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)

Nuclear oncoproteins are among the most rapidly degraded intracellular proteins. Previous work has implicated the ubiquitin-mediated proteolytic system in the turnover of short-lived intracellular proteins. In the present study, we have evaluated the potential role of the ubiquitin system in the degradation of the specific nuclear oncoproteins encoded by the N-myc, c-myc, c-fos, p53 and E1A genes. Each of these nuclear oncoproteins was synthesized in vitro by transcription of the appropriate cDNA and translation of the resulting mRNA in the presence of [35S]methionine. Degradation of labeled proteins was monitored in the ubiquitin cell-free system. ATP stimulated the degradation of all the proteins between 3- and 10-fold. The degradation was completely inhibited by neutralizing antibody directed against the ubiquitin-activating enzyme, E1, the first enzyme in the ubiquitin-mediated proteolytic cascade. Moreover, degradation in E1-depleted lysates could be restored in each case by the addition of affinity-purified E1. These data suggest that the ubiquitin system mediates the degradation of these oncoproteins in vitro. Degradation of other proteins, such as superoxide dismutase, cytochrome c, enolase, RNase A, and ornithine decarboxylase, is not mediated by the ubiquitin cell-free system. This suggests that the nuclear oncoproteins studied here possess specific signals that target them for rapid turnover by this proteolytic pathway. Furthermore, the relative sensitivity to degradation of various E1A mutants in vivo is also maintained in the cell-free system, suggesting that the ubiquitin pathway may play a role in the cellular degradation of these proteins as well.
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PMID:Degradation of nuclear oncoproteins by the ubiquitin system in vitro. 184 34

We have studied the effects of food restriction (FR) and substitution of fish oil (FO; omega 3) for corn oil (CO; omega 6) on breast tumor incidence and survival in mouse mammary tumor virus/v-Ha-ras transgenic (Onco) mice. The diets were as follows: group 1, 5% (wt/wt) CO fed ad libitum (AL); group 2, 5% CO, restricted calories (40% fewer calories than AL; FR); group 3, 20% CO fed AL; and group 4, 20% FO fed AL. After 3 years, 40% of FR Onco (group 2) mice were alive, whereas there were no survivors in the other three groups. Similarly, tumor incidence was reduced to 27% (5 out of 18) in FR animals (group 2), whereas it was 83% (11 out of 13) in group 1 mice, 89% (16 out of 18) in group 3 mice, and 71% (10 out of 14) in group 4 mice. These protective effects of FR on survival and tumor incidence were paralleled by higher expression of the tumor suppressor gene p53 (wild type) and free-radical scavenging enzymes (catalase and superoxide dismutase) in breast tumors. Immunoblotting showed less ras gene product, p21, and increased p53 levels in the tumors of FR mice. In addition, FR decreased RNA levels of c-erbB-2, interleukin 6, and the transgene v-Ha-ras in tumors. In contrast, analysis of hepatic mRNA from tumor-bearing FR mice revealed higher expression of catalase, glutathione peroxidase, and superoxide dismutase. Survival and tumor incidence were not influenced significantly by dietary supplementation with FO in place of CO. Taken together, our studies suggest that moderate restriction of energy intake significantly inhibited the development of mammary tumors and altered expression of cytokines, oncogenes, and free-radical scavenging enzymes.
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PMID:Dietary lipids and calorie restriction affect mammary tumor incidence and gene expression in mouse mammary tumor virus/v-Ha-ras transgenic mice. 760 20

Aziridinylbenzoquinones are a group of antitumor agents that elicit cytotoxicity by generating either alkylating intermediates or reactive oxygen species. The mechanism of toxicity may not always, however, involve profound damage of cellular constituents, but may involve a cytostatic effect through interference with the cell cycle. In this context, we have examined the induction of the cell cycle inhibitor p21 (WAF1, CIP1, or sdi1), whose overexpression suppresses the growth of various tumor cells, in human tumor cells metabolizing 3,6-diaziridinyl-1,4-benzoquinone (DZQ) and its C2,C5-substituted derivatives: 2,5-bis-(carboethoxyamino) (AZQ) and 2, 5-bis-2(-hydroxyethylamino) (BZQ). Both DZQ and AZQ were effectively activated by HCT116 human colonic carcinoma cells; the activation of the former involved largely a dicoumarol-sensitive activity, whereas that of the latter appeared to be accomplished primarily by one-electron transfer reductases. BZQ was not a substrate for the dicoumarol-sensitive enzyme in HCT116 cells. Cellular activation of the first two quinones was associated with formation of oxygen-centered radicals as detected by EPR in conjunction with the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide. The redox transitions of DZQ involved hydroxyl radical formation and were strongly inhibited by catalase, whereas those of AZQ showed a strong superoxide anion component sensitive to superoxide dismutase. These signals were suppressed by N-acetylcysteine with concomitant production of a thiyl radical adduct. This suggests an effective electron transfer between the thiol and free radicals formed during the activation of these quinones. DZQ and AZQ induced significantly the expression of p21 in HCT116 cells, but a 10-fold higher concentration of AZQ was required to achieve the level of induction elicited by DZQ. BZQ had little effect on p21 expression. p21 induction at both mRNA and protein levels correlated with the inhibition of either cyclin-dependent kinase activity or cell proliferation. p21 induction elicited by the above quinones was inhibited by N-acetylcysteine, whereas the non-sulfur analog, N-acetylalanine, was without effect. Catalase and superoxide dismutase did not effect p21 induction by aziridinylbenzoquinones in HCT116 cells, thus suggesting that extracellular sources of oxygen radicals generated by plasma membrane reductases have no influence in the expression of this gene. Hydrogen peroxide, a product of quinone redox cycling, elicited an increase of p21 mRNA levels in HCT116 and K562 human chronic myelogenous leukemia cells. The latter lacks p53, one of the activators of p21 transcription, thus suggesting that p21 expression can be accomplished in a p53-independent manner in these cells. This study suggests that p21 induction is mediated by an increase in the cellular steady-state concentration of oxygen radicals and that the greater effectiveness in p21 induction by DZQ may be related to its efficient metabolism by NAD(P)H:quinone oxidoreductase activity in HCT116 cells.
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PMID:Induction of p21 mediated by reactive oxygen species formed during the metabolism of aziridinylbenzoquinones by HCT116 cells. 894 36

Female transgenic mice (C57BL/6 x CBA/J)F1 with a 1-fold increase in expression of glutathione peroxidase (GP) or with a 1-fold increase in the expression of GP and a 3-4-fold increase in the expression of superoxide dismutase (SOD) had an enhanced carcinogenic response to initiation by 7,12-dimethylbenz[a]anthracene (DMBA) followed by promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). GP- or GP+SOD-transgenic mice that were initiated by a single topical application of 200 nmol of DMBA followed by promotion with 8 nmol of TPA twice weekly for 30 weeks developed an average of 10.9 or 11.0 skin tumors per mouse and a 100% tumor incidence in comparison with the corresponding nontransgenic mice, which had 3.9 tumors per mouse and an 83% tumor incidence. After stopping TPA application, partial skin tumor regression occurred more rapidly in nontransgenic mice than in either type of transgenic mouse. At 10 weeks after termination of TPA treatment, 9-11% of the tumor-bearing transgenic mice and 26% of the tumor-bearing nontransgenic mice had complete regression of their tumors. Histopathological examination of 96 skin papillomas revealed that the area, location, degree of tumor dysplasia, bromodeoxyuridine labeling index, and p53 protein levels were closely intercorrelated. Further analysis indicated that papillomas with the same grade of dysplasia had a higher bromodeoxyuridine labeling index and a greater p53 protein level in GP- or GP+SOD-transgenic mice than those in nontransgenic mice. The data indicated that overexpression of skin antioxidant enzymes GP or GP+SOD, which are enzymes that are believed to protect cells from oxidative damage by scavenging reactive oxygen species, lead to the increased, rather than the decreased, tumorigenesis in a DMBA/TPA two-stage skin carcinogenesis model.
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PMID:Enhanced skin carcinogenesis in transgenic mice with high expression of glutathione peroxidase or both glutathione peroxidase and superoxide dismutase. 910 47

Deletions of loci on chromosomes 5q, 17p, 18q, and 22q, together with the incidence of p53 mutations and amplification of the double minute-2 gene were investigated in the sporadic colorectal tumors of 44 patients from a Spanish community. Chromosome deletions were analyzed by means of loss of heterozygosity analysis using a restriction fragment length polymorphism assay. Allelic losses were also detected by polymerase chain reaction (PCR)-single-stranded conformation polymorphism (SSCP) analysis of a polymorphic site in intron 2 of the p53 gene. The percentages of genetic deletions on the screened chromosomes were 39.3% (5q), 58.3% (17p), 40.9% (18q), and 40% (22q). Mutations in p53 exons 2-9 were examined by PCR-SSCP analysis and direct sequencing of the mutated region. Twenty of 44 tumor samples (45.45%) showed mutations at various exons except for exons 2, 3, and 9, the most frequent changes being G-->T transversion and C-->T transition. Because oxygen-free radicals play a role in the carcinogenesis process, we evaluated the oxidative status of the colorectal tumors. Antioxidant activities, lipid peroxidation, and DNA-damaged product concentrations in colon tumors and normal mucosa were compared. In tumor tissues, superoxide dismutase and catalase decreased fourfold and twofold, respectively, whereas glutathione peroxidase and reduced glutathione increased threefold. Malondialdehyde and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels were twofold higher in colorectal tumors than in normal mucosa. Seven of 10 DNA tumor samples (70%) showing higher values of 8-OHdG also had genetic alterations at different chromosomal loci. In these samples, the p53 gene was deleted or mutated in 71.4% of cases. We concluded that the observed changes in the oxidative metabolism of the tumor cells and the consecutive increase in DNA damage may potentiate the genomic instability of different chromosomal regions, leading to further cell malignancy and tumor expansion.
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PMID:Genetic alterations and oxidative metabolism in sporadic colorectal tumors from a Spanish community. 914 18

During proliferative glomerulonephritis, the early phase of mesangiolysis is linked to increased nitric oxide (NO) production. NO. as well as superoxide (O2-) are inflammatory mediators that are generated by mesangial cells (MC) after cytokine stimulation. Added individually, both radicals induce MC apoptosis. However, the co-existence of a defined NO./O2- ratio is cross-protective. Apoptosis is characterized by specific features such as chromatin condensation, DNA strand breaks, and the occurrence of apoptotic regulating proteins. The tumor suppressor p53 and Bax (Bcl-2 associated protein x) are considered to be classical death promotors, which accumulate after toxic insults. To study p53 and Bax protein accumulation in NO. and/or O2(-)-induced apoptosis, we used the NO-donor S-nitrosoglutathione (GSNO) and the redox cycler 2,3-dimethoxy-1,4-naphtoquione (DMNQ). Both agonists initiated DNA fragmentation in a concentration dependent manner associated with transient p53 and Bax up-regulation. Co-generation of NO./O2- resulted not only in reduced DNA fragmentation, but also in decreased Bax accumulation. Comparable to the NO./O2- co-generation, cytokines failed to induce apoptosis. In contrast, cytokines in combination with pyrrolidine dithiocarbamate, which blocks endogenous superoxide dismutase, allowed p53 and Bax accumulation as well as DNA fragmentation. Our results demonstrate p53 and Bax as early components in NO. and O2(-)-induced rat MC apoptosis and point to the NO./O2- interaction as a naturally occurring cell defense mechanism.
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PMID:Nitric oxide and superoxide induced p53 and Bax accumulation during mesangial cell apoptosis. 926 93

The teratogenicity of many xenobiotics is thought to depend at least in part upon their bioactivation by embryonic cytochromes P450, prostaglandin H synthase (PHS) and lipoxygenases (LPOs) to electrophilic and/or free radical reactive intermediates that covalently bind to or oxidize cellular macromolecules such as DNA, protein and lipid, resulting in in utero death or teratogenesis. Using as models the tobacco carcinogens benzo[a]pyrene (B[a]P) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the anticonvulsant drug phenytoin, structurally related anticonvulsants (e.g. mephenytoin, nirvanol, trimethadione, dimethadione) and the sedative drug thalidomide, we have examined the potential teratologic relevance of free radical-initiated, reactive oxygen species (ROS)-mediated oxidative molecular target damage, genotoxicity (micronucleus formation) and DNA repair in mouse and rabbit models in vivo and in embryo culture, and in vitro using purified enzymes or cultured rat skin fibroblasts. These teratogens were bioactivated by PHS and LPOs to free radical reactive intermediary metabolites, characterized by electron spin resonance spectrometry, that initiated ROS formation, including hydroxyl radicals, which were characterized by salicylate hydroxylation. ROS-initiated oxidation of DNA (8-hydroxy-2'-deoxyguanosine formation), protein (carbonyl formation), glutathione (GSH) and lipid (peroxidation), and embryotoxicity were shown for phenytoin, its major hydroxylated metabolite 5-(p-hydroxyphenyl)-5-phenylhydantoin [HPPH], thalidomide, B[a]P and NNK in vivo and/or in embryo culture, the latter indicating a teratologically critical role for embryonic, as distinct from maternal, processes. DNA oxidation and teratogenicity of phenytoin and thalidomide were reduced by PHS inhibitors. Oxidative macromolecular lesions and teratogenicity also were reduced by the free radical trapping agent phenylbutylnitrone (PBN), and the antioxidants caffeic acid and vitamin E. In embryo culture, addition of superoxide dismutase (SOD) to the medium enhanced embryonic SOD activity, and SOD or catalase blocked the oxidative lesions and embryotoxicity initiated by phenytoin and B[a]P, suggesting a major contribution of ROS, as distinct from covalent binding, to the teratologic mechanism. In in vivo studies, other antioxidative enzymes like GSH peroxidase, GSH reductase and glucose-6-phosphate dehydrogenase (G6PD) were similarly protective. Even untreated G6PD-deficient mice had enhanced embryopathies, indicating a teratological role for endogenous oxidative stress. In cultured fibroblasts, B[a]P, NNK, phenytoin and HPPH initiated DNA oxidation and micronucleus formation, which were inhibited by SOD. Oxidation of DNA may be particularly critical, since transgenic mice with +/- or -/- deficiencies in the p53 tumor suppressor gene, which facilitates DNA repair, are more susceptible to phenytoin and B[a]P teratogenicity. Even p53-deficient mice treated only with normal saline showed enhanced embryopathies, suggesting the teratological importance of endogenous oxidative stress, as observed with G6PD deficiency. These results suggest that oxidative macromolecular damage may play a role in the teratologic mechanism of xenobiotics that are bioactivated to a reactive intermediate, as well in the mechanism of embryopathies occurring in the absence of xenobiotic exposure.
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PMID:Oxidative damage in chemical teratogenesis. 943 60

The 2-nitroimidazoles have been used clinically to radiosensitize resistant hypoxic cells, but a dose-limiting peripheral neuropathy has restricted their therapeutic effectiveness. A model compound, 1-methyl-2-nitroimidazole (INO2), was used to investigate the possible role of oxidative stress in this normal tissue toxicity. Chinese hamster ovary (CHO) cells were 10-15 times more resistant to 20 mM INO2 under aerobic than hypoxic conditions. In comparison, a pair of transformed rat embryo fibroblasts (ER17-1wtp53 and ER12L5mtpP53), differing in their p53 genotype, were approximately 3- to 4-fold more sensitive than Chinese hamster ovary cells to INO2 under aerobic conditions, but had the same sensitivity as Chinese hamster ovary cells under hypoxic conditions. These results are consistent with an earlier hypothesis that the mechanism of aerobic toxicity is different from that of hypoxic toxicity (nitroreduction) and show that neither toxicity is dependent on cellular p53 status. There was an increase in the production of reactive oxygen intermediates and a decrease in the antioxidant glutathione following aerobic exposure to INO2, which correlated with cell survival in all three cell lines. No evidence of reductive adducts of the 2-nitroimidazole 2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)acetam ide (EF5) was found by immunofluorescent techniques in aerobic cells. Differing activities of the antioxidant enzymes superoxide dismutase and catalase could be correlated with INO2 aerobic cytotoxicity. DNA strand breaks, as measured by the comet assay, paralleled the appearance of INO2 aerobic cytotoxicity in all three cell lines. Taken together, these results strongly support the conclusion that the aerobic toxicity of IN02 is due to active oxygen species created by futile redox cycling of the parent compound.
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PMID:Oxidative stress and 1-methyl-2-nitroimidazole cytotoxicity. 974 71

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

Benzoyl peroxide (BzPO), a free-radical generator, has tumor-promoting activity. As a method for approaching the mechanism of tumor promoter function, the ability of oxidative DNA damage by BzPO was investigated by using (32)P-labeled DNA fragments obtained from the human p53 tumor suppressor gene and c-Ha-ras-1 protooncogene. BzPO induced piperidine-labile sites at the 5'-site guanine of GG and GGG sequences of double-stranded DNA in the presence of Cu(I), whereas the damage occurred at single guanine residues of single-stranded DNA. Both methional and dimethyl sulfoxide (DMSO) inhibited DNA damage induced by BzPO and Cu(I), but typical hydroxyl radical ((*)OH) scavengers, superoxide dismutase (SOD) and catalase, did not inhibit it. On the other hand, H(2)O(2) induced piperidine-labile sites at cytosine and thymine residues of double-stranded DNA in the presence of Cu(I). Phenylhydrazine, which is known to produce phenyl radicals, induced Cu(I)-dependent damage at thymine residues but not at guanine residues. These results suggest that the BzPO-derived reactive species causing DNA damage is different from (*)OH and phenyl radicals generated from benzoyloxyl radicals. BzPO/Cu(I) induced 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation in double-stranded DNA more effectively than that in single-stranded DNA. Furthermore, we observed that BzPO increased the amount of 8-oxodG in human cultured cells. Consequently, it is concluded that benzoyloxyl radicals generated by the reaction of BzPO with Cu(I) may oxidize the 5'-guanine of GG and GGG sequences in double-stranded DNA to lead to 8-oxodG formation and piperidine-labile guanine lesions, and the damage seems to be relevant to the tumor-promoting activity of BzPO.
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PMID:Site-specific oxidation at GG and GGG sequences in double-stranded DNA by benzoyl peroxide as a tumor promoter. 1060 4


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