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)

In addition to controlling the transition of resting normal cells from the G0-state of the cell cycle into S-phase, expression of the cellular protein p53 also seems to be necessary for the proliferation of cycling normal cells in an as yet undefined manner. To further elaborate the role of p53 in growing cells, we analysed p53 expression and its regulation in cells going into, and after release from, growth arrest at the restriction point (R-point) in the G1-phase of the cell cycle, induced by isoleucine depletion. Since growth arrest at the R-point is subject to internal control mechanisms of the cell cycle, this approach allowed us to include in our analyses normal Balb/c 3T3 fibroblasts, as well as cells of the chemically induced Balb/c fibrosarcoma cell line Meth A, expressing mutated p53. Isoleucine depletion induced a viable growth arrest at the R-point in cells of both cell lines, marked by a synchronous shut-down of DNA synthesis when the cells went into growth arrest, and a synchronous resumption of DNA synthesis after a lag period of about 2-4 h when the cells were released from growth arrest, as well as a shift to a G1 DNA content at the R-point. p53 expression in both cell lines showed a phenotypically similar regulation, as its synthesis was specifically reduced at the R-point. At the molecular level, however, p53 expression in growth arrested 3T3 cells was controlled at the transcriptional/post-transcriptional level, whereas control in growth arrested Meth A cells seemed to be at the level of mRNA translation. After release from growth arrest, p53 synthesis in both types of cells was rapidly restored, preceding resumption of total protein synthesis, and exhibiting a p53-specific profile.
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PMID:Cell cycle control by p53 in normal (3T3) and chemically transformed (Meth A) mouse cells. I. Regulation of p53 expression. 226 35

To further characterize the role of p53 in growing normal Balb/c 3T3 fibroblasts, as well as of p53 in cells of the methylcholanthrene induced fibrosarcoma cell line Meth A, we analysed the effect of inhibition of p53 synthesis by microinjection of p53-specific monoclonal antibody PAb 122 into the nuclei of these cells after release from growth arrest induced by isoleucine starvation (see preceding paper [Steinmeyer et al., this issue] ). We show that microinjection of PAb 122, but not of control immunoglobulins, into the nuclei of both types of cells effectively blocked their re-entry into the S-phase of the cell cycle. Since isoleucine depletion of these cells was shown to lead to a growth arrest at the restriction point (R-point) in the G1-phase of the cell cycle, our results (i) define more precisely the role of p53 in growing cells as a protein controlling transition of the cells through this restriction point, and (ii) demonstrate that mutated p53 in Meth A cells still is functional with regard to cell cycle control at this restriction point. We suggest that p53 acts as a 'gate-keeping' protein at restriction points in the cell cycle, exerting a positive effect on the transition of cells through the cell cycle.
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PMID:Cell cycle control of p53 in normal (3T3) and chemically transformed (Meth A) mouse cells. II. Requirement for cell cycle progression. 226 36

Our previous study revealed that mutations of the p53 gene were detected by cDNA sequencing in one of four (25%) primary gastric tumors and in five of six (83%) gastric cancer cell lines. It was of interest that all five cell lines established from metastatic lesions had p53 gene mutations, while the single cell line established from a primary tumor lacked an abnormality. Thus, the current study was initiated to determine the frequency of p53 mutations in 10 pairs of samples from primary gastric carcinomas and their lymph node metastases, in addition to morphologically normal gastric mucosa. In addition, we correlated the findings with other relevant molecular markers including the metastasis associated nm23-H1 gene and loss of heterozygosity (LOH) using multiple polymorphic markers for chromosome 17p and sequencing the entire open reading frame (ORF) of the p53 gene. Five of ten (50%) patients were constitutionally heterozygous for one or more 17p and/or p53 probes (pYNZ 22, BamHI RFLP; pMct35.1, Mspl RFLP; php53cl, Bg/II RFLP), while none had LOH at the 17p and/or p53. A Bg/II RFLP for analysis of possible nm23-H1 somatic allelic deletion revealed no LOH out of four informative cases. One paired sample demonstrated the substitution of valine for isoleucine at codon 41 (GTT to ATT) in both primary gastric tumor and metastasis. Another metastatic sample demonstrated the substitution of proline for threonine at codon 278 (CCT to C/ACT) in addition to a non-mutated codon, while only the wild-type p53 sequence was present in the paired primary gastric tumor tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparison of p53 gene mutations in paired primary and metastatic gastric tumor tissues. 790 5

Deregulated expression of the c-myc proto-oncogene can lead to apoptosis under certain physiological conditions. By introducing a conditionally active Myc allele into primary embryo fibroblasts null for p53, and into fibroblasts without endogenous p53 expression but ectopically expressing a temperature-sensitive p53 allele, we show that expression of wild-type p53 is required for susceptibility to Myc-mediated apoptosis. Although ectopic expression of wild-type p53 blocked cells in the G1 phase of the cell cycle, G1 arrest by isoleucine starvation, in a manner independent of p53, did not confer susceptibility to apoptosis. Thus, growth arrest per se is not sufficient to induce Myc-mediated apoptosis; instead, a property intrinsic to p53 is specifically required. Moreover, apoptosis did not require induction of p53 target proteins, including the cyclin-dependent kinase inhibitor p21waf1/cip1. Therefore, the role of p53 in apoptosis may be distinct from its role in cell cycle arrest.
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PMID:Myc-mediated apoptosis requires wild-type p53 in a manner independent of cell cycle arrest and the ability of p53 to induce p21waf1/cip1. 799 20

To clarify gene alterations in functional human adrenal tumors, we performed molecular analysis for p53 abnormalities in 23 cases with adrenal neoplasms. The immunohistochemical study with anti-p53 monoclonal antibody pAb1801 demonstrated that 10 of 23 (43.5%) cases overexpressed p53 protein in the tumor cells. Using a polymerase chain reaction-single strand conformation polymorphism study, 5 of 6 (83.3%) pheochromocytoma tissues (1 malignant and 5 benign) and 11 of 15 (73.3%) adrenocortical adenomas (2 with Cushing's syndrome and 13 with primary aldosteronism, all benign) showed an apparent electrophoretic mobility shift between the tumor and its paired adjacent normal adrenal tissue. Such differences were detected in exon 4 (12 cases), exon 5 (2 cases), and exon 7 (3 cases). The types of these mutations in exon 4 were a substitution from threonine (ACC) to isoleucine (ATC) at codon 102 in 5 cases, from glutamine (CAG) to histidine (CAC) at codon 104 in 1 case, from glycine (GGG) to alanine (CGG) at codon 117 in 1 case, from glutamate (GAG) to glutamine (CAG) at codon 68 in 1 case, and single base changes resulting in a premature stop codon at codon 100 in 2 cases. A 2-basepair deletion at codon 175 in exon 5 resulting in a frame shift was identified in 1 case. A single point mutation was identified, resulting in the substitution of glutamine (CAG) for arginine (CGG) at codon 248 of exon 7 in 1 case. A single basepair deletion at codon 249 resulted in a frame shift in 2 cases. There was 1 case with malignant pheochromocytoma that combined a single point mutation in exon 4 and a single base deletion in exon 7. Only 2 of 23 cases showed a loss of a normal allele encoding in the p53 gene. Northern blot analysis with 1.8-kilobase p53 cDNA revealed that p53 mRNA was overexpressed in 6 cases. Our results indicate that high frequencies of p53 gene mutation, especially in exon 4, exist in functional adrenal tumors. As p53 protein is a regulator of guanine nucleotide synthesis, the loss of normal inhibitory regulation by the p53 mutation would serve to increase the availability of GTP for the transduction of signals essential for increased cell growth and hormone expression in the adrenal tumors. These findings suggest that the p53 gene mutation may play a role in the tumorigenesis of benign and functional human adrenal tumors.
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PMID:Mutations of the p53 gene in human functional adrenal neoplasms. 810 38

A temperature-sensitive mutant of murine p53 (p53Val-135) was transfected by electroporation into murine erythroleukemia cells (DP16-1) lacking endogenous expression of p53. While the transfected cells grew normally in the presence of mutant p53 (37.5 degrees C), wild-type p53 (32.5 degrees C) was associated with a rapid loss of cell viability. Genomic DNA extracted at 32.5 degrees C was seen to be fragmented into a characteristic ladder consistent with cell death due to apoptosis. Following synchronization by density arrest, transfected cells released into G1 at 32.5 degrees C were found to lose viability more rapidly than did randomly growing cultures. Following release into G1, cells became irreversibly committed to cell death after 4 h at 32.5 degrees C. Commitment to cell death correlated with the first appearance of fragmented DNA. Synchronized cells allowed to pass out of G1 prior to being placed at 32.5 degrees C continued to cycle until subsequently arrested in G1; loss of viability occurred following G1 arrest. In contrast to cells in G1, cells cultured at 32.5 degrees C for prolonged periods during S phase and G2/M, and then returned to 37.5 degrees C, did not become committed to cell death. G1 arrest at 37.5 degrees C, utilizing either mimosine or isoleucine deprivation, does not lead to rapid cell death. Upon transfer to 32.5 degrees C, these G1 synchronized cell populations quickly lost viability. Cells that were kept density arrested at 32.5 degrees C (G0) lost viability at a much slower rate than did cells released into G1. Taken together, these results indicate that wild-type p53 induces cell death in murine erythroleukemia cells and that this effect occurs predominantly in the G1 phase of actively cycling cells.
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PMID:Cell cycle analysis of p53-induced cell death in murine erythroleukemia cells. 841 61

Generalized glucocorticoid resistance is associated with chronic hyperactivation of the hypothalamic-pituitary-adrenal axis, compensating for impaired glucocorticoid receptor function. We report a unique patient with sporadic generalized glucocorticoid resistance who, at age 33, presented with infertility and hypertension and, at 38, developed pituitary Cushing's disease. Leukocyte-binding studies revealed normal affinity of the glucocorticoid receptor but a reduction of binding sites by 50%. [3H]thymidine incorporation by this patient's lymphocytes was not suppressible by dexamethasone. He had a novel heterozygous missense mutation in the glucocorticoid receptor gene (isoleucine 559 to asparagine 559). The mutant receptor exhibited a strong dominant-negative effect on the ability of the wild-type receptor to induce gene transcription in vitro. The mutation was present in all of the patient's cultured lymphoblasts and fibroblasts as well as in 50% of his sperm, as demonstrated by single-cell polymerase chain reaction; it was not present in his parents and seven siblings. This novel mutation was thus both de novo and present in the germ line. Immunohistochemical staining of this patient's pituitary corticotropinoma revealed accumulation of p53 protein, indicating the presence of a putative somatic oncogenic mutation in the p53 gene in the tumor cells. Investigation of the lymphoblast and skin fibroblast cultures for p53 abnormalities did not show any aberration. Thus, a novel de novo germ line mutation of the glucocorticoid receptor with strong dominant-negative activity caused severe sporadic generalized glucocorticoid resistance, which preceded corticotroph adenoma formation. The latter probably was due to the combined effects of chronic corticotroph hyperstimulation, decreased glucocorticoid negative feedback, and at least one subsequent somatic defect in the control of the cell cycle.
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PMID:Cushing's disease preceded by generalized glucocorticoid resistance: clinical consequences of a novel, dominant-negative glucocorticoid receptor mutation. 886 43

Although numerous studies have demonstrated increased expression of p53 protein in the Reed-Sternberg cells of Hodgkin's disease, little data exist as to whether mutations of the p53 gene is a common occurrence in this neoplasm. Using a microdissection technique coupled with PCR, single-strand conformation analysis, and DNA sequencing, we studied 23 cases of Hodgkin's disease for mutations within exons 5 to 8 of the p53 gene. We found seven mutations within six cases; six were missense mutations. An identical missense mutation was found in three cases (codon 243, methionine to isoleucine), and another identical missense mutation was found in an additional two cases (codon 204, glutamic acid to lysine). Verification of the mutations was accomplished either by direct Southern blotting of PCR-amplified p53 exon products from re-extracted DNA or by hybridization of cloned PCR-amplified p53 exon products from re-extracted DNA with a mutant-specific oligonucleotide. There was no good correlation between the presence of p53 mutations and the level of p53 protein expression, which was found to be overexpressed in all cases, the level of MDM2 protein expression, or the proliferation rate as determined by K-67 antibody. None of the cases with p53 mutation had evidence of Epstein-Barr virus within the Reed-Sternberg cells, as compared with 7 of 17 of the other cases (p < 0.06). These results suggest that p53 mutation may represent an important mechanism in the pathogenesis of Hodgkin's disease, and this mechanism may be independent of Epstein-Barr virus.
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PMID:p53 mutations in Hodgkin's disease. 887 83

The CDKN2A gene encodes p16 (CDKN2A), a cell-cycle inhibitor protein which prevents inappropriate cell cycling and, hence, proliferation. Germ-line mutations in CDKN2A predispose to the familial atypical multiple-mole melanoma (FAMMM) syndrome but also have been seen in rare families in which only 1 or 2 individuals are affected by cutaneous malignant melanoma (CMM). We therefore sequenced exons 1alpha and 2 of CDKN2A using lymphocyte DNA isolated from index cases from 67 families with cancers at multiple sites, where the patterns of cancer did not resemble those attributable to known genes such as hMLH1, hMLH2, BRCA1, BRCA2, TP53 or other cancer susceptibility genes. We found one mutation, a mis-sense mutation resulting in a methionine to isoleucine change at codon 53 (M531) of exon 2. The individual tested had developed 2 CMMs but had no dysplastic nevi and lacked a family history of dysplastic nevi or CMM. Other family members had been diagnosed with oral cancer (2 persons), bladder cancer (1 person) and possibly gall-bladder cancer. While this mutation has been reported in Australian and North American melanoma kindreds, we did not observe it in 618 chromosomes from Scottish and Canadian controls. Functional studies revealed that the CDKN2A variant carrying the M531 change was unable to bind effectively to CDK4, showing that this mutation is of pathological significance. Our results have confirmed that CDKN2A mutations are not limited to FAMMM kindreds but also demonstrate that multi-site cancer families without melanoma are very unlikely to contain CDKN2A mutations.
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PMID:CDKN2A mutation in a non-FAMMM kindred with cancers at multiple sites results in a functionally abnormal protein. 938 68

Cystosarcoma phyllodes (CSP) is a rare breast neoplasm composed of stromal and epithelial elements. It usually runs a benign course but it may metastasize. In a 31-year-old patient with recurring CSP, a mesenchymal tumor in the leg developed. The question arose whether the latter tumor could be a metastasis from the CSP, which would have major treatment consequences. The problem was addressed using molecular methods, i.e., comparison of the pattern of polymorphic repeat markers on chromosome 17p as well as single strand conformation polymorphism analysis and sequencing of exons 5 to 8 of the TP53 gene in both tumor and normal tissue. An identical pattern of loss of heterozygosity in both breast tumors was demonstrated, but a different pattern was shown in the tumor in the leg. This led to the conclusion that the latter tumor had to be a new primary tumor. A mutation in codon 162 of the TP53 gene was found in the tumor tissue as well as in the normal tissue of this patient. This germ line mutation leads to the replacement of isoleucine by asparagine and most likely has functional consequences. In all four examined tumors of this patient, the normal TP53 allele was lost. This is strong evidence that this germ line TP53 mutation causes the genesis of these two rare primary mesenchymal tumors in this young patient. The current study exemplifies the power of molecular diagnostic methods in investigating the specific clinical problem of clonal relation between two separate tumors. The germ line mutation found in codon 162 of the TP53 gene and the association with cystosarcoma phyllodes have not been described previously.
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PMID:Molecular assessment of clonality leads to the identification of a new germ line TP53 mutation associated with malignant cystosarcoma phyllodes and soft tissue sarcoma. 1020 67

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