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 Escherichia coli MutY gene was cloned into a modified pET-11 plasmid which was then transfected into an E.coli HMS174 host for overproduction of the MutY mismatch repair (MR) enzyme. Approximately 30-50% of the total cellular protein in the transformed HMS174 cells was isopropyl-beta-D-thiogalactoside-induced MutY protein, as estimated from the staining intensity on an SDS-PAGE gel following electrophoresis. The MutY protein was purified to near homogeneity by cellulose phosphate ion-exchange chromatography followed by gel filtration chromatography. The purified MutY protein had enzyme activities which cleaved the A of a G/A mismatch at the 3' end of the first phosphodiester bond and then the 5' end of the second phosphodiester bond of the A. It also cut the A of a C/A mismatch, but to a much lesser extent, and the activity was DNA sequence-dependent. The reliability of the assay in determining the site and nature of a DNA mutation was examined in human tumor DNA samples with known or unknown p53 mutations. In the assay, polymerase chain reaction-amplified DNA fragments from normal and mutated p53 genes were mixed, denatured and annealed to generate mismatches of G/A or C/A for cleavage by the MutY MR enzyme. The assay results revealed the site and nature of known G:C<-->T:A mutations. In addition, a previously unknown G:C to T:A mutation, which was misread in the sequencing analysis of a tumor DNA preparation, was identified by this assay.
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PMID:Determining the site and nature of DNA mutations with the cloned MutY mismatch repair enzyme. 862 58

In adult mice of the transgenic strain TG66.19, in which expression of herpes simplex type 1 virus thymidine kinase (HSVI-TK) is driven in thyrocytes from the thyroglobulin promoter, the drug Ganciclovir causes the death (ablation) of thyrocytes. Ablation occurred in the absence of thyrocyte proliferation or nuclear DNA synthesis, but was accompanied by transient expression of proliferating cell nuclear antigen and the dying thyrocytes exhibited the ultrastructural features of apoptosis. Control experiments show that the apoptosis is a result of the production of Ganciclovir phosphates in thyrocytes that express HSV1-TK. However, cell death was not dependent upon the presence of a functional copy of the oncosuppressor gene p53. We conclude that the apoptosis is probably not mediated by induction of DNA damage and occurs via a pathway that is independent of p53. The fact that Ganciclovir phosphate can kill cells by a p53-independent apoptotic pathway is encouraging in relation to tumour ablation by methods based on transfection with HSV1-tk genes and administration of Ganciclovir.
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PMID:Ganciclovir-induced ablation non-proliferating thyrocytes expressing herpesvirus thymidine kinase occurs by p53-independent apoptosis. 870 May 54

We investigated the effects of transfection of wild-type TP53 on the growth properties of a human gingival carcinoma cell line, KOSC-3, in which the TP53 gene is mutated at codon 248 and overexpressed. The wild-type TP53 expression plasmid, pCDM8-p53/neo and the control plasmid, pCDM8/neo, were each stably transfected into KOSC-3 cells by using the calcium phosphate method. The number of G418-resistant colonies from wild-type TP53-transfected cells was approximately half that from plasmid controls. Exogenous wild-type TP53 transcripts were identified in four of the 20 G418-resistant clones analysed by reverse transcription PCR. Although the growth rates of the wild-type TP53+ clones did not drastically change during log phase, their saturation density was significantly reduced. The wild-type TP53+ cells were morphologically flat and enlarged when cultured in vitro, and were less able to form colonies in soft agar. In nude mice, the wild-type TP53+ clones formed subcutaneous tumours with conspicuous keratinisation and notable cell death that was not manifested in the parental and plasmid control cells. These findings indicate that the wild-type TP53 gene, even when it coexists with a mutated form, may function as a growth suppressor and differentiation inducer under restricted conditions in gingival squamous cell carcinoma.
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PMID:Transfection of wild-type TP53 induces differentiation in human gingival carcinoma cells. 881 3

The p53 tumor suppressor protein induces cell-cycle arrest or cell death in response to DNA-damaging agents, such as radiation and many of the chemotherapeutics used in cancer therapy. The function of p53 is dependent on its ability to bind DNA in a sequence-specific manner, but in one-half of all human tumors, its sequence-specific DNA binding domain is compromised by single-amino acid substitutions. The nature of these substitutions, which target residues that directly contact DNA or that stabilize the structure of the DNA binding domain, has raised concerns as to whether the function of p53 mutants could ever be rescued. Nevertheless, pharmaceuticals that restore function to p53 mutants could specifically suppress proliferation of cancer cells in patients. To determine whether tumor-derived p53 mutants are irreversibly inactivated, we introduced basic residues in their DNA binding domains, aiming to establish novel contacts between p53 and the DNA phosphate backbone. In three of the seven most common p53 mutants, replacement of Thr284 with Arg significantly enhanced DNA binding affinity, without affecting DNA binding specificity, and rescued their transactivation and tumor suppressor functions. Thus, many tumor-derived p53 mutants retain their sequence-specific DNA binding determinants and can be activated to suppress tumor growth.
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PMID:Structure-based rescue of common tumor-derived p53 mutants. 883 16

Nuclear accumulation of the tumorsuppressor protein p53 indicates the occurrence of chromatin injury (J. Cancer Res. Clin. Oncol. 1991, 117, 30; Oncogene 1993, 8, 307) and may be used as an analytical tool to detect genotoxic agents. This mechanism was used to evaluate the DNA-damaging potency (clastogenicity) of the tar- and aerosol-free, gaseous phase of cigarette smoke which is obtained by filtration through Cambridge glass fiber filters. This condensate-free gas phase was absorbed by phosphate-buffered saline and immediately thereafter poured onto monolayers of the murine cell line L929 for 10 min. Eighteen hours later the nuclear accumulation of p53, an indicator for DNA damage, was determined. The elicited level of p53 was similar to that obtained by direct incubation with the gas phase of filtered cigarette smoke for 2 min or with several micrograms of mitomycin C per ml. Previous exhaustive filtration obviously does not inhibit the clastogenic property of tobacco smoke to exert severe DNA damage.
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PMID:DNA damage by filtered, tar- and aerosol-free cigarette smoke in rodent cells: a novel evaluation. 892 Jul 10

Sphingolipid metabolites are important regulators of cell growth and differentiation. Recent studies have suggested that sphingosine-1-phosphate, a biologically active sphingolipid metabolite, acts as a crucial messenger in apoptosis. In the present work, we examined the expression levels of the members of the bcl-2-related gene family to determine their roles in sphingosine-1-phosphate-induced apoptosis is human hepatoma cells. Our results indicate that sphinogosine-1-phosphate-induced apoptosis is associated with enhanced expression of Bax protein. Moreover, the regulation of bax gene expression by sphingosine-1-phosphate is independent of the p53 tumor suppressor.
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PMID:Induction of apoptosis by sphingosine-1-phosphate in human hepatoma cells is associated with enhanced expression of bax gene product. 895 76

Transgenic mice with both alleles of the p53 tumor suppressor gene product 'knocked out' by gene targeting are susceptible to early development of tumors, chiefly lymphomas and sarcomas. Compared with the control group, administration of dehydroepiandrosterone (DHEA) at 0.3% of the diet to male p53-deficient mice extended their lifespan by delaying death due to neoplasms (from 105 to 166 days on study, P = 0.002), primarily by suppressing lymphoblastic lymphoma (from 45 to 6% of neoplastic deaths, P = 0.010). Treatment with a synthetic DHEA analog, 16alpha-fluoro-5-androsten-17-one (compound 8354), at 0.15% of the diet also increased lifespan, to 140 days for mice that developed tumors (P = 0.037). The effects of these steroids on lifespan and tumor development did not appear to be strongly related to inhibition of food consumption and weight gain, in that a group pair-fed with control diet to the reduced food consumption of the DHEA-treated group developed and died of the same types of neoplasms at the same rate as the controls fed ad libitum. The chemopreventive effect of these steroids has been proposed to be due to suppression of DNA synthesis by inhibition of glucose 6-phosphate dehydrogenase, the rate-limiting enzyme of the pentose phosphate pathway. Although DHEA and its analog are strong non-competitive inhibitors of this enzyme in vitro, treatment with DHEA did not deplete cellular nucleotide pools in the liver, as would have been predicted. The chemopreventive effect of DHEA in this model may be due to steroid-induced thymic atrophy and suppression of T cell lymphoma, permitting these mice to survive long enough to develop tumors with longer latency.
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PMID:Chemoprevention of spontaneous tumorigenesis in nullizygous p53-deficient mice by dehydroepiandrosterone and its analog 16alpha-fluoro-5-androsten-17-one. 916 85

The tumour suppressor gene p53 is expressed in response to DNA-damage; its protein product blocks cells in the G1-phase of the cell cycle. This gives cells additional time to repair their DNA-damage. However, it may trigger apoptosis if damage is too high. Loss of p53 function appears to be an important step in carcinogenesis because 50% of human tumours have lost functional p53. In order to study the role of p53 in experimental hepatocarcinogenesis, we determined the expression of p53 in rat liver in response to various hepatocarcinogenic and hepatotoxic compounds. Administration of hepatocarcinogenic compounds increased p53 protein levels in the liver as detected by immunoprecipitation followed by SDS-PAGE and Western blotting with ECL-detection. The hepatocarcinogens included N-hydroxy-2-acetylaminofluorene, aflatoxin B1, and diethylnitrosamine. Their structural analogues N-hydroxy-4-acetylaminobiphenyl and ethyl methane-sulphonate which are not hepatocarcinogenic, did not induce p53. Also, two hepatotoxic compounds (carbon tetrachloride, D-galactosamine) did not induce p53. Other compounds that induced p53 in the rat liver were 2-aminofluorene (administered by drinking water for two weeks) and tris-(2,3-dibromopropyl)phosphate. Benzo[a]pyrene did not induce p53. N-Hydroxy-2-acetylaminofluorene, aflatoxin B1, and diethylnitrosamine are potent hepatic tumour promoters. At the same time, they induce p53 protein expression and inhibit proliferation of normal hepatocytes. Because this is not observed with non-hepatocarcinogenic analogues, it suggests an involvement of p53 expression in hepatic tumour promotion. A possible mechanism is discussed.
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PMID:p53 protein expression by hepatocarcinogens in the rat liver and its potential role in mitoinhibition of normal hepatocytes as a mechanism of hepatic tumour promotion. 916 91

The oncogene product MDM2 can be phosphorylated by protein kinase CK2 in vitro 0.5-1 mol of phosphate were incorporated per mol MDM2 protein. The catalytic subunit of protein kinase CK2 (alpha-subunit) catalyzed the incorporation of twice as much phosphate into the MDM2 protein as it was obtained with the holoenzyme. Polylysine stimulated MDM2 phosphorylation by CK2 holoenzyme threefold in contrast to the alpha-subunit-catalyzed MDM2 phosphorylation which was reduced by about 66% when polylysine was added. Full length p53, but also a peptide representing a C-terminal fragment of the tumor suppressor gene product p53 (amino acids 264-393 which also harbors the CK2beta interaction site at amino acids 287-340) mimicked the polylysine effect in all respects, ie. stimulation of phosphate incorporation by CK2 holoenzyme and inhibition in the presence of the catalytic CK2 alpha-subunit. Stimulation by p53(264-393) was on the average close to twofold and inhibition in the case of the alpha-subunit-catalyzed MDM2 phosphorylation was about 40%. Phosphorylation of MDM2 by CK2 holoenzyme in the presence of the p21(WAF1/CIP1), known to be a potent inhibitor of cyclin-dependent protein kinases, also led to a significant reduction of phosphate incorporation into MDM2 indicating that p21(WAF1/CIP1) does not exclusively inhibit cell cycle kinases. Furthermore, these data add new insight into the autoregulatory loop which include p21(WAF1/CIP1), MDM2 protein, CK2 and p53.
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PMID:The carboxy terminus of p53 mimics the polylysine effect of protein kinase CK2-catalyzed MDM2 phosphorylation. 917 66

Multiple doses of retinoic acid (RA) were administered intraperitoneally to three groups of male Fischer 344 rats over a 36 h period. The p53 isoforms from bone marrow nuclei in these three groups of rats were analyzed over time by two-dimensional polyacrylamide gel electrophoresis (PAGE) and fluorography for the incorporation of [35S]methionine (p53-synthesis) and [32P]phosphate (p53-phosphorylation). Two groups of rats, young (3.5 months) ad libitum (Y/AL) and old (28 months) ad libitum (O/AL), had free access to Purina rat chow; a third group of old (28 months) diet-restricted rats (O/DR) were maintained on a restricted caloric intake (60% of the AL diet) from 3 months of age. After 36 h of RA dosing, the PAGE patterns of p53 synthesis and phosphorylation in Y/AL and O/DR rats were very similar. In both groups, an increase in complexity was observed with labeling of additional isotypes possessing more acidic isoelectric values. In contrast, the O/AL animals showed a pattern of p53 isoform synthesis and phosphorylation that was considerably less complex and lacked the pronounced shift to more acidic forms following RA dosing. The p53 isoforms of O/AL rats as recognized by wild type (wt) Pab 246 antibody, were also much less dramatic in their increase to more acidic forms. Two-dimensional phospho-tryptic maps of Y/AL and O/DR rats were also very similar, both exhibiting two additional minor 32P-labeled fragments after RA dosing. The maps of O/AL rats did not show the two additional fragments following RA administration. After RA dosing, cyclin protein inhibitors (p16, p21, p27) revealed robust labeling with their respective antibodies in Y/AL and O/DR rats as analyzed by Western blotting. The O/AL animals showed marginally detectable antibody recognition of the cyclin inhibitors after RA dosing. Taken together, these data suggest that the biosynthesis and phosphorylation of p53 isoforms and the expression of cyclin dependent kinase inhibitor proteins is not significantly different between Y/AL and O/DR rats. Further, these results confirm and extend our previous observations that chronic diet-restriction attenuates the age related decline in the metabolic activity of nuclear protein products.
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PMID:P53 synthesis and phosphorylation in the aging diet-restricted rat following retinoic acid administration. 922 23


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