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

Exposure of mammalian cells to ionizing radiation causes a delay in progression through the cycle at several checkpoints. Cells from patients with ataxia-telangiectasia (A-T) ignore these checkpoint controls postirradiation. The tumour suppressor gene product p53 plays a key role at the G1/S checkpoint preventing the progression of cells into S phase. The induction of p53 by radiation is reduced and/or delayed in A-T cells, which appears to account for the failure of delay at the G1/S checkpoint. We have investigated further this defect in radiation signal transduction in A-T. While the p53 response was defective after radiation, agents that interfered with cell cycle progression such as mimosine, aphidicolin and deprivation of serum led to a normal p53 response in A-T cells. None of these agents caused breaks in DNA, as determined by pulse-field gel electrophoresis, in order to elicit the response. Since this pathway is mediated by protein kinases, we investigated the activity of several of these enzymes in control and A-T cells. Ca+2-dependent and -independent protein kinase C activities were increased by radiation to the same extent in the two cell types, a variety of serine/threonine protein kinase activities were approximately the same and anti-tyrosine antibodies failed to reveal any differences in protein phosphorylation between A-T and control cells. It is not evident what is the nature of the defect in signal transduction in A-T cells. However, it is clear that the p53 response is normal in these cells after exposure to some agents and it is mediated through protein kinase C or another serine/threonine kinase.
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PMID:Defect in radiation signal transduction in ataxia-telangiectasia. 753 Jul 54

Tumor necrosis factor-alpha (TNF-alpha) demonstrated antimitogenic activity in MCF-7 cells (estrogen receptor-positive human breast cancer cells) in a dose- and time-dependent manner (EC-50 of 2.5 ng/ml). This antimitogenic effect of TNF-alpha was accompanied by a decreased number of cells in S phase in a dose- and time-dependent manner. Based on growth arrest experiments using aphidicolin, it is apparent that TNF-alpha acted in early G1 phase. It did not show antimitogenic effects once cells reentered the S phase based on [3H]thymidine incorporation into DNA and cell cycle analysis. Specificity of TNF-alpha was established by using monoclonal anti-human TNF-alpha antibody. On the basis of Western immunoblot analysis of Rb, p53 and cell cycle inhibitory protein (Cip1) (p21) proteins, TNF-alpha decreased Rb protein expression in a dose- and time-dependent manner whereas it increased the expression level of tumor suppressor p53 protein. TNF-alpha also increased the expression level of Cip1 (p21) protein in a dose-dependent manner. This induction of Cip1 (p21) protein was preceded by the induction of p53 protein in MCF-7 cells. Cip1 (p21) protein associated with cyclin D was also increased. Tumor suppressor Rb protein expression was increased during G1 to S phase progression. Cyclin D protein expression levels were not changed in response to TNF-alpha treatment, although serine/threonine kinase inhibitors such as H7 and the protein kinase C inhibitor staurosporine decreased cyclin D expression levels in MCF-7 cells. Based on experiments with staurosporine, it appears that TNF-alpha does not utilize a protein kinase C pathway in MCF-7 cells. Other cell cycle-related proteins such as Cdk2, Cdc2, and Cdk4 did not show any change in response to TNF-alpha. TNF-alpha did not affect complexes between cyclin D and Cdk2, Cdk4, and Rb proteins in MCF-7 cells. Taken together these results suggest that Rb, p53, and Cip1 (p21) proteins mediate TNF-alpha antimitogenic activity, and TNF-alpha induces growth arrest in the G1 phase in MCF-7 cells.
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PMID:Effects of tumor necrosis factor-alpha on antimitogenicity and cell cycle-related proteins in MCF-7 cells. 762 60

The expression level of tumor suppressor p21 protein in response to protein kinase inhibitors was examined in MCF-7 cells. Both H7 (serine/threonine kinase inhibitor) and staurosporine (protein kinase C inhibitor) were able to induce p21 protein in a time- and dose-dependent manner. Induction of p21 by H7 but not staurosporine required the induction of p53 protein. Induction of p21 was preceded by the induction of p53 protein. Based on FACS analysis, both H7 and staurosporine act as antimitogenic agents.
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PMID:Induction of tumor suppressor p21 protein by kinase inhibitors in MCF-7 cells. 767 42

We have previously shown that heat shock induces p53-dependent WAF1 expression. To understand the role of protein kinases in the heat-induced p53-mediated signal transduction pathway, the effects of H-7, a serine/threonine kinase inhibitor, on WAF1 accumulation were investigated using two human glioblastoma cell lines differing in p53 status or their transfectants with various p53-expression vectors. Unexpectedly, H-7 alone induced p53-dependent WAF1 accumulation with a biphasic pattern depending on H-7 dose; i.e., low doses of H-7 induced the accumulation of both p53 and WAF1, whereas, a high dose of H-7 induced p53 but no WAF1 accumulation, suggesting that p53 accumulation and p53-dependent WAF1 expression are separable. Heat shock and H-7 induce p53-dependent WAF1 accumulation through different pathways as shown in A-172 cells stably expressing a temperature-sensitive mutant p53. However, our results show that these two pathways cross-talk with each other in the combined treatment of H-7 and heat shock studies. These findings indicate that inhibition of protein kinases can act as a novel stress to evoke the p53 pathway and that p53 activation by heat shock requires activation of yet unidentified protein kinases in vivo. The cross-talks between H-7 and heat shock in the p53 pathway provide the first evidence for the complex interactions between different stress signaling pathways in the modulation of p53 in vivo.
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PMID:Bifunctional effects of a protein kinase inhibitor (H-7) on heat-induced p53-dependent WAF1 accumulation. 941 81

Transcriptional activation and stabilization of p53 is a major response of mammalian cells to U.V.-light induced genetic damages, and possibly responsible for cell damage control. We have studied here by gel mobility shift and immunoblotting assays the activation and accumulation of p53 by U.V.C. and its dependency on cell cycle, protein synthesis and protein phosphorylation. In G0/G1 synchronized cells U.V.C.-induced p53 DNA-binding activity, but not its accumulation, whereas both events took place in G1/S and S-phase cells. The kinetics of p53 activation by U.V.C. were slow requiring at least 1 h and slowly increasing thereafter with full activation observed at 6 h. Treatment of cells with cycloheximide (CHX) prevented the activation of p53 in all phases of the cell cycle and its accumulation in G1/S and S. However, removing CHX-block allowed full activation and accumulation of p53 with fast kinetics even if 4 h had lapsed since the initial U.V.C. insult. This suggests that the protein synthesis-dependent signal initiating p53 activation by U.V.C. remains continuous in the cells. The requirement of protein phosphorylation as mediator of p53 activation by U.V.C. was studied by using chemical protein kinase inhibitors. Of the tested inhibitors, only staurosporine, a known inhibitor of protein kinase C (PKC) and various other kinases, inhibited both p53 activation and accumulation, whereas specific PKC inhibitors, tyrosine kinase inhibitors and a serine/threonine kinase inhibitor did not. PKC-mediation of the p53 U.V.-response was further ruled out by the reactivity of the activated p53 to C-terminal antibody PAb 421. Kinetic studies showed that staurosporine-mediated inhibition of p53 function is an early event in cell damage response. Thus dual, kinetically different events, de novo protein synthesis and staurosporine-inhibited protein phosphorylation are required for p53 activation and accumulation in all phases of the cell cycle. Notably, in the absence of U.V.-induced accumulation in G0/G1 cells, p53 activation is still subject to inhibition of protein synthesis.
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PMID:U.V.C.-induction of p53 activation and accumulation is dependent on cell cycle and pathways involving protein synthesis and phosphorylation. 948 35

A polyomavirus mutant (315YF) blocked in binding phosphatidylinositol 3-kinase (PI 3-kinase) has previously been shown to be partially deficient in transformation and to induce fewer tumors and with a significant delay compared to wild-type virus. The role of polyomavirus middle T antigen-activated PI 3-kinase in apoptosis was investigated as a possible cause of this behavior. When grown in medium containing 1D-3-deoxy-3-fluoro-myo-inositol to block formation of 3'-phosphorylated phosphatidylinositols, F111 rat fibroblasts transformed by wild-type polyomavirus (PyF), but not normal F111 cells, showed a marked loss of viability with evidence of apoptosis. Similarly, treatment with wortmannin, an inhibitor of PI 3-kinase, stimulated apoptosis in PyF cells but not in normal cells. Activation of Akt, a serine/threonine kinase whose activity has been correlated with regulation of apoptosis, was roughly twofold higher in F111 cells transformed by either wild-type virus or mutant 250YS blocked in binding Shc compared to cells transformed by mutant 315YF. In the same cells, levels of apoptosis were inversely correlated with Akt activity. Apoptosis induced by serum withdrawal in Rat-1 cells expressing a temperature-sensitive p53 was shown to be at least partially p53 independent. Expression of either wild-type or 250YS middle T antigen inhibited apoptosis in serum-starved Rat-1 cells at both permissive and restrictive temperatures for p53. Mutant 315YF middle T antigen was partially defective for inhibition of apoptosis in these cells. The results indicate that unlike other DNA tumor viruses which block apoptosis by inactivation of p53, polyomavirus achieves protection from apoptotic death through a middle T antigen-PI 3-kinase-Akt pathway that is at least partially p53 independent.
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PMID:Evidence of a role for phosphatidylinositol 3-kinase activation in the blocking of apoptosis by polyomavirus middle T antigen. 952 48

We have previously reported a correlation between high endogenous expression of the protein product of the RAF-1 proto-oncogene, intrinsic cellular radiosensitivity and rapid exit from a G2/M delay induced by 2 Gy of gamma-irradiation. Raf1 is a positive serine/threonine kinase signal transduction factor that relays signals from the cell membrane to the MAP kinase system further downstream and is believed to be involved in an ionizing radiation signal transduction pathway modulating the G1/S checkpoint. We therefore extended our flow cytometric studies to investigate relationships between radiosensitivity, endogenous expression of the Raf1 protein and perturbation of cell cycle checkpoints, leading to alterations in the G1, S and G2/M populations after 2 Gy of gamma-irradiation. Differences in intrinsic radiosensitivity after modulation of the G1/S checkpoint have generally been understood to involve p53 function up to the present time. A role for dominant oncogenes in control of G1/S transit in radiation-treated cells has not been identified previously. Here, we show in 12 human in vitro cancer cell lines that late G1 accumulation after 2 Gy of radiation is related to both Raf1 expression (r = 0.91, P = 0.0001) and the radiosensitivity parameter SF2 (r = -0.71, P = 0.009).
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PMID:Late G1 accumulation after 2 Gy of gamma-irradiation is related to endogenous Raf-1 protein expression and intrinsic radiosensitivity in human cells. 957 26

The tumor suppressor p53 is a multifunctional protein that plays a critical role in modulating cellular responses upon DNA damage or other stresses. These functions of p53 are regulated both by protein-protein interactions and phosphorylation. The double-stranded RNA activated protein kinase PKR is a serine/threonine kinase that modulates protein synthesis through the phosphorylation of translation initiation factor eIF-2alpha. PKR is an interferon (IFN)-inducible protein that is thought to mediate the anti-viral and anti-proliferative effects of IFN via its capacity to inhibit protein synthesis. Here we report that PKR physically associates with p53. The interaction of PKR with p53 is enhanced by IFNs and upon conditions that p53 acquires a wild type conformation. PKR/p53 complex formation in vitro requires the N-terminal regulatory domain of PKR and the last 30 amino acids of the C-terminus of human p53. In addition, p53 may function as a substrate of PKR since phosphorylation of human p53 on serine392 is induced by activated PKR in vitro. These novel findings raise the possibility of a functional interaction between PKR and p53 in vivo, which may account, at least in part, for the ability of each protein to regulate gene expression at both the transcriptional and the translational levels.
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PMID:The double-stranded RNA activated protein kinase PKR physically associates with the tumor suppressor p53 protein and phosphorylates human p53 on serine 392 in vitro. 1034 43

Protein kinase CK2 is a pleiotropic serine/threonine kinase which has been shown to phosphorylate numerous substrates. Evidence is accumulating that CK2 may exist complexed to a variety of cellular proteins, e.g. p53, MDM2, and A-Raf. Here, we explored the effects of the chemotherapeutic drugs cisplatin and carboplatin on the mRNA and protein levels of p53, MDM2 and CK2 in a murine teratocarcinoma cell line F9. Northern and Western blot analyses were performed and the CK2 activity was determined. The degree of apoptosis after drug treatment was assessed using the TUNEL test. Six hours after cisplatin and carboplatin treatment, the RNA level of p53 dropped by 59% +/- 9% and 86% +/- 8% respectively, whereas the observed level of p53 protein rose to 7 and 10 times over the untreated control, respectively. Treatment with 33 microM cisplatin prompted apoptosis as early as 4 h after drug treatment. More than 50% apoptotic cells were seen after 6 h. We conclude that cisplatin and its second generation drug carboplatin act similarly i.e. both drugs cause a concomitant decrease in p53 mRNA and an increase in p53 protein level. After 4 h treatment with either of the two drugs, p53 levels reach a threshold which leads to the initiation of apoptosis.
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PMID:Determination of mRNA, and protein levels of p53, MDM2 and protein kinase CK2 subunits in F9 cells after treatment with the apoptosis-inducing drugs cisplatin and carboplatin. 1040 39

Repair pathways of DNA are now better defined, and some important findings have been discovered in the last few years. DNA non-homologous end-joining (NEHJ) is a crucial process in the repair of radiation-induced double-strand breaks (DSBs). NHEJ implies at least three steps: the DNA free-ends must get closer, preparation of the free-ends by exonucleases and then a transient hybridisation in a region of DNA with weak homology. DNA-dependent protein kinase (DNA-PK) is the key enzyme in this process. DNA-PK is a nuclear serine/threonine kinase that comprises three components: a catlytic subunit (DNA-PKCS) and two regulatory subunits, DNA-binding proteins, Ku80 and Ku70. The severe combined immunodeficient (scid) mice are deficient in DNA-PKCS: this protein is involved both in DNA repair and in the V(D)J recombination of immunoglobulin and T-cell receptor genes. It is a protein-kinase of the P13-kinase family and which can phosphorylates Ku proteins, p53 and probably some other proteins still unknown. DNA-PK is an important actor of DSBs repair (induced by ionising radiations or by drugs like etoposide), but obviously it is not the only mechanism existing in the cell for this function. Some others, like homologous recombination, seem also to have a great importance for cell survival.
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PMID:[DNA-dependent protein kinase (DNA-PK), a key enzyme in the re-ligation of double-stranded DNA breaks]. 1048 39


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