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)

Constitutive overexpression of insulin-like growth factor-1 (IGF-1) in myocytes protects them from apoptosis and interferes with myocyte hypertrophy in the normal and pathological heart. Conversely, angiotensin II (Ang II) triggers cell death and promotes myocyte hypertrophy. Moreover, activation of p53 upregulates the cellular renin-angiotensin system (RAS). Therefore, IGF-1 overexpression in FVB.Igf+/- mice may downregulate the local RAS through the attenuation of p53 and p53-inducible genes. On this basis, p53 DNA binding activity to angiotensinogen (Aogen), bax, and the AT1 receptor was determined in left ventricular myocytes from FVB.Igf-/- and FVB.Igf+/- mice. The quantity of Bax, Bcl-2, Aogen, and AT1 receptor in these cells was evaluated. The presence of Mdm2-p53 complexes was also established. Finally, Ang II levels in myocytes were measured. Upregulation of IGF-1 in myocytes was associated with a protein-to-protein interaction between Mdm2 and p53, which attenuated p53 transcriptional activity for bax, Aogen, and AT1 receptor. Similarly, the amount of Bax, Aogen, and AT1 receptor proteins in these cells decreased. In contrast, the expression of Bcl-2 remained constant. The downregulation of Aogen in myocytes from FVB.Igf+/- mice was characterized by a reduction in Ang II. In conclusion, IGF-1 negatively influences the myocyte RAS through the upregulation of Mdm2 and its binding to p53. This may represent the molecular mechanism responsible for the effects of IGF-1 on cell viability and myocyte hypertrophy in the nonpathological and pathological heart in vivo.
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PMID:Overexpression of insulin-like growth factor-1 attenuates the myocyte renin-angiotensin system in transgenic mice. 1020 43

We have previously reported that loss of p53 tumor suppressor protein results in centrosome hyperamplification, which leads to aberrant mitosis and chromosome instability. Since p53 is either deleted or mutated in human cancers at a high frequency, we investigated whether human cancers showed centrosome hyperamplification. Screening of advanced stage breast ductal carcinomas and squamous cell carcinomas of the head and neck (SCCHN) revealed that centrosome hyperamplification is frequent in both tumor types. Moreover, through the analyses of p53 in SCCHN samples by direct sequencing and by loss-of-heterozygosity test, we found that p53 mutations correlated with occurrence of centrosome hyperamplification. However, in some cases, we observed centrosome hyperamplification in tumors that retained wild-type p53. These tumors contained high levels of Mdm2. Since Mdm2 can inactivate p53 through physical association, we investigated whether Mdm2 overexpression induced centrosome hyperamplification. We found that Mdm2 overexpression, like loss of p53, induced centrosome hyperamplification and chromosome instability in cultured cells.
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PMID:Centrosome hyperamplification in human cancer: chromosome instability induced by p53 mutation and/or Mdm2 overexpression. 1020 15

Abundance and activity of p53 are predominantly regulated posttranslationally. Structural disturbance in transcribed genes induced by radiation, e.g. DNA damage, or by transcriptional inhibitors cause p53 protein stabilization by a yet unknown mechanism. Using stable and transient transfections for the analysis of p53 mutant proteins, we have ruled out a role in stabilization by UV, gamma irradiation or actinomycin C for the following putative phosphorylation sites in the p53 protein: serines 6, 9, 15, 33, 315 and 392, and threonine 18. By double mutation combinations of phosphorylations were also ruled out; 6,9; 15,18; 15,37. These mutations eliminate modifications by casein kinases I and II, DNA-PK, ATM, CDK and JNK. Also the 30 carboxyterminal amino acids are not required for induced p53 stabilization. Thus neither phosphorylations of individual amino acids nor interactions of the carboxyterminus of p53 with cellular macromolecules appear to play a role in the stabilization process. The only single prerequisite for induced stabilization of p53 is its prior destabilization by Mdm2. However, the level of active Mdm2 must be controlled carefully: overexpression of Mdm2 inhibits UV induced p53 stabilization.
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PMID:DNA damage induced p53 stabilization: no indication for an involvement of p53 phosphorylation. 1020 33

The p19ARF product of the INK4a/ARF locus is induced in response to potentially oncogenic hyperproliferative signals and activates p53 by interfering with its negative regulator, Mdm2. Mice lacking ARF are highly prone to tumor development, and in this study, 80% of these animals spontaneously developed tumors and died within their first year of life. Mice that were heterozygous for ARF also developed tumors after a longer latency, whereas their wild-type littermates did not. In heterozygotes, tumor formation was accompanied by loss of the residual ARF allele and/or lack of ARF mRNA expression, implying that ARF can act as a canonical "two-hit" tumor suppressor gene. Tumors occurred earlier in life in ARF-null animals that were neonatally irradiated or given dimethylbenzanthrene, and several animals treated with carcinogen simultaneously developed multiple forms of malignancy arising from distinct cell lineages. Although p53-null mice primarily develop lymphomas and fibrosarcomas, the frequency of these two tumor types was inverted in ARF-null animals, with undifferentiated sarcomas predominating in a 3:2 ratio; 28% of ARF-null animals developed carcinomas and tumors of the nervous system, which have been rarely observed in untreated p53-null mice. The longer latency of tumor formation in ARF-null versus p53-null mice, therefore, appears to enable a broader spectrum of tumors to emerge.
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PMID:Tumor spectrum in ARF-deficient mice. 1023 11

The alternative reading frame product (p19ARF) of the mouse INK4a/ARF locus is induced by oncoproteins such as Myc and E1A as part of a checkpoint response that limits cell cycle progression in response to hyperproliferative signals. ARF binds directly to Mdm2 to prevent down-regulation of p53 and thereby promotes p53-dependent transcription and cell cycle arrest. However, ARF is not required for p53 induction in response to ionizing radiation or other forms of DNA damage. Animals lacking a functional ataxia telangiectasia (Atm) gene are exquisitely sensitive to ionizing radiation; Atm-null mouse embryo fibroblasts (MEFs) undergo premature replicative arrest, which is relieved by the loss of p53. Here we show that the loss of ARF expands the life expectancy of Atm-null MEFs, but alters neither the sensitivity of Atm-null mice to ionizing radiation nor their propensity to develop lymphomas early in life. Therefore, whereas ARF and Atm signal to p53 through distinct pathways, the loss of ARF can modify p53-dependent features of the Atm-null phenotype.
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PMID:Loss of the ARF tumor suppressor reverses premature replicative arrest but not radiation hypersensitivity arising from disabled atm function. 1034 59

beta-catenin is a multifunctional protein, acting both as a structural component of the cell adhesion machinery and as a transducer of extracellular signals. Deregulated beta-catenin protein expression, due to mutations in the beta-catenin gene itself or in its upstream regulator, the adenomatous polyposis coli (APC) gene, is prevalent in colorectal cancer and in several other tumor types, and attests to the potential oncogenic activity of this protein. Increased expression of beta-catenin is an early event in colorectal carcinogenesis, and is usually followed by a later mutational inactivation of the p53 tumor suppressor. To examine whether these two key steps in carcinogenesis are interrelated, we studied the effect of excess beta-catenin on p53. We report here that overexpression of beta-catenin results in accumulation of p53, apparently through interference with its proteolytic degradation. This effect involves both Mdm2-dependent and -independent p53 degradation pathways, and is accompanied by augmented transcriptional activity of p53 in the affected cells. Increased p53 activity may provide a safeguard against oncogenic deregulation of beta-catenin, and thus impose a pressure for mutational inactivation of p53 during the later stages of tumor progression.
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PMID:Excess beta-catenin promotes accumulation of transcriptionally active p53. 1035 17

The INK4a-ARF locus encodes two distinct tumor suppressors, p16(INK4a) and p19(ARF). Whereas p16(INK4a) restrains cell growth through preventing phosphorylation of the retinoblastoma protein, p19(ARF) acts by attenuating Mdm2-mediated degradation of p53, thereby stabilizing p53. Recent data indicate that Mdm2 shuttles between the nucleus and the cytoplasm and that nucleo-cytoplasmic shuttling of Mdm2 is essential for Mdm2's ability to promote p53 degradation. Therefore, Mdm2 must export p53 from the nucleus to the cytoplasm where it targets p53 for degradation. We show here that coexpression of p19(ARF) blocks the nucleo-cytoplasmic shuttling of Mdm2. Moreover, subnuclear localization of Mdm2 changes from the nucleoplasm to the nucleolus in a shuttling time-dependent manner, whereas p19(ARF) is exclusively located in the nucleolus. In heterokaryons containing Mdm2 and p19(ARF), the longer the Mdm2 shuttling is allowed, the more Mdm2 protein colocalizes with p19(ARF) in the nucleolus, implying that Mdm2 moves from the nucleoplasm to the nucleolus and then associates with p19(ARF) there. Furthermore, whether or not Mdm2 colocalizes with p19(ARF) in the nucleolus, p19(ARF) prevents Mdm2 shuttling. This observation suggests that Mdm2 might be exported through the nucleolus and p19(ARF) could inhibit the nuclear export of Mdm2 by tethering Mdm2 in the nucleolus. Taken together, p19(ARF) could stabilize p53 by inhibiting the nuclear export of Mdm2.
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PMID:P19(ARF) stabilizes p53 by blocking nucleo-cytoplasmic shuttling of Mdm2. 1035 17

Recent developments in molecular biology have revealed that several oncogenes, suppressor genes and adhesion molecules are involved in the development of oesophageal cancer; however, the role of these genes is still unknown. To evaluate which molecular biological factors are related to patients' prognosis and recurrence, we checked p53, p16, p21/Waf1, cyclin D1, Ki-67, epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), Mdm2, Bcl2, E-cadherin and MRP1/CD9 by means of immunohistochemical analysis in 116 cases of oesophageal cancer (R0). We also checked the regrowth capability of the primary cultures of the resected tumours and the effect of post-operative treatment. Although univariate analysis revealed that pN (pTNM), pT (pTNM), sex, cyclin D1, Ki-67, VEGF, E-cadherin and cell regrowth capability were prognostic factors, multivariate analysis revealed that pN (risk ratio (RR) 3.17), sex (RR 8.13), cell regrowth capability (RR 3.03) and E-cadherin (RR 0.30) were prognostic factors. Interestingly, step-wise analysis revealed that the following five factors were prognostic factors: pN (RR 5.74), sex (RR 3.14), cyclin D1 (RR 2.29), E-cadherin (RR 0.26) and cell regrowth capability (RR 1.94). Logistic regression analysis revealed that the risk factors of haematogenous recurrence were pN (odds ratio (OR) 8.97), cyclin D1 (OR 4.52) and EGFR (OR 0.18). On the other hand, the risk factor of lymph node recurrence was pN (OR 5.16). With regard to the effect of postoperative treatment, post-operative radiotherapy was a favourable risk factor (RR 0.43) and reduced the haematogenous recurrence (OR 0.18). Our data indicate that combination analysis using pN, sex, cyclin D1, E-cadherin, EGFR and cell regrowth capability may be useful for the prediction of patient survival and recurrence.
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PMID:Prognostic factors of oesophageal squamous cell carcinoma from the perspective of molecular biology. 1037 85

Caspases are responsible for the proteolysis of many cytoskeletal proteins in apoptotic cells. It has been demonstrated here that during cisplatin-induced apoptosis of human embryo retinoblasts both E- and P-cadherin were degraded by caspases, giving initially major polypeptide products of apparent molecular weights 48 K and 104 K respectively. This proteolysis occurred over a similar time-scale to the observed degradation of PARP and to the onset of DNA fragmentation but appreciably later than p53 induction and cleavage of Mdm2 and p21. Addition of caspase inhibitors such as Z-VAD-FMK inhibited apoptosis and cadherin degradation. Co-immunoprecipitation studies carried out on viable cells confirmed previously observed complexes between cadherins and alpha and beta catenin and between the catenins themselves. These interactions were sustained in apoptotic cells as long as the protein components remained intact. Using confocal microscopy it has been shown that cytoskeletal changes associated with apoptosis precede degradation of catenins and cadherins by several hours. In particular, after addition of cisplatin relatively rapid (within 3 h) re-localization of adherens junction proteins from the cell periphery to the cytoplasm was observed whereas little cadherin or catenin degradation occurred until 10 h. We conclude that neither caspase-mediated degradation of cytoskeletal components nor disruption of adherens junction protein-protein interactions is required for morphological change.
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PMID:The fate of E- and P-cadherin during the early stages of apoptosis. 1038 31

The function of the p53 tumor suppressor protein is regulated by interaction with Mdm2, which targets p53 for ubiquitin dependent degradation. We show here that like p53, p73 alpha forms an interaction with Mdm2, both in vitro and in cells, but this does not result in the degradation of the p73 alpha protein. The human papillomavirus E6 protein also fails to degrade p73 alpha, suggesting that the mechanisms governing p73 alpha stability are distinct from those known to regulate p53 stability. However, the interaction of Mdm2 with 73 alpha is sufficient to impede p73 alpha transcriptional function, despite the lack of degradation.
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PMID:Mdm2 binds p73 alpha without targeting degradation. 1043 14


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