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)

In response to UV irradiation, mouse NIH3T3 fibroblasts transiently arrest predominantly in the G1 phase of the cell cycle. Here, we investigate the role of the retinoblastoma-related pocket proteins in this biological process. We report here that UV induces an increase in p107/E2F complexes, shown previously to be repressors of E2F-dependent transcriptional activity. Several lines of evidence indicate that the increase of p107/E2F complexes following UV irradiation is a consequence of rapid dephosphorylation of p107. First, UV-mediated p107 dephosphorylation could be abolished by pretreatment of NIH3T3 fibroblasts with the serine/threonine phosphatase inhibitors calyculin A and okadaic acid. Second, alteration of protein phosphatase 2A holoenzyme composition by over-expression of specific B subunits interfered with UV-mediated dephosphorylation of p107. Consistent with this, p107 could be dephosphorylated in vitro with PP2A. Moreover, dephosphorylation of p107 was shown to be independent of the activity of p53 and p21, as it occurred also in UV-treated p53-null as well as p21-null mouse fibroblasts. We observed a close correlation between the UV dosages required for G1 cell cycle arrest and p107 dephosphorylation. Our data suggest a model in which UV radiation-induced cell cycle arrest depends, at least in part, on the induction of a PP2A-like phosphatase that acts on p107.
 ...
PMID:Rapid dephosphorylation of p107 following UV irradiation. 998 18

The tumor suppressor p53 plays a key role in inducing G1 arrest and apoptosis following DNA damage. The double-stranded-RNA-activated protein PKR is a serine/threonine interferon (IFN)-inducible kinase which plays an important role in regulation of gene expression at both transcriptional and translational levels. Since a cross talk between IFN-inducible proteins and p53 had already been established, we investigated whether and how p53 function was modulated by PKR. We analyzed p53 function in several cell lines derived from PKR+/+ and PKR-/- mouse embryonic fibroblasts (MEFs) after transfection with the temperature-sensitive (ts) mutant of mouse p53 [p53(Val135)]. Here we report that transactivation of transcription by p53 and G0/G1 arrest were impaired in PKR-/- cells upon conditions that ts p53 acquired a wild-type conformation. Phosphorylation of mouse p53 on Ser18 was defective in PKR-/- cells, consistent with an impaired transcriptional induction of the p53-inducible genes encoding p21(WAF/Cip1) and Mdm2. In addition, Ser18 phosphorylation and transcriptional activation by mouse p53 were diminished in PKR-/- cells after DNA damage induced by the anticancer drug adriamycin or gamma radiation but not by UV radiation. Furthermore, the specific phosphatidylinositol-3 (PI-3) kinase inhibitor LY294002 inhibited the induction of phosphorylation of Ser18 of p53 by adriamycin to a higher degree in PKR+/+ cells than in PKR-/- cells. These novel findings suggest that PKR enhances p53 transcriptional function and implicate PKR in cell signaling elicited by a specific type of DNA damage that leads to p53 phosphorylation, possibly through a PI-3 kinase pathway.
 ...
PMID:Double-stranded-RNA-activated protein kinase PKR enhances transcriptional activation by tumor suppressor p53. 1008 13

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.
 ...
PMID:DNA damage induced p53 stabilization: no indication for an involvement of p53 phosphorylation. 1020 33

We investigated DNA damage induced by aminoacetone, a metabolite of threonine and glycine. Pulsed-field gel electrophoresis revealed that aminoacetone caused cellular DNA cleavage. Aminoacetone increased the amount of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in human cultured cells in a dose-dependent manner. The formation of 8-oxodG in calf thymus DNA increased due to aminoacetone only in the presence of Cu(II). DNA ladder formation was observed at higher concentrations of aminoacetone than those causing DNA cleavage. Flow cytometry showed that aminoacetone enhanced the generation of hydrogen peroxide (H2O2) in cultured cells. Aminoacetone caused damage to 32P-5'-end-labeled DNA fragments, obtained from the human c-Ha-ras-1 and p53 genes, at cytosine and thymine residues in the presence of Cu(II). Catalase and bathocuproine inhibited DNA damage, suggesting that H2O2 and Cu(I) were involved. Analysis of the products generated from aminoacetone revealed that aminoacetone underwent Cu(II)-mediated autoxidation in two different pathways: the major pathway in which methylglyoxal and NH+4 are generated and the minor pathway in which 2,5-dimethylpyrazine is formed through condensation of two molecules of aminoacetone. These findings suggest that H2O2 generated by the autoxidation of aminoacetone reacts with Cu(I) to form reactive species capable of causing oxidative DNA damage.
 ...
PMID:Oxidative DNA damage induced by aminoacetone, an amino acid metabolite. 1022 39

Paraffin embedded tissues from twenty-two Thai patients with non-small cell lung cancer were studied for p53 gene mutations in exon 5 to 8 using polymerase chain reaction and single-stranded conformation polymorphism (PCR-SSCP) followed by thermal cycle sequencing. Results showed that point mutations in this region of p53 gene were present in 3 cases. One harboured the base change from GAC to AAC at codon 281, changing amino acid from aspartic acid to asparagine, whilst the other cases were transversion of AAA (lysine) to ACA (threonine) at codon 292. All subjects with p53 mutation had a past history of tobacco smoking.
 ...
PMID:p53 gene mutations in non-small cell lung cancer from Thai patients. 1041 Apr 79

Okadaic acid (OA), a toxin from the black sponge Halicondria okadai, is a specific inhibitor of serine/threonine protein phosphatases 1 (PP1) and 2A (PP2A). OA is a tumor promoter but also induces apoptosis in some tumor cell lines. In this study, we determined whether ras mutation and/or p53 status are characteristics associated with the cell's sensitivity to the induction of apoptosis by OA. Several cell lines that differed in ras and p53 mutations were treated with OA (10-100 nM). At 24 to 48 h after treatment, the percentage of cells undergoing apoptosis was quantitated. The cell lines with mutations in either H-ras (human bladder carcinoma cell line T24 and mouse keratinocyte cell line 308), or K-ras (human colon carcinoma cell lines DLD-1 and HCT116; human prostate cancer cell lines LNCaP and PC-3; human lung cancer cell lines Calu-6 and SKLU-1; and human pancreatic cancer cell line MIAPaCa2) were more sensitive to OA-induced apoptosis (3- to 10-fold) than the cell lines that lacked the ras mutation (mouse epidermal cell lines C50 and JB6; murine fibroblast cell line NIH3T3; human colon cancer cell line HT29; human kidney epithelial cell line Hs715.K; and human pancreatic cancer cell line Bx-PC3). Similarly, using isogenic cell lines we found that overexpression of mutated H-ras in NIH3T3 and in SV40 immortalized human uroepithelial cells (SVHUC) enhanced their sensitivity to undergo apoptosis in response to OA treatment. The T24, DLD-1, SKLU-1, Calu-6, and MIAPaCa2 cell lines express mutated p53. The SVHUC as well as their ras-transfected counterparts have inactive p53 due to complex formation between large "T" antigen and p53. Taken together, these results imply that OA-induced apoptosis may involve a p53-independent pathway. The transfectants (NIH3T3-ras and SVHUC-ras), which express mutated H-ras, have up-regulated PP2A activity. OA treatment inhibited in vivo the levels of PP1 and PP2A activity, and induced apoptosis in SVHUC-ras and other cell lines. We conclude that OA-induced cell death pathway in ras-activated cell lines may involve a cross talk between PP1 and PP2A and ras signaling pathways. In light of the present results, the current theory that OA promotes mouse skin tumor formation by selective expansion of initiated cells that harbor ras mutations needs reevaluation.
 ...
PMID:Ras mutation, irrespective of cell type and p53 status, determines a cell's destiny to undergo apoptosis by okadaic acid, an inhibitor of protein phosphatase 1 and 2A. 1046 39

Overexpression of p53 causes G2 arrest, attributable in part to the loss of CDC2 activity. Transcription of cdc2 and cyclin B1, determined using reporter constructs driven by the two promoters, was suppressed in response to the induction of p53. Suppression requires the regions -287 to -123 of the cyclin B1 promoter and -104 to -74 of the cdc2 promoter. p53 did not affect the inhibitory phosphorylations of CDC2 at threonine 14 or tyrosine 15 or the activity of the cyclin-dependent kinase that activates CDC2 by phosphorylating it at threonine 161. Overexpression of p53 may also interfere with the accumulation of CDC2/cyclin B1 in the nucleus, required for cells to enter mitosis. Constitutive expression of cyclin B1, alone or in combination with the constitutively active CDC2 protein T14A Y15F, did not reverse p53-dependent G2 arrest. However, targeting cyclin B1 to the nucleus in cells also expressing CDC2 T14A Y15F did overcome this arrest. It is likely that several distinct pathways contribute to p53-dependent G2 arrest.
 ...
PMID:Mechanisms of G2 arrest in response to overexpression of p53. 1056 59

p53 is a potent transcription factor which is regulated by sequential multisite phosphorylation and acetylation. In this paper, we identify threonine 18 of p53, a key site in regulating the interaction between p53 and its regulatory partner MDM2, as a novel site phosphorylated in vitro by purified recombinant casein kinase 1 (CK1) delta. Strikingly, phosphorylation of threonine 18 is dependent upon prior phosphorylation of serine 15. These data highlight an additional and physiologically important target residue for CK1 in p53 and suggest a potential mechanism by which sequential modification of a pivotal N-terminal residue in p53 may occur following stress-activated modification of serine 15.
 ...
PMID:Protein kinase CK1 is a p53-threonine 18 kinase which requires prior phosphorylation of serine 15. 1060 44

Ataxia telangiectasia mutated (ATM) phosphorylates p53 protein in response to ionizing radiation, but the complex phenotype of AT cells suggests that it must have other cellular substrates as well. To identify substrates for ATM and the related kinases ATR and DNA-PK, we optimized in vitro kinase assays and developed a rapid peptide screening method to determine general phosphorylation consensus sequences. ATM and ATR require Mn(2+), but not DNA ends or Ku proteins, for optimal in vitro activity while DNA-PKCs requires Mg(2+), DNA ends, and Ku proteins. From p53 peptide mutagenesis analysis, we found that the sequence S/TQ is a minimal essential requirement for all three kinases. In addition, hydrophobic amino acids and negatively charged amino acids immediately NH(2)-terminal to serine or threonine are positive determinants and positively charged amino acids in the region are negative determinants for substrate phosphorylation. We determined a general phosphorylation consensus sequence for ATM and identified putative in vitro targets by using glutathione S-transferase peptides as substrates. Putative ATM in vitro targets include p95/nibrin, Mre11, Brca1, Rad17, PTS, WRN, and ATM (S440) itself. Brca2, phosphatidylinositol 3-kinase, and DNA-5B peptides were phosphorylated specifically by ATR, and DNA Ligase IV is a specific in vitro substrate of DNA-PK.
 ...
PMID:Substrate specificities and identification of putative substrates of ATM kinase family members. 1060 6

Replicative senescence in human fibroblasts is absolutely dependent on the function of the phosphoprotein p53 and correlates with activation of p53-dependent transcription. However, no evidence for posttranslational modification of p53 in senescence has been presented, raising the possibility that changes in transcriptional activity result from upregulation of a coactivator. Using a series of antibodies with phosphorylation-sensitive epitopes, we now show that senescence is associated with major changes at putative regulatory sites in the N and C termini of p53 consistent with increased phosphorylation at serine-15, threonine-18, and serine-376 and decreased phosphorylation at serine-392. Ionizing and UV radiation generated overlapping but distinct profiles of response, with increased serine-15 phosphorylation being the only common change. These results support a direct role for p53 in signaling replicative senescence and are consistent with the generation by telomere erosion of a signal which shares some but not all of the features of DNA double-strand breaks.
 ...
PMID:Posttranslational modifications of p53 in replicative senescence overlapping but distinct from those induced by DNA damage. 1073 83


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