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)

The large T antigen encoded by simian virus 40 (SV40) plays essential roles in the infection of permissive cells, leading to production of progeny virions, and in the infection of nonpermissive cells, leading to malignant transformation. Primary mouse embryo fibroblasts (MEFs) are nonpermissive for SV40, and infection by wild-type SV40 leads to immortalization and transformation of a small percentage of infected cells. We examined the ability of an extensive set of mutants whose lesions affect SV40 large T antigen to immortalize MEFs. We found that immortalization activity was retained by all mutants whose lesions are located upstream of codon 346. This includes a mutant lacking amino acids 168 to 346. We previously showed (M. J. Tevethia, J. M. Pipas, T. Kierstead, and C. Cole, Virology 162:76-89, 1988) that sequences downstream of amino acid 626 are not required for immortalization of primary MEFs. Studies by Thompson et al. (D. L. Thompson, D. Kalderon, A. Smith, and M. Tevethia, Virology 178:15-34, 1990) indicate that all sequences upstream of residue 250, including the domain for binding of tumor suppressor protein Rb, are not required for transformation of MEFs. Together, these studies demonstrate that the immortalization activity of large T antigen for MEFs maps to sequences between 347 and 626. Several mutants with lesions between 347 and 626 retained the ability to immortalize at nearly the wild-type frequency, while others, with small insertions at amino acid 409 or 424 or a deletion of residues 587 to 589, failed to immortalize. The abilities of mutant T antigens to form a complex with tumor suppressor protein p53 were examined. We found that all mutants able to immortalize retained the ability to complex with p53, while all mutants which lost the ability to immortalize were no longer able to bind p53. This suggests that inactivation of the growth-suppressive properties of p53 is essential for immortalization of MEFs.
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PMID:The ability of simian virus 40 large T antigen to immortalize primary mouse embryo fibroblasts cosegregates with its ability to bind to p53. 165 80

The expression of the 7B2 protein, secreted from a variety of neural and endocrine tissues, increases dramatically in specific neuroendocrine tumors. We have recently shown that human 7B2 can act as a molecular chaperone in the deaggregation of proteins in vitro. In order to identify polypeptides which might bind 7B2 in vivo, the yeast two-hybrid system was employed. Surprisingly, mere covalent linkage of 7B2 to the DNA-binding domains of two yeast transcription activators, Ace1 and Gal4, activates transcription from the ACE1 and GAL4 operon. 7B2's ability to activate nuclear transcription surpasses that of Ace1 and compares favourably with the strong activation domain of the tumor suppressor protein, p53. Our results suggest that 7B2 must possess an activating sequence, a domain which defines all transcriptional activator proteins. Like the acidic activation domains of some transcriptional activators, 7B2 also binds the yeast TATA-box binding protein, an essential polypeptide in the basic transcription machinery. Deletion analysis of the gene encoding 7B2 reveals two independent transcriptional activating sequences in the 185 amino acid protein. It is therefore conceivable that 7B2 not only has a functional role in the secretory pathway but also in the nucleus. Moreover, these findings raise an intriguing question regarding the activation domains of 7B2 and their possible link to 7B2's oncogenic potential.
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PMID:The neuroendocrine protein 7B2 contains unusually potent transcriptional activating sequences. 748 73

Recent evidence suggests that the tumor suppressor protein, p53, protects somatic cells against the accumulation of genomic mutations. The genomes of cells lacking normal p53 function may become hypermutable, a condition that might result in the accumulation of multiple genetic alterations as the affected cells proliferate. Such cells may then become more susceptible to malignant transformation. We hypothesized that some high-grade prostate cancers might arise from foci of morphologically benign cells that had previously sustained p53 lesions. As an initial test of this hypothesis, we employed a microdissection technique to isolate morphologically benign cells within hyperplastic glands located near foci of high-grade adenocarcinoma. Genomic DNA from these cells was subjected to polymerase chain reaction amplification and single-stranded conformational polymorphism analysis for detecting alterations in the p53 locus. With use of this approach, gross alterations in the p53 locus were demonstrated in benign cells in 1 of 20 (5%) specimens harboring high-grade malignancy (Gleason grade 7 or higher). Thus, in some cases, hyperplastic prostatic epithelium harbors preneoplastic genetic alterations that could possibly give rise to high-grade malignancies.
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PMID:Alteration of the p53 locus in benign hyperplastic prostatic epithelium associated with high-grade prostatic adenocarcinoma. 753 28

The tumor suppressor protein, p53, protects somatic cells against the accumulation of genomic alterations. Cells harboring mutant or inactivated wild-type p53 protein are at risk for the development of genomic instability. Nuclear accumulation of p53 protein is associated with the stepwise dedifferentiation of papillary carcinoma. We asked whether nuclear p53 accumulation is associated with two known indicators of poor prognosis in papillary carcinoma. We studied 55 consecutive papillary cancers (28 from Russia, and 27 from upstate New York). Nuclear p53 immunoreactivity was assessed using a monoclonal antibody, DO-1, on Formalin-fixed paraffin-embedded specimens. The DNA index was determined by computerized image analysis of Feulgen-stained sections. Nearly all cases were well differentiated and none were associated with distant metastases or extrathyroidal invasion. All primary lesions were less than 4 cm in diameter, and almost all patients were female. Nuclear p53 immunoreactivity was associated with a high-risk group characterized by two known indicators of poor prognosis: age > 50, aneuploid DNA content, or both. In the high-risk group (N = 24) 33% of cases displayed nuclear p53 positivity, compared with only 6% in a low-risk group (N = 31) which lacked both features (P = 0.015, two-tailed Fisher exact test). Nuclear accumulation of immunoreactive p53 protein is associated with two established indicators of poor prognosis in papillary carcinoma of the thyroid. This result is consistent with the idea that aberrations in p53 function are associated with the stepwise loss of differentiation in this cancer.
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PMID:Nuclear p53 immunoreactivity in papillary thyroid cancers is associated with two established indicators of poor prognosis. 755 91

The tumor suppressor protein, p53, is proposed to have a critical role in maintaining the integrity of the genetic material. It has been established that p53 induces a cell cycle block in the G1 phase upon cellular DNA damage. Recent evidence also indicates the involvement of p53 directly and indirectly in nucleotide excision repair (NER). We have examined the role of p53 with respect to UV-induced mutagenesis. By gene transfer, we established a mouse fibroblast cell line overexpressing the val135 temperature-sensitive p53 allele. In this line, p53 activity can be modulated through temperature shift, as confirmed by Western blot and by cell cycle analysis. This cell line was also constructed to contain a recoverable lambda phage shuttle vector carrying the supF mutation reporter gene. Induction of p53 was found to enhance the clonogenic survival of the cells following UV-irradiation compared to the p53-deficient parental mouse cell line. The transfectant line also displayed a 4-fold reduction in the frequency of UV-induced mutations as measured in the chromosomally integrated supF reporter gene. Our results are consistent with a p53-induced cell cycle block at G1 allowing cells to repair chromosomal damage before DNA replication. However, our data may also reflect a more direct role of p53 in the repair of UV-induced lesions as suggested by studies showing that p53 can interact directly with repair factors.
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PMID:Induction of p53 in mouse cells decreases mutagenesis by UV radiation. 758 25

p53 is a tumor suppressor protein that is overexpressed in a variety of human neoplasms, including prostatic adenocarcinoma. Recent studies have demonstrated a significant positive correlation between extent of p53 overexpression and tumor grade in prostatic adenocarcinoma. Because it appears that mutations of p53 might play a role in the pathogenesis of a subset of biologically aggressive prostatic neoplasms, we sought to examine the frequency of p53 overexpression in primary and metastatic prostatic adenocarcinoma. Using a monoclonal antibody (D07) directed against both the wild-type and mutant forms of p53, we examined p53 immunoreactivity in 36 cases of primary prostatic adenocarcinoma, 17 cases of metastatic prostatic adenocarcinoma involving lymph nodes and 15 cases of metastatic prostatic adenocarcinoma involving bone. Twenty-eight percent (10/36) of the primary tumors displayed nuclear staining for p53. Increased p53 immunoreactivity was observed in only 6% (1/16) of prostatic adenocarcinomas with a total Gleason score of 6 or less, as compared with 45% (9/20) of those adenocarcinomas with a Gleason score of 7 or more. Fifty-nine percent (10/17) of the lymph node metastases and 43% (6/14) of the bone metastases displayed nuclear immunoreactivity for p53. Our results indicate that increased p53 expression is positively correlated with increased histologic grade and with the presence of metastatic disease in patients with prostatic adenocarcinoma, and they suggest that mutations of the p53 gene may play a role in mediating the behavior of a biologically aggressive subset of this common neoplasm.
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PMID:p53 immunoreactivity in primary and metastatic prostatic adenocarcinoma. 767 61

Molecular changes associated with cellular aging in a strain of human diploid fibroblasts, IMR-90, were addressed by analyzing the expression of the tumor suppressor protein, p53. In all studies, IMR-90 cultures were characterized as "young" or "near-senescent" based on morphology, rate of population doubling, capacity for DNA synthesis, and presence of established markers for senescence. When p53 was immunoprecipitated by monoclonal antibodies and detected by Western immunoblot analysis, more protein per cell was detected in the near-senescent cultures. A greater than 10-fold increase in p53 protein was measured with the PAb 1801 (N-terminal-specific) anti-p53 antibody, whereas PAb 122 (C-terminal-specific) measured a 5-fold increase. Although near-senescent cultures demonstrated a higher level of p53 than young cells, these cultures had similar charges and molecular weight p53 isoforms when analyzed by two-dimensional Western blots. When p53 RNA was compared to total RNA there was a decrease in p53 RNA with age, but on a per cell basis p53 RNA was elevated. These results provide evidence for transcriptional regulation of p53 during aging and support the hypothesis that elevated levels of p53 protein may play a role in cellular senescence.
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PMID:Increased p53 protein associated with aging in human diploid fibroblasts. 769 34

Several in vitro studies have provided evidence that the tumor suppressor protein, p53, is involved in the cell death process referred to as apoptosis. The recent development of p53 knock-out mice has enabled further investigation into the function of p53 for apoptosis, in vivo. Radiation-induced apoptosis is suppressed in such mice, yet other forms of apoptosis do not seem to be significantly affected. In this report, we present evidence that such male p53 nullizygous mice have less apoptosis in the prostate glands associated with the first 4 days following castration. Ventral prostate glands were obtained from normal, heterozygous p53-null and p53 nullizygous mice at daily intervals after castration. These tissues were stained for apoptosis with the use of the in situ and labeling method and apoptotic bodies were quantified by microscopy. Although labeled apoptotic bodies were observed in post-castrated tissues from all of these genetic variant mice, the onset of apoptosis was delayed and the occurrence of apoptosis was significantly reduced in the p53 nullizygous mice when compared to normal controls. Heterozygous p53-null mice were intermediate for these criteria. Examination of the internucleosomal DNA fragmentation pattern at 2 days of castration supports a significant diminution of prostate cell apoptosis in nullizygous p53 mice. Additionally, large nucleated and multinucleated cells were detected in the prostate epithelium of noncastrated p53 nullizygous mice and these abnormal cells were increased after castration. Flow cytometric analysis of these tissues confirmed a high number of 4C and 8C DNA content cells in the p53 nullizygous prostates and their frequency was increased by castration. In concordance with an earlier study, we conclude that functional p53 protein is not essential for prostate epithelial cells to undergo castration-induced apoptosis. However, wild-type p53 does appear to enhance this process, especially in the early period following castration, and this protein may regulate an aberrant prostate cell cycling activity that follows castration.
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PMID:Androgen suppressed apoptosis is modified in p53 deficient mice. 773 76

The IE2 gene product of human cytomegalovirus (HCMV) is one of a few viral regulatory proteins expressed immediately upon infection of the host cell. It is a potent transcriptional activator of many viral and cellular promoters. We found that the retinoblastoma susceptibility gene product (Rb) dramatically suppressed this IE2 transactivation of various promoters. However, unlike another tumor suppressor protein, p53, Rb did not have any significant effect on basal levels of transcription, suggesting that Rb specifically interacts with IE2 rather than other cellular factors involved in the general transcription machinery. We found by protein-affinity chromatography that Rb in nuclear extracts or produced by in vitro translation directly bound to IE2. Our results suggest that Rb may regulate the life cycle of HCMV, which is endemic in the human population. Furthermore, these data may provide new insights into the slow rate of HCMV DNA replication in cells and the possible involvement of HCMV in tumorigenesis.
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PMID:The retinoblastoma gene product negatively regulates transcriptional activation mediated by the human cytomegalovirus IE2 protein. 774 17

It has recently become clear that cyclin-dependent kinase (cdk) complex regulates the cell cycle by phosphorylating Rb protein, a tumor suppressor protein. It is likely that this complex is a target of various growth factors and anti-growth factors (UV, TGF-beta etc.) in keratinocyte (KC). It has also been suggested that abnormalities in the cell cycle regulating mechanism such as increased activity of cyclin-cdk due to mutation of p53, a tumor suppressor gene, and overexpression of cyclin D may be concerned with carcinogenesis of KC. Thus, recent studies indicate that the cyclin-cdk complex is a common target of proliferation and carcinogenesis in KC.
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PMID:Cell cycle regulators in the keratinocyte (cyclin-cdk). 775 27


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