Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The oncoprotein MDM2 binds and inactivates p53. MDM2 also binds to the tumor suppressor pRB, as well as E2F-1. E2F-1 is a transcription factor that regulates S phase entry and has been shown to cause apoptosis in some cell types when overexpressed. To investigate the effect of adenovirus-mediated E2F-1 overexpression, MDM2-overexpressing tumor cell lines were treated by mock infection, infection with an adenoviral vector expressing beta galactosidase, or E2F-1 (Ad5CMV-E2F-1). Western blot analysis confirmed significant overexpression of E2F-1 in Ad5CMV-E2F-1-infected cells. E2F-1 overexpression resulted in marked growth inhibition and rapid loss of cell viability. Ad5CMV-E2F-1 infection resulted in early S phase entry, followed by apoptotic cell death. E2F-1 overexpression was associated with a marked decrease in MDM2 levels and no evidence of increased Bax levels, whereas p53 and Bcl-2 levels remained undetectable. Cleavage of poly-ADP-ribose polymerase and caspase 3/CPP32 implicated activation of the caspase cascade in E2F-1-mediated apoptosis. These results indicate that adenovirus-mediated E2F-1 overexpression in MDM2-overexpressing tumor cells results in decreased MDM2 expression and widespread apoptosis. Because MDM2-overexpressing tumors are often resistant to p53 gene therapy, adenovirus-mediated E2F-1 gene therapy may be a promising alternative strategy.
 ...
PMID:Adenovirus-mediated E2F-1 gene transfer inhibits MDM2 expression and efficiently induces apoptosis in MDM2-overexpressing tumor cells. 1047 12

This study deals with the apoptotic effect exerted on human retinoblastoma Y79 cells by both sodium butyrate and an inhibitor of 26S proteasome [z-Leu-Leu-Leu-CHO (MG132)] and their synergistic effect. Exposure to sodium butyrate (1-4 mM) induced an accumulation of cells in the G2-M phase that was already visible after 24 h of treatment, when morphological and biochemical signs of apoptosis appeared only in a small number of cells (5-10%). Thereafter, the apoptotic effects increased progressively with slow kinetics, reaching a maximum after 72 h of exposure, when they concerned a large fraction of cells (>75% with 4 mM sodium butyrate). Sodium butyrate stimulated the conversion of procaspase-3 into caspase-3 and also induced the cleavage of poly-(ADP-ribose) polymerase and lamin B, two hallmarks of apoptosis. All of the apoptotic signals were suppressed by benzyloxy carbonyl-Val-Ala-Asp-fluoromethylketone (a general inhibitor of caspase activities), whereas acetyl-Asp-Glu-Val-Asp aldehyde, a specific inhibitor of caspase-3 activity, only induced a partial reversion of the apoptotic effects. Sodium butyrate also decreased the Bcl-2 level, whereas it increased the Bax level and stimulated the release of cytochrome c from the mitochondria, an event that was most likely responsible for the activation of caspase-3. Finally, sodium butyrate activated 26S proteasome, the major extralysosomal degradative machinery, which is responsible for the degradation of short-lived proteins. Consequently, the levels of p53, N-myc, and IkappaBalpha (factors that play regulatory roles in apoptosis) diminished, whereas the nuclear level of nuclear factor kappaB concomitantly increased. Treatment of Y79 cells with MG132 induced apoptosis with more rapid kinetics than with sodium butyrate. The effects appeared after 8 h of incubation, reaching a maximum at 24 h, and they were accompanied by increased levels of N-myc, p53, and IkappaBalpha. MG132 also favored the release of cytochrome c from the mitochondria and increased the activity of caspase-3. When Y79 cells were exposed to combinations of sodium butyrate and MG132, the latter compound suppressed the decreasing effect induced by sodium butyrate on the levels of p53, N-myc, and IkappaBalpha and the increasing effect on the nuclear level of nuclear factor kappaB. Moreover, an increase in the level of Bax and an enhancement in the release of cytochrome c from the mitochondria were observed. Clear synergistic effects concerning the activation of both caspase-3 and apoptosis were induced by a combination of suboptimal doses of sodium butyrate and MG132. The results support the conclusion that MG132 potentiates the apoptotic effect of sodium butyrate by suppressing its stimulatory effect on 26S proteasome activity. Synergistic interactions between butyrate and inhibitors of proteasome could represent a new important tool in tumor therapy and, in particular, the treatment of retinoblastoma.
 ...
PMID:The apoptotic effects and synergistic interaction of sodium butyrate and MG132 in human retinoblastoma Y79 cells. 1055 39

The sensitivity of normal diploid Syrian hamster embryo (SHE) cells to apoptosis was tested after treatment with the topoisomerase inhibitors camptothecin and etoposide and after serum withdrawal. Programmed cell death (PCD) was identified through morphological, biochemical, and molecular changes and compared with that of HL60 cell line. The results showed that topoisomerase inhibitors, which were shown to be potent PCD inducers in the HL60 cell line, induced a weaker apoptotic response in SHE cells than after growth factor deprivation. In addition, serum-free medium, which rapidly induced apoptosis in SHE cells, did not affect the HL60 cell line. In both cell types, PCD was expressed by condensed chromatin, fragmented nuclei, and DNA laddering on electrophoretic gels, an indisputable sign of apoptosis. In apoptotic HL60 cells, the cleavage of 113-kDa poly(ADP-ribose)polymerase (PARP) resulted in the so-called apoptotic 89-kDa fragment and was associated with increased caspase-3 activity. In apoptotic SHE cells, PARP degraded early but the degradation profile was not characterized by the appearance of an 89-kDa fragment. Moreover, no activation of caspase-3 was noted. ZnCl(2), which is known to prevent protease activity responsible for apoptosis features, inhibited PARP cleavage and nuclear modifications induced by apoptotic stimuli in both cell types, but with a higher sensitivity in SHE cells. Apoptosis induced by serum deprivation was linked with c-myc negative regulation in SHE cells, but not with p53 protein accumulation, while topoisomerase inhibitors led to p53 stabilization without any change in c-myc expression. Serum-free medium and topoisomerase inhibitors did not modify c-myc expression in the HL60 cell line. The overall results demonstrated that apoptosis, which is a carefully regulated process of cell death, may proceed through mechanisms varying according to cell type or apoptosis inducer. In addition, markers which are generally considered hallmarks of apoptosis may fail to appear in some cell types.
 ...
PMID:Detection of apoptosis induced by topoisomerase inhibitors and serum deprivation in syrian hamster embryo cells. 1066 31

Induction of apoptosis seems to be a key function in maintaining normal cell growth by exerting negative controls on cell proliferation and suppressing tumorigenesis. The adenovirus E1A oncogene shows both cell cycle progression and apoptotic functions. To understand the mechanism of E1A-induced apoptosis, the apoptotic function of E1A 13S was investigated in p53-null cells. We show here that E1A is sufficient by itself to induce substantial apoptosis independent of p53 and other adenoviral genes. The apoptotic function of E1A is accompanied by processing of caspase-3 and cleavage of poly(ADP-ribose)-polymerase. Cell death is significantly blocked by the caspase inhibitor zVAD-fmk and when coexpressed with E1B19K, Bcl-2 or the retinoblastoma protein (RB). Analyses of E1A mutants indicated that the apoptotic activity of E1A correlates closely with the ability to bind the key regulators of E2F1-induced apoptosis, p300 and RB. Finally, in vivo relevance of down-modulation of p53-independent apoptosis for efficient transformation is demonstrated.
 ...
PMID:E1A is sufficient by itself to induce apoptosis independent of p53 and other adenoviral gene products. 1071 32

The prognosis for patients with esophageal cancer remains poor, prompting the search for new treatment strategies. Overexpression of E2F-1 has been shown to induce apoptosis in several cancer cell types. In the present study, the effect of adenovirus-mediated E2F-1 overexpression on human esophageal cancer cell lines Yes-4 and Yes-6 was evaluated. Cells were treated by mock infection, infection with an adenoviral vector expressing beta-galactosidase (Ad5CMV-LacZ), or E2F-1 (Ad5CMVE2F-1). Western blot analysis confirmed marked overexpression of E2F-1 in Ad5CMVE2F-1-infected cells. Overexpression of E2F-1 resulted in marked growth inhibition and rapid loss of cell viability due to apoptosis, although Yes-6 cells were somewhat more resistant to E2F-1-mediated growth inhibition than Yes-4 cells. Cell cycle analysis revealed that overexpression of E2F-1 led to G2 arrest, followed by apoptotic cell death. p53 expression remained undetectable in both cell lines after E2F-1 overexpression. The apoptosis inhibitor proteins of the Bcl-2 gene family, Bcl-2, Mcl-1, and BcI-XL, decreased at 48 h after infection in Yes-4 cells, but remained unchanged in Yes-6 cells. Levels of retinoblastoma gene product (pRb) declined at 48 h after E2F-1 infection in Yes-4 cells, at which apoptosis predominated, whereas pRb expression remained constant in Yes-6 cells. Expression of p14ARF did not change after E2F-1 infection in either cell line. Involvement of caspase 3 and caspase 6 in E2F-1-mediated apoptosis was demonstrated by cleavage of caspase 3/CPP32 and poly-ADP-ribose polymerase, as well as fragmentation of the caspase 6 substrate, lamin B. These results indicate that the sensitivity of esophageal cancer cells to E2F-1-mediated apoptosis may be related to differential expression of Bcl-2 family member proteins and suggest that the adenovirus-mediated E2F-1 gene therapy may be a promising treatment strategy for the treatment of this disease.
 ...
PMID:Caspase activation and changes in Bcl-2 family member protein expression associated with E2F-1-mediated apoptosis in human esophageal cancer cells. 1077 92

The biochemical basis of the anti-proliferative effect of exogenous glutathione was investigated in A2780 ovarian carcinoma cells. Previous observations have implicated gamma-glutamyl transpeptidase-mediated pro-oxidant reactions as a primary mechanism of the extracellular effects of glutathione. In 2 cell lines (A2780 and IGROV-1), glutathione led to H(2)O(2) production, but only A2780 cells, characterized by low expression of detoxification enzymes, were sensitive to the thiol compound. In A2780 cells, glutathione exposure resulted in DNA single-strand break formation, as measured by alkaline elution. Glutathione-induced DNA damage generated significant levels of apoptosis in A2780 cells, but not in IGROV-1 cells. The capability of glutathione to induce apoptosis was associated with cleavage of poly(ADP-ribose)polymerase and with generation of a low-molecular-weight form of the pro-apoptotic protein bax. In A2780 cells, glutathione exposure was followed by p21 and Bax induction and p53 up-regulation, as expected for genotoxic stress. Consistently, analysis of cell-cycle perturbations demonstrated the occurrence of G(2)M accumulation after exposure to glutathione, similar to what was observed for H(2)O(2). Taken together, these results indicate that the cytotoxic effect of extracellular glutathione, related to membrane metabolism, is mediated by production of H(2)O(2) leading to DNA damage and a cellular response involving p53. These findings might also provide insights into the cellular and molecular determinants of chemosensitivity to DNA damaging agents, as oxidative stress is implicated in p53-dependent apoptosis.
 ...
PMID:Apoptosis induced by extracellular glutathione is mediated by H(2)O(2) production and DNA damage. 1089 38

Poly(ADP-ribose) polymerase (PARP) is a DNA binding zinc finger protein that catalyzes the transfer of ADP-ribose residues from NAD(+) to itself and different chromatin constituents, forming branched ADP-ribose polymers. The enzymatic activity of PARP is induced upon DNA damage and the PARP protein is cleaved during apoptosis, which suggested a role of PARP in DNA repair and DNA damage-induced cell death. We have generated transgenic mice that lack PARP activity in thymocytes owing to the targeted expression of a dominant negative form of PARP. In the presence of single-strand DNA breaks, the absence of PARP activity correlated with a strongly increased rate of apoptosis compared to cells with intact PARP activity. We found that blockage of PARP activity leads to a drastic increase of p53 expression and activity after DNA damage and correlates with an accelerated onset of Bax expression. DNA repair is almost completely blocked in PARP-deficient thymocytes regardless of p53 status. We found the same increased susceptibility to apoptosis in PARP null mice, a similar inhibition of DNA repair kinetics, and the same upregulation of p53 in response to DNA damage. Thus, based on two different experimental in vivo models, we identify a direct, p53-independent, functional connection between poly(ADP-ribosyl)ation and the DNA excision repair machinery. Furthermore, we propose a p53-dependent link between PARP activity and DNA damage-induced cell death.
 ...
PMID:DNA excision repair and DNA damage-induced apoptosis are linked to Poly(ADP-ribosyl)ation but have different requirements for p53. 1095 67

Poly(ADP-ribose) is formed in possibly all multicellular organisms by a familiy of poly(ADP-ribose) polymerases (PARPs). PARP-1, the best understood and until recently the only known member of this family, is a DNA damage signal protein catalyzing its automodification with multiple, variably sized ADP-ribose polymers that may contain up to 200 residues and several branching points. Through these polymers, PARP-1 can interact noncovalently with other proteins and alter their functions. Here we report the discovery of a poly(ADP-ribose)-binding sequence motif in several important DNA damage checkpoint proteins. The 20-amino acid motif contains two conserved regions: (i) a cluster rich in basic amino acids and (ii) a pattern of hydrophobic amino acids interspersed with basic residues. Using a combination of alanine scanning, polymer blot analysis, and photoaffinity labeling, we have identified poly(ADP-ribose)-binding sites in the following proteins: p53, p21(CIP1/WAF1), xeroderma pigmentosum group A complementing protein, MSH6, DNA ligase III, XRCC1, DNA polymerase epsilon, DNA-PK(CS), Ku70, NF-kappaB, inducible nitric-oxide synthase, caspase-activated DNase, and telomerase. The poly(ADP-ribose)-binding motif was found to overlap with five important functional domains responsible for (i) protein-protein interactions, (ii) DNA binding, (iii) nuclear localization, (iv) nuclear export, and (v) protein degradation. Thus, PARPs may target specific signal network proteins via poly(ADP-ribose) and regulate their domain functions.
 ...
PMID:Poly(ADP-ribose) binds to specific domains in DNA damage checkpoint proteins. 1101 34

In mammals, visual experience during early postnatal life is critical for normal development of the visual system. Here we report that monocular deprivation for 2, 7, and 14 consecutive days causes p53 accumulation, cell death, and progressive loss of neurones in the dorsal lateral geniculate nucleus (dLGN) of newborn rats and these are prevented by NMDA and non-NMDA glutamate receptor antagonists, and by L-NAME, an inhibitor of nitric oxide synthesis. Monocular deprivation also increases dLGN levels of citrulline, the coproduct of nitric oxide synthesis, and this, as well as cell death and neuronal loss, is abolished by antagonists of glutamate receptors and by L-NAME. Finally, poly-(ADP-ribose) polymerase (PARP) knock-out mice appear to be protected from monocular deprivation-induced cell death. In conclusion, during early postnatal development of the rat visual system monocular deprivation causes excitotoxic, nitric oxide-mediated, cell death in the dLGN that appears to be apoptotic and also requires activation of PARP.
 ...
PMID:Apoptosis in the dorsal lateral geniculate nucleus after monocular deprivation involves glutamate signaling, NO production, and PARP activation. 1109 43

DNA single-strand breaks induced by cell treatment with hydrogen peroxide are repaired and simultaneously trigger programmed cell death in resting human blood lymphocytes. Apoptosis is accompanied by special morphological changes in lymphocytes (15% of total cell number), internucleosomal DNA degradation, and p53 level elevation. According to morphological criteria, a major part (up to 40% of total cell number) displayed necrotic death features. Nicotinamide inhibited repair in cells with 2.5-fold elevation of the apoptotic cell proportion, whereas the fraction of cells with necrotic nuclear morphology decreased 4.5-fold. Both the inhibition of repair and the protective effect of nicotinamide against necrotic death indicate that the repair process and related poly(ADP-ribose)polymerase (PARP) activation induce a decrease in intracellular NAD+ and ATP contents below the threshold at which necrosis becomes the preferential mechanism of cell death. The mixed pattern of cell death induced by hydrogen peroxide observed in resting lymphocytes can be explained in the context of a concept of cell de-energization as a consequence of effective single-stand break repair during the first hours after removing the genotoxic agent.
 ...
PMID:Hydrogen peroxide-induced DNA repair and death of resting human blood lymphocytes. 1111 44


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>