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)

We present a new approach towards the detection of the mRNAs in formalin-fixed, paraffin-embedded samples using a reverse transcriptase (RT)-polymerase chain reaction (PCR). The total RNAs were extracted from 10-micron-thick sections and were reverse-transcribed, then the RT-products were subjected to PCR amplification of GAPDH mRNA for screening the mRNA degradation. Next, nested PCR was performed for examining the expression of p53-related genes, p21WAF1, MDM2, p33ING1 and p14ARF. GAPDH mRNA expression was detectable in 12 out of 21 oral squamous cell carcinoma (SCC) samples. p21WAF1 mRNA expression was detectable in 5 out of 12 SCC samples, MDM2 mRNA expression was detectable in 5 our of 12 SCC samples and p33ING1 mRNA expression was detectable in 6 out of 12 SCC samples. However, the expression of p14ARF mRNA was not detectable in any of the samples. Seven out of 12 oral SCC samples showed abnormal nuclear accumulation of p53 protein by immunohistochemical staining, whereas 5 out of 12 oral SCCs showed negative staining for p53 protein. Of of p33ING1 mRNA. One of these was a verrucous carcinoma in which the p53 gene products might be inactivated by the oncoprotein E6 of human papilloma virus. Thus, the p53 tumor suppressor pathway was disrupted in most oral SCCs at the cellular levels, due to either an abnormality in p53 itself or loss of expression of p53 regulatory factors. This method would assist in making diagnosis, determining therapeutic strategy and predicting the prognosis of various cancers including oral SCCs.
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PMID:RT-PCR amplification of RNA extracted from formalin-fixed, paraffin-embedded oral cancer sections: analysis of p53 pathway. 1292 30

Butyric acid, a short chain fatty-acid derived from bacterial fermentation of complex carbohydrates in the large intestine has been shown to be a growth inhibitory in many colon cancer cell lines. Butyrate induced inhibition of cellular proliferation is considered to result from the induction of P21 gene expression through the activation of this gene transcription. P21 is an inhibitor of cyclin-dependent protein kinases that are required for the cells to enter the DNA synthesis phase. In the present study the kinetics of the changes of the P21 transcription in Caco-2 colon adenocarcinoma cells treated with various concentrations of sodium butyrate was determined using a novel real-time quantitative RT-PCR (TaqMan) technique. Beta-actin mRNA and GAPDH mRNA levels were used as the endogenous references. Colonocytes were incubated with sodium butyrate at concentrations of 5 mM, 10 mM and 20 mM for 3, 6, 12, 24 and 48 h. The results of this study indicated that butyrate strongly induced P21 gene expression as early as 3 h after treatment. Characteristic patterns of time-dependent changes of the target gene expression were observed. The increases in P21 mRNA level were generally more pronounced at higher butyrate concentrations. Because Caco-2 cells are lacking the wild allele of the P53 gene, the present results support the hypothesis that butyrate induces P21 gene expression by P53-independent mechanism.
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PMID:Quantification of p21 gene expression in Caco-2 cells treated with sodium butyrate using real-time reverse transcription-PCR (RT-PCR) assay. 1367 14

The ATM protein kinase regulates the DNA damage response by phosphorylating proteins involved in cell cycle checkpoints and DNA repair. We report here on the function of the predicted leucine zipper (LZ) motif, and sequences adjacent to this, in regulating ATM activity. The predicted LZ sequence was deleted from ATM, generating ATMDeltaLZ, and expressed in an ATM-negative AT cell line. ATM increased cell survival following exposure to ionizing radiation, whereas expression of ATMDeltaLZ failed to increase cell survival. ATMDeltaLZ retained in vitro kinase activity, but was unable to phosphorylate p53 in vivo. Leucine zippers mediate homo- and heterodimerization of proteins. However, the predicted LZ of ATM did not mediate the formation of ATM dimers. We examined if the predicted LZ of ATM was a dominant-negative inhibitor of ATM function in SW480 cells. Expression of amino acids 769-1436 of ATM, including the predicted LZ, sensitized SW480 cells to ionizing radiation, but did not inhibit ATM's kinase activity or its ability to phosphorylate Brca1. Further, this dominant-negative activity was not dependent on the predicted LZ domain. The central region of the ATM protein therefore contains multiple sequences which regulate cell survival following DNA damage.
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PMID:ATM's leucine-rich domain and adjacent sequences are essential for ATM to regulate the DNA damage response. 1450 13

Cdc7 kinase plays an essential role in firing of replication origins by phosphorylating components of the replication complexes. Cdc7 kinase has also been implicated in S phase checkpoint signaling downstream of the ATR and Chk1 kinases. Inactivation of Cdc7 in yeast results in arrest of cell growth with 1C DNA content after completion of the ongoing DNA replication. In contrast, conditional inactivation of Cdc7 in undifferentiated mouse embryonic stem (ES) cells leads to growth arrest with rapid cessation of DNA synthesis, suggesting requirement of Cdc7 functions for continuation of ongoing DNA synthesis. Furthermore, loss of Cdc7 function induces recombinational repair (nuclear Rad51 foci) and G2/M checkpoint responses (inhibition of Cdc2 kinase). Eventually, p53 becomes highly activated and the cells undergo massive p53-dependent apoptosis. Thus, defective origin activation in mammalian cells can generate DNA replication checkpoint signals. Efficient removal of those cells in which replication has been perturbed, through cell death, may be beneficial to maintain the highest level of genetic integrity in totipotent stem cells. Partial, rather than total, loss of Cdc7 kinase expression results in retarded growth at both cellular and whole body levels, with especially profound impairment of germ cell development.
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PMID:Functions of mammalian Cdc7 kinase in initiation/monitoring of DNA replication and development. 1464 27

It has been estimated that approximately 1% of the general population are ataxia telangiectasia (AT) mutated (ATM) heterozygotes. The ATM protein plays a central role in DNA-damage response pathways; however, the functional consequences of the presence of either heterozygous truncating or missense mutations on ATM expression and the ionising radiation (IR)-induced cellular phenotype remain to be fully determined. To investigate this relationship, the ATM mRNA and protein levels and several cellular end points were characterised in 14 AT heterozygote (AT het) lymphoblastoid cell lines, compared to normal and AT homozygote lines. The AT het cell lines displayed a wide range of IR-induced responses: despite lower average levels of ATM mRNA and protein expression compared to normal cells, 13 out of 14 were capable of phosphorylating the ATM substrates p53-ser15 and Chk2, leading to a normal cell cycle progression after irradiation. However, cell survival was lower than in the normal cell lines. The presence of a missense compared to a truncating mutation was associated with lower cell survival after exposure to 2 Gy irradiation (P=0.005), and a higher level of ATM mRNA expression (P=0.047). Our results underline the difficulty in establishing a reliable test for determining ATM heterozygosity.
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PMID:Cellular responses to ionising radiation of AT heterozygotes: differences between missense and truncating mutation carriers. 1497 Aug 66

We used primary cultures of cortical neurons to examine the relationship between beta-amyloid toxicity and hyperphosphorylation of the tau protein, the biochemical substrate for neurofibrillary tangles of Alzheimer's brain. Exposure of the cultures to beta-amyloid peptide (betaAP) induced the expression of the secreted glycoprotein Dickkopf-1 (DKK1). DKK1 negatively modulates the canonical Wnt signaling pathway, thus activating the tau-phosphorylating enzyme glycogen synthase kinase-3beta. DKK1 was induced at late times after betaAP exposure, and its expression was dependent on the tumor suppressing protein p53. The antisense induced knock-down of DKK1 attenuated neuronal apoptosis but nearly abolished the increase in tau phosphorylation in betaAP-treated neurons. DKK1 was also expressed by degenerating neurons in the brain from Alzheimer's patients, where it colocalized with neurofibrillary tangles and distrophic neurites. We conclude that induction of DKK1 contributes to the pathological cascade triggered by beta-amyloid and is critically involved in the process of tau phosphorylation.
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PMID:Induction of Dickkopf-1, a negative modulator of the Wnt pathway, is associated with neuronal degeneration in Alzheimer's brain. 1522 49

The wild-type p53-induced phosphatase PPM1D (or Wip1) is a serine/threonine phosphatase that is transcriptionally upregulated by p53 following ultraviolet and ionizing radiation. PPM1D is an oncogene in transformation assays and is amplified or overexpressed in several human tumor types. Here, we demonstrate that PPM1D interacts with the nuclear isoform of uracil DNA glycosylase, UNG2, and suppresses base excision repair (BER). Point mutations that inactivate PPM1D phosphatase activity abrogate BER suppression, indicating that dephosphorylation by PPM1D is important for BER inhibition. We have identified UNG2 phosphorylation sites at threonines 6 and 126 that exhibit enhanced phosphorylation following UV irradiation. The UV-induced phosphorylated forms of UNG2 are more active than nonphosphorylated forms in mediating uracil-associated DNA cleavage. PPM1D dephosphorylation of UNG2 at phosphothreonine 6 is associated with reduced UNG2 activity. Thus, PPM1D may inhibit BER by dephosphorylating UNG2 to facilitate its inactivation after completion of DNA repair.
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PMID:The p53-induced oncogenic phosphatase PPM1D interacts with uracil DNA glycosylase and suppresses base excision repair. 1532 77

The DNA damage checkpoint kinase, CHK2, promotes growth arrest or apoptosis through phosphorylating targets such as Cdc25A, Cdc25C, BRCA1, and p53. Both germline and somatic loss-of-function CHEK2 mutations occur in human tumours, the former linked to the Li-Fraumeni syndrome, and the latter found in diverse types of sporadic malignancies. Here we examined the status of CHK2 by genetic and immunohistochemical analyses in 53 breast carcinomas previously characterized for TP53 status. We identified two CHEK2 mutants, 470T>C (Ile157Thr), and a novel mutation, 1368insA leading to a premature stop codon in exon 13. The truncated protein encoded by CHEK2 carrying the 1368insA was stable yet mislocalized to the cytoplasm in tumour sections and when ectopically expressed in cultured cells. Unexpectedly, we found CHEK2 to be subject to extensive alternative splicing, with some 90 splice variants detected in our tumour series. While all cancers expressed normal-length CHEK2 mRNA together with the spliced transcripts, we demonstrate and/or predict some of these splice variants to lack CHK2 function and/or localize aberrantly. We conclude that cytoplasmic sequestration may represent a novel mechanism to disable CHK2, and propose to further explore the significance of the complex splicing patterns of this tumour suppressor gene in oncogenesis.
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PMID:Alternative splicing and mutation status of CHEK2 in stage III breast cancer. 1536 33

Axin and p53 are tumor suppressors, controlling cell growth, apoptosis, and development. We show that Axin interacts with homeodomain-interacting protein kinase-2 (HIPK2), which is linked to UV-induced p53-dependent apoptosis by interacting with, and phosphorylating Ser 46 of, p53. In addition to association with p53 via HIPK2, Axin contains a separate domain that directly interacts with p53 at their physiological concentrations. Axin stimulates p53-dependent reporter transcription in 293 cells, but not in 293T, H1299, or SaOS-2 cells that are defective in p53 signaling. Axin, but not AxindeltaHIPK2, activates HIPK2-mediated p53 phosphorylation at Ser 46, facilitating p53-dependent transcriptional activity and apoptosis. Specific knockdown of Axin by siRNA reduced UV-induced Ser-46 phosphorylation and apoptosis. Kinase-dead HIPK2 reduced Axin-induced p53-dependent transcriptional activity, indicating that Axin stimulates p53 function through HIPK2 kinase activity. Interestingly, HIPK2deltaAxin that lacks its Axin-binding region acts as a dominant-positive form in p53 activation, suggesting that the Axin-binding region of HIPK2 is a putative autoinhibitory domain. These results show that Axin acts as a tumor suppressor by facilitating p53 function through integration of multiple factors.
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PMID:Axin stimulates p53 functions by activation of HIPK2 kinase through multimeric complex formation. 1552 30

The ataxia telangiectasia mutated (ATM) and ATR (ATM and Rad3-related) protein kinases exert cell cycle delay, in part, by phosphorylating Checkpoint kinase (Chk) 1, Chk2, and p53. It is well established that ATR is activated following UV light-induced DNA damage such as pyrimidine dimers and the 6-(1,2)-dihydro-2-oxo-4-pyrimidinyl-5-methyl-2,4-(1H,3H)-pyrimidinediones, whereas ATM is activated in response to double strand DNA breaks. Here we clarify the activation of these kinases in cells exposed to IR, UV, and hyperoxia, a condition of chronic oxidative stress resulting in clastogenic DNA damage. Phosphorylation on Chk1(Ser-345), Chk2(Thr-68), and p53(Ser-15) following oxidative damage by IR involved both ATM and ATR. In response to ultraviolet radiation-induced stalled replication forks, phosphorylation on Chk1 and p53 required ATR, whereas Chk2 required ATM. Cells exposed to hyperoxia exhibited growth delay in G1, S, and G2 that was disrupted by wortmannin. Consistent with ATM or ATR activation, hyperoxia induced wortmannin-sensitive phosphorylation of Chk1, Chk2, and p53. By using ATM- and ATR-defective cells, phosphorylation on Chk1, Chk2, and p53 was found to be ATM-dependent, whereas ATR also contributed to Chk1 phosphorylation. These data reveal activated ATM and ATR exhibit selective substrate specificity in response to different genotoxic agents.
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PMID:Ataxia telangiectasia mutated (ATM) and ATM and Rad3-related protein exhibit selective target specificities in response to different forms of DNA damage. 1553 33


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