Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Functional suppression of spindle checkpoint protein activity results in apoptotic cell death arising from mitotic failure, including defective spindle formation, chromosome missegregation, and premature mitotic exit. The recently identified p31(comet) protein acts as a spindle checkpoint silencer via communication with the transient Mad2 complex. In the present study, we found that p31(comet) overexpression led to two distinct phenotypic changes, cellular apoptosis and senescence. Because of a paucity of direct molecular link of spindle checkpoint to cellular senescence, however, the present report focuses on the relationship between abnormal spindle checkpoint formation and p31(comet)-induced senescence by using susceptible tumor cell lines. p31(comet)-induced senescence was accompanied by mitotic catastrophe with massive nuclear and chromosomal abnormalities. The progression of the senescence was completely inhibited by the depletion of p21(Waf1/Cip1) and partly inhibited by the depletion of the tumor suppressor protein p53. Notably, p21(Waf1/Cip1) depletion caused a dramatic phenotypic conversion of p31(comet)-induced senescence into cell death through mitotic catastrophe, indicating that p21(Waf1/Cip1) is a major mediator of p31(comet)-induced cellular senescence. In contrast to wild-type p31(comet), overexpression of a p31 mutant lacking the Mad2 binding region did not cause senescence. Moreover, depletion of Mad2 by small interfering RNA induced senescence. Here, we show that p31(comet) induces tumor cell senescence by mediating p21(Waf1/Cip1) accumulation and Mad2 disruption and that these effects are dependent on a direct interaction of p31(comet) with Mad2. Our results could be used to control tumor growth.
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PMID:p31comet Induces cellular senescence through p21 accumulation and Mad2 disruption. 1927 88

Checkpoint kinase-1 (CHK1) is a key regulator of the DNA damage-elicited G(2)-M checkpoints. The aim of the present study was to investigate the effects of a selective CHK1 inhibitor, Chir124, on cell survival and cell cycle progression following ionizing radiation (IR). Treatment with Chir-124 resulted in reduced clonogenic survival and abrogated the IR-induced G(2)-M arrest in a panel of isogenic HCT116 cell lines after IR. This radiosensitizing effect was relatively similar between p53(-/-) and p53-sufficient wild type (WT) HCT116 cells. However, the number of mitotic cells (as measured by assessing the phosphorylation of mitotic proteins) increased dramatically in p53(-/-) HCT116 cells after concomitant Chir-124 exposure, compared to IR alone, while no such effect was observed in p53-sufficient WT HCT116 cells. In p53(-/-) cells, Chir-124 treatment induced a marked accumulation of polyploid cells that were characterized by micronucleation or multinucleation. p21(-/-) HCT116 cells displayed a similar pattern of response as p53(-/-) cells. Chir-124 was able to radiosensitize HCT116 cells that lack checkpoint kinase-2 (CHK2) or that were deficient for the spindle checkpoint protein Mad2. Finally, Chir-124 could radiosensitize tetraploid cell lines, which were relatively resistant against DNA damaging agents. Altogether these results suggest that Chir-124-mediated radiosensitization is profoundly influenced by the p53 and cell cycle checkpoint system.
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PMID:Radiosensitization by Chir-124, a selective CHK1 inhibitor: effects of p53 and cell cycle checkpoints. 1930 58

Chk1 is a conserved protein kinase originally identified in fission yeast, required to delay entry of cells with damaged or unreplicated DNA into mitosis. The requirement of Chk1 for both S and G2/M checkpoints has been elucidated while only few studies have connected Chk1 to the mitotic spindle checkpoint. We used a small interference RNA strategy to investigate the role of Chk1 in unstressed conditions. Chk1 depletion in U2OS human osteosarcoma cells inhibited cell proliferation and raised the percentage of cells with a 4N DNA content, which correlated with accumulation of giant polynucleated cells morphologically distinct from apoptotic cells, while no increased number of cells in G2 or mitosis could be detected. Down-regulation of Chk1 also caused accumulation of cells in the last step of cytokinesis, and of tetraploid cells in G1 phase, which coincided with activation of p53 and increased levels of p21. In addition, Chk1-depleted U2OS cells failed to arrest in mitosis after spindle disruption by nocodazole and showed decreased protein levels of Mad2 and BubR1. These studies show that U2OS cells lacking Chk1 undergo abnormal mitosis and fail to activate the spindle checkpoint, suggesting a role of Chk1 in this checkpoint.
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PMID:U2OS cells lacking Chk1 undergo aberrant mitosis and fail to activate the spindle checkpoint. 1977 78

Because heat shock factor 1 (HSF1) phosphorylation by Plk1 has been previously reported to be involved in mitotic regulation and p53 function may be involved in this mitotic regulation, we have further examined HSF1 functions in mitotic regulation according to p53 status. Nocodazole-mediated aneuploidy was increased in p53-defective (p53Mut) cells; however, it was not increased in p53 wild-type (p53WT) cells. Phosphorylation of HSF1 at Ser216 was increased in p53Mut cells with increased stability of securin and cyclin B1 in mitosis compared with p53WT cells. The interaction of p53 with Plk1 that was shown in p53WT cells and that induced normal mitotic checkpoint function was not observed in p53Mut cells; instead, the binding of HSF1 with Plk1 and HSF1 phosphorylation at Ser216 were seen in p53Mut cells, which resulted in increased aneuploidy production. Moreover, the interaction affinity of Cdc20 with Mad2 was inhibited in p53Mut cells, whereas the interaction between Cdc20 and HSF1 was increased. From the data, it was suggested that HSF1-mediated aneuploidy was more facilitated in p53-defective cells, indicating the importance of novel mechanisms for p53 function in HSF1-mediated mitotic regulation and genomic instability.
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PMID:Heat shock factor 1-mediated aneuploidy requires a defective function of p53. 1993 26

The molecular mechanisms regulating cell death during mitosis are poorly understood. We show here a critical role for p73, but not p53, in regulating mitotic cell death induced by various means. Prolonged mitotic arrest and the activation of spindle checkpoint are required for mitotic death, which occurs before mitotic exit and which can be ameliorated by accelerated mitotic exit. Absence or silencing of p73 expression abrogated mitotic death without accelerating mitotic exit, and was independent of BubR1 and Mad2, the loss of which promotes mitotic exit. However, the absence of p73 reduced mitotic death by compromising the expression of the proapoptotic BH3-only protein Bim and thereby affecting cytochrome c release and caspase activation. p73 was found to induce bim expression through direct binding to regulatory elements in intron 1. Congruently, mitotic cell death was rescued to similar extents by silencing either bim or p73 expression. Taken together, the data show an important role for the p73-Bim axis in regulating cell death during mitosis that is independent of p53.
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PMID:An essential role for p73 in regulating mitotic cell death. 2001 Jul 85

Adeno-associated virus (AAV) type 2 or UV-inactivated AAV (UV-AAV2) infection provokes a DNA damage response that leads to cell cycle arrest at the G2/M border. p53-deficient cells cannot sustain the G2 arrest, enter prolonged impaired mitosis, and die. Here, we studied how non-replicating AAV2 kills p53-deficient osteosarcoma cells. We found that the virus uncouples centriole duplication from the cell cycle, inducing centrosome overamplification that is dependent on Chk1, ATR and CDK kinases, and on G2 arrest. Interference with spindle checkpoint components Mad2 and BubR1 revealed unexpectedly that mitotic catastrophe occurs independently of spindle checkpoint function. We conclude that, in the p53-deficient cells, UV-AAV2 triggers mitotic catastrophe associated with a dramatic Chk1-dependent overduplication of centrioles and the consequent formation of multiple spindle poles in mitosis. As AAV2 acts through cellular damage response pathways, the results provide information on the role of Chk1 in mitotic catastrophe after DNA damage signaling in general.
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PMID:The DNA damage response to non-replicating adeno-associated virus: Centriole overduplication and mitotic catastrophe independent of the spindle checkpoint. 2019 89

Definitive information about the number and nature of discrete steps of tumorigenesis is enigmatic. To understand the multistep nature of carcinogenesis, an in vitro model of 20-Methylcholanthrene-treated primary fibroblast cells CNCI-PM-20, from 20-day old Swiss mouse embryo was used. Visible neoplastic changes with distinct morphological variations along with specific chromosomal aberrations like Robertsonian metacentrics, double and single-minute chromosomes and aneuploidy were observed from Passage-20 onwards. The cell cycle profile showed gradual increase in G(2)/M population till P-32, followed by evasion of block from P-36 onwards. Gradual increase in expression of C-myc, CyclinD1 and a decrease in expression of P21 was observed from P-20 onwards. CDC25A expression was significantly increased at P-27 and remained more or less constant in subsequent passages. Additionally, an increased P16 and P53 expression were seen at P-20 followed by their significant down-regulation at P-32. An increased level of phosphorylated retinoblastoma (ppRb) was observed from P-27, probably responsible for a compromised G(1)/S checkpoint. The inactivation of p21 and p16 might be due to their promoter hyper-methylation as suggested through de-methylation experiment by 5-aza-deoxycytidine at P-42. G(2)/M checkpoint abrogation was marked by gradual increase in expression of CyclinB1 and Cdc20, and a significant increase of Mad2 at P-20. Interestingly, increased expression of phospho-ATM, ATR and phospho-Chk1 were also seen at P-20 followed by their down-regulation at subsequent passages, indicating a perturbation of DNA damage response pathway at early passages. Our findings therefore dramatize the multiple genetic events that can cooperate to promote tumorigenesis.
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PMID:Sequential loss of cell cycle checkpoint control contributes to malignant transformation of murine embryonic fibroblasts induced by 20-methylcholanthrene. 2023 3

10-[(3-Hydroxy-4-methoxybenzylidene)]-9(10H)-anthracenone (HMBA), a synthetic compound, has been reported to have a potent antitumor activity. In this study, we found that HMBA depolymerized microtubules in MCF-7 cells and produced aberrant spindles in the MCF-7 cells. It also reduced the distance between the centrosomes and activated the mitotic checkpoint proteins BubR1 and Mad2. Further, HMBA inhibited the progression of MCF-7 cells in mitosis and induced apoptotic cell death involving p53 pathway. In vitro, HMBA bound to purified brain tubulin with a dissociation constant of 4.1+/-0.9 microM. It inhibited microtubule assembly and increased the GTP hydrolysis rate of microtubule assembly. The compound did not alter the binding of 2'(or 3')-O-(trinitrophenyl) guanosine 5'-triphosphate (TNP-GTP), a fluorescent analogue of GTP, to tubulin suggesting that it did not inhibit the binding of GTP to tubulin. However, we obtained evidence indicating that HMBA perturbed the conformation of the GTP binding site in tubulin. In addition, an analysis of the modified Dixon plot suggested that HMBA competitively inhibited the binding of colchicine to tubulin. A computational analysis of the binding of HMBA to tubulin supported the finding that HMBA shared its binding site with colchicine in tubulin and indicated that the binding of HMBA to tubulin was primarily stabilized through hydrogen bonding.
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PMID:HMBA depolymerizes microtubules, activates mitotic checkpoints and induces mitotic block in MCF-7 cells by binding at the colchicine site in tubulin. 2079 14

Checkpoint kinase 1 (Chk1) is a key element in the DNA-damage response pathway that is required for maintaining genomic stability. To study the potential role of Chk1 in mammary tumorigenesis, we disrupted it using a Cre/loxP system. We showed that although Chk1 heterozygosity caused abnormal development of the mammary gland, it was not sufficient to induce tumorigenesis. Simultaneous deletion of one copy of p53 failed to rescue the developmental defects; however, it synergistically induced mammary tumor formation in Chk1(+/-);MMTV-Cre animals with a median time to tumor latency of about 10 months. Chk1 deficiency caused a preponderance of abnormalities, including prolongation, multipolarity, misalignment, mitotic catastrophe and loss of spindle checkpoint, that are accompanied by reduced expression of several cell cycle regulators, including Mad2. On the other hand, we also showed that Chk1 deficiency inhibited mammary tumor formation in mice carrying a homozygous deletion of p53, uncovering a complex relationship between Chk1 and p53. Furthermore, inhibition of Chk1 with a specific inhibitor, SB-218078, or acute deletion of Chk1 using small hairpin RNA killed mammary tumor cells effectively. These data show that Chk1 is critical for maintaining genome integrity and serves as a double-edged sword for cancer: although its inhibition kills cancer cells, it also triggers tumorigenesis when favorable mutations are accumulated for cell growth.
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PMID:Genetic instability and mammary tumor formation in mice carrying mammary-specific disruption of Chk1 and p53. 2047 25

In this study, curcumin, a potential anticancer agent, was found to dampen the dynamic instability of individual microtubules in living MCF-7 cells. It strongly reduced the rate and extent of shortening states, and modestly reduced the rate and extent of growing states. In addition, curcumin decreased the fraction of time microtubules spent in the growing state and strongly increased the time microtubules spent in the pause state. Brief treatment with curcumin depolymerized mitotic microtubules, perturbed microtubule-kinetochore attachment and disturbed the mitotic spindle structure. Curcumin also perturbed the localization of the kinesin protein Eg5 and induced monopolar spindle formation. Further, curcumin increased the accumulation of Mad2 and BubR1 at the kinetochores, indicating that it activated the mitotic checkpoint. In addition, curcumin treatment increased the metaphase/anaphase ratio, indicating that it can delay mitotic progression from the metaphase to anaphase. We provide evidence suggesting that the affected cells underwent apoptosis via the p53-dependent apoptotic pathway. The results support the idea that kinetic stabilization of microtubule dynamics assists in the nuclear translocation of p53. Curcumin exerted additive effects when combined with vinblastine, a microtubule depolymerizing drug, whereas the combination of curcumin with paclitaxel, a microtubule-stabilizing drug, produced an antagonistic effect on the inhibition of MCF-7 cell proliferation. The results together suggested that curcumin inhibited MCF-7 cell proliferation by inhibiting the assembly dynamics of microtubules.
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PMID:Curcumin suppresses the dynamic instability of microtubules, activates the mitotic checkpoint and induces apoptosis in MCF-7 cells. 2064 66


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