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)

Initiation of nitric oxide (NO.)-mediated apoptotic cell death in RAW 264.7 macrophages is associated with up-regulation of mitochondrial manganese superoxide dismutase (MnSOD; SOD2) and down-regulation of cytosolic copper zinc superoxide dismutase (CuZnSOD; SOD1) at their individual mRNA and protein levels. To evaluate the decreased CuZnSOD expression and the initiation of apoptosis we stably transfected macrophages to overexpress human CuZnSOD. Individual clones revealed a 2-fold increase in CuZnSOD activity. Expression of a functional and thus protective CuZnSOD was verified by attenuated superoxide (O2(.)-)-mediated apoptotic as well as necrotic cell death. In this study we showed that SOD-overexpressing macrophages (R-SOD1-12) were also protected against NO.-initiated programmed cell death. Protection was substantial towards NO. derived from exogenously added NO donors or when NO. was generated by inducible NO synthase activation, and was evident at the level of p53 accumulation, caspase activation and DNA fragmentation. Stimulation of parent and SOD-overexpressing cells with a combination of lipopolysaccharide and murine interferon gamma produced equivalent amounts of nitrite/nitrate, which ruled out attenuated inducible NO. synthase activity during protection. Because protection by a O2(.)--scavenging system during NO. -intoxication implies a role of NO. and O2(.)- in the progression of cell damage, we used uric acid to delineate the role of peroxynitrite during NO.-elicited apoptosis. The peroxynitrite scavenger uric acid left S-nitrosoglutathione or spermine-NO-elicited apoptosis unaltered, blocking only 3-morpholinosydnonimine-mediated cell death. As a result we exclude peroxynitrite from contributing, to any major extent, to NO. -mediated apoptosis. Therefore protection observed with CuZnSOD overexpression is unlikely to stem from interference with peroxynitrite formation and/or action. Unequivocally, the down-regulation of CuZnSOD is associated with NO. cytotoxicity, whereas CuZnSOD overexpression protects macrophages from apoptosis.
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PMID:Overexpression of CuZn superoxide dismutase protects RAW 264.7 macrophages against nitric oxide cytotoxicity. 1002 4

The spectrum of somatic cancer-associated missense mutations in the human TP53 gene was studied in order to assess the potential structural and functional importance of various intra-molecular properties associated with these substitutions. Relating the observed frequency of particular amino acid substitutions in the p53 DNA-binding domain to their expected frequency, as calculated from DNA sequence-dependent mutation rates, yielded estimates of their relative clinical observation likelihood (RCOL). Several biophysical properties were found to display significant covariation with RCOL values. Thus RCOL values were observed to decrease with increasing solvent accessibility of the substituted residue and with increasing distance from the p53 DNA-binding and Zn2+ -binding sites. The number of adverse steric interactions introduced by an amino acid replacement was found to be positively correlated with its RCOL value, irrespective of the magnitude of the interactions. A gain in hydrogen bond number was found to be only half as likely to come to clinical attention as mutations involving either a reduction or no change in hydrogen bond number. When the difference in potential energy between the wild-type and mutant DNA-binding domains was considered, RCOL values exhibited a minimum around changes of zero. Finally, classification of mutated residues in terms of their protein/solvent environment yielded, for somatic p53 mutations, RCOL values that resembled those previously determined for inherited mutations of human factor IX causing haemophilia B, suggesting that similar mechanisms may be responsible for the mutation-related perturbation of biological function in different protein folds.
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PMID:Disentangling the perturbational effects of amino acid substitutions in the DNA-binding domain of p53. 1007 Nov 87

The MDM2 oncoprotein encodes a 90 kDa nuclear phosphoprotein capable of abrogating the growth suppressive functions of p53 and pRb tumor suppressor proteins by direct interaction. Alternative splicing of MDM2 protein coding sequences has been documented during tumor progression in human ovarian and bladder carcinomas. The aim of this study was to determine whether alternative splicing of MDM2 occurs during breast tumorigenesis in mice and humans and whether protein coding sequences were affected. Specimens representing normal and malignant breast tissues from the murine D2 mammary tumor model system and human breast carcinomas were examined. Three distinct mdm2 mRNA transcripts of 3.3, 1.6 and 1.5 kb were detected in normal and malignant murine mammary tissues by Northern blot analysis using a full-length mdm2 cDNA probe. Additional Northern blot analysis using a probe derived from exon 12 of murine mdm2 demonstrated that the 1.5 and 1.6 kb transcripts lack sequences encoding the C-terminus of the protein. No evidence of internal deletions of protein coding sequences of mdm2 was detected in any of the normal mammary tissues or D2 murine mammary tumors examined by reverse transcription PCR (RT-PCR). Three distinct MDM2 transcripts of 6.7, 4.7 and 1.9 kb were detected in malignant human breast tissue by Northern blot analysis using a cDNA probe specific for the complete open reading frame of human MDM2. However, a cDNA probe specific for the last exon of human MDM2 hybridized only to the 6.7 and 4.7 kb transcripts, demonstrating that the 1.9 kb transcript lacked protein coding sequences contained in exon 12. Similarly, no internal deletions were detected in a panel of malignant human breast tissues using RT-PCR and analogous primers within human MDM2. Therefore, breast tumors differ from other solid tumors reported previously in that no internal deletions of MDM2 protein coding sequences were observed. However, the data document the presence of multiple MDM2 mRNA transcripts in both normal and malignant breast tissues. A subset of MDM2 transcripts were shown to lack the last exon which contains sequences coding for the RING and zinc fingers and domains which are targets for caspase-3 mediated proteolytic degradation and are required to target p53 for proteosomal degradation.
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PMID:Expression of MDM2 during mammary tumorigenesis. 1018 33

Recently we have shown that wild-type human p53 protein binds preferentially to supercoiled (sc) DNA in vitro in both the presence and absence of the p53 consensus sequence (p53CON). This binding produces a ladder of retarded bands on an agarose gel. Using immunoblotting with the antibody DO-1, we show that the bands obtained correspond to ethidium-stained DNA, suggesting that each band of the ladder contains a DNA-p53 complex. The intensity and the number of these hands are decreased by physiological concentrations of zinc ions. At higher zinc concentrations, binding of p53 to scDNA is completely inhibited. The binding of additional zinc ions to p53 appears much weaker than the binding of the intrinsic zinc ion in the DNA binding site of the core domain. In contrast to previously published data suggesting that 100 microM zinc ions do not influence p53 binding to p53CON in a DNA oligonucleotide, we show that 5-20 microM zinc efficiently inhibits binding of p53 to p53CON in DNA fragments. We also show that relatively low concentrations of dithiothreitol but not of 2-mercaptoethanol decrease the concentration of free zinc ions, thereby preventing their inhibitory effect on binding of p53 to DNA. Nickel and cobalt ions inhibit binding of p53 to scDNA and to its consensus sequence in linear DNA fragments less efficiently than zinc; cobalt ions are least efficient, requiring >100 microM Co2+ for full inhibition of p53 binding. Modulation of binding of p53 to DNA by physiological concentrations of zinc might represent a novel pathway that regulates p53 activity in vivo.
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PMID:Effect of transition metals on binding of p53 protein to supercoiled DNA and to consensus sequence in DNA fragments. 1038 Aug 83

The binding of p53 to its DNA consensus sequence is modulated by the redox state of the protein in vitro. We have shown previously that reduced wild-type p53 binds strongly to supercoiled DNA (scDNA) regardless of the presence or absence of p53CON. Here we compare the effects of oxidation of p53 by azodicarboxylic acid bis[dimethylamide] (diamide) and other agents on p53 binding to p53CON and to scDNA. Oxidation decreases the binding of p53 to scDNA; however, under conditions where binding to p53CON in a DNA fragment is completely abolished, some residual binding to scDNA is still observed. Increasing the concentration of oxidized p53 confers minimal changes in p53 binding to both scDNA and p53CON. Reduction of the oxidized protein by dithiothreitol neither restores its binding to DNA nor to p53CON in DNA fragments. In the presence of excess zinc ions, oxidation of p53 is, however, reversible. We conclude that the irreversibility of p53 oxidation is due, at least in part, to the removal of intrinsic zinc from its position in the DNA binding domain accompanied by a conformational change of the p53 molecule after oxidation of the three cysteines to which the zinc ion is coordinated in the reduced protein.
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PMID:Effect of p53 protein redox states on binding to supercoiled and linear DNA. 1046 13

The changes in subcellular localization of metallothionein (MT) during differentiation were studied in two muscle cell lines, L6 and H9C2, myoblasts in order to understand the nuclear presence of MT and its antiapoptotic property. In myoblasts, MT and zinc were localized mainly in the cytoplasm but were translocated into the nucleus of newly formed myotubes during early stage of differentiation, which was initiated by lowering FBS from 10% to 1%. In fully differentiated myotubes, metallothionein content was decreased with a cytoplasmic localization. These changes in subcellular localization of MT and Zn were accompanied by increased apoptosis in myotubes. The changes in the apoptosis at different stages of differentiation were measured by both DNA ladder formation and TUNEL technique. The results also show that the apoptosis may be initiated by free radical generation and may be accompanied by p53 expression. The H9C2 cells contained high levels of MT, differentiated slowly, and had low incidence of apoptotic bodies compared to L6 cell line.
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PMID:Metallothionein and apoptosis during differentiation of myoblasts to myotubes: protection against free radical toxicity. 1048 4

Codon 273 is one of the hot spots of missense mutation of the p53 tumor suppressor gene found in human cancers. We have previously reported that a mutation at codon 273, p53-273L (Arg --> Leu), suppresses cell growth despite its having no p53-specific transactivation activity. To further elucidate the mechanism of growth suppression caused by p53-273L, we used squamous cell carcinoma cell line HSC3 to isolate subclones containing Zn2+-inducible wild-type (wt) p53, p53-175H, and p53-273L. Northern blot hybridization of the HSC3 cells possessing an inducible function of p53 as well as a luciferase assay for the p21Waf1/Cip1/Sdi1 promoter showed that only wt p53 could induce p21Waf1/Cip1/Sdi1 transcription. Meanwhile, the expression of bax remained unchanged between, before, and after the induction of any analyzed p53s. When wt p53 was induced in HSC3 cells cultured in medium containing 5% fetal bovine serum, cell growth was suppressed through G1 arrest. On the other hand, in medium with 0.1% fetal bovine serum, the growth of HSC3 cells expressing p53-273L was suppressed to a greater degree than that of cells expressing wt p53. Flow cytometric analysis and DNA ladder formation revealed that, unlike wt p53-SN3- and p53-175H-expressing HSC3 cells, p53-273L-expressing cells contained a larger sub-G1 fraction under this culture condition. These findings suggest that p53-273L can induce apoptosis in HSC3 cells without transactivation of p21Waf1/Cip1/Sdi1 and bax.
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PMID:Induction of apoptosis by the p53-273L (Arg --> Leu) mutant in HSC3 cells without transactivation of p21Waf1/Cip1/Sdi1 and bax. 1048 21

The p53 tumor suppressor protein is a transcription factor that binds DNA in a sequence-specific manner through a protein domain stabilized by the coordination of zinc within a tetrahedral cluster of three cysteine residues and one histidine residue. We show that cadmium, a metal that binds thiols with high affinity and substitutes for zinc in the cysteinyl clusters of many proteins, inhibits the binding of recombinant, purified murine p53 to DNA. In human breast cancer MCF7 cells (expressing wild-type p53), exposure to cadmium (5-40 microM) disrupts native (wild-type) p53 conformation, inhibits DNA binding, and down-regulates transcriptional activation of a reporter gene. Cadmium at 10-30 microM impairs the p53 induction in response to DNA-damaging agents such as actinomycin D, methylmethane sulfonate, and hydrogen peroxide. Exposure to cadmium at 20 microM also suppresses the p53-dependent cell cycle arrest in G(1) and G(2)/M phases induced by gamma-irradiation. These observations indicate that cadmium at subtoxic levels impairs p53 function by inducing conformational changes in the wild-type protein. There is evidence that cadmium is carcinogenic to humans, in particular for lung and prostate, and cadmium is known to accumulate in several organs. This inhibition of p53 function could play a role in cadmium carcinogenicity.
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PMID:Cadmium induces conformational modifications of wild-type p53 and suppresses p53 response to DNA damage in cultured cells. 1053 75

The p53 tumour suppressor protein exerts multiple, antiproliferative effects in response to genotoxic exposures. Reactive oxygen intermediates (ROI) play several distinct roles in the p53 pathway. First, they are important activators of p53 through their capacity to induce DNA strand breaks. Second, they regulate the DNA-binding activity of p53 by modulating the redox status of a critical set of cysteines in the DNA-binding domain, which are also involved in the coordination of zinc. Third, they play a role in the signalling pathways regulated by p53, as several genes encoding redox effectors are transcriptionally controlled by p53. In this review, we summarize the evidence for the involvement of ROI at these three levels. Emphasis is placed on the role of metals and ROI as potential regulators of p53 protein conformation and functions, and on the putative toxicological consequences of such a regulation.
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PMID:Redox signalling and transition metals in the control of the p53 pathway. 1060 31

The p53 protein has proven to be central in tumorigenesis by its cell cycle regulatory properties and both gene mutations and protein accumulation have been associated with poor prognosis in breast cancer. The present study was undertaken to investigate the prognostic significance of gene mutations, p53 protein accumulation and of loss of heterozygosity (LOH) at the TP53 locus in young (age < 37 years) breast cancer patients. In total, gene mutations were found in 21 of the 123 patients (17%), LOH in 20 of the 47 informative cases (43%) and protein accumulation in 47 of the 102 available cases (46%). Log rank analysis revealed no significant association between survival and TP53 mutations (in general), p53 protein accumulation or LOH. However, missense mutations localised to the zinc binding domain were significantly (P = 0.0007) associated with poorer prognosis. As indicated in this as well as other studies, p53 protein accumulation is frequently found in young breast cancer patients, but this protein overexpression appears to be of minor significance for survival. Nevertheless, the present report also suggests that specific mutations contribute substantially to tumour aggressiveness.
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PMID:p53 and survival in early onset breast cancer: analysis of gene mutations, loss of heterozygosity and protein accumulation. 1061 30


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