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)

A hybrid clone was developed by the fusion of a pluripotent mouse teratocarcinoma cell line PCC-4 AzaR to the Zajdela ascitic hepatoma (ZAH) of rat origin. This hybrid cell line, F2231A, possessed a predominantly teratocarcinoma morphology with a large nucleus and prominent nucleoli, and grew in nests. F2231A cells formed undifferentiated tumours in irradiated Sv/129 mice. It formed aggregates when subcultured at high densities in bacteriological Petri dishes. The hybrid cell line differentiated in response to retinoic acid and also underwent spontaneous differentiation upon overgrowth. Karyological analysis showed the presence of several rat chromosomes in the hybrid and upon isozyme analysis it was found that only the rat variant of the X-linked enzyme HGPRT was expressed. Analysis of the genomic DNA with a cloned probe, specific for rat repetitive sequences, gave strong positive signals in the hepatoma parent and F2231A cells while the parental embryonal carcinoma (EC) cells were negative. The hybrid cell line, like the PCC-4 cells, expressed the SSEA-1 surface marker but not SSEA-3, intercellular fibronectin and EGF receptors. Upon differentiation of F2231A cells there was a loss of expression of SSEA-1. The mRNA for alpha-fetoprotein was expressed by the hybrid cell line and in this respect it resembled the hepatoma parent. Albumin mRNA was not detectable in the hybrid cell line. The mRNA for the transformation-related protein, p53, was expressed at a high level in F2231A cells. The hybrid cell line F2231A retained several of the biochemical and immunological properties of the teratocarcinoma cells.
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PMID:A malignant, stem cell-like somatic hybrid between a mouse teratocarcinoma and a rat ascitic hepatoma is differentiation competent. 247 69

Nitric oxide (NO) is a cellular messenger which is mutagenic in bacteria and human TK6 cells and induces deamination of 5-methylcytosine (5meC) residues in vitro. The aims of this study were: (i) to investigate whether NO induces 5meC deamination in codon 248 of the p53 gene in cultured human bronchial epithelial cells (BEAS-2B); and (ii) to compare NO mutagenicity to that of ethylnitrosourea (ENU), a strong mutagen. Two approaches were used: (i) a novel genotypic assay, using RFLP/PCR technology on purified exon VII sequence of the p53 gene; and (ii) a phenotypic (HPRT) mutation assay using 6-thioguanine selection. BEAS-2B cells were either exposed to 4 mM DEA/NO (Et2N[N2O2]Na, an agent that spontaneously releases NO into the medium) or transfected with the inducible nitric oxide synthase (iNOS) gene. The genotypic mutation assay, which has a sensitivity of 1 x 10(-6), showed that 4 mM ENU induces detectable numbers of G --> A transitions in codon 248 of p53 while 5-methylcytosine deamination was not detected in either iNOS-transfected cells or cells exposed to 4 mM DEA/NO. Moreover, ENU was dose-responsively mutagenic in the phenotypic HPRT assay, reaching mutation frequencies of 24 and 96 times that of untreated control cells at ENU concentrations of 4 and 8 mM respectively; by contrast, 4 mM DEA/NO induced no detectable mutations in this assay, nor were any observed in cells transfected with murine iNOS. We conclude that if NO is at all promutagenic in these cells, it is significantly less so than the ethylating mutagen, ENU.
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PMID:Nitric oxide and ethylnitrosourea: relative mutagenicity in the p53 tumor suppressor and hypoxanthine-phosphoribosyltransferase genes. 755 56

Denaturing gradient gel electrophoresis (DGGE) separates (DNA) molecules based on their sequence. Using the proper conditions, all base-pair substitutions can be resolved from the wild-type sequence using DGGE. Polymerase chain reaction (PCR) permits rapid amplification of a given region of the genome. In this paper, we demonstrate the utility of DGGE combined with PCR for mutation analysis by presenting different examples: (i) analysis of mouse p53 cDNA for mutations, (ii) simultaneous analysis of thousands of 4NQO-induced mutants for mutations in HPRT exon 3, (iii) examination of the fidelity of the thermostable DNA polymerase isolated from Pyrococcus furiosus (Pfu), (iv) purification of mutant DNA from contaminating wild-type DNA from mouse spleenic T-cell clones.
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PMID:Mutational analysis using denaturing gradient gel electrophoresis and PCR. 768 54

To elucidate the molecular basis for malignant and premalignant states in Bloom syndrome (BS), p53 mutations were analyzed using Southern blot analysis and DNA sequencing of exons 5-9. p53 point mutations with and without loss of heterozygosity on 17p were detected in malignantly transformed BS cell lines carrying malignant lymphoma (ML) and stomach cancer (STC) antigens on the cell surface. However, p53 mutations were not detected in fresh lymphocytes and B-lymphoblastoid cell lines from four BS patients carrying high sister chromatid exchange (SCE) levels, using Southern blot and DNA sequencing of exons 5-9. Based on these results, we concluded that the p53 gene may not play a key role in the high spontaneous mutation rates (HGPRT locus) in somatic cells of BS patients and that the p53 mutation with an allelic loss of the p53 gene is an important factor in malignant conditions in BS.
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PMID:p53 mutation in fresh lymphocytes, B-lymphoblastoid cell lines and their transformed cell lines originating from Bloom syndrome patients. 833 Feb 85

Preventable environmental causes of cancer, including tobacco smoke and other carcinogens in the diet, workplace, and ambient environment are responsible for the vast majority of human cancers. This paper reviews recent molecular epidemiologic studies that have focused on environmental carcinogenesis and environment-host interactions. Biomarkers such as carcinogen-DNA and carcinogen-protein adducts, mutations in reporter or target genes (e.g., HPRT, GPA, ras, p53), or genetic or acquired susceptibility factors (e.g., polymorphisms in the P450 or glutathione-S-transferase genes and serum levels of antioxidants) have shown significant potential in prevention. They should be useful in early identification of at risk individuals and in designing and monitoring interventions (smoking cessation, exposure reduction, and chemoprevention).
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PMID:Molecular epidemiology and prevention of cancer. 874 89

Previous work with two closely related human lymphoblast cell lines demonstrated that WTK1 cells are more resistant than TK6 cells to X-ray-induced cytotoxicity, but more mutable at both the TK and HPRT loci. It was subsequently determined that WTK1 cells overexpress a mutant form of the tumor suppressor gene p53, while TK6 cells correctly express wild-type p53. Thus these two cell lines allowed us to examine the mutational spectra at the HPRT locus in related human lymphoblast cell lines differentially expressing p53. Previously, we isolated sets of X-ray-induced and spontaneous WTK1 mutants and spontaneous TK6 mutants and analyzed the mutational spectra by the combination of multiplex polymerase chain reaction (PCR) and Southern blot analysis. Somewhat unexpectedly, we found that even though there were approximately four times as many mutants induced by X rays in WTK1 cells as in TK6 cells, there was very little difference in the mutational spectra. In the present study, to determine if there was a higher frequency of intragenic deletions among the X-ray-induced WTK1 mutants, we further examined the subsets of mutants that contained HPRT point mutations. cDNA sequence analysis was used to define the mutation precisely in 19 X-ray-induced and 25 spontaneous WTK1 mutants and 25 spontaneous TK6 mutants. While subtle differences exist in the spectra of HPRT mutations between these two cell lines, the data again suggest that p53 is associated with an increase in the frequency of mutations at HPRT without an obvious effect on the types of mutations recovered.
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PMID:Spectra of X-ray-induced and spontaneous intragenic HPRT mutations in closely related human cells differentially expressing the p53 tumor suppressor gene. 900 5

To determine whether a tumor suppressor gene of importance to epithelial ovarian cancer resides on the X chromosome, we examined loss of heterozygosity (LOH) in 123 epithelial ovarian cancer cases. In 54 such cases, we examined LOH at 26 loci on the human X chromosome. In eight cases, we examined LOH in 14 loci and in 61 cases we examined LOH in 13 loci. Matched DNA samples from tumors and corresponding normal tissues were analyzed by polymerase chain reaction (PCR) amplification of microsatellite markers. Frequent losses were found in epithelial carcinomas at the Xq25-26.l region, including DXS1206 (34.5% loss in informative cases), DXS1047 (27.7%), HPRT (24.1%), and DXS1062 (33.3%). The minimum overlapping region of LOH was approximately 5 megabases (Mb), flanked by DXS1206 (Xq25) and HPRT (Xq26.1). The methylation status of the remaining allele of the androgen receptor gene in the tumors exhibiting LOH at the Xq25-26.1 region suggested that the loss was exclusively in the inactive X chromosome. We next determined whether a significant relationship exists between Xq LOH and other parameters, including histologic grade and/or clinical stage of the tumors and LOH at TP53. The Xq LOH had a significant association with grade 2 to 3 tumors at stages II to IV. Sixteen of 18 cases that showed Xq LOH revealed LOH at the TP53 locus, and 45% of tumors exhibiting LOH at TP53 showed Xq LOH. These results suggest that there may be a tumor suppressor gene or genes which escape inactivation of the X chromosome at Xq25-26.1, and that the loss of the gene(s) at Xq25-26.1 is frequently accompanied by loss of the TP53 or loss of another gene on chromosome 17. These losses may contribute to the progression from a well-differentiated to a more poorly differentiated state or to metastatic aggressiveness.
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PMID:Loss of heterozygosity at chromosome segment Xq25-26.1 in advanced human ovarian carcinomas. 936 30

Loss of heterozygosity (LOH) plays an important role in the expression of recessive mutations in mammalian cells. To gain insight into the rate and mechanisms of LOH the autosomal HLA-A gene was used as a model system. Spontaneous HLA-A2 mutants originated with a rate of respectively 4.1 x 10(-6) and 6.9 x 10(-6) per cell per generation in TK6 and WI-L2-NS, two isogenic lymphoblastoid cell lines which differ in TP53 status. The rate of loss of HLA-A2 is 10-50 times higher compared to the mutation rate of the X-linked HPRT gene. The homozygous TP53 mutation in WI-L2-NS had no effect on the rate of HLA-A2 loss or the spectrum of these mutations. Microsatellite analysis of most of the HLA-A2 mutants (84%) showed LOH for multiple markers on chromosome arm 6p telomeric of a recombination breakpoint, LOH for all 6p markers, or LOH for markers on both the 6p- and 6q-arms. Cytogenetic analysis showed that these mechanisms gave mutant cells which harbored two intact chromosomes 6 and which were indistinguishable from non-mutant cells. Therefore, loss of HLA-A2 is mainly caused by somatic recombination (33-50%) or chromosome loss with duplication of the remaining chromosome (34-40%). These findings correspond to the mechanisms behind loss of the wild-type RBI allele in retinoblastoma and suggest that both somatic recombination and chromosome loss followed by duplication contribute to tumorigenesis.
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PMID:Chromosome loss with concomitant duplication and recombination both contribute most to loss of heterozygosity in vitro. 944 39

The reactivity of guanines in an oligonucleotide containing mutational hot spots within the p53 gene (codons 248 and 249), 5'-CCG1G2AG3G4CCCA-3', toward dimethyl sulfate (DMS) and aflatoxin B1-8,9-epoxide (AFB1-8,9-epoxide) was investigated by a modified Maxam-Gilbert technique. 5-Methylcytosine in the CpG site of codon 248 did not appear to modulate the reactivity of target guanines G1, G2, G3, and G4 toward either genotoxin when compared to the sequence containing a nonmethylated CpG site. A similar experiment was conducted in which a 0.5-kb fragment of the human HPRT gene containing exon 1 and several CpG sites was treated with UV-activated aflatoxin B1. Results showed that guanine adduct formation was independent of the methylation status of the CpG site. These findings are discussed in relation to other studies that have shown that cytosine methylation has an inhibiting effect, an enhancing effect, or no effect on adduct formation with nearby guanine nucleotides.
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PMID:5-Methylcytosine in CpG sites and the reactivity of nearest neighboring guanines toward the carcinogen aflatoxin B1-8,9-epoxide. 992 Jul 42

The first p53 gene mutation arising in a human tumor was described a decade ago by Baker et al. [S.J. Baker, E.R. Fearon, J.M. Nigro, S.R. Hamilton, A.C. Preisinger, J.M. Jessup, P. van Tuinen, D.H. Ledbetter, D.F. Barker, Y. Nakamura, R. White, B. Vogelstein, Chromosome 17 deletions and p53 gene mutations in colorectal carcinomas, Science 244 (1989) 217-221]. There are now over 10,000 mutations extracted from the published literature in the IARC database of human p53 tumor mutations [P. Hainaut, T. Hernandez, A. Robinson, P. Rodriguez-Tome, T. Flores, M. Hollstein, C.C. Harris, R. Montesano, IARC database of p53 gene mutations in human tumors and cell lines: updated compilation, revised formats and new visualization tools, Nucleic Acids Res. 26 (1998) 205-213; Version R3, January 1999]. A large and diverse collection of tumor mutations in cancer patients provides important information on the nature of environmental factors or biological processes that are important causes of human gene mutation, since xenobiotic mutagens as well as endogenous mechanisms of genetic change produce characteristic types of patterns in target DNA [J.H. Miller, Mutational specificity in bacteria, Annu. Rev. Genet. 17 (1983) 215-238; T. Lindahl, Instability and decay of the primary structure of DNA, Nature 362 (1993) 709-715; S.P. Hussain, C.C. Harris, Molecular epidemiology of human cancer: contribution of mutation spectra studies of tumor suppressor genes, Cancer Res. 58 (1998) 4023-4037; P. Hainaut, M. Hollstein, p53 and human cancer: the first ten thousand mutations, Adv. Cancer Res. 2000]. P53 gene mutations in cancers can be compared to point mutation spectra at the HPRT locus of human lymphocytes from patients or healthy individuals with known exposure histories, and accumulated data indicate that mutation patterns at the two loci share certain general features. Hypotheses regarding specific cancer risk factors can be tested by comparing p53 tumor mutations typical of a defined patient group against mutations generated experimentally in rodents or in prokaryotic and eukaryotic cells in vitro. Refinements of this approach to hypothesis testing are being explored that employ human p53 sequences introduced artificially into experimental organisms used in laboratory mutagenesis assays. P53-specific laboratory models, combined with DNA microchips designed for high through-put mutation screening promise to unmask information currently hidden in the compilation of human tumor p53 mutations.
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PMID:New approaches to understanding p53 gene tumor mutation spectra. 1063 83


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