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 murine erythroleukemic cell line (1-2-3) which expresses only the temperature-sensitive mutant p53 gene (Ala-to-Val substitution at codon 135) was established. These cells showed typical characteristics of apoptosis, when they were cultured at 32 degrees C. In this process, p53 recovered the wild-type p53 function and the expression of the p21 (waf1/cip1/sdi1), cyclin G1 and gadd45 genes was increased. However, no significant changes were detected in the expression of the mdm2, bcl-2, bax, fas and fasl genes, suggesting the existence of other genes associated with apoptosis. Genes up-regulated by p53 were screened by the mRNA differential display method. One of the up-regulated genes was identified as the elongation factor 1 alpha (EF-1 alpha) gene. EF-1 alpha is also a microtubule-severing protein. Upon the temperature-shift, the cells developed the morphology and the localization of alpha-tubulin similar to those of the cells treated with vincristine, a drug that affects microtubules. The microtubule-severing associated with up-regulation of EF-1 alpha by p53 may be a cause of the cell death. On the other hand, the function of cyclin G1 is not so clear despite the fact that 1-2-3 cells showed a significant increase of the cyclin G1 gene during the early stage of apoptosis. The yeast two-hybrid system was used to identify cyclin G1-associated proteins. One is a cytochrome c (Cyt c) oxidase subunit II (COXII). Cyclin G1 and COXII were co-immunoprecipitated from an extract of human osteosarcoma cell line that expressed high levels of cyclin G1. COX activity was also increased by temperature-shift in this cell line. The pattern of changes in COX activity was closely reflected by the expression of the cyclin G1 gene. Cyclin G1 and COXII associate physically with each other in vivo and that activation of COXII by binding to cyclin G1 upregulated by p53 may be associated with apoptosis. These two new pathways, p53-EF-1 alpha-microtubule-severing (-distortion of cytoskeleton) and p53-cyclin G1-COXII (-CytC, ATP-caspase-3 activation), may cooperate to induce apoptosis in this cell line.
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PMID:The mechanisms of death of an erythroleukemic cell line by p53: involvement of the microtubule and mitochondria. 1019 36

Lonidamine (LND), a selective inhibitor of the energy metabolism of tumor cells, induces apoptosis, independently of the p53 gene, in the adriamycin(ADR)-resistant MCF7 breast-cancer cell line (MCF7 ADR). On the contrary, LND fails to activate the apoptotic program in the parental MCF7-sensitive cell line (MCF7 WT). The extent of bcl-2 expression might account for the different effect of LND on these cell lines. In fact, the MCF7 ADR line shows a low level of bcl-2 protein, whereas MCF7 WT expresses a high level of bcl-2. We therefore investigated the relationship between the amount of bcl-2 and the ability of LND to induce apoptosis, using 4 clones over-expressing bcl-2. The effect of bcl-2 on the energy metabolism was also evaluated. We demonstrated that over-expression of bcl-2 inhibited LND-induced apoptosis, while reducing 14CO2 production, oxygen uptake and ATP content, whereas aerobic lactate production was essentially unaffected. In addition, LND decreased the oxidative metabolism of the MCF7 ADR cells to a greater extent than it did in the bcl-2 transfectants.
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PMID:bcl-2 inhibits mitochondrial metabolism and lonidamine-induced apoptosis in adriamycin-resistant MCF7 cells. 1036 Aug 31

We investigated expression of a human p53-inducible gene, P2XM, a member of the P2X-receptor family of ATP-gated ion channels, in 56 human primary soft-tissue tumours including 47 sarcomas and nine benign tumors. Among the 47 sarcomas examined by reverse transcription polymerase chain reaction, 12 had lost expression of this gene and 22 revealed altered splicing patterns; among the nine benign tumours, four showed no expression of P2XM and three revealed aberrant splicing patterns involving transmembrane domains M1 and/or M2. As the aberrant transcripts lacked either or both of those domains, the protein products probably lacked normal function. We also looked for p53 mutations and mdm2 overexpression in the same panel of tumours and found them in 13 tumours, all but three of which had shown altered expression of P2XM. However, 31 (72%) of the 43 tumours that carried wild-type p53 without mdm2 overexpression had revealed aberrant P2XM expression. Our results suggest that disorder of P2XM expression may play a crucial role in the genesis of benign and malignant tumours in soft tissues, and that one or more genetic factors other than p53 or mdm2 contribute significantly to aberrant P2XM expression.
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PMID:Frequent loss of expression or aberrant alternative splicing of P2XM, a p53-inducible gene, in soft-tissue tumours. 1037 70

Interaction with DNA is essential for the tumor suppressor functions of p53. We now show, for the first time, that the interaction of p53 with DNA can be stabilized by small molecules, such as ADP and dADP. Our results also indicate an ATP/ADP molecular switch mechanism which determines the off-on states for p53-DNA binding. This ATP/ADP molecular switch requires dimer-dimer interaction of the p53 tetramer. Dissociation of p53-DNA complexes by ATP is independent of ATP hydrolysis. Low-level ATPase activity is nonetheless associated with ATP-p53 interaction and may serve to regenerate ADP-p53, thus recycling the high-affinity DNA binding form of p53. The ATP/ADP regulatory mechanism applies to two distinct types of p53 interaction with DNA, namely, sequence-specific DNA binding (via the core domain of the p53 protein) and binding to sites of DNA damage (via the C-terminal domain). Further studies indicate that ADP not only stabilizes p53-DNA complexes but also renders the complexes susceptible to dissociation by specific p53 binding proteins. We propose a model in which the DNA binding functions of p53 are regulated by an ATP/ADP molecular switch, and we suggest that this mechanism may function during the cellular response to DNA damage.
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PMID:An ATP/ADP-dependent molecular switch regulates the stability of p53-DNA complexes. 1052 38

Apoptosis in response to stress signals activates effector caspases known to be regulated by the release of cytochrome c (Cyt c) from mitochondria and the subsequent ATP-dependent activation of the death regulator apoptotic protease-activating factor 1 (Apaf-1). Experiments were carried out to determine whether the release of Cyt c is evoked by NO. in RAW 264.7 macrophages and to position signaling components relative to mitochondria. S-nitrosoglutathione and spermine-NO caused a fast p53 accumulation, followed by Bcl-xL downregulation, Cyt c release, and caspase activation. These alterations were absent in p53 antisense expressing macrophages (R delta p53asn-11). In Bcl-2 overexpressing cells (Rbcl2-14) Cyt c relocation and caspase activation were abrogated although p53 accumulation remained intact. The use of caspase inhibitors revealed Cyt c release and decreased Bcl-xL expression to be caspase independent. ATP-depleted cells showed a shift from apoptosis towards necrosis and no p53 accumulation or caspase activation upon NO. addition. Conclusively, NO.-mediated apoptosis in macrophages is entirely controlled by the mitochondrial pathway with the implication that Cyt c relocation demands p53 accumulation. Moreover, pulse-chase-experiments in combination with the ATP-depletion protocol identified p53 accumulation and stabilization as an energy requiring process. This allowed to dissect two ATP-dependent steps, one is in association with Apaf-1 formation, while the other resides in p53 accumulation.
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PMID:p53 accumulation in apoptotic macrophages is an energy demanding process that precedes cytochrome c release in response to nitric oxide. 1059 41

Cells of solid tumours tend to rely on glycolysis for energy. On the other hand, increased glycolysis in solid tumour cells expressing the multidrug resistance protein MDR-1 has been associated with increased malignancy in tumours. We have previously shown that cells of the MDR-1-positive CEM/VLB100 leukaemic cell line have increased mitochondrial electron transport chain (mtETC) activity compared with parental CEM cells. In the present study we used infrared (IR) spectroscopy to demonstrate that the mitochondrial DNA (mtDNA) content in the CEM/VLB100 cell line was significantly increased compared to that in the parental CEM cells. The increase in mtDNA was not accompanied by an increase in mitochondrial protein as both lipid and protein levels were decreased in CEM/VLB100 mitochondria. The ATP content was similar in these two cell lines. However, the ATP-dependent membrane efflux pump function in CEM/VLB100 cells was significantly reduced when mitochondrial ATP synthesis was inhibited by oligomycin, a specific inhibitor of mitochondrial F0F1-ATPase. Proliferation of CEM/VLB100 cells was significantly decreased compared to parental CEM cells, and was independent of p53 expression. Thus, we conclude that: (1) IR spectroscopy is a potential powerful technique for detecting mtDNA, protein and lipid contents simultaneously; (2) leukaemic cells mainly rely on mtDNA for energy; (3) increased expression of an ATP-dependent membrane efflux pump such as Pgp may up-regulate ATP generation and mtDNA content. These metabolic perturbations may exist merely to serve the efflux pump and do not result in an increase in leukaemic cell proliferation. In addition, the associated reduction in mitochondrial lipid and protein may contribute to sensitize the cells to cytochrome c release.
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PMID:Pgp-positive leukaemic cells have increased mtDNA but no increased rate of proliferation. 1060 95

The multicatalytic protease complex or proteasome is a fundamental nonlysosomal tool that the cell uses to process or degrade proteins at a fast rate through the ubiquitin and ATP-dependent proteolytic pathway. Examples of these important proteins include the tumor suppressor protein p53, various cyclins, the cyclin-dependent kinase inhibitor p27, NFkappaB, IkappaB, c-fos, and c-jun. The activation of proteolytic enzymes, including certain cystein-proteases of the ced-3/ICE (interleukin-1beta-converting enzyme) family, is a characteristic feature of the apoptotic program. However, the role of the multicatalytic protease complex in apoptosis is not well known. In order to obtain further information regarding the participation of the ubiquitin-mediated pathway in the decision of the cell to execute the cell death program, we have used a specific inhibitor of the multicatalytic protease complex, lactacystin, in cultured cerebellar granule cells. Cells were obtained from the cerebellum of 6- to 8-day-old Wistar rats and cultured in Neurobasal medium supplemented with B-27. Addition of lactacystin to the cultures induced apoptosis of the granule cells in a time-dependent fashion. The morphological changes produced by the proteasome inhibitor included nuclear condensation and DNA fragmentation measured by the diphenylamine test, as well as a positive labeling by the TUNEL (terminal deoxynucleotidyltransferase mediated-dUTP nick end labeling) assay, all of them typical features of apoptosis. Concomitant with apoptosis, there were changes in the expression of the ubiquitin mRNA, a progressive depletion in the free ubiquitin pool, and an increase in the high molecular weight ubiquitin-protein conjugates. Caspase-3, a member of the ced-3/ICE family of cystein-proteases, showed a marked increase in activity in the lactacystin-treated cells. In flow cytometry studies, the amount of cells in the S phase of the cell cycle was smaller in the lactacystin-treated cells than in controls, suggesting that apoptosis could be due, in part, to an alteration of the cell cycle.
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PMID:Lactacystin, a specific inhibitor of the proteasome, induces apoptosis and activates caspase-3 in cultured cerebellar granule cells. 1068 88

The simian double strand DNA tumor virus SV40 encodes the 90-kDa multi-functional protein, large T antigen (LT). LT functions by binding to DNA, as well as to many cellular target proteins such as p53 and retinoblastoma protein (pRB). We report here the identification of a cellular heat shock protein, HSP90, as a previously undescribed LT-associated protein. Immunoprecipitates by anti-HSP90 antibodies from LT-expressing cell lysates contained LT protein, as revealed by Western blotting. Conversely, anti-LT antibody co-immunoprecipitated HSP90. Co-immunoprecipitation of HSP90 and LT was observed even after complete immuno-depletion of p53, indicating that the association of LT with HSP90 is p53-independent. LT-HSP90 complexes can be reconstituted from purified HSP90 and unfolded-LT in vitro in an ATP-independent manner but not from HSP90 and native LT, suggesting that non-mature conformation of LT is required for the efficient association with HSP90. Moreover, geldanamycin, an anti-tumor drug that specifically binds and inhibits HSP90, reduced the intracellular concentration of LT by destabilizing newly synthesized LT. The above results suggest that HSP90 associates with immature forms of LT both in vivo and in vitro, and thus might assist LT in the formation of a functional, mature structure.
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PMID:p53-independent association between SV40 large T antigen and the major cytosolic heat shock protein, HSP90. 1072 40

Ku is a heterodimeric protein composed of approximately 70- and approximately 80-kDa subunits (Ku70 and Ku80) originally identified as an autoantigen recognized by the sera of patients with autoimmune diseases. Ku has high binding affinity for DNA ends and that is why originally it was known as a DNA end binding protein, but now it is known to also bind the DNA structure at nicks, gaps, hairpins, as well as the ends of telomeres. It has been reported also to bind with sequence specificity to DNA and with weak affinity to RNA. Ku is an abundant nuclear protein and is present in vertebrates, insects, yeast, and worms. Ku contains ssDNA-dependent ATPase and ATP-dependent DNA helicase activities. It is the regulatory subunit of the DNA-dependent protein kinase that phosphorylates many proteins, including SV-40 large T antigen, p53, RNA-polymerase II, RP-A, topoisomerases, hsp90, and many transcription factors such as c-Jun, c-Fos, oct-1, sp-1, c-Myc, TFIID, and many more. It seems to be a multifunctional protein that has been implicated to be involved directly or indirectly in many important cellular metabolic processes such as DNA double-strand break repair, V(D)J recombination of immunoglobulins and T-cell receptor genes, immunoglobulin isotype switching, DNA replication, transcription regulation, regulation of heat shock-induced responses, regulation of the precise structure of telomeric termini, and it also plays a novel role in G2 and M phases of the cell cycle. The mechanism underlying the regulation of all the diverse functions of Ku is still obscure.
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PMID:Ku autoantigen: a multifunctional DNA-binding protein. 1075 64

DNA topoisomerase II is an essential nuclear enzyme for proliferation of eukaryotic cells and plays important roles in many aspects of DNA processes. In this report, we have demonstrated that the catalytic activity of topoisomerase IIalpha, as measured by decatenation of kinetoplast DNA and by relaxation of negatively supercoiled DNA, was stimulated approximately 2-3-fold by the tumor suppressor p53 protein. In order to determine the mechanism by which p53 activates the enzyme, the effects of p53 on the topoisomerase IIalpha-mediated DNA cleavage/religation equilibrium were assessed using the prototypical topoisomerase II poison, etoposide. p53 had no effect on the ability of the enzyme to make double-stranded DNA break and religate linear DNA, indicating that the stimulation of the enzyme catalytic activity by p53 was not due to alteration in the formation of covalent cleavable complexes formed between topoisomerase IIalpha and DNA. The effects of p53 on the catalytic inhibition of topoisomerase IIalpha were examined using a specific catalytic inhibitor, ICRF-193, which blocks the ATP hydrolysis step of the enzyme catalytic cycle. Clearly manifested in decatenation and relaxation assays, p53 reduced the catalytic inhibition of topoisomerase IIalpha by ICRF-193. ATP hydrolysis assays revealed that the ATPase activity of topoisomerase IIalpha was specifically enhanced by p53. Immunoprecipitation experiments revealed that p53 physically interacts with topoisomerase IIalpha to form molecular complexes without a double-stranded DNA intermediary in vitro. To investigate whether p53 stimulates the catalytic activity of topoisomerase II in vivo, we expressed wild-type and mutant p53 in Saos-2 osteosarcoma cells lacking functional p53. Wild-type, but not mutant, p53 stimulated topoisomerase II activity in nuclear extract from these transfected cells. Our data propose a new role for p53 to modulate the catalytic activity of topoisomerase IIalpha. Taken together, we suggest that the p53-mediated response of the cell cycle to DNA damage may involve activation of topoisomerase IIalpha.
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PMID:The p53 tumor suppressor stimulates the catalytic activity of human topoisomerase IIalpha by enhancing the rate of ATP hydrolysis. 1076 86


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