Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We recently discovered human p51, a new gene structurally and functionally related to human p53. This gene encodes two major splicing variants, p51A and p51B, which differ in their carboxyl-terminal structure. However, p51A shows strong transactivation potential, while p51B has only weak potential. To clarify the reason for this difference, we made chimeric gene constructs expressing fusion proteins of p53-p51A and p53-p51B, having an N-terminus of p53 and a C-terminus of p51A or p51B, respectively. In a BAX promoter-luciferase assay using p53-deficient SAOS-2 cells, they exhibited up to 30-fold stronger transactivation potential than p53 and p51A themselves, suggesting that the C-terminus of p51B does not simply serve as a repressor. We obtained similar results with p21WAF1 promoter-reporter plasmids. These chimeras will be valuable tools for gene therapy.
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PMID:Human p53-p51 (p53-related) fusion protein: a potent BAX transactivator. 1042 49

Macrophages are a major source of cytokines and proinflammatory radicals such as superoxide. These mediators can be both produced and utilized by macrophages in autocrine-regulatory pathways. Therefore, we studied the potential role of oxygen radical-regulatory mechanisms in reprogramming macrophage apoptosis. Preactivation of RAW 264.7 cells with a nontoxic dose of the redox cycler 2,3-dimethoxy-1,4-naphthoquinone (5 microM) for 15 h attenuated S-nitrosoglutathione (1 mM)-initiated apoptotic cell death and averted accumulation of the tumor suppressor p53, which is indicative for macrophage apoptosis. Preactivation with superoxide promoted cyclooxygenase-2 induction that was NF-kappa B and AP-1 mediated. NF-kappa B activation was confirmed by p50/p65-heterodimer formation, I kappa B-alpha degradation, and stimulation of a NF-kappa B luciferase reporter construct. Furthermore, a NF-kappa B decoy approach abrogated cyclooxygenase-2 (Cox-2) expression as well as inducible protection. The importance of AP-1 for superoxide-mediated Cox-2 expression and cell protection was substantiated by using the extracellular signal-regulated kinase-inhibitor PD98059 and the p38-inhibitor SB203580, which blocked Cox-2 expression. In corroboration, Cox-2 expression was hindered by a dominant-negative c-jun mutant (TAM67). Protection from apoptosis was verified in human macrophages with the notion that superoxide promoted Cox-2 expression, which in turn attenuated nitric oxide-evoked caspase activation. We conclude that the sublethal generation of oxygen radicals reprograms macrophages by NF-kappa B and AP-1 activation. The resulting hyporesponsiveness reveals an attenuated apoptotic program in association with Cox-2 expression.
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PMID:Superoxide attenuates macrophage apoptosis by NF-kappa B and AP-1 activation that promotes cyclooxygenase-2 expression. 1045 32

BAG-1 is an anti-apoptotic protein that interacts with Bcl-2, Bcl-XL, Hsp70/Hsc70, Raf-1 and numerous hormone or growth factor receptors. Recently, BAG-1 has been found to be overexpressed in a variety of human cancer cell lines and some tumors. However, the molecular mechanism of BAG-1 upregulation is still unclear. In this study, we cloned 0.9 kb of human genomic DNA, BGEV, 5' flanking the BAG-1 open reading frame. BGEV subcloned into a promoterless luciferase reporter vector conferred high promoter activity in various human cancer cell lines. Deletion analysis of this sequence localized the region of maximal BAG-1 promoter activity from nucleotide positions -353 to -54, upstream of the first start codon CTG. Sequence analysis of the BAG-1 promoter region showed the absence of a TATA box but identified a CCAAT box, several GC boxes, a CpG island and several transcriptional factor binding sites, which may be important in the regulation of BAG-1 transcription. Most importantly, functional characterization of the BAG-1 promoter in vivo demonstrated that gain-of-function p53 mutants derived from human tumors upregulated the transcription of BAG-1 RNA and the expression of a reporter gene from the BAG-1 promoter. These results indicated that we have isolated the functional constitutive BAG-1 promoter. Furthermore, the data suggested that overexpression of BAG-1 in some tumors may be due to upregulation of the human BAG-1 promoter by mutant p53.
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PMID:Cloning and characterization of the human BAG-1 gene promoter: upregulation by tumor-derived p53 mutants. 1046 99

Codon 273 is one of the hot spots of missense mutation of the p53 tumor suppressor gene found in human cancers. We have previously reported that a mutation at codon 273, p53-273L (Arg --> Leu), suppresses cell growth despite its having no p53-specific transactivation activity. To further elucidate the mechanism of growth suppression caused by p53-273L, we used squamous cell carcinoma cell line HSC3 to isolate subclones containing Zn2+-inducible wild-type (wt) p53, p53-175H, and p53-273L. Northern blot hybridization of the HSC3 cells possessing an inducible function of p53 as well as a luciferase assay for the p21Waf1/Cip1/Sdi1 promoter showed that only wt p53 could induce p21Waf1/Cip1/Sdi1 transcription. Meanwhile, the expression of bax remained unchanged between, before, and after the induction of any analyzed p53s. When wt p53 was induced in HSC3 cells cultured in medium containing 5% fetal bovine serum, cell growth was suppressed through G1 arrest. On the other hand, in medium with 0.1% fetal bovine serum, the growth of HSC3 cells expressing p53-273L was suppressed to a greater degree than that of cells expressing wt p53. Flow cytometric analysis and DNA ladder formation revealed that, unlike wt p53-SN3- and p53-175H-expressing HSC3 cells, p53-273L-expressing cells contained a larger sub-G1 fraction under this culture condition. These findings suggest that p53-273L can induce apoptosis in HSC3 cells without transactivation of p21Waf1/Cip1/Sdi1 and bax.
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PMID:Induction of apoptosis by the p53-273L (Arg --> Leu) mutant in HSC3 cells without transactivation of p21Waf1/Cip1/Sdi1 and bax. 1048 21

Uridine phosphorylase (UPase) plays an important role in the activation of 5-fluorouracil and in the regulation of tissue and plasma concentration of uridine, a potential biochemical modulator of 5-fluorouracil therapy. UPase expression is affected by the c-H-ras oncogene and various cytokines through unknown mechanisms. To understand its expression and regulation, we cloned the murine UPase gene, defined its genomic organization, determined its 5'- and 3'-end flanking sequences, and evaluated the promoter activity. The UPase gene contains nine exons and eight introns, spanning a total of approximately 18.0 kb. Its promoter lacks canonical TATA and CCAAT boxes, although a CAATAAAAA TATA-like box is seen from -41 to -49. Furthermore, IFN regulatory factor 1, c/v-Myb, and p53 binding sites are present in the promoter region, indicating that UPase expression may be directly regulated by cytokines and oncogene products. The 1.2-kb flanking fragment showed promoter activity driving the expression of the luciferase gene in various mammalian cells. A TGGGG repeat sequence is seen in the 3'-end flanking region. This element is considered to be a potential recombination consensus hot spot that may contribute to the encoding of different UPase isoforms present in different tissues, both normal and neoplastic.
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PMID:Genomic structure, chromosomal mapping, and promoter region analysis of murine uridine phosphorylase gene. 1051 14

Exposure of p53 mutated estrogen-receptor-negative MDA-MB231 human breast tumor cells to a pharmacological concentration of estradiol enhances liposome-mediated uptake and expression of SV-40 luciferase. Unexpectedly, the effect of estradiol on SV-40 expression is evident even when estradiol exposure occurs after the initial uptake phase; this suggests that estradiol may influence gene expression by mechanisms other than increasing gene uptake alone, such as altering the intracellular distribution of the gene. We determined that while uptake of SV-40 luciferase is increased only three-fold by estradiol, there is a 30-fold increase in the nuclear/cytoplasmic ratio of the gene. In order to demonstrate that the influence of estradiol on gene uptake and expression is translated into a functional response, the effects of estradiol on the function of an exogenous gene, in this case the apoptotic function of p53, were assessed in the p53 mutated MDA-MB231 breast tumor cell. While liposome-mediated delivery of CMV-p53 alone was ineffective in promoting cell death, incubation with estradiol and the liposomal p53 complex resulted in a two-fold increase in cell killing over that observed in cells transfected with the corresponding mock vector (empty vector for p53). Evidence that cell killing was occurring through apoptosis included apoptotic body formation, cell shrinkage and an increase in fluorescence after terminal transferase end-labeling. The capacity of estradiol to promote apoptosis in MDA-MB231 cells by a p53-liposome complex is likely to be related to the preferential redistribution of the gene from the cytoplasm to the nucleus which could occur during both the uptake and post-uptake phases. Consequently, although direct effects on gene expression, and the stability of message and protein cannot be ruled out, the predominant effect of estradiol in this experimental system appears to be to influence DNA translocation from the cytoplasm to the cell nucleus.
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PMID:Estradiol enhances liposome-mediated uptake, preferential nuclear accumulation and functional expression of exogenous genes in MDA-MB231 breast tumor cells. 1055 77

Bcl-2-associated X protein (Bax) is a proapoptotic protein and is suggested to have an important role in carcinogenesis. To investigate the mechanism of bax gene transcriptional regulation, we isolated and sequenced the genomic DNA fragment of the 5' flanking region of the murine bax gene, and subcloned its promoter region into a luciferase reporter construction. The murine bax promoter is TATA-less, and the sequence is only partially homologous to that of the human bax promoter. Transient transfection into NIH 3T3 cells using unidirectionally deleted promoters and mutants of Sp1 sites revealed that two Sp1 sites were partially responsible for the basal activity. The murine bax promoter was not responsive to exogenous p53, suggesting that the p53-responsive element may not exist in the region used in our current experiments.
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PMID:Molecular cloning and functional analysis of the murine bax gene promoter. 1057 Sep 68

The Sp1 transcription factor plays an important role in mediating the p53-independent activation of the p21(WAF1) (WAF1) promoter by phorbol 12-myristate13-acetate (PMA) in hematopoietic cells. Using GAL4-Sp1 fusion proteins and a luciferase reporter, PMA is shown to activate the transcriptional activity of Sp1 independent of the WAF1 promoter. This activation does not require the Ser/Thr-rich region of Sp1 and can be mediated by 41 amino acids (152-193) of Sp1 that are important for the interaction with human TAF130. Because transforming growth factor-beta enhances WAF1 promoter activity through both Sp1 and Smad proteins, the role of Smads in PMA transcriptional activation was examined. PMA addition to hematopoietic cells was found to activate a GAL4/Smad-dependent promoter and the transforming growth factor-beta-responsive promoter, p3TP-lux. Immunofluorescence data demonstrate that PMA addition to hematopoietic cells induces the translocation of Smad3 to the nucleus. However, Smad3 does not stimulate the WAF1 promoter, but rather slightly inhibits the PMA-mediated induction of transcription from this upstream region. Additionally, transfection of Smad3 did not enhance the activation of GAL4/Sp1 by PMA. These results demonstrate that, while PMA can activate Smad-mediated transcription, Smad proteins do not appear to play a major role in the PMA induction of the WAF1 promoter.
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PMID:The role of the Smad3 protein in phorbol ester-induced promoter expression. 1060 Dec 54

The candidate tumor suppressor p73 has a high sequence homology with p53 within the NH2-terminal transactivation domain, the sequence-specific DNA-binding region, and the oligomerization domain. However, p73alpha, which is most abundantly expressed in many tissues and cells among the alternatively spliced forms of p73, has an additional long COOH-terminal tail that might distinguish the function of p53 and p73alpha or other p73 splicing variants. To examine the functional role of the p73alpha COOH-terminal region, we generated a series of p73alpha truncation mutants including p73alpha(1-247) (retaining only a transactivation domain), p73alpha(1-427) (lacking the most COOH-terminal region including a SAM domain), and p73alpha(1-548) (deleting an extreme COOH-terminal region except a SAM domain). When transfected into COS cells, all of p73alpha, p73alpha(1-548), and p73alpha(1-427) localized in the cellular nucleus, whereas p73alpha(1-247) localized in both nucleus and cytoplasm. Intriguingly, when compared with p73alpha, both p73alpha(1-427) and p73alpha(1-548) showed a significant stimulation of the transcription of luciferase reporters harboring three p53-responsive promoters (p21(Waf1), Mdm2, and Bax) in p53-deficient SAOS-2 cells. Gel retardation assays showed that DNA-binding activity of p73alpha(1-427) and p73alpha(1-548) was increased as compared with that of the full-length p73alpha. However, the colony formation assays using SAOS-2 cells demonstrated that, contrary to p73alpha, transfection of p73alpha(1-427) or p73alpha(1-548) resulted in no significant reduction of the number of colonies. These suggest that the distal COOH-terminal region of p73alpha is a cis- or trans-acting regulatory domain and regulates its functions diversely.
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PMID:Deletion of the COOH-terminal region of p73alpha enhances both its transactivation function and DNA-binding activity but inhibits induction of apoptosis in mammalian cells. 1060 32

The transcriptional activity of the p53 tumor suppressor protein is crucial for the regulation of cell growth, apoptosis and tumor progression. The first identified p53 relative, p73, was reported to be monoallelically expressed in normal tissues. In some tumors, loss of heterozygosity was associated with overexpression of the silent allele. Human p73alpha was transfected into the wild-type p53-expressing human ovarian carcinoma cell line A2780. Unlike human osteosarcoma Saos-2 cells, A2780 cells could tolerate hyperexpression of p73alpha and clones over-expressing p73alpha could be isolated. No p53-p73 protein-protein interaction was found in these clones in co-immunoprecipitation experiments. Endogenous p53 transcriptional activity was markedly decreased both when p73 was integrated into the genome and in transient transfections using a reporter plasmid containing the p53 binding site linked to luciferase. Transient transfection of p73 with a mutation in the DNA-binding domain did not show these effects. The competition for p53 DNA binding by p73alpha was also evident in gel shift experiments. The results suggest that p73 can modulate p53 function by inhibiting its DNA binding and that overexpression of p73 in tumors might be a novel mechanism of inactivation of p53.
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PMID:p73 competes with p53 and attenuates its response in a human ovarian cancer cell line. 1060 50


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