid nitrogen and warmed in the presence of mitotic or interphase cytosol. Using a morphological assay, we found invagination to be inhibited only when mitotic cells were incubated in mitotic cytosol. This inhibition was reversed by diluting the cytosol during the incubation. Reversal was sensitive to okadaic acid, a potent phosphatase inhibitor, showing that phosphorylation was involved in the inhibition of invagination. This was confirmed using purified cdc2 kinase which alone could partially substitute for mitotic cytosol.
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PMID:Mitotic cytosol inhibits invagination of coated pits in broken mitotic cells. 191 51

The cdr1 gene in Schizosaccharomyces pombe was identified as a mutation affecting the nutritional responsiveness of the mitotic size control. cdr1 alleles have been further analyzed for genetic interactions with elements of the mitotic control pathway and cloned by plasmid rescue of a conditional lethal cdr1-76 cdc25-22 double mutant. These analyses show that the cdr1 gene is allelic to nim1, a gene identified as a high copy number plasmid suppressor of the mitotic control gene, cdc25. The gene structure for cdr1 differs from the described nim1 gene in the carboxyl-terminal portion of the gene. The published nim1 sequence encoded a product of predicted Mr 45,000, and included 356 amino acids from the amino-terminal region of the gene and 14 amino acids from a noncontiguous carboxyl-terminal fragment. The cdr1 sequence includes an additional 237 amino acids of the contiguous fragment and encodes a product of predicted Mr 67,000. The sequence shows a high level of identity with protein kinases over the amino-terminal catalytic domain, and limited identity with yeast protein kinases SNF1, KIN2 and KIN1 over part of the carboxyl-terminal domain. The effect of overexpression of the full length gene has been examined in various genetic backgrounds. These data show that the full length gene product is required to give a normal cell cycle response to nitrogen starvation. A detailed examination of the genetic interaction of cdr1 mutants with various mutants of mitotic control genes (cdc2, cdc25, wee1, cdc13) demonstrated strong interactions with cdc25, some cdc2 alleles, and with cdc13-117. Overall, the results are interpretable within the framework of the existing model of cdr1/nim1 action in mitotic control, i.e., cdr1 functions upstream of wee1 to relieve mitotic inhibition.
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PMID:Genetic and molecular analysis of cdr1/nim1 in Schizosaccharomyces pombe. 200 5

Fission yeast cell division is initiated by the cdc2/cdc13-cyclin protein kinase which in its catalytically active state comprises the mitotic inducer. During interphase the cdc2/cyclin complex is assembled in an inactive state that requires cdc25+ gene function for M-phase activation. The cdc25+ product, a 76 kd phosphoprotein, is shown to oscillate in abundance during the cell cycle, reaching a peak at G2/M, and to be sensitive to nitrogen starvation. The level of cdc25 is subject to feedback regulation involving both cdc25 and cdc2.
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PMID:Fission yeast cdc25 is a cell-cycle regulated protein. 217 10

G2 arrest induced by nitrogen mustard in human lymphoma CA46 cells is associated with a failure to activate hyperphosphorylated cdc2/cyclin B1 complexes. We investigated the possibility that this might be due to a suppression of cdc25C phosphatase activity. cdc25C from interphase cells migrated as a 54- to 57-kDa doublet in SDS gels and exhibited basal phosphatase activity. cdc25C from mitotic cells migrated as a 66-kDa hyperphosphorylated species and exhibited elevated phosphatase activity. cdc25C hyperphosphorylation and activation were mediated by cdc2, supporting the view of a cdc2-cdc25C autocatalytic feedback loop. Immunofluorescence and cell fractionation studies suggested cdc2-cdc25C interaction occurred within the cytoplasm. Cells arrested in G2 phase following nitrogen mustard treatment or cells arrested in S phase with aphidicolin failed to dephosphorylate and activate cdc2, and this correlated with failure to convert cdc25C into the most active hyperphosphorylated species. Our findings suggest that checkpoints guarding against mitotic entry in the presence of unreplicated or damaged DNA suppress formation of the cdc2-cdc25C autocatalytic feedback loop that normally brings about rapid activation of cdc2.
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PMID:Role of the cdc25C phosphatase in G2 arrest induced by nitrogen mustard. 793 93

The thioether phospholipid derivative ilmofosine (BM41440), a selective inhibitor of protein kinase C, is a new anticancer drug presently undergoing Phase II clinical trials. We have examined the influence of the compound on cell cycle progression. Ilmofosine was found to induce a dose-dependent accumulation of CA46 cells in G2-phase of the cell cycle. G2-arrest correlated with suppression of cdc2 kinase activation. Ilmofosine did not affect cdc2 kinase activity in vitro, consistent with an indirect locus of action. Ilmofosine treated CA46 cells failed to accumulate hyperphosphorylated-cdc2/cyclin B1 complexes that are observed when G2-arrest is induced by either nitrogen mustard or ionizing radiation. Indeed, cdc2 became dephosphorylated and cyclin B1 protein levels decreased as ilmofosine treated cells became arrested in G2. Our findings suggest that ilmofosine down-regulates cdc2 kinase activation through a mechanism that affects the formation of cdc2/cyclin B1 complexes.
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PMID:The protein kinase C inhibitor ilmofosine (BM 41 440) arrests cells in G2 phase and suppresses CDC2 kinase activation through a mechanism different from that of DNA damaging agents. 813 43

We investigated the temporal regulation of cyclin A- and B1-dependent kinases in human lymphoma cells treated with nitrogen mustard (HN2) and pentoxifylline, to determine whether the activity of these complexes correlated with cell cycle arrest induced by DNA damage. Cells were synchronized in G1/S, treated with HN2, and then postincubated with pentoxifylline. HN2-induced a protracted delay in G2 phase. This delay correlated with suppression of cyclin B1- and cdc2-kinase activities, and stabilization of hyperphosphorylated-cdc2 in the presence of similar cyclin B1 levels to those found in mitosis. HN2 had no discernible effect on the S phase activity of cyclin A- or cdk2-immune complexes. Entry of control cells into mitosis correlated with destruction of cyclin A, disappearance of cyclin A-bound cdk2 and decreased cdk2 kinase activity. G2 delay induced by HN2 was associated with stabilization of cyclin A, increased abundance of cyclin A-bound cdk2, and increased cdk2 activity. Cyclin A was also associated with cdc2, which, contrary to complexes containing cdk2, were only activated upon entry into mitosis. Pentoxifylline abrogated cell cycle arrest induced by aphidicolin and HN2 in human lymphoma cells. Pentoxifylline also reverted the activity of cyclin A- and B1-kinases in HN2-treated cells to approximately that observed in controls. Our findings suggest that delayed entry into mitosis following DNA damage correlates with suppression of cyclin B1/cdc2 and cyclin A/cdc2 complexes, while maintaining cyclin A/cdc2 complexes in an active state. Furthermore, we found that pentoxifylline disrupts the signal transduction pathway that regulates these complexes when damaged DNA is present, resulting in abrogation of cell cycle arrest.
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PMID:G2 delay induced by nitrogen mustard in human cells affects cyclin A/cdk2 and cyclin B1/cdc2-kinase complexes differently. 846 39

The product of the human immunodeficiency virus type 1 (HIV-1) vpr gene induces cell cycle arrest in the G2 phase of the cell cycle and is characterized by an accumulation of the hyperphosphorylated form of cdc2 kinase. This phenotype is similar to the effect of DNA-damaging agents, which can also cause cells to arrest at G2. We previously reported that Vpr mimicked some of the effects of a DNA alkylating agent known as nitrogen mustard (HN2). Here we extend these earlier observations by further comparing the activation state of cdc2 kinase, the kinetics of G2 arrest, and the ability to reverse the arrest with chemical compounds known as methylxanthines. Infection of cells synchronized in the G1 phase of the cell cycle with a pseudotyped HIV-1 resulted in arrest at G2 within 12 h postinfection, before the first mitosis. Similar to that induced by HN2, Vpr-induced arrest led to a decrease in cdc2 kinase activity. Vpr-mediated G2 arrest was alleviated by methylxanthines at concentrations similar to those needed to reverse the G2 arrest induced by HN2, and cells proceeded apparently normally through at least one complete cell cycle. These results are consistent with the hypothesis that Vpr induces G2 arrest through pathways that are similar to those utilized by DNA-damaging agents.
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PMID:Human immunodeficiency virus type 1 vpr gene induces phenotypic effects similar to those of the DNA alkylating agent, nitrogen mustard. 909 73

The fission yeast cdr1/nim1 protein kinase phosphorylates and inactivates the weel cdc2-inhibitory kinase. We have investigated the role played by cdr1/nim1 in the connection between nutritional signals and the cell cycle machinery. We show that loss of nim1 activity impairs the appropriate cellular adaptation to nutritional changes. However, the reduction in cell size at division in response to nitrogen starvation is independent of nim1. Moreover, we report that nim1 is an unstable protein that is rapidly degraded upon starvation, through a mechanism that is dependent upon protein synthesis. We propose that nim1, as a constitutive indirect activator of cdc2 at mitosis, favors the cellular response to starvation but does not actively participate in it. On the contrary, upon nitrogen starvation nim1 must be actively destroyed to protect the cells from a commitment into the cell cycle under unfavourable growth conditions.
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PMID:Role of the fission yeast nim 1 protein kinase in the cell cycle response to nutritional signals. 912 32


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