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)

During the past few years molecular genetics has been providing answers concerning the mechanisms that are involved in the pathogenesis of human malignancies. Essentially two different mechanisms are involved. One results in the activation of cellular protooncogenes. This activation can occur by activation of transcription, mutation, or gene fusion. Chromosomal translocations and inversions in malignant cells have provided very powerful tools to identify and characterize genes involved in malignant transformation and to probes specific for breakpoint cluster regions are being used extensively for the diagnosis, prognosis, and clinical monitoring of hematopoietic malignancies. The other mechanism results in loss of function of cancer suppressor genes or antioncogenes. Loss of heterozygosity at specific sites of the human genome has provided the means to identify, by the molecular genetic approach, genes the function of which is eliminated or suppressed in human cancers. During the last few years a number of such genes, such as Rb and p53, have been identified and characterized. By this approach a potential candidate involved in the 3p deletion characteristic of lung cancer has been identified. Interestingly, this gene codes for a protein tyrosine phosphatase (14). If this gene should turn out to be involved in the pathogenesis of lung and kidney tumors, it will indicate that transmembrane protein tyrosine phosphatase may represent a class of tumor suppressors.
 ...
PMID:Genetic approaches to the study of the molecular basis of human cancer. 165 9

The p53 tumor suppressor protein is tightly regulated in the cell and is phosphorylated at multiple sites by several different protein kinases. We have investigated the phosphorylation of p53 by mitogen-activated protein (MAP) kinase, a protein kinase that plays a central role in mediating many mitogenic and differentiation signals. Recombinant wild-type mouse p53 was phosphorylated in vitro by activated recombinant p42-MAP kinase but not by inactive MAP kinase or by the activating protein, MAP kinase kinase. Phosphorylation of p53 by MAP kinase occurred at two N-terminal sites, threonine residues 73 and 83. Tryptic phosphopeptides of recombinant p53 phosphorylated in vitro by MAP kinase comigrated on two-dimensional maps with p53 from SV3T3 cells labeled in vivo with [32P]orthophosphate, suggesting that MAP kinase targets a site in p53 that is phosphorylated in the cell. Following serum stimulation of quiescent C57MG cells, two p53 kinases, which were resolved by chromatography on Mono Q, were stimulated 15-20-fold within 5 min. Each of these kinase activities co-eluted with myelin basic protein kinase activity and could be inactivated following treatment with protein phosphatase 2A, a serine/threonine phosphatase, or leukocyte antigen receptor, a protein tyrosine phosphatase, suggesting that these activities were members of the MAP kinase family. The two kinase activities from the lysates targeted the same phosphorylation sites on p53 as the purified recombinant MAP kinase. These protein kinase activities were also stimulated following exposure of the cells to ultraviolet radiation, but with slightly delayed kinetics. Phorbol ester treatment of SV3T3 cells led to increased phosphorylation of the peptide containing the residues targeted by MAP kinase. The data suggest that p53 may be phosphorylated by MAP kinase physiologically and that this interaction may be involved in the cell's response to UV exposure, growth factor stimulation, or transformation by oncogenes.
 ...
PMID:Phosphorylation of the tumor suppressor protein p53 by mitogen-activated protein kinases. 751 Jul 6

Hypophosphorylation of retinoblastoma protein (RB) accompanies the DNA damage-induced, p53-independent G1 arrest and apoptosis in two p53-null human leukemic cell lines, HL-60 and U937 (Q.P. Dou et al., Proc. Natl. Acad. Sci. USA, 92: 9019-9023, 1995). When an HL-60 cell line resistant to cytosine arabinoside was exposed to this DNA-damaging agent, neither RB hypophosphorylation nor apoptosis were observed. In contrast, treatment of these cells with another DNA-damaging agent, etoposide, dramatically induced these events, which were inhibitable by the addition of zinc chloride, a protein tyrosine phosphatase inhibitor. Induction of hypophosphorylation of RB may be an important novel strategy for treating drug-resistant cancers.
 ...
PMID:Failure to dephosphorylate retinoblastoma protein in drug-resistant cells. 758 79

Incubation of Hela cells in the presence of insulin results in suppression of p53 expression. Treatment of cells with vanadate, an inhibitor of protein tyrosine phosphatase, likewise led to a dramatic reduction in the level of p53 transcript. On the other hand, significant induction of p53 message was demonstrated when Hela cells were exposed to genistein, a protein tyrosine kinase inhibitor. When cells were cultured in the presence of phosphotyrosine, there was a marked decrease in p53 expression. Neither phosphoserine nor phosphothreonine had an effect on p53 expression. Furthermore, simultaneous presence of both insulin and phosphotyrosine did not result in a greater suppression of the p53 message than when either of the agents was acting singly.
 ...
PMID:Regulation of p53 expression in HeLa cells. 882 21

Somatostatin (SST) exerts direct antiproliferative effects in tumor cells, triggering either growth arrest or apoptosis. The cellular actions of SST are transduced through a family of five distinct somatostatin receptor subtypes (SSTR1-5). Whereas growth inhibition has been reported to follow stimulation of protein tyrosine phosphatase via SSTR2 or inhibition of Ca2+ channels via SSTR5 in heterologous expression systems, the subtype selectivity for signaling apoptosis has not been investigated. The tumor suppressor protein p53 and the protooncogene product c-Myc regulate cell cycle progression (growth factors present) or apoptosis (growth factors absent). The p53-induced G1 arrest requires induction of p21, an inhibitor of cyclin-dependent kinases, whereas apoptosis requires induction of Bax. c-Myc is capable of abrogating p53-induced G1 arrest by interfering with the inhibitory action of p21 on cyclin-dependent kinases. We have, therefore, investigated the regulation of p53, p21, c-Myc, and Bax and cellular apoptosis in relation to cell cycle progression in CHO-K1 cells stably expressing individual human SSTR1-5. We demonstrate that apoptosis is signaled uniquely through human SSTR3 and is associated with dephosphorylation-dependent conformational change in wild-type (wt) p53 as well as induction of Bax. The induction of wt p53 occurs rapidly and precedes the onset of apoptosis. We show that the increase in wt p53 is not associated with the induction of p21 or c-Myc when octreotide-induced apoptosis becomes evident, suggesting that such apoptosis does not require G1 arrest and is not c-Myc dependent. These findings provide the first evidence for hormonal induction of wt p53-associated apoptosis via G protein-coupled receptor in a subtype-selective manner.
 ...
PMID:Subtype-selective induction of wild-type p53 and apoptosis, but not cell cycle arrest, by human somatostatin receptor 3. 896 Dec 77

Exposure of mammalian cells to adverse stimuli triggers the expression of numerous stress response genes, many of which are presumed to enhance cell survival. In this study, we examined the mechanisms contributing to the induction of p21Waf1 by stress and its influence on the survival of cells subjected to short-wavelength UVC irradiation. UVC was found to elevate p21Waf1 mRNA expression in mouse embryonal fibroblasts (MEFs) and human colorectal carcinoma (RKO) cells in a p53-dependent manner. The lack of p21Waf1 induction in p53-deficient MEFs and RKO cells correlated with diminished cell survival following UVC irradiation. Unexpectedly, UVC treatment was also found to block the induction of p21Waf1 by various stress-inducing agents such as mimosine in the p53-deficient cells. Additional studies indicated that induction of p21Waf1 by UVC occurs primarily through enhanced mRNA stability rather than increased transcription; in p53-/- MEFs, failure to elevate p21Waf1 after treatment with UVC appears to be due to their inability to stabilize the p21Waf1 transcripts. Treatment of the p53-/- MEFs with the protein tyrosine phosphatase inhibitor vanadate reversed the UVC-induced block on p21Waf1 induction and resulted in their enhanced survival following irradiation. Thus, in cells bearing normal p53, UVC augments p21Waf1 expression by increasing the half-life of p21Waf1 mRNA; without p53, p21Waf1 mRNA remains unstable after UVC, apparently due to a pathway involving tyrosine phosphatase activity.
 ...
PMID:p53-dependent elevation of p21Waf1 expression by UV light is mediated through mRNA stabilization and involves a vanadate-sensitive regulatory system. 948 55

The influence of p53 on cytokine-triggered Janus kinase-STAT signaling was investigated in human hepatoma Hep3B cell lines engineered to constitutively express the temperature-sensitive Val135 mutant of p53. In comparison to the parental p53-free Hep3B cells, these p53-Val135-containing Hep3B cell lines displayed a reduced response to IL-6 at the wild-type-like p53 temperature (32.5 degrees C). In these cells, IL-6 induced a marked reduction in the immunologic accessibility of cytoplasmic and nuclear STAT3 and STAT5 within 20 to 30 min that lasted 2 to 4 h (STAT-masking) provided that the cells had been previously cultured at 32.5 degrees C for at least 18 to 20 h. The onset of IL-6-induced STAT-masking required protein tyrosine kinase, protein tyrosine phosphatase, proteasomal, phospholipase C, and mitogen-activated protein kinase kinase 1 activities. The maintenance of IL-6-induced STAT-masking was dependent on continued signaling through the phosphatidylinositol-dependent phospholipase C pathway. Despite a reduction in IL-6-induced STAT3 DNA binding activity in the nuclear compartment during STAT-masking, there was increased and prolonged accumulation of tyrosine-phosphorylated STAT3 in both the cytoplasmic and nuclear compartments, indicating that the capacity of tyrosine-phosphorylated STAT3 to bind DNA was reduced during STAT-masking. Thus, IL-6-induced STAT-masking, as dramatically evident on immunomicroscopy, is a visible consequence of a novel cellular process by which a p53-Val135-induced gene product(s) regulates the association of masking protein(s) with and the DNA-binding capacity of STAT3.
 ...
PMID:Regulation of IL-6 signaling by p53: STAT3- and STAT5-masking in p53-Val135-containing human hepatoma Hep3B cell lines. 964 40

SHP-1 protein tyrosine phosphatase is a critical regulator of signal transduction in hematopoietic cells. In the present study, we derived two pre-B cell lines, PBCL-1 and PBCL-2, from normal and SHP-1-deficient motheaten mice, respectively, and characterized hyperphosphorylated proteins in PBCL-2 cells to identify SHP-1-regulated molecules. Two proteins of 56 and 53 kDa (p56/p53) in PBCL-2 cells showed heightened phosphorylation (3- to 6-fold) in comparison with those in PBCL-1. p56/p53 were identified as the two forms of the lyn protein tyrosine kinase (p56/p53lyn), which showed increased kinase activity in PBCL-2 cells. Interestingly, the protein levels of p56/53lyn were found to be 3- to 6-fold higher in PBCL-2 cells than those in PBCL-1, whereas the transcript levels of lyn in the two cell lines were comparable. A modest increase in p56/53lyn protein expression was also detected in primary spleen B cells of motheaten mice. Thus SHP-1 deficiency in B-lineage cells, especially pre-B cells, is associated with increased lyn protein expression and kinase activity. These data indicate a role for SHP-1 in regulating lyn through a post-transcriptional mechanism.
 ...
PMID:SHP-1 deficiency in B-lineage cells is associated with heightened lyn protein expression and increased lyn kinase activity. 980 51

The biological activity of p53 in IW32 erythroleukemia cells was investigated. IW32 cells had no detectable levels of p53 mRNA and protein expression. By transfecting a temperature-sensitive mutant p53 cDNA, tsp53val135, into the cells, we have established several clones stably expressing the mutant p53 allele. At permissive temperature, these p53 transfectants were arrested in G1 phase and underwent apoptosis. Moreover, differentiation along the erythroid pathway was observed as evidenced by increased benzidine staining and mRNA expression of beta-globin and the erythroid-specific delta-aminolevulinic acid synthase (ALAS-E). Treatment of cells with protein tyrosine phosphatase inhibitor vanadate blocked the p53-induced differentiation, but not that of cell death or growth arrest. Increased protein tyrosine phosphatase activity as well as mRNA levels of PTPbeta2 and PTPepsilon could be observed by wildtype p53 overexpression. These results indicate that p53 induced multiple phenotypic consequences through separate signal pathways in IW32 erythroleukemia cells, and protein tyrosine phosphatase is required for the induced differentiation.
 ...
PMID:Induction of IW32 erythroleukemia cell differentiation by p53 is dependent on protein tyrosine phosphatase. 1091 55

To determine the role of Src homology protein tyrosine phosphatase (SHP-1) in the ionizing radiation-induced stress response, we analyzed the apoptotic response and cell cycle function in irradiated spleen cells of motheaten (me/me) mice. The defect in me/me mice has been attributed to mutations of the HCPH: gene, which encodes SHP-1. Homozygotes develop severe systemic autoimmune and inflammatory disease, whereas heterozygotes live longer and develop hematopoietic and lymphoid malignance. Spleen cells from C57BL/6 (B6)-me/me and B6-+/+ controls were analyzed after gamma-irradiation from a (137)Cs source. B6-me/me cells were significantly more resistant than B6-+/+ cells to gamma-irradiation-induced apoptosis exhibiting a higher LD(50). The defective apoptosis response of the B6-me/me cells was exhibited by T and B cells and macrophages. Of the Bcl-2 family members analyzed, a significant difference was observed in the transcription of Bax mRNA, which was up-regulated early after irradiation in B6-+/+ cells, but not B6-me/me cells. Analysis of 3,3'-dihexyloxacarbocyanine iodide revealed resistance to the gamma-irradiation-induced mitochondrial transmembrane permeability transition in the B6-me/me cells. The blocking of the cell cycle in the G(0)/G(1) phase characteristic of the irradiated B6-+/+ cells was not observed in the B6-me/me cells. There was decreased phosphorylation of p38 mitogen-activated protein kinase and increased phosphorylation of p53 from spleen cell lysates of irradiated B6-me/me mice compared with wild-type mice. These data suggest that SHP-1 plays an important role in regulation of apoptosis and cell cycle arrest after a gamma-irradiation-induced stress response.
 ...
PMID:Mutation of the hematopoietic cell phosphatase (Hcph) gene is associated with resistance to gamma-irradiation-induced apoptosis in Src homology protein tyrosine phosphatase (SHP)-1-deficient "motheaten" mutant mice. 1114 49


1 2 3 4 Next >>