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)

In the present study, we show that treatment of wild-type (p53+/+) mouse embryonic fibroblast (MEF) cells with a DNA-alkylating agent, N-methyl-N'-nitro-N-nitro-soguanidine (MNNG), resulted in increased levels of adenomatous polyposis coli (APC) mRNA compared to p53 gene-knocked out (p53-/-) MEF cells, indicating that p53 is required for APC expression after alkylation damage. By using HCT-116 colon cancer cells (containing wild-type p53 gene) or p53-/- MEF cells transfected with a pCMV-p53 overexpression plasmid [p53-/-(CMV-p53)], we show that p53 is a labile factor for APC gene expression, and that pretreating HCT-116 cells with a protein synthesis inhibitor, cycloheximide (CHX), inhibited MNNG-induced APC mRNA levels by inhibiting p53 protein synthesis. The effect of CHX on p53 protein synthesis was reversible, as the withdrawal of CHX permitted p53 protein synthesis to resume with a concomitant increase in APC mRNA levels after MNNG treatment. To examine whether p53 regulates APC gene expression at the transcriptional level, we treated HCT-116 or p53-/-(CMV-p53) MEF cells with 5,6-dichloro-1-beta-D-ribofuranosylbenzamidazole (DRB; a transcriptional inhibitor), before the MNNG treatment. Although treatment of cells with DRB resulted in increased p53 protein levels, that the APC mRNA levels were decreased suggests that p53 may enhance APC gene expression upstream of the transcriptional machinery where DRB interacts. That the withdrawal of DRB, and subsequent MNNG treatment, increased the level of APC mRNA indicated that the binding of DRB to the transcriptional machinery was reversible.
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PMID:Protein synthesis and transcriptional inhibitors control N-methyl-N'-nitro-N-nitrosoguanidine-induced levels of APC mRNA in a p53-dependent manner. 973 3

The mechanisms by which the p53 response is triggered following exposure to DNA-damaging agents have not yet been clearly elucidated. We and others have previously suggested that blockage of RNA polymerase II may be the trigger for induction of the p53 response following exposure to ultraviolet light. Here we report on the correlation between inhibition of mRNA synthesis and the induction of p53, p21WAF1 and apoptosis in diploid human fibroblasts treated with either UV light, cisplatin or the RNA synthesis inhibitors actinomycin D, DRB, H7 and alpha-amanitin. Exposure to ionizing radiation or the proteasome inhibitor LLnL, however, induced p53 and p21WAF1 without affecting mRNA synthesis. Importantly, induction of p53 by the RNA synthesis or proteasome inhibitors did not correlate with the induction of DNA strand breaks. Furthermore, cisplatin-induced accumulation of active p53 in repair-deficient XP-A cells occurred despite the lack of DNA strand break induction. Our results suggest that the induction of the p53 response by certain toxic agents is not triggered by DNA strand breaks but rather, may be linked to inhibition of mRNA synthesis either directly by the poisoning of RNA polymerase II or indirectly by the induction of elongation-blocking DNA lesions.
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PMID:Inhibition of RNA polymerase II as a trigger for the p53 response. 998 8

The transcription factor E2F-1 directs the expression of genes that induce or regulate cell division, and a role for E2F-1 in driving cells into apoptosis is the subject of intense discussion. Recently it has been shown that E2F-1 binds and coprecipitates with the mouse double-minute chromosome 2 protein (Mdm2). A domain of E2F-1 (amino acids 390 to 406) shows striking similarity to the Mdm2 binding domain of the tumor suppressor protein p53. It is known that interaction of Mdm2 with p53 through this domain is required for Mdm2-dependent degradation of p53. We show here that E2F-1 protein is upregulated in response to DNA damage. The kinetics of induction are dependent upon the source of DNA damage, i.e., fast and transient after irradiation with X rays and delayed and stable after irradiation with UVC, and thus match the kinetics of p53 induction in response to DNA damage. We show further that E2F-1 is also upregulated by treatment with the transcription inhibitor actinomycin D and with the kinase inhibitor DRB, as well as by high concentrations of the kinase inhibitor H7, all conditions which also upregulate p53. In our experiments we were not able to see an increase in E2F-1 RNA production but did find an increase in protein stability in UVC-irradiated cells. Upregulation of E2F-1 in response to DNA damage seems to require the presence of wild-type p53, since we did not observe an increase in the level of E2F-1 protein in several cell lines which possess mutated p53. Previous experiments showed that p53 is upregulated after microinjection of an antibody which binds to a domain of Mdm2 that is required for the interaction of Mdm2 with p53. Microinjection of the same antibody also increases the expression of E2F-1 protein, while microinjection of a control antibody does not. Furthermore, microinjection of Mdm2 antisense oligonucleotides upregulates E2F-1 protein, while microinjection of an unrelated oligonucleotide does not. These data suggest that E2F-1 is upregulated in a similar way to p53 in response to DNA damage and that Mdm2 appears to play a major role in this pathway.
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PMID:Transcription factor E2F-1 is upregulated in response to DNA damage in a manner analogous to that of p53. 1020 94

We describe the pro-inflammatory and cytotoxic effects of nitric oxide in vivo in human skin. Nitrite and ascorbic acid were mixed on the skin of 12 normal volunteers, three times daily, to release nitric oxide. Exposure to nitric oxide was varied by randomizing the concentration of nitrite and duration of application. Nitric oxide treated skin showed significant increases in cells expressing CD3, CD4, CD8, CD68, neutrophil elastase, ICAM-1, VCAM-1, nitrosotyrosine, p53, and apoptotic cells compared with skin treated with ascorbic acid alone. There was no significant increase in mast cells. Following application of nitric oxide there were significantly fewer CD1a positive Langerhans cells in the epidermis. These appeared to lose dendritic morphology and migrate from the epidermis. There was no significant difference in staining for Ki-67, a marker related to proliferating cell nuclear antigen, between active and control skin but staining was greater after exposure to higher dose nitric oxide than the low dose. Apoptosis, cytotoxicity, and p53 staining were relatively greater after 48 h exposure than after 24 h. These results suggest that nitric oxide is pro-inflammatory and is toxic to DNA, leading to the accumulation of p53 and subsequent apoptosis. High-dose nitric oxide paradoxically led to a smaller increase in macrophages and T cells than low dose suggesting an immunosuppressive effect of higher levels.
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PMID:The inflammatory and cytotoxic effects of a nitric oxide releasing cream on normal skin. 1046 39

Formation of apoptotic bodies is a typical character of apoptotic cell death, but how the processes are controlled is not known. In this study, we compared two apoptosis inducing systems in vascular endothelial cells (VEC). We found that the formation of apoptotic bodies during apoptosis induced by rattlesnake venom, which is an unique and specific apoptosis inducer to vascular endothelial cells, was much faster than that induced by deprivation of survival factors (aFGF and serum). When we blocked the synthesis of mRNAs in cells treated with rattlesnake venom by DRB (5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole), an inhibitor of transcription, the formation of apoptotic bodies was dramatically inhibited. We examined the expression of p53 gene and found that its expression was much higher in apoptosis induced by rattlesnake venom than that in apoptosis induced by deprivation of aFGF and serum. Our results suggest that gene expression is important and p53 gene may play a major role in inducing the formation of apoptotic bodies in VEC.
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PMID:Involvement of gene expressions in apoptosis of vascular endothelial cells induced by rattlesnake venom. 1052 Jun 6

High level activation of p53-dependent transcription occurs following cellular exposure to genotoxic damaging agents such as UV-C, while ionizing radiation damage does not induce a similarly potent induction of p53-dependent gene expression. Reasoning that one of the major differences between UV-C and ionizing radiation damage is that the latter does not inhibit general transcription, we attempted to reconstitute p53-dependent gene expression in ionizing irradiated cells by co-treatment with selected transcription inhibitors that alone do not activate p53. p53-dependent transcription can be dramatically enhanced by the treatment of ionizing irradiated cells with low doses of DRB, which on its own does not induce p53 activity. The mechanism of ionizing radiation-dependent activation of p53-dependent transcription using DRB is more likely due to inhibition of gene transcription rather than prolonged DNA damage, as the non-genotoxic and general transcription inhibitor Roscovitine also synergistically activates p53 function in ionizing irradiated cells. These results identify two distinct signal transduction pathways that cooperate to fully activate p53-dependent gene expression: one responding to lesions induced by ionizing radiation and the second being a kinase pathway that regulates general RNA Polymerase II activity.
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PMID:Synergistic activation of p53-dependent transcription by two cooperating damage recognition pathways. 1095 76

The tumor suppressor p53 is a nucleocytoplasmic shuttling protein that accumulates in the nucleus of cells exposed to various cellular stresses. One important role of nuclear p53 is to mobilize a stress response by transactivating target genes such as the p21(Waf1) gene. In this study, we investigated more closely the localization of p53 in cells following various stresses. Immunocytochemistry of fixed human fibroblasts treated with either UV light, the kinase and transcription inhibitor DRB or the proteasome inhibitor MG132 revealed abundant p53 localized to the nucleus. When cells treated with UV or DRB were permeabilized prior to fixation to allow soluble proteins to diffuse, the nuclear p53 signal was abolished. However, in cells treated with MG132, residual p53 localized to distinct large foci. Furthermore, nucleolin co-localized with p53 to these foci, suggesting that these foci were nucleolar structures. Interestingly, the MDM2 protein was found to co-localize with p53 to nucleolar structures following proteasome inhibition. Our results suggest that the p53 proteins accumulating in the nucleus following UV-irradiation or blockage of transcription are freely soluble and, thus, should be able to roam the nucleus to ensure high occupancy of p53 binding sites. However, inhibition of proteasome activity may be a unique stress in that it leads to the sequestering of p53 proteins to the nucleolus, thereby blunting the p53-mediated transactivation of target genes.
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PMID:Accumulation of soluble and nucleolar-associated p53 proteins following cellular stress. 1132 73

Two specific inhibitors of cyclin-dependent kinase 2 (Cdk2), roscovitine and olomoucine, have been shown recently to induce nuclear accumulation of wt p53 and nucleolar unravelling in interphase human untransformed IMR-90 and breast tumor-derived MCF-7 cells. Here, we show that the early response of MCF-7 cells to roscovitine is fully reversible since a rapid restoration of nucleolar organization followed by an induction of p21(WAF1/CIP1), a downregulation of nuclear wt p53 and normal cell cycle resumption occurs if the compound is removed after 4 h. Interestingly, similar reversible effects are also induced by the casein kinase II (CKII) inhibitor, 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole. Upon short-term treatment also, both compounds significantly, but reversibly, reduce the level of 45S precursor ribosomal RNA. Cells exposed to the two types of protein kinase inhibitors for longer times keep exhibiting altered nucleolar and wt p53 features, yet they strikingly differentiate in that most roscovitine-treated cells fail to ever accumulate high levels of p21(WAF1/CIP1) in contrast with DRB-treated ones. In both cases, however, the cells eventually fall into an irreversible state and die. Moreover, we found that constitutive overexpression of p21(WAF1/CIP1) alters the nucleolar unravelling process in the presence of DRB, but not of roscovitine, suggesting a role for this physiological Cdk inhibitor in the regulation of nucleolar function. Our data also support the notion that both roscovitine- and DRB-sensitive protein kinases, probably including Cdk2 and CKII, via their dual implication in the p53-Rb pathway and in ribosomal biogenesis, would participate in coupling cell growth with cell division.
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PMID:Common and reversible regulation of wild-type p53 function and of ribosomal biogenesis by protein kinases in human cells. 1159 2

Blockage of transcription has been shown to induce the tumor suppressor p53 in human cells. We here show that RNA synthesis inhibitors blocking the phosphorylation of the carboxyl terminal domain (CTD) of RNA polymerase II, such as DRB and H7, induced rapid nuclear accumulation of p53 proteins that were not phosphorylated at ser15 or acetylated at lys382. In contrast, agents that inhibit the elongation phase of transcription, such as UV light, camptothecin or actinomycin D, induced the accumulation of nuclear p53 proteins that were modified at both of these sites. Furthermore, using a panel of DNA repair-deficient cells we show that persistent DNA lesions in the transcribed strand of active genes are responsible for the induction of the ser15 and lys382 modifications following UV-irradiation. We conclude that inhibition of transcription is sufficient for the accumulation of p53 in the nucleus regardless of whether the ser15 site of p53 is phosphorylated or not. Importantly, blockage of the elongation phase of transcription triggers a distinct signaling pathway leading to p53 modifications on ser15 and lys382. We propose that the elongating RNA polymerase complex may act as a sensor of DNA damage and as an integrator of cellular stress signals.
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PMID:Induction of ser15 and lys382 modifications of p53 by blockage of transcription elongation. 1159 3

p53 undergoes phosphorylation on several residues in response to cellular stresses that include UV and ionizing radiation, however the influence of spindle damage on this parameter is relatively unclear. Consequently, the effect of nocodazole on serine 392 phosphorylation was examined in two epithelial cell lines. We show that this process is dependent upon the stepwise activation of p38 mitogen-activated protein kinase (p38 MAPK) and protein kinase casein kinase 2 (CK2). Furthermore, this activation correlated with the biochemical regulation of the maturation-promoting factor (MPF, cdc2/cyclin B), as both DRB and antisense depletion of CK2, as well as SB203580 were associated with an inhibition of its activation in response to nocodazole. Strikingly, when the cell cycle characteristics of nocodazole treated cells were examined, we observed that depletion or inhibition of the catalytic subunit of CK2, in the presence of microtubule inhibitors, resulted in a compromise of the G2 arrest (spindle checkpoint). Furthermore, CK2-depleted, nocodazole treated cells demonstrated a dramatic reduction in the apoptotic cell fraction, confirming that these cells had been endowed with oncogenic properties. These changes were observed in both HeLa cells and HCT116 cells. We also show that this effect is dependent on the presence of functional wild-type p53, as this phenomenon is not apparent in HCT116 p53(-/-) cells. Collectively, our results indicate two novel roles for CK2 in the spindle checkpoint arrest, in concert with p53. Firstly, to maintain increased cyclinB/cdc2 kinase activity, as a component of G2 arrest, and secondly, a role in p53-mediated apoptosis. These findings may have implications for an improved understanding of abnormalities of the spindle checkpoint in human cancers, which is a prerequisite for defining future therapies.
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PMID:Protein kinase CK2 is involved in G2 arrest and apoptosis following spindle damage in epithelial cells. 1170 24


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