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)

Cdc25 regulates entry into mitosis by regulating the activation of cyclin B/cdc2. In humans, at least two cdc25 isoforms have roles in controlling the G2/M transition. Here we show, using bacterially expressed recombinant proteins, that two cdc25B splice variants, cdc25B2 and cdc25B3, are capable of activating cyclin A/cdk2 and cyclin B/cdc2, but that mitotic hyperphosphorylation of these proteins increases their activity toward only cyclin B1/cdc2. Cdc25C has only very low activity in its unphosphorylated form, and following hyperphosphorylation it will efficiently catalyze the activation of only cyclin B/cdc2. This was reflected by the in vivo activity of the immunoprecipitated cdc25B and cdc25C from interphase and mitotic HeLa cells. The increased activity of the hyperphosphorylated cdc25s toward cyclin B1/cdc2 was in large part due to increased binding of this substrate. The substrate specificity, activities, and timing of the hyperphosphorylation of cdc25B and cdc25C during G2 and M suggest that these two mitotic cdc25 isoforms are activated by different kinases and perform different functions during progression through G2 into mitosis.
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PMID:Hyperphosphorylation of the N-terminal domain of Cdc25 regulates activity toward cyclin B1/Cdc2 but not cyclin A/Cdk2. 935 26

Arsenite, a unique human carcinogen, induces many types of cytogenetic alterations, such as sister chromatid exchanges, chromosome aberrations, and endoreduplication in a variety of in vivo and in vitro systems. Cytogenetic alterations are frequently associated with cancer development. The purpose of this study was to explore how arsenite induces cytogenetic alterations in human skin fibroblasts (HFW). The present results show that treatment of G2-enriched HFW cells with 5 microM arsenite results in significant delay of cell cycle progression, accumulation of mitotic cells, and prolongation of mitosis. Arsenite-induced G2 and mitotic delay are accompanied by accumulation of cyclin B1 and hyperphosphorylation of cdc2 and Mos proteins. In addition to mitotic delay and prolongation, arsenite treatment also induced out-of-phase centromere separation and alterations of chromosome segregation, such as the appearance of c-metaphase, ball-metaphase, and lagged chromosomes. Unlike spindle poisons, arsenite at the dose range used did not inhibit the spindle fiber formation but conceivably deranges the spindle apparatus. By analyzing the karyotype of established subclones surviving arsenite injury, 18% (8 of 44) showed one chromosome loss, whereas all 26 subclones derived from the untreated cultures were diploid. Furthermore, most arsenite-treated clones manifest prolonged life span (86 +/- 18 population doublings) as compared to those derived from the untreated cultures (44 +/- 11 population doublings). Unfortunately, none became immortal. Collectively, treatment of the G2-enriched HFW cells with arsenite can disturb the mitotic events and subsequently induce chromosome loss.
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PMID:Sodium arsenite disturbs mitosis and induces chromosome loss in human fibroblasts. 937 2

Cytolethal distending toxins (CDT) constitute an emerging heterogeneous family of bacterial toxins whose common biological property is to inhibit the proliferation of cells in culture by blocking their cycle at G2/M phase. In this study, we investigated the molecular mechanisms underlying the block caused by CDT from Escherichia coli on synchronized HeLa cell cultures. To this end, we studied specifically the behavior of the two subunits of the complex that determines entry into mitosis, i.e., cyclin B1, the regulatory unit, and cdc2 protein kinase, the catalytic unit. We thus demonstrate that CDT causes cell accumulation in G2 and not in M, that it does not slow the progression of cells through S phase, and that it does not affect the normal increase of cyclin B1 from late S to G2. On the other hand, we show that CDT inhibits the kinase activity of cdc2 by preventing its dephosphorylation, an event which, in normal cells, triggers mitosis. This inhibitory activity was demonstrated for the three partially related CDTs so far described for E. coli. Moreover, we provide evidence that cells exposed to CDT during G2 and M phases are blocked only at the subsequent G2 phase. This observation means that the toxin triggers a mechanism of cell arrest that is initiated in S phase and therefore possibly related to the DNA damage checkpoint system.
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PMID:Escherichia coli cytolethal distending toxin blocks the HeLa cell cycle at the G2/M transition by preventing cdc2 protein kinase dephosphorylation and activation. 939

The cytotoxicity of a recombinant adenovirus expressing the wild type tumor suppressor gene p53 (AdWTp53) was studied in two human breast cancer MCF-7 sublines selected for resistance to adriamycin (MCF-Adr) and mitoxantrone (MCF-Mito). Although the levels of wild type p53 protein following infection with AdWTp53 are comparable in all cell lines, the two drug-resistant MCF-7 sublines were 300- and 18-fold more sensitive to killing by AdWTp53 compared with the drug-sensitive parental MCF-7 cell lines. In each cell line, AdWTp53 infection led to cell cycle arrest, and reduction of Cdk2 and cyclin B1-Cdc2 activity. Nucleosomal DNA fragmentation analysis (as a function of apoptosis) following AdWTp53 infection revealed that, while the parental MCF-7 cells failed to undergo apoptosis, both drug-resistant cell lines showed distinct DNA laddering. In MCF-Adr cells, a combination treatment of AdWTp53 and adriamycin was much more toxic than either of the reagents used individually. Finally, exposure of a mixed population of MCF-Adr and CD34+ cells to AdWTp53 selectively prevented MCF-Adr cell colony formation, while there was no inhibition of CFU-GM colony formation from CD34+ cells. These findings suggest that some drug-resistant human breast cancers may be effectively treated with adenovirus expressing wild type p53.
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PMID:A recombinant adenovirus expressing wild type p53 induces apoptosis in drug-resistant human breast cancer cells: a gene therapy approach for drug-resistant cancers. 940 9

Study of the function and regulation of the important cell cycle regulator cdc25 phosphatase has been hampered by the lack of a sensitive and specific substrate and assay. Here we report the production of a specific and sensitive substrate for the cdc25 phosphatase. The substrate is human cyclin B1/cdc2 phosphorylated on the inhibitory Thr14 and Tyr15 residues and activating Thr161 on cdc2, and is relatively simple to produce from readily available materials. The assay is based on the cdc25-specific dephosphorylation and activation of the phosphorylated cyclin B1/cdc2 substrate (PY15), using the increased histone H1 kinase activity of the activated PY15 as a read-out of cdc25 activity.
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PMID:Production of a soluble cyclin B/cdc2 substrate for cdc25 phosphatase. 941 82

In this study, NIH3T3 cells stably transfected with a cyclin B1-luciferase reporter vector were utilized to investigate if cyclin B1 promoter activity is linked to either DNA replication or the activities of various cyclin-cyclin dependent kinases (cdks). Synchronized cells treated at the time of serum re-stimulation with 2 micrograms/ml of the DNA synthesis inhibitor, aphidicolin, did not display an increase in luciferase activity in comparison to control cells. When treated with aphidicolin during S phase, luciferase activity decreased. In contrast, luciferase activity increased in cells treated at the time of serum re-stimulation with 200 microM olomoucine, a cyclin-cdk inhibitor. These results indicate that (1) cyclin B1 promoter activity in NIH3T3 cells is linked to a DNA replication checkpoint control mechanism; (2) the cyclin B1 gene can be activated in the absence of functional cyclin E-cdk2, cyclin A-cdk2, or cyclin B-cdk2; and (3) cyclin B1 gene activation can occur in G1 arrested cells under conditions in which the arrest is not directly linked to inhibition of DNA synthesis.
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PMID:Differential response of the human cyclin B1 promoter to inhibitors of the cell cycle in NIH3T3 cells. 951 74

When full-grown oocytes of the newt Cynops pyrrhogaster were treated with progesterone in O-R2 solution containing antibiotics, approximately 85% of the oocytes completed meiosis synchronously. Maturation-promoting factor (MPF) activity appeared just before germinal vesicle breakdown (GVBD) and the oocytes maintained high MPF activity throughout metaphase I and metaphase II of meiosis. A slight decrease of MPF activity was observed at the first polar body emission. The distribution of cyclin B1 was investigated with anti-cyclin B1 antibody. No cyclin B1 was found in the oocytes before progesterone treatment. Cyclin B1 appeared in the cortex of animal hemispheres, especially around and inside germinal vesicle just before GVBD. A large amount of cyclin B1 accumulated at metaphase I, approximately half disappeared at the first polar body emission, and then cyclin B1 accumulated again at metaphase II. An inactive form of cdc2 kinase was observed in both the germinal vesicles and the oocyte cytoplasm, while an active form appeared at the M phase. No MPF was observed in the oocytes from which the germinal vesicle had been removed. A cdk7-like molecule was localized in the germinal vesicle, but not in oocyte cytoplasm, indicating that inactive cdc2 kinase associated with cyclin B1 derived from cytoplasm is activated by phosphorylation in the germinal vesicle. The changes in the amount of cyclin B1 were synchronous with the first cell cycle after fertilization. Cyclin B1 was primarily localized in the cortex of the animal hemisphere. A shift in band mobility upon electrophoresis of cyclin B1 was observed from samples taken during the cell cycle; this shift was probably due to the protein's phosphorylation state.
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PMID:Changes in cyclin B during oocyte maturation and early embryonic cell cycle in the newt, Cynops pyrrhogaster: requirement of germinal vesicle for MPF activation. 952 Mar 24

Alzheimer's disease (AD) is a major dementing illness characterized by regional concentrations of senile plaques, neurofibrillary tangles, and extensive neuronal cell death. Although cell and synaptic loss is most directly linked to the severity of symptoms, the mechanisms leading to the neuronal death remain unclear. Based on evidence linking neuronal death during development to unexpected reappearance of cell cycle events, we investigated the brains of 12 neuropathologically verified cases of Alzheimer's disease and eight age-matched, disease-free controls for the presence of cell cycle proteins. Aberrant expression of cyclin D, cdk4, proliferating cell nuclear antigen, and cyclin B1 were identified in the hippocampus, subiculum, locus coeruleus, and dorsal raphe nuclei, but not inferotemporal cortex or cerebellum of AD cases. With only one exception, control subjects showed no significant expression of cell cycle markers in any of the six regions. We propose that disregulation of various components of the cell cycle is a significant contributor to regionally specific neuronal death in AD.
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PMID:Ectopic cell cycle proteins predict the sites of neuronal cell death in Alzheimer's disease brain. 952 97

Two B-type cyclins, B1 and B2, have been identified in mammals. Proliferating cells express both cyclins, which bind to and activate p34(cdc2). To test whether the two B-type cyclins have distinct roles, we generated lines of transgenic mice, one lacking cyclin B1 and the other lacking cyclin B2. Cyclin B1 proved to be an essential gene; no homozygous B1-null pups were born. In contrast, nullizygous B2 mice developed normally and did not display any obvious abnormalities. Both male and female cyclin B2-null mice were fertile, which was unexpected in view of the high levels and distinct patterns of expression of cyclin B2 during spermatogenesis. We show that the expression of cyclin B1 overlaps the expression of cyclin B2 in the mature testis, but not vice versa. Cyclin B1 can be found both on intracellular membranes and free in the cytoplasm, in contrast to cyclin B2, which is membrane-associated. These observations suggest that cyclin B1 may compensate for the loss of cyclin B2 in the mutant mice, and implies that cyclin B1 is capable of targeting the p34(cdc2) kinase to the essential substrates of cyclin B2.
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PMID:Cyclin B2-null mice develop normally and are fertile whereas cyclin B1-null mice die in utero. 953 39

M-phase-promoting factor (MPF), a complex of cdc2 and a B-type cyclin, is a key regulator of the G2/M cell cycle transition. Cyclin B1 accumulates in the cytoplasm through S and G2 phases and translocates to the nucleus during prophase. We show here that cytoplasmic localization of cyclin B1 during interphase is directed by its nuclear export signal (NES)-dependent transport mechanism. Treatment of HeLa cells with leptomycin B (LMB), a specific inhibitor of the NES-dependent transport, resulted in nuclear accumulation of cyclin B1 in G2 phase. Disruption of an NES which has been identified in cyclin B1 here abolished the nuclear export of this protein, and consequently the NES-disrupted cyclin B1 when expressed in cells accumulated in the nucleus. Moreover, we show that expression of the NES-disrupted cyclin B1 or LMB treatment of the cells is able to override the DNA damage-induced G2 checkpoint when combined with caffeine treatment. These results suggest a role of nuclear exclusion of cyclin B1 in the DNA damage-induced G2 checkpoint.
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PMID:Nuclear export of cyclin B1 and its possible role in the DNA damage-induced G2 checkpoint. 958 66


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