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)

Chk1 is a checkpoint kinase and an important regulator of mammalian cell division. Because null mutation of Chk1 in mice is embryonic lethal, we used the Cre-loxP system and the Lck promoter to generate conditional mutant mice in which Chk1 was deleted only in the T lineage. In the absence of Chk1, the transition of CD4(-)CD8(-) double-negative (DN) thymocytes to CD4(+)CD8(+) double-positive (DP) cells was blocked due to an increase in apoptosis at the DN2 and DN3 stages. Strikingly, loss of Chk1 activated the checkpoint kinase Chk2 as well as the tumor suppressor p53 in these thymocytes. However, the developmental defects caused by Chk1 deletion were not rescued by p53 inactivation. Significantly, even though Chk1 deletion is highly lethal in proliferating tissues, we succeeded in using in vivo methods to generate Chk1/Chk2 double-knockout T cells. Analysis of these T cells revealed an interesting interaction between Chk1 and Chk2 functions that partially rescued the apoptosis of the double-mutant cells. Thus, Chk1 is both critical for the survival of proliferating cells and engages in cross-talk with the Chk2 checkpoint kinase pathway. These factors have implications for the targeting of Chk1 as an anticancer therapy.
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PMID:Cross-talk between Chk1 and Chk2 in double-mutant thymocytes. 1736 Apr 34

Protein-protein interactions are crucial to biological functions. Consequently, designing drugs to control protein-protein interactions is receiving increasing attention. Protein structures can associate in different ways. Analysis of the structures of protein-protein complexes using amino acid sequence order-independent multiple structural comparison algorithms, led us to conclude that the amino acids Trp, Met, and Phe are important for protein-protein interactions. Hence, in principle, drug design targeting the Trp/Met/Phe should modulate protein functions effectively. Several clusters of the Trp/Met/Phe residues are involved in the p53 protein-protein interactions. The best example in this regard is the Phe19/Trp23 of p53, which binds to transcriptional factors and to the MDM2 protein. In the HIV related proteins, the Trp/Met/Phe residues have roles in the dimerization of the transcriptase (p51/p66) and in cell-fusion processes, including the gp120-CD4 interaction and the gp41 six-helix bundle formation. Trp/Met/Phe residues are preferred in 'normal' functional protein-protein interactions and they also appear to be exploited in amyloid formation, especially the phenylalanine. Comparison of binding propensity and amyloid formation preference reveals that apart from Lysine, Isoleucine is the least structurally conserved in protein binding sites and has a high propensity in sequences forming amyloids. Thus, this may suggest that nature tends to avoid Ile conservation in protein-protein interaction to avoid amyloid formation. In this regards, Trp/Met/Phe as well as Ile may be targeted to modulate protein-protein interaction.
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PMID:Trp/Met/Phe hot spots in protein-protein interactions: potential targets in drug design. 1750 33

The protein p53 has been shown to be an efficient tumour antigen in both murine and human cancer vaccine studies and cancer vaccines targeting p53 based on major histocompatibility complex (MHC) class I binding p53-derived peptides that induce cytotoxic T lymphocytes (CTLs) without p53-specific CD4(+) T-cell help have been tested by several research groups including ours. To obtain such CD4(+) T-cell help and cover a broader repertoire of MHC haplotypes we have previously attempted to produce recombinant human p53 for vaccination purposes. However, attempts to refold a hexahis-tagged p53 protein in our laboratory were unsuccessful. Here, we show that fusion of an 11-amino-acid region of the human immunodeficiency virus TAT protein transduction domain (PTD) to human p53 increases the solubility of the otherwise insoluble p53 protein and this rTAT-p53 protein can be transduced into human monocyte-derived dendritic cells (DCs). The induction of a p53-specific HLA-A*0201 immune response was tested in HLA-A*0201/K(b) transgenic mice after immunization with rTAT-p53-transduced bone-marrow-derived DCs. In these mice, p53-specific CD4(+) and CD8(+) T-cell proliferation was observed and immunization resulted in the induction of HLA-A*0201-restricted CTLs specific for two human p53-derived HLA-A*0201-binding peptides, p53(65-73) and p53(149-157). Addition of GrpE to generate rTAT-GrpE-p53 led to a further increase in protein solubility and to a small increase in DC maturation but did not increase the observed p53-specific T-cell responses. The use of rTAT-p53 in ongoing clinical protocols should be applicable and offers advantages to current strategies omitting the use of HLA-typed patients.
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PMID:Addition of TAT protein transduction domain and GrpE to human p53 provides soluble fusion proteins that can be transduced into dendritic cells and elicit p53-specific T-cell responses in HLA-A*0201 transgenic mice. 1761 May 3

p63, a homologue of the tumor suppressor p53, is pivotal for epithelial development, because its loss causes severe epithelial dysgenesis, although no information is so far available on the role of p63 in the thymus. We identified the expression of all p63 isoforms in the developing thymus. The p63(-/-) thymi show severe abnormalities in size and cellularity, even though the organ expresses normal levels of keratins 5 and 8, indicating a p63-independent differentiation of thymic epithelial cells (TEC). TEC were sufficiently developed to allow a significant degree of education to produce CD4/CD8 single- and double-positive T cells. To study the selective contribution of transactivation-active p63 (TAp63) and amino-deleted p63 (DeltaNp63) isoforms to the function of the TEC, we genetically complemented p63(-/-) mice by crossing p63(+/-) mice with transgenic mice expressing either TAp63alpha or DeltaNp63alpha under the control of the keratin 5 promoter. Thymic morphology and cellularity were partially restored by complementation with DeltaNp63, but not TAp63, one downstream effector being fibroblast growth factor receptor 2-IIIb (FgfR2-IIIb). Indeed, FgfR2-IIIb is regulated directly by p63, via its interaction with apobec-1-binding protein-1, and its knockout shows thymic defects similar to those observed in p63(-/-) thymi. In addition, expression of Jag2, a component of the Notch signaling pathway known to be required for thymic development, was enhanced by p63 in vivo genetic complementation. Like Jag2(-/-) thymi, p63(-/-) thymi also show reduced gammadelta cell formation. Therefore, p63, and particularly the DeltaNp63 isoform, is essential for thymic development via enhanced expression of FgfR2 and Jag2. The action of DeltaNp63 is not due to a direct regulation of TEC differentiation, but it is compatible with maintenance of their "stemness," the thymic abnormalities resulting from epithelial failure due to loss of stem cells.
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PMID:DeltaNp63 regulates thymic development through enhanced expression of FgfR2 and Jag2. 1762 81

The transcription factor c-Maf is critical for IL-4 production and the development of Th2 cells, which promote humoral immunity and protect against extracellular parasites. Yet, little else is known of c-Maf function in CD4 cells. Here, we identify a novel role for c-Maf in regulating susceptibility to apoptosis. Overexpression of c-Maf results in increased susceptibility of CD4 cells to apoptosis induced by multiple stimuli, including growth factor withdrawal, dexamethasone, irradiation, and TCR engagement. This effect is independent of Fas or p53; however, Bcl-2 expression is reduced in c-Maf Tg CD4 cells. Immunoprecipitation and Western blot analyses demonstrate that c-Maf-c-Myb complex formation is enhanced among T cells from c-Maf Tg mice compared to non-Tg littermates following TCR engagement. Unlike non-Tg T cells, c-Myb binding to the Bcl-2 promoter is not detectable in c-Maf Tg T cells by chromatin immunoprecipitation. In reporter assays, Bcl-2 promoter activity is reduced by c-Maf in a dose-dependent manner. Furthermore, transgene-mediated Bcl-2 expression corrects the apoptosis defect observed among c-Maf Tg CD4 cells. These data suggest that c-Maf can interact with c-Myb to reduce Bcl-2 expression, thereby limiting CD4 cell survival following TCR engagement.
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PMID:c-Maf interacts with c-Myb to down-regulate Bcl-2 expression and increase apoptosis in peripheral CD4 cells. 1782 80

The principal aim of the immune system is to establish a balance between defense against pathogens and avoidance of autoimmune disease. This balance is achieved partly through regulatory T cells (Tregs). CD4(+)CD25(+) Tregs are either naturally occurring or induced by antigens and are characterized by the expression of the X-linked forkhead/winged helix transcription factor, Foxp3. Here we report a previously unrecognized subset of CD4(+)CD25(+) Tregs derived from CD4(+)CD25(-) T cells induced by nitric oxide (NO). The induction of Tregs (NO-Tregs) is independent of cGMP but depends on p53, IL-2, and OX40. NO-Tregs produced IL-4 and IL-10, but not IL-2, IFNgamma, or TGFbeta. The cells were GITR(+), CD27(+), T-bet(low), GATA3(high), and Foxp3(-). NO-Tregs suppressed the proliferation of CD4(+)CD25(-) T cells in vitro and attenuated colitis- and collagen-induced arthritis in vivo in an IL-10-dependent manner. NO-Tregs also were induced in vivo in SCID mice adoptively transferred with CD4(+)CD25(-) T cells in the presence of LPS and IFNgamma, and the induction was completely inhibited by N(G)-monomethyl-L-arginine, a pan NO synthase inhibitor. Therefore, our findings uncovered a previously unrecognized function of NO via the NO-p53-IL-2-OX40-survivin signaling pathway for T cell differentiation and development.
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PMID:Nitric oxide induces CD4+CD25+ Foxp3 regulatory T cells from CD4+CD25 T cells via p53, IL-2, and OX40. 1787 88

Cell proliferation is strictly controlled during differentiation. In T cell development, the cell cycle is normally arrested at the CD4(+)CD8(+) stage, but the mechanism underlying such differentiation-specific exit from the cell cycle has been unclear. Fbxw7 (also known as Fbw7, Sel-10, hCdc4, or hAgo), an F-box protein subunit of an SCF-type ubiquitin ligase complex, induces the degradation of positive regulators of the cell cycle, such as c-Myc, c-Jun, cyclin E, and Notch. FBXW7 is often mutated in a subset of human cancers. We have now achieved conditional inactivation of Fbxw7 in the T cell lineage of mice and found that the cell cycle is not arrested at the CD4(+)CD8(+) stage in the homozygous mutant animals. The mutant mice manifested thymic hyperplasia as a result of c-Myc accumulation and eventually developed thymic lymphoma. In contrast, mature T cells of the mutant mice failed to proliferate in response to mitogenic stimulation and underwent apoptosis in association with accumulation of c-Myc and p53. These latter abnormalities were corrected by deletion of p53. Our results suggest that Fbxw7 regulates the cell cycle in a differentiation-dependent manner, with its loss resulting in c-Myc accumulation that leads to hyperproliferation in immature T cells but to p53-dependent cell-cycle arrest and apoptosis in mature T cells.
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PMID:Conditional inactivation of Fbxw7 impairs cell-cycle exit during T cell differentiation and results in lymphomatogenesis. 1798 2

To identify positive or negative factors for HIV-1 infectivity, clones from the U937 promonocytic cell line that express similar levels of CD4 and CXCR4, but differ in HIV-1 susceptibility, were compared. In contrast to HIV-1 permissive clone 10 (plus), nonpermissive clone 17 (minus) was adherent to coverslips coated with chemokines, was phagocytic, killed bacteria, and expressed human leukocyte elastase (HLE) in a granule-like compartment (HLEG) that was never detected at the cell surface (HLECS). In contrast to the minus clone, the plus clone expressed HLE on the cell surface and was adherent to coverslips coated with the HLECS ligands alpha1proteinase inhibitor (alpha1PI, alpha1antitrypsin) and the HIV-1 fusion peptide. The phosphorylation status of several important signaling proteins was studied at the single cell level. Tumor suppressor p53, NF-kappaB p65, and Akt were constitutively phosphorylated in the plus clone, but not in the minus clone. Surprisingly, both alpha1PI and LPS induced phosphorylation of NF-kappaB p65 Ser-536 in both clones, but induced dephosphorylation of Ser-529 in the plus clone only. HIV-1 permissivity was conferred to the minus clone in a manner that required stimulation by both alpha1PI and LPS and was coincident to NF-kappaB p65 phosphorylation/dephosphorylation events as well as translocation of HLE to the cell surface. Even when stimulated, the minus clone exhibited greater reverse transcriptase activity, but less p24, than the plus clone. Results presented suggest that HIV-1 uptake and production efficiency are influenced by signaling profiles, receptor distribution, and the phagocytic capacity specific to the stage of differentiation of the CD4+ target cell.
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PMID:NF-kappaB signaling, elastase localization, and phagocytosis differ in HIV-1 permissive and nonpermissive U937 clones. 1809 51

The expression of beta-catenin, a potent oncogene, is causally linked to tumorigenesis. Therefore, it was surprising that the transgenic expression of oncogenic beta-catenin in thymocytes resulted in thymic involution instead of lymphomagenesis. In this report, we demonstrate that this is because the expression of oncogenic beta-catenin induces DNA damage, growth arrest, oncogene-induced senescence (OIS), and apoptosis of immature thymocytes. In p53-deficient mice, the expression of oncogenic beta-catenin still results in DNA damage and OIS, but the thymocytes survive and eventually progress to thymic lymphoma. beta-Catenin-induced thymic lymphomas are distinct from lymphomas that arise in p53(-/-) mice. They are CD4(-) CD8(-), while p53-dependent lymphomas are largely CD4(+) CD8(+), and they develop at an earlier age and in the absence of c-Myc expression or Notch1 signaling. Thus, we report that oncogenic beta-catenin-induced, p53-independent growth arrest and OIS and p53-dependent apoptosis protect developing thymocytes from transformation by oncogenic beta-catenin.
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PMID:Beta-catenin expression results in p53-independent DNA damage and oncogene-induced senescence in prelymphomagenic thymocytes in vivo. 1816 Jul 17

CD8+ T cells play a pivotal role in protection against Mycobacterium tuberculosis infection. We identified a novel HLA-A*0201-restricted CD8+ T-cell epitope on a dominant secreted antigen of M. tuberculosis, MPT51, in HLA-A*0201 transgenic HHD mice. HHD mice were immunized with plasmid DNA encoding MPT51 with gene gun bombardment, and gamma interferon (IFN-gamma) production by the immune splenocytes was analyzed. In response to overlapping synthetic peptides covering the mature MPT51 sequence, the splenocytes were stimulated to produce IFN-gamma by only one peptide, p51-70. Three-color flow cytometric analysis of intracellular IFN-gamma and cell surface CD4 and CD8 staining revealed that the MPT51 p51-70 peptide contains an immunodominant CD8+ T-cell epitope. Further analysis using computer algorithms permitted identification of a bona fide T-cell epitope, p53-62. A major histocompatibility complex class I stabilization assay using T2 cells confirmed that this epitope binds to HLA-A*0201. The T cells were capable of lysing MPT51 p53-62 peptide-pulsed T2 cells. In addition, MPT51 p53-62-specific memory CD8+ T cells were found in tuberculin skin test-positive HLA-A*0201+ healthy individuals. Use of this HLA-A*0201-restricted CD8+ T-cell epitope for analysis of the role of MPT51-specific T cells in M. tuberculosis infection and for design of vaccines against tuberculosis is feasible.
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PMID:Identification of an HLA-A*0201-restricted T-cell epitope on the MPT51 protein, a major secreted protein derived from Mycobacterium tuberculosis, by MPT51 overlapping peptide screening. 1821 86


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