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)

Expression of simian virus 40 (SV40) large T antigen efficiently immortalizes and transforms primary cells. We previously reported that a hybrid polyomavirus-SV40 large T antigen, PyT1-521-SVT336-708, binds to both p53 and pRb but does not transform an established rat cell line (J. J. Manfredi and C. Prives, J. Virol. 64:5250-5259, 1990). Here we show that this hybrid large T antigen is capable of immortalizing primary rat cells. Plasmids that express resistance to G418 sulfate and either SV40 large T antigen or PyT1-521-SVT336-708 were transfected into primary rat embryo fibroblasts, and cell lines were established. The cell lines that expressed PyT1-521-SVT336-708 were not fully transformed but did exhibit altered growth properties. Although these PyT1-521-SVT336-708-expressing lines did not form foci, they did grow in low serum and grew to a high saturation density; these cell lines also formed colonies in soft agar, but their colonies were much smaller than those seen with an SV40 large-T-antigen-expressing line. PyT1-521-SVT336-708 also demonstrated the ability to cooperate with activated Ha-ras to form foci on primary rat embryo fibroblasts. Surprisingly, two types of morphologies in such lines were observed: refractile and spindle shaped. Although there was no correlation between T-antigen level and morphology, all lines that displayed refractile morphology expressed high levels of p21ras. Since the p53 binding activity of PyT1-521-SVT336-708 appears to be intact, these results suggest that there are functions residing in the amino end of SV40 large T antigen which are necessary for full transformation that are missing from the amino end of polyomavirus large T antigen. Conversely, conferring the ability to bind to p53 on an amino-terminal fragment of polyomavirus large T antigen, although not enough to allow full transformation function, does increase its oncogenic activity in saturation density and soft agar growth assays.
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PMID:Primary rat cells expressing a hybrid polyomavirus-simian virus 40 large T antigen have altered growth properties. 839 12

Engagement of the B-cell antigen receptor complex induces immediate activation of receptor-associated Src family tyrosine kinases including p55blk, p59fyn, p53/56lyn, and perhaps p56lck, and this response is accompanied by tyrosine phosphorylation of distinct cellular substrates. These kinases act directly or indirectly to phosphorylate and/or activate effector proteins including p42 (microtubule-associated protein kinase) (MAPK), phospholipases C-gamma 1 (PLC gamma 1) and C-gamma 2 (PLC gamma 2), phosphatidylinositol 3-kinase (PI 3-K), and p21ras-GTPase-activating protein (GAP). Although coimmunoprecipitation results indicate that the Src family protein tyrosine kinases interact physically with some of these effector molecules, the molecular basis of this interaction has not been established. Here, we show that three distinct sites mediate the interaction of these kinases with effectors. The amino-terminal 27 residues of the unique domain of p56lyn mediate association with PLC gamma 2, MAPK, and GAP. Binding to PI 3-K is mediated through the Src homology 3 (SH3) domains of the Src family kinases. Relatively small proportions of cellular PI 3-K, PLC gamma 2, MAPK, and GAP, presumably those which are tyrosine phosphorylated, bind to the SH2 domains of these kinases. Comparative analysis of binding activities of Blk, Lyn, and Fyn shows that these kinases differ in their abilities to associate with MAPK and PI 3-K, suggesting that they may preferentially bind and subsequently phosphorylate distinct sets of downstream effector molecules in vivo. Fast protein liquid chromatography Mono Q column-fractionated MAPK maintains the ability to bind bacterially expressed Lyn, suggesting that the two kinases may interact directly.
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PMID:Mapping of sites on the Src family protein tyrosine kinases p55blk, p59fyn, and p56lyn which interact with the effector molecules phospholipase C-gamma 2, microtubule-associated protein kinase, GTPase-activating protein, and phosphatidylinositol 3-kinase. 839 16

Cross-linking membrane Ig (mIg) on B cells stimulates tyrosine phosphorylation of proteins involved in signal transduction including the mIg-associated proteins Ig-alpha and Ig-beta, the tyrosine kinases p53/p56lyn, p55blk, p59fyn, and PTK72, phosphatidylinositol 3-kinase, phospholipase C gamma 1 and gamma 2, and the mitogen-activated protein kinase. We now show that the p21ras GTPase-activating protein (GAP) is also a substrate for mIg-activated tyrosine kinases. p21ras is a key regulator of cell growth and GAP may act as both a regulator of p21ras activity and as a downstream effector of p21ras. We found that mIg cross-linking caused a rapid increase in tyrosine phosphorylation of GAP in the immature B cell line WEHI-231, the mature B cell lines BAL 17 and Daudi, and the IgG-bearing B cell line A20. In fibroblasts, tyrosine kinase activation causes GAP to associate with two other tyrosine-phosphorylated proteins, p62 and p190, which have homologies to an RNA-binding protein and a transcriptional repressor, respectively. Similarly, mlg cross-linking induced the association of GAP with a 62-kDa tyrosine-phosphorylated protein in BAL 17, WEHI-231, and Daudi cells. Anti-Ig treatment also increased the amount of a 190-kDa tyrosine-phosphorylated protein associated with GAP in WEHI-231 and Daudi cells. After separation by SDS-PAGE and transfer to nitrocellulose, the tyrosine-phosphorylated p62 and p190 present in anti-GAP immunoprecipitates from B cells were capable of binding radiolabeled recombinant GAP, as previously reported for the GAP-associated p62 and p190 from fibroblasts. The amount of p62 that could be detected in this way after immunoprecipitation with antiphosphotyrosine antibodies was much greater from anti-IgM-treated BAL 17 cells than from unstimulated BAL 17 cells. This probably reflects anti-Ig-induced tyrosine phosphorylation of p62. In any case, GAP, p62, and/or p190 may be involved in signal transduction by mIg in B cells.
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PMID:Targets of B lymphocyte antigen receptor signal transduction include the p21ras GTPase-activating protein (GAP) and two GAP-associated proteins. 841 71

Mutant p53 alleles that have a recessive phenotype in human tumors can, in cooperation with an activated H-ras gene, transform rat embryo fibroblasts (REFs). Mutant p53 proteins differ from wild type, and from each other in conformation, localization and transforming potential. Missense mutations in codons 143, 175 and 275 confer strong transforming potential. A serine 135 p53 mutant has an intermediate transforming potential, while the histidine codon 273 allele transforms weakly, if at all. In contrast to the wild type p53 gene, mutant p53 alleles with strong transforming ability cannot suppress the transformation of REFs by other oncogenes. The His273 allele retains partial suppressor function in this assay. The relevance of p53 oligomerization, phosphorylation and nuclear translocation to the transforming potential of mutant p53 and to wild type p53 suppressor function were examined. The inability of mutant p53 polypeptides to form homodimers correlates with loss of transforming function. Monomeric variants of wild type p53 protein, however, retain the ability to suppress focus formation. Phosphorylation of serine residues 315 and 392 is not required for the transforming function of mutant p53, nor is serine 315 required for suppressor function when these alleles are constitutively expressed in REF assays. Nuclear translocation-defective mutant and wild type p53 proteins retain transforming and suppressor function in REF assays.
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PMID:The transforming and suppressor functions of p53 alleles: effects of mutations that disrupt phosphorylation, oligomerization and nuclear translocation. 845 21

Rat embryo fibroblasts (REFs) are inefficiently transformed by the T24-ras oncogene. A contributing factor to cellular resistance to transformation is the limited tolerance to p21-ras oncoprotein expression. Here we present data suggesting that long-term glucocorticoid treatment of ras oncogene-transfected REFs results in increased tolerance to p21-ras oncoproteins, leading to expression of the transformed phenotype. Stably transformed cell lines that expressed high levels of H-ras and could be maintained in the absence of hormone were isolated. In three out of four lines studied, the AP-1-dependent collagenase gene was expressed at a low level. In one of these lines, low collagenase expression was paralleled by lack of c-jun mRNA. Immunochemical analysis revealed that progression to hormone independence was not paralleled by mutations in the p53 gene. We propose that a decreased expression of AP-1-driven genes may result in increased tolerance to p21-ras oncoprotein.
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PMID:Lack of c-jun expression in a transformed cell line isolated by glucocorticoid promotion of ras-transfected rat embryo fibroblasts. 847 51

Efforts to investigate the progression of events that lead normal human cells in culture to become neoplastic in response to carcinogenic agents have been aided by the development of the suitable in vitro model systems. For initial human cell transformation studies, a flat, nontumorigenic clonal line, originally derived from a human osteosarcoma (HOS), was used. When treated with chemical carcinogens such as N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and 3-methyl-cholanthrene (3MC), the HOS cells underwent morphological alterations and acquired tumorigenic properties. These cell lines were very useful inasmuch as a non-ras cellular transforming gene, met, and an activated H-ras oncogene have been isolated from MNNG-transformed and 3MC-transformed HOS lines, respectively, by DNA transfection procedure. Alteration of p53 gene in chemically transformed HOS cell lines has recently been shown. Although carcinogens cause human cancer, normal human cells in culture have proven difficult to achieve. Neoplastic transformation of human cells in culture has recently been achieved by a stepwise fashion-immortalization and conversion of the immortalized cells to tumorigenic cells. One of the critical initial events in the progression of normal human cells to tumor cells is the escape from cellular senescence. With few exceptions, normal human cells require immortalization to provide a practical system for transformation studies. Thus, the role of carcinogenic agents in the development of human cancers is now being defined using a variety of human cells. The neoplastic transformation in human cell cultures is reviewed. In doing so, this author attempts to put into perspective the history of human cell transformation by carcinogenic agents, and to discuss the current state of the art in transformation of human cells in culture; thus providing insight into the molecular and cellular mechanisms involved in the conversion of normal cells to a neoplastic state of growth.
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PMID:Neoplastic transformation of human cells in vitro. 848 2

Non-familial human adrenocortical adenomas and carcinomas were screened for mutations in exons 5-8 of the p53 tumor suppressor gene by single-strand-conformation-polymorphism (SSCP) analysis, followed by direct sequencing of PCR-amplified DNA. Point mutations in codons 12, 13 and 61 in H-ras, K-ras and N-ras proto-oncogenes were similarly assessed by direct DNA sequencing. Three out of 15 primary adrenocortical carcinomas (20%) contained a mis-sense point mutation in the conserved regions (exons 5 and 8) of the p53 gene. Mutations were located in codon 157 (GTC-->TTC; Val-->Phe), codon 163 (TAC-->AAC; Tyr-->Asn), and codon 273 (CGT-->TGT; Arg-->Cys). The mutation in codon 157 was detected in the primary tumor as well as in brain and lymph-node metastases. Among 18 adrenocortical adenomas, there was only a single non-miscoding mutation in codon 295 (CCT-->CCC; Pro-->Pro). These data suggest that mutational inactivation of the p53 gene occurs in a minority (20%) of sporadic adrenocortical carcinomas and that these mutations constitute a late event in the multi-step process of malignant transformation. No ras mutations were detected in any of these tumors, suggesting that these genes are not involved in the development of tumors originating from the adrenal cortex.
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PMID:p53 mutations in sporadic adrenocortical tumors. 850 16

Carcinogenesis is a multigenic phenomenon where 3 prevailing types of genes are involved: oncogenes which stimulate the cell proliferation, tumor suppressor genes which act as inhibitors and metastagenes which contribute to the tumor progress. In animal models it has been shown that epithelial skin carcinogenesis proceeds stepwise: initiation, promotion, premalignant progression and finally malignant conversion. The oncogene c-H-ras and the tumor suppressor gene P53 are the genes whose involvement in these steps of epithelial skin cancers are duly established. Less experimental data are available concerning melanoma. the role of the oncogene N-ras, the tumor suppressor gene MTS-1 (encoding for protein p16) ans the metastagene nm 23 has recently be emphasized. Some cytogenetic abnormalities on chromosomes 1, 6, 9, 10, 11 and 17 have also been observed and incite to look for other genes potentially involved in the development of this tumor.
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PMID:[Genetic bases of cutaneous tumors]. 852 16

Relationships between radiation-induced apoptosis and oncogenes or suppressor genes (p53, MDM2, c-myc, p21ras and bcl-2) were immunohistochemically studied in 7 human tumors transplanted to nude mice. The most radiosensitive ependymoblastoma was negative for p53 and c-myc, however, the other 6 tumors were positive for them. Following irradiation, the ependymoblastoma became p53 positive, and showed the highest incidence of apoptosis among the 7 tumors. In addition, bcl-2 expression in this tumor was slightly different from that in the others.
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PMID:[Immunohistochemical study of radiation-induced apoptosis and oncogenes]. 853 13

We investigated the effects of bile acid feeding on the mRNA levels and transcriptional activity of genes involved in various facets of hepatic cell function. Rats were maintained for 10 days on standard diet supplemented with combinations of 1 and 0.4% deoxycholic acid and ursodeoxycholic acid. Significant reductions in mRNA levels for liver fatty acid binding protein, albumin, the asialoglycoprotein receptor, connexins 32 and 26, and cytochromes P-450IIB1 and P-450IIE1 were associated with 1% deoxycholic acid feeding. Conversely, the 1% deoxycholic acid-fed animals exhibited increased mRNA levels for cholesterol 7 alpha-hydroxylase, 3-hydroxy-3-methylglutaryl-CoA reductase, multidrug resistance, procollagens, extracellular matrix, protooncogenes, tumor suppressors, and cyclins. The 0.4% deoxycholic acid-fed animals exhibited increased mRNA levels for c-jun, H-ras, p53, cyclins D1 and D3, fibronectin, and procollagens alpha 1(I) and alpha 1(III). Transcriptional rate changes could not account for the observed changes in steady-state mRNA levels. Ursodeoxycholic acid feeding had no significant effect on gene expression and almost completely inhibited the changes associated with 1% deoxycholic acid when coadministered. The results indicate that dietary ingestion of deoxycholic acid profoundly affects hepatic gene expression in the rat, and regulation occurs primarily at the posttranscriptional level.
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PMID:Posttranscriptional regulation of mRNA levels in rat liver associated with deoxycholic acid feeding. 857 28


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