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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Immunization with wild-type sequence (wt) p53 epitopes represents a novel therapeutic strategy for cancer patients with tumors accumulating mutant p53. To evaluate usefulness of p53-derived peptides as future cancer vaccines, frequencies of wt p53(264-272) peptide-specific CD8+ T cells were determined in the peripheral circulation of patients with squamous cell carcinoma of the head and neck (SCCHN). T cells of 30 HLA-A2.1+ patients and 31 HLA-A2.1+ healthy individuals were evaluated by multicolor flow cytometry analysis using peptide-HLA-A2.1 complexes (tetramers). T cells specific for an influenza matrix peptide (a model recall antigen) or an HIV reverse transcriptase peptide (a model novel antigen) were studied in parallel. Patients with SCCHN had a significantly higher mean frequency of CD8+ T cells specific for wt p53(264-272) than normal donors (P = 0.0041). Surprisingly, the frequency of epitope-specific T cells in the circulation of patients did not correlate with p53 accumulation in the tumor. In patients whose tumors had normal p53 expression or had p53 gene mutations preventing presentation of this epitope, high frequencies of wt p53(264-272)-specific CD8+ T cells were found, of which many were memory T cells. In contrast, patients whose tumors accumulated p53 had low frequencies of wt p53(264-272)-specific CD8+ T cells, which predominantly had a naive phenotype and were unable to proliferate ex vivo in response to the epitope, as reported by us previously (T. K. Hoffmann, J. Immunol., 165: 5938-5944, 2000). This seemingly contradictory relationship between the high frequency of epitope-specific T cells and wt p53 expression in the tumor suggests that other factors may contribute to the observed anti-p53 responses. Human papillomavirus-16 E6/E7 expression is common in SCCHN, and E6 is known to promote presentation of wt p53 epitopes. Although human papillomavirus-16 E6/E7 expression was detected in 46% of the tumors, it did not correlate with the frequency of wt p53(264-272)-specific CD8+ T cells or with p53 expression in the tumor. These findings emphasize the complexity of interactions between the tumor and the host immune system, and, thus, have particularly important implications for future p53-based immunization strategies.
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PMID:Frequencies of tetramer+ T cells specific for the wild-type sequence p53(264-272) peptide in the circulation of patients with head and neck cancer. 1206 99

Post-translational modifications (PTMs) are known to regulate biological processes by controlling protein function. The effect of a PTM on protein function depends critically on the position and the number of modifications. While there are convenient methods available to qualitatively examine modifications like phosphorylation, glycosylation, acetylation and methylation, methods available for their quantitative assessment are cumbersome. We have developed a new tool that allows quantitation of the number of phosphorylation events in proteins with ease. The "ProteoMod" tool depends on shifts in the isoelectric points of proteins upon post-translational change. The extent of shift exhibited upon phosphorylation is algorithmically converted into the number of phosphorylations conferred. The validity of ProteoMod was confirmed by examining proteins with previously known number of phosphorylations. The list of proteins examined included HSP27, HSP70 and tumor suppressor p53. The approach can also be applied to estimate modifications like acetylation, methylation and sialylation in proteins. We analyzed shifts in isoelectric points due to sialylation events in N-glycoproteins. Using influenza hemagglutinin we show that shifts in isoelectric points correlate with intracellular distribution of this model membrane protein. In addition to extending the application of two dimensional gel electrophoresis to quantitate modifications, our study also highlights its potential use in cell biology.
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PMID:ProteoMod: A new tool to quantitate protein post-translational modifications. 1517 36

p53 is a major target for tumor therapy. Attempts have been made to restore or enhance p53 activity in tumor cells, including overexpression of exogenous p53 and small molecules that can rescue mutant p53. Notably, p53 peptides corresponding to the p53 carboxyl terminus can trigger a p53 response in both wild-type or mutant p53-containing cells. The recent protein transduction domain (PTD)-mediated cell entry might solve the obstacle of efficient delivery of peptides or large molecular biological cargos into cells. PTD-mediated transfer through the cell membrane occurs through a kind of endocytosis, macropinocytosis. Destabilization of macropinocytosomes by the influenza virus hemagglutinin protein (HA2) helps the escape of the PTD-cargo from macropinocytosomes and therefore significantly enhances the functional impact of transduced cargo.
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PMID:Targeting p53 by PTD-mediated transduction. 1533 Dec 19

Because of the central role of CD4(+) T cells in antitumour immunity, the identification of the MHC class II-restricted peptides to which CD4(+) T cells respond has become a priority of tumour immunologists. Here, we describe a strategy permitting us to rapidly determine the immunogenicity of candidate HLA-DR-restricted peptides using peptide immunisation of HLA-DR-transgenic mice, followed by assessment of the response in vitro. This strategy was successfully applied to the reported haemaglutinin influenza peptide HA(307-319), and then extended to three candidate HLA-DR-restricted p53 peptides predicted by the evidence-based algorithm SYFPEITHI to bind to HLA-DRbeta1*0101 (HLA-DR1) and HLA-DRbeta1*0401 (HLA-DR4) molecules. One of these peptides, p53(108-122), consistently induced responses in HLA-DR1- and in HLA-DR4-transgenic mice. Moreover, this peptide was naturally processed by dendritic cells (DCs), and induced specific proliferation in the splenocytes of mice immunised with p53 cDNA, demonstrating that immune responses could be naturally mounted to the peptide. Furthermore, p53(108-122) peptide was also immunogenic in HLA-DR1 and HLA-DR4 healthy donors. Thus, the use of this transgenic model permitted the identification of a novel HLA-DR-restricted epitope from p53 and constitutes an attractive approach for the rapid identification of novel immunogenic MHC class II-restricted peptides from tumour antigens, which can ultimately be incorporated in immunotherapeutic protocols.
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PMID:Peptide immunisation of HLA-DR-transgenic mice permits the identification of a novel HLA-DRbeta1*0101- and HLA-DRbeta1*0401-restricted epitope from p53. 1544 37

Protein transduction therapy is a newly developing method that allows proteins, peptides, and biologically active compounds to penetrate across the plasma membrane by being fused with cell-penetrating peptides such as polyarginine. Polyarginine-fused p53 protein penetrates across the plasma membrane of cancer cells and inhibits the growth of the cells. However, the protein is often entrapped inside macropinosomes in the cytoplasm. Therefore, high dose concentrations of the protein are needed for it to function effectively. To overcome this problem, in the present study, polyarginine-fused p53 was linked with the NH(2)-terminal domain of influenza virus hemagglutinin-2 subunit (HA2), which is a pH-dependent fusogenic peptide that induces the lysis of membranes at low pH levels. The protein was capable of efficiently translocating into the nucleus of glioma cells and induced p21(WAF1) transcriptional activity more effectively than did polyarginine-fused p53 protein. Moreover, low concentrations of the protein significantly inhibited the growth of cancer cells. These results suggest that protein transduction therapy using polyarginine and HA2 may be useful as a method for cancer therapy.
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PMID:The NH2 terminus of influenza virus hemagglutinin-2 subunit peptides enhances the antitumor potency of polyarginine-mediated p53 protein transduction. 1561 Nov 9

The induction of apoptotic cell death is a hallmark of influenza virus infection. Although a variety of cellular and viral proteins have been implicated in this process, to date no conserved cellular pathway has been identified. In this study, we report that the tumor suppressor protein p53 is essential for the induction of cell death in influenza virus-infected cells. In primary human lung cells, influenza virus increased p53 protein levels. This was also noted in the human lung cell line A549, along with the up-regulation of p53-dependent gene transcription. Reduction of p53 activity in A549 cells inhibited influenza virus-induced cell death as measured by trypan blue exclusion and caspase activity. These findings were not cell type specific. Influenza virus-induced cell death was absent in mouse embryo fibroblasts isolated from p53 knockout mice, which was not the case in wild-type mouse embryo fibroblasts, suggesting that p53 is a common cellular pathway leading to influenza virus-induced cell death. Surprisingly, inhibiting p53 activity led to elevated virus replication. Mechanistically, this may be due to the decrease in interferon signaling in p53-deficient cells, suggesting that functional p53 is involved in the interferon response to influenza infection. To our knowledge, these are the first studies demonstrating that p53 is involved in influenza virus-induced cell death and that inhibiting p53 leads to increased viral titers, potentially through modulation of the interferon response.
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PMID:Influenza virus infection increases p53 activity: role of p53 in cell death and viral replication. 1599 74

Since 1999 we have developed two computational mutation approaches to analyze the protein primary structure whose methodology and implications were reviewed in 2002. Our first approach is the calculation of predictable and unpredictable portions of amino-acid pairs in a protein, and the second is the calculation of amino-acid distribution rank in a protein. Both approaches provide quantitative measures to present a protein, which we have used to study a number of proteins with numerous mutations such as p53 proteins. More recently, we focussed our efforts on analyzing the proteins mutating frequently over time such as hemagglutinins of influenza A viruses. In this review we summarise our findings and their implications for hemagglutinin mutations in combination with some newly available data. Our approaches throw light on the true nature of genetic heterogeneity of influenza virus hemagglutinins; that is, the protein variability is highly relevant to its amino-acid construction. Using these approaches, we can monitor new mutations from influenza virus hemagglutinins and may predict their mutations in the future.
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PMID:Mutation trend of hemagglutinin of influenza A virus: a review from a computational mutation viewpoint. 1662 5

Many biomedical problems relate to mutant functional properties across a sequence space of interest, e.g., flu, cancer, and HIV. Detailed knowledge of mutant properties and function improves medical treatment and prevention. A functional census of p53 cancer rescue mutants would aid the search for cancer treatments from p53 mutant rescue. We devised a general methodology for conducting a functional census of a mutation sequence space by choosing informative mutants early. The methodology was tested in a double-blind predictive test on the functional rescue property of 71 novel putative p53 cancer rescue mutants iteratively predicted in sets of three (24 iterations). The first double-blind 15-point moving accuracy was 47 percent and the last was 86 percent; r = 0.01 before an epiphanic 16th iteration and r = 0.92 afterward. Useful mutants were chosen early (overall r = 0.80). Code and data are freely available (http://www.igb.uci.edu/research/research.html, corresponding authors: R.H.L. for computation and R.K.B. for biology).
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PMID:Functional census of mutation sequence spaces: the example of p53 cancer rescue mutants. 1704 98

Redistribution technology is a cell-based assay technology that uses protein translocation as the primary readout for the activity of cellular signaling pathways and other intracellular events. Protein targets are labeled with the green fluorescent protein, and stably transfected cell lines are generated. The assays are read using a high-throughput, optical microscope-based instrument, several of which have become available commercially. Protein translocation assays can be formatted as agonist assays, in which compounds are tested for their ability to promote protein translocation, or as antagonist assays, in which compounds are tested for their ability to inhibit protein translocation caused by a known agonist. Protein translocation assays are high-content, high-throughput assays primarily used for profiling of lead series, primary screening of compound libraries, and as readouts for gene-silencing studies using siRNAs. This chapter describes two novel high-content Redistribution assay technologies: (1) The p53:hdm2 GRIP interaction assay, in which one high-content image feature is used for detection of primary hits, whereas a different feature is used to deselect compounds with unwanted mode of action, and (2) application of siRNAs to Redistribution assays, exemplified by knockdown of Akt isoforms in a FKHR translocation assay reporting on the PI3 kinase signaling pathway.
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PMID:Protein translocation assays: key tools for accessing new biological information with high-throughput microscopy. 1711 Feb 9

In our previous study, we demonstrated that azurin could selectively trigger apoptosis in human osteosarcoma cell line U2OS cells. However, the rate of apoptosis (35.8 +/- 3.2%) is not very high, and azurin is too expensive to obtain readily. To solve these problems, we constructed a eukaryotic expression plasmid containing the azurin gene with an influenza virus haemagglutinin 9 peptide HA epitope tag, and transfected the recombinant plasmid pcDNA3.1(+)/azurin into U2OS cells. RT-PCR and Western blot analysis validated the successful transfection and the expression of the azurin-HA protein. Conspicuous apoptosis of the transfected cells was detected by flow cytometry (FCM) and the DNA ladder test. The apoptosis rate reached 64.3 +/- 13.1%. The transcriptional levels of the Bax and p53 genes increased significantly in U2OS cells transfected with pcDNA3.1(+)/azurin, but the Bcl-2 mRNA level decreased. There was no difference in the levels of Bcl-xl mRNA and Survivin mRNA. We propose that the transfection of the recombinant plasmid pcDNA3.1(+)/azurin can significantly induce apoptosis in U2OS cells. This is closely associated with the up-regulation of the transcriptional level of the Bax and p53 genes, and the down-regulation of that of the Bcl-2 gene.
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PMID:The construction of the eukaryotic expression plasmid pcDNA3.1/azurin and the increased apoptosis of U2OS cells transfected with it. 1741 34


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