UNIPROT:P04637 - FACTA Search

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Query: UNIPROT:P04637 (p53)
77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epigallocatechin gallate (EGCG) is a major water-soluble component of green tea. The antimutagenic activity of EGCG against benzo[a]pyrene (B[a]P)-induced mutations was assessed by using transgenic mice carrying the rpsL gene as a monitor of mutations. Seven-week-old male mice were given drinking water containing EGCG for 3 weeks. On day 7, mice were treated with a single i.p. injection of B[a]P (500 mg/kg body wt). Two weeks after the injection, the mutations in the rpsL gene were analyzed. B[a]P treatment resulted in an approximately 4-fold increase of mutation frequency at the rpsL gene in the lung. An approximately 60% reduction in the B[a]P-induced mutations in the lung was observed when mice were given EGCG at concentrations >0.005%. B[a]P-induced mutations mainly occurred at G:C basepairs in the several specific nucleotide sequences of the rpsL gene. These were AGG, CGG, CGT, TGG, TGC and GGT: all of them contained a guanine residue. Mutations seen similarly in the human Ki-ras codon 12 or p53 codons 157, 248, and 273 of lung tumor were also found in the rpsL gene, and the mutations were suppressed by the EGCG treatment. In conclusion, the antimutagenic effects of EGCG for B[a]P-induced mutagenesis in vivo suggest that drinking green tea may reduce the tumor-initiating potency of B[a]P in the lung.
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PMID:Inhibition of benzo[a]pyrene-induced mutagenesis by (-)-epigallocatechin gallate in the lung of rpsL transgenic mice. 1019 May 56

The ability of cells to maintain genomic integrity is vital for cell survival and proliferation. Lack of fidelity in DNA replication and maintenance can result in deleterious mutations leading to cell death or, in multicellular organisms, cancer. The purpose of this review is to discuss the known signal transduction pathways that regulate cell cycle progression and the mechanisms cells employ to insure DNA stability in the face of genotoxic stress. In particular, we focus on mammalian cell cycle checkpoint functions, their role in maintaining DNA stability during the cell cycle following exposure to genotoxic agents, and the gene products that act in checkpoint function signal transduction cascades. Key transitions in the cell cycle are regulated by the activities of various protein kinase complexes composed of cyclin and cyclin-dependent kinase (Cdk) molecules. Surveillance control mechanisms that check to ensure proper completion of early events and cellular integrity before initiation of subsequent events in cell cycle progression are referred to as cell cycle checkpoints and can generate a transient delay that provides the cell more time to repair damage before progressing to the next phase of the cycle. A variety of cellular responses are elicited that function in checkpoint signaling to inhibit cyclin/Cdk activities. These responses include the p53-dependent and p53-independent induction of Cdk inhibitors and the p53-independent inhibitory phosphorylation of Cdk molecules themselves. Eliciting proper G1, S, and G2 checkpoint responses to double-strand DNA breaks requires the function of the Ataxia telangiectasia mutated gene product. Several human heritable cancer-prone syndromes known to alter DNA stability have been found to have defects in checkpoint surveillance pathways. Exposures to several common sources of genotoxic stress, including oxidative stress, ionizing radiation, UV radiation, and the genotoxic compound benzo[a]pyrene, elicit cell cycle checkpoint responses that show both similarities and differences in their molecular signaling.
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PMID:Cell cycle control, checkpoint mechanisms, and genotoxic stress. 1022 3

The polycyclic aromatic hydrocarbon (PAH) dibenzo[a,l]pyrene (DB[a,l]P), the most carcinogenic PAH tested in rodent bioassays, exerts its pathobiological activity via metabolic formation of electrophilically reactive DNA-binding fjord region (+)-syn-(11S,12R,13S,14R)- or (-)-anti-(11R,12S,13S,14R)-DB[a,l]P-dihydrodiol epoxides (DB[a,l]-PDEs). DB[a,l]P is metabolized to these DB[a,l]PDEs which bind to DNA in human mammary carcinoma MCF-7 cells. The molecular response of MCF-7 cells to DNA damage caused by DB[a,l]PDEs was investigated by analyzing effects on the expression of the tumor suppressor protein p53 and one of its target gene products, the cyclin-dependent kinase inhibitor p21WAF1. Treatment of MCF-7 cells with (+)-syn- and (-)-anti-DB[a,l]PDE at a concentration range of 0.001-0.1 microM resulted in DB[a,l]PDE-DNA adduct levels between 2 and 30, and 3 and 80 pmol/mg DNA, respectively, 8 h after exposure. (-)-anti-DB[a,l]PDE exhibited a higher binding efficiency that correlated with a significantly stronger p53 response at low concentrations of the dihydrodiol epoxides. The level of p53 increased by 6-8 h after treatment. The p21WAF1 protein amount exceeded control levels by 12 h and remained elevated for 96 h. At a dose of 0.01 microM (+)-syn-DB[a,l]PDE, an increase in p21WAF1 was observed in the absence of a detectable change in p53 levels. The results indicate that the increase in p53 induced by DB[a,l]PDEs in MCF-7 cells requires an adduct level of approximately 15 pmot/mg DNA and suggest that the level of adducts rather than the specific structure of the DB[a,l]PDE-DNA adduct formed triggers the p53 response. The PAH-DNA adduct level formed may determine whether p53 and p21VAF1 pathways respond, resulting in cell-cycle arrest, or fail to respond and increase the risk of mutation induction by these DNA lesions.
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PMID:The level of DNA modification by (+)-syn-(11S,12R,13S,14R)- and (-)-anti-(11R,12S,13S,14R)-dihydrodiol epoxides of dibenzo[a,l]pyrene determined the effect on the proteins p53 and p21WAF1 in the human mammary carcinoma cell line MCF-7. 1033 4

We have used the UvrABC nuclease incision method in combination with ligation-mediated polymerase chain reaction (LMPCR) techniques to map and quantify (+/-)anti-7beta, 8alpha-dihydroxy-9alpha, 10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]-pyrene (BPDE) adduct formation in the p53 gene of human cells. We found that BPDE adduct formation, as revealed by UvrABC incision, preferentially occurred at methylated CpG sites that correspond to the mutational hotspots observed in human lung cancers. Our hypothesis is that it is this methylated CpG sequence-dependent preferential adduct formation, rather than selective growth advantage, that is the major determinant of the p53 mutation pattern in human cancers. Given the far reaching ramifications of such conclusions for cancer etiology, a legitimate question is raised regarding the reliability of using the UvrABC incision method for quantifying and determining the sequence-dependency of adduct formation. Is the higher frequency of UvrABC cutting at methylated versus unmethylated CpG sites due to the preference of the nuclease for cutting at those sites or due to the preferential formation of BPDE adducts at those sites? In order to distinguish between these two possibilities, we have analyzed the kinetics of UvrABC incision at BPDE adducts formed at either methylated CpG sites versus other sequences, or unmethylated CpG sites versus other sequences in exon 5 of the p53 gene. We have found that the UvrABC cutting kinetics are identical for both cases. On the basis of these results we conclude that under proper cutting conditions, UvrABC nuclease reacts with and incises with equal efficiency, BPDE adducts formed at methylated or unmethylated CpG sites as well as other sequences, and that the extent of UvrABC incision accurately reflects the extent of BPDE-DNA adduct formation. These conclusions were further supported by results obtained using a DNA synthesis blockage assay.
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PMID:Use of UvrABC nuclease to quantify benzo[a]pyrene diol epoxide-DNA adduct formation at methylated versus unmethylated CpG sites in the p53 gene. 1035 92

The p53 mutation spectrum can generate hypotheses linking carcinogen exposure to human cancer. Although it is well-documented that tobacco smoking is a major cause of lung cancer, the contribution of air pollution is less well-established. We determined the molecular and immunohistochemical changes (p53 gene mutations, p53 protein accumulation and WAF1 protein expression) and genetic polymorphisms of GSTM1, CYP1A1 and CYP2D6 genes in a case series of non-small-cell lung cancers from Silesia. This region of southern Poland is highly industrialized with considerable environmental pollution. More than 50% of lung cancers (90/164) contained p53 mutations and 75% showed the combined alteration of the p53 gene and protein accumulation. Males occupationally exposed to coal-derived substances showed a relatively high frequency of squamous and large-cell carcinomas, relatively frequent mutations in codon 298 of p53 and a low frequency of p53 immunohistochemically positive tumours. Codon 298 GAG-->TAG mutations have rarely been found in lung cancers in other populations. We found no correlation between WAF1 protein expression and mutations in the p53 gene or p53 protein accumulation. No statistically significant relationship was found between p53 mutations and GSTM1, CYP1A1, CYP2D6 genotypes. Never smokers with lung cancers from Silesia had a higher frequency of G:C-->T:A transversions than previously reported of the p53 mutation spectrum in never smokers (6/15 vs 4/34; P = 0.06 by chi2). These data are a tentative indication that occupational and environmental exposure to polycyclic aromatic hydrocarbons, such as benzo(a)pyrene, in polluted air contributes to the molecular pathogenesis of lung cancer in never smokers.
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PMID:Molecular epidemiological study of non-small-cell lung cancer from an environmentally polluted region of Poland. 1042 49

p53 has been postulated to be the guardian of the genome. However, results supporting the prediction that point mutation frequencies are elevated in p53-deficient cells either have not been forthcoming or have been equivocal. To analyse the effect of p53 on point mutation frequency, we used the supF gene of the pYZ289 shuttle vector as a mutagenic target. pYZ289 was treated in vitro by ultraviolet irradiation, aflatoxin B1, (+/-)7,8-dihydroxy-9, 10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and meta-chloroperoxybenzoic acid and then transfected into p53-deficient cells with or without a p53 expression vector. p53 reduced the mutant frequency up to fivefold when pYZ289 was treated with aflatoxin B1, (+/-)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene or meta-chloroperoxybenzoic acid but not when it was ultraviolet-irradiated. The p53-dependent mutation frequency reduction was higher at a higher level of premutational lesions for aflatoxin B1 and (+/-)7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and at a lower level of lesions for meta-chloroperoxybenzoic acid. This suggests that the chemical mutagens produce, in a dose-dependent fashion, two kinds of DNA damage, one subject to p53-dependent mutation frequency reduction and the other not. These results indicate that p53 can reduce the point mutation frequency in a shuttle vector treated by chemical mutagens and suggest that p53 can act as guardian of the genome for at least some kinds of point mutations.
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PMID:The p53 tumor suppressor protein reduces point mutation frequency of a shuttle vector modified by the chemical mutagens (+/-)7, 8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, aflatoxin B1 and meta-chloroperoxybenzoic acid. 1046 14

The level of p53 tumor suppressor protein increases in response to DNA damage caused by benzo[a]pyrene (B[a]P). The most used tumor promoter in the two step mouse skin carcinogenesis model, 12-O-tetradecanoylphorbol-13-acetate (TPA) decreases this response in mouse skin. In this study the effect of another promoter, thapsigargin was tested on B[a]P-induced p53 response using immunohistochemistry, western blotting and immunoelectron microscopy. We also studied the localization of p53 protein after treatments with BP and TPA or thapsigargin. Thapsigargin had a TPA-like effect on the acute induction of p53 protein related to benzo[a]pyrene-7, 8-diol-9,10-epoxide-DNA adducts in the skin of C57BL/6 mouse. After B[a]P treatment, there was slightly more putatively wild-type p53 protein in nuclei than in cytoplasm of the cells. Neither TPA nor thapsigargin affected the localization of p53 protein. Since both compounds increase the level of intracellular calcium, the inhibition of the p53 response may depend on the level of intracellular calcium. Inhibition of the putatively genome-protecting increase in p53 protein may be one of the critical effects of tumor promoters.
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PMID:Thapsigargin has similar effect on p53 protein response to benzo[a]pyrene-DNA adducts as TPA in mouse skin. 1046 21

Genomic alterations in primary breast cancer play a role in the initiation and progression of the disease. We have analyzed the molecular events involved in the initiation and progression of the neoplastic process in an in vitro experimental system. Immortalization of human breast epithelial cells (HBEC) is associated with 3:9 translocation, p53 mutation and microsatellite instability (MSI) of chromosomes 11p13, and 17p. BP1-E cells, derived from the immortalized MCF-10F cells transformed by the carcinogen benzo(a)pyrene (BP), express in vitro growth advantage, anchorage independence, enhanced chemoinvasiveness, loss of ductulogenic capabilities and tumorigenesis in a heterologous host. This neoplastic progression is also associated with mutations and/or amplification of c-H-ras, int-2, c-neu, c-myc and MDM2, MSI at 11q25 and 13q12-q13 and loss of heterozygosity at 17p. In order to test whether chromosomes 11 or 17 play a functional role in the phenotypic expression of transformation of BP1E cells, we utilized microcell-mediated chromosome transfer (MMCT) technique for inserting the corresponding normal chromosomes to these transformed cells. BP1E cells were transfected with PsV2neo plasmid and fused with microcells obtained from the mouse cell line A9, containing a normal chromosome 11 or 17 (A9-11neo and A9-17neo cells, selected in G418 and cloned. Sixteen primary microcell hybrids from each chromosome transfer, designated BP1E-11neo and BP1E-17neo survived selection in G-418 containing medium. A single clone from each group, BP1E-11neo #145 and BP1E-17neo D100, survived subcloning and were utilized for a detailed panel of analyses. The presence of a donor chromosome was confirmed by dual color fluorescence in situ hybridization (FISH), southern blot analysis of the marker vector pSV2neo, and microsatellite polymorphism analysis. The transfer of the normal chromosomes 11 and 17 resulted in a 50% and 90% inhibition of cell growth respectively, and reduced both colony efficiency and colony size. Telomerase activity was significantly reduced only by chromosome 17 insertion, providing a possible explanation for the more significant senescence observed in BP1E-17neo D100 cells. Microsatellite polymorphism analysis revealed that three loci, 11q13-23, 11q23.1, and 11q23.3 (markers D11S911, DRD2, and D11S29) were retained in BP1E-11neo #145 cells, and two, 17q24.2-25.2, 17q25.2 (markers D17S515 and D17S785 were retained in BP1E-17neo D100 cells. We conclude that the specific regions of normal chromosomes 11 and 17 transferred play a functional role in the expression of immortal and transformed phenotypes of HBEC in vitro.
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PMID:Functional roles of chromosomes 11 and 17 in the transformation of human breast epithelial cells in vitro. 1049 42

XPA-deficient mice have a complete deficiency in nucleotide excision repair, and as such they display a cancer predisposition after exposure to several carcinogens. Besides being sensitive to genotoxic agents applied to the skin, they are also susceptible to human carcinogens given orally, like benzo[a]pyrene (B[a]P). To study the role of the tumor suppressor gene p53 in DNA repair, gene mutation, and tumor induction, we crossed XPA-deficient mice with p53 knockout mice and lacZ (pUR288) gene marker mice. When treated orally (by gavage) with B[a]P, the XPA(-/-)/p53(+/-) double transgenic mice developed tumors much earlier and with higher frequency compared to their single transgenic counterparts. The major tumor type found in all genotypes was generalized lymphoma mainly residing in the spleen; several sarcomas were observed in p53(+/-) and XPA(-/-)/p53(+/-) mice. Next, we determined lacZ mutation frequencies in several (non)target tissues. It appeared that in the spleen (the major tumor target tissue) of XPA(-/-) and XPA(-/-)/p53(+/-) mice the lacZ mutation frequency was significantly elevated (80-100 x 10(-5)), and was two times higher as found in spleens of B[a]P-treated WT and p53(+/-) mice (P = 0.003). In nontumor target tissues like liver and lung, we found a moderate increase in the lacZ gene mutation frequency (30-40 x 10(-5)), which was independent of the genotype. The results obtained with the DNA-repair deficient XPA mice indicate that a significantly increased lacZ mutation frequency in a particular organ/tissue is an early marker for tumor development at later stages at the same site. However, the synergistic effect of a XPA(-/-)- and a p53(+/-)-deficiency in tumor development is not reflected by an absolute increase in the lacZ mutation frequency in the major tumor target tissue of XPA(-/-)/p53(+/-) or p53(+/-) mice compared to that of XPA(-/-) and WT mice, respectively.
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PMID:Effect of heterozygous loss of p53 on benzo[a]pyrene-induced mutations and tumors in DNA repair-deficient XPA mice. 1052 36

p53 is known to be recruited in response to DNA-damaging genotoxic stress and plays an important role in maintaining the integrity of the genome. In the present study, the effect of a potent lung cancer carcinogen, benzo[a]pyrene (B[a]P) on p53 expression was investigated. We showed that exposure of A549 and NIH 3T3 cells to B[a]P resulted in an increase in p53 mRNA levels and in p53 promoter activation, indicating that B[a]P-induced p53 expression is partly regulated at the transcriptional level. The p53 promoter region which extends from -58 to -43, overlapping the kappaB motif, is essential for both the p53 basal promoter activity and p53 promoter activation induced by B[a]P. Nuclear factor kappaB (NF-kappaB) proteins have been revealed to be activated in B[a]P-induced p53 expression. Activated NF-kappaB complexes were shown to contain predominantly p50 and p65 subunit components in A549 cells and p65 subunit in NIH 3T3 cells. In addition, the overexpression of IkappaBalpha completely inhibited NF-kappaB activation, p53 promoter transactivation and the stimulatory effect on p53 transcription induced by B[a]P. We therefore conclude that B[a]P transcriptionally activates the human p53 gene through the induction of NF-kappaB activity.
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PMID:Benzo[a]pyrene activates the human p53 gene through induction of nuclear factor kappaB activity. 1057 10

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