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Sample records for functional p53 binding

  1. HCV NS5A abrogates p53 protein function by interfering with p53-DNA binding

    Institute of Scientific and Technical Information of China (English)

    Guo-Zhong Gong; Yong-Fang Jiang; Yan He; Li-Ying Lai; Ying-Hua Zhu; Xian-Shi Su

    2004-01-01

    AIM: To evaluate the inhibition effect of HCV NS5A on p53 transactivation on p21 promoter and explore its possible mechanism for influencing p53 function.METHODS: p53 function of transactivation on p21 promoter was studied with a luciferase reporter system in which the luciferase gene is driven by p21 promoter, and the p53-DNA binding ability was observed with the use of electrophoretic mobility-shift assay (EMSA). Lipofectin mediated p53 or HCV NS5A expression vectors were used to transfect hepatoma cell lines to observe whether HCV NS5A could abrogate the binding ability of p53 to its specific DNA sequence and p53 transactivation on p21 promoter.Western blot experiment was used for detection of HCV NS5A and p53 proteins expression.RESULTS: Relative luciferase activity driven by p21 promoter increased significantly in the presence of endogenous p53 protein. Compared to the control group, exogenous p53 protein also stimulated p21 promoter driven luciferase gene expression in a dose-dependent way. HCV NS5A protein gradually inhibited both endogenous and exogenous p53 transactivation on p21 promoter with increase of the dose of HCV NS5A expression plasmid. By the experiment of EMSA, we could find p53 binding to its specific DNA sequence and, when co-transfected with increased dose of HCV NS5A expression vector, the p53 binding affinity to its DNA gradually decreased and finally disappeared. Between the Huh 7 cells transfected with p53 expression vector alone or co-transfected with HCV NS5A expression vector, there was no difference in the p53 protein expression.CONCLUSION: HCV NS5A inhibits p53 transactivation on p21 promoter through abrogating p53 binding affinity to its specific DNA sequence. It does not affect p53 protein expression.

  2. NAD+ Modulates p53 DNA Binding Specificity and Function

    Science.gov (United States)

    McLure, Kevin G.; Takagi, Masatoshi; Kastan, Michael B.

    2004-01-01

    DNA damage induces p53 DNA binding activity, which affects tumorigenesis, tumor responses to therapies, and the toxicities of cancer therapies (B. Vogelstein, D. Lane, and A. J. Levine, Nature 408:307-310, 2000; K. H. Vousden and X. Lu, Nat. Rev. Cancer 2:594-604, 2002). Both transcriptional and transcription-independent activities of p53 contribute to DNA damage-induced cell cycle arrest, apoptosis, and aneuploidy prevention (M. B. Kastan et al., Cell 71:587-597, 1992; K. H. Vousden and X. Lu, Nat. Rev. Cancer 2:594-604, 2002). Small-molecule manipulation of p53 DNA binding activity has been an elusive goal, but here we show that NAD+ binds to p53 tetramers, induces a conformational change, and modulates p53 DNA binding specificity in vitro. Niacinamide (vitamin B3) increases the rate of intracellular NAD+ synthesis, alters radiation-induced p53 DNA binding specificity, and modulates activation of a subset of p53 transcriptional targets. These effects are likely due to a direct effect of NAD+ on p53, as a molecule structurally related to part of NAD+, TDP, also inhibits p53 DNA binding, and the TDP precursor, thiamine (vitamin B1), inhibits intracellular p53 activity. Niacinamide and thiamine affect two p53-regulated cellular responses to ionizing radiation: rereplication and apoptosis. Thus, niacinamide and thiamine form a novel basis for the development of small molecules that affect p53 function in vivo, and these results suggest that changes in cellular energy metabolism may regulate p53. PMID:15509798

  3. SCH529074, a small molecule activator of mutant p53, which binds p53 DNA binding domain (DBD), restores growth-suppressive function to mutant p53 and interrupts HDM2-mediated ubiquitination of wild type p53.

    Science.gov (United States)

    Demma, Mark; Maxwell, Eugene; Ramos, Robert; Liang, Lianzhu; Li, Cheng; Hesk, David; Rossman, Randall; Mallams, Alan; Doll, Ronald; Liu, Ming; Seidel-Dugan, Cynthia; Bishop, W Robert; Dasmahapatra, Bimalendu

    2010-04-02

    Abrogation of p53 function occurs in almost all human cancers, with more than 50% of cancers harboring inactivating mutations in p53 itself. Mutation of p53 is indicative of highly aggressive cancers and poor prognosis. The vast majority of mutations in p53 occur in its core DNA binding domain (DBD) and result in inactivation of p53 by reducing its thermodynamic stability at physiological temperature. Here, we report a small molecule, SCH529074, that binds specifically to the p53 DBD in a saturable manner with an affinity of 1-2 microm. Binding restores wild type function to many oncogenic mutant forms of p53. This small molecule reactivates mutant p53 by acting as a chaperone, in a manner similar to that previously reported for the peptide CDB3. Binding of SCH529074 to the p53 DBD is specifically displaced by an oligonucleotide with a sequence derived from the p53-response element. In addition to reactivating mutant p53, SCH529074 binding inhibits ubiquitination of p53 by HDM2. We have also developed a novel variant of p53 by changing a single amino acid in the core domain of p53 (N268R), which abolishes binding of SCH529074. This amino acid change also inhibits HDM2-mediated ubiquitination of p53. Our novel findings indicate that through its interaction with p53 DBD, SCH529074 restores DNA binding activity to mutant p53 and inhibits HDM2-mediated ubiquitination.

  4. Blocking of p53-Snail Binding, Promoted by Oncogenic K-Ras, Recovers p53 Expression and function

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    Sun-Hye Lee

    2009-01-01

    Full Text Available Differentially from other kinds of Ras, oncogenic K-Ras, which is mutated approximately 30% of human cancer, does not induce apoptosis and senescence. Here, we provide the evidence that oncogenic K-Ras abrogates p53 function and expression through induction of Ataxia telangiectasia-mutated and Rad3-related mediated Snail stabilization. Snail directly binds to DNA binding domain of p53 and diminishes the tumor-suppressive function of p53. Thus, elimination of Snail through si-RNA can induce p53 in K-Ras-mutated cells, whereas Snail and mutant K-Ras can suppress p53 in regardless of K-Ras status. Chemicals, isolated from inhibitor screening of p53-Snail binding, can block the Snail-mediated p53 suppression and enhance the expression of p53 as well as the transcriptional activity of p53 in an oncogenic K-Ras-dependent manner. Among the chemicals, two are very similar in structure. These results can answer why K-Ras can coexist with wild type p53 and propose the Snail-p53 binding as the new therapeutic target for K-Ras-mutated cancers including pancreatic, lung, and colon cancers.

  5. Aurora B interacts with NIR-p53, leading to p53 phosphorylation in its DNA-binding domain and subsequent functional suppression.

    Science.gov (United States)

    Wu, Liming; Ma, Chi A; Zhao, Yongge; Jain, Ashish

    2011-01-21

    NIR (novel INHAT repressor) is a transcriptional co-repressor with inhibitor of histone acetyltransferase (INHAT) activity and has previously been shown to physically interact with and suppress p53 transcriptional activity and function. However, the mechanism by which NIR suppresses p53 is not completely understood. Using a proteomic approach, we have identified the Aurora kinase B as a novel binding partner of NIR. We show that Aurora B, NIR and p53 exist in a protein complex in which Aurora B binds to NIR, thus also indirectly associates with p53. Functionally, overexpression of Aurora B or NIR suppresses p53 transcriptional activity, and depletion of Aurora B or NIR causes p53-dependent apoptosis and cell growth arrest, due to the up-regulation of p21 and Bax. We then demonstrate that Aurora B phosphorylates multiple sites in the p53 DNA-binding domain in vitro, and this phosphorylation probably also occurs in cells. Importantly, the Aurora B-mediated phosphorylation on Ser(269) or Thr(284) significantly compromises p53 transcriptional activity. Taken together, these results provide novel insight into NIR-mediated p53 suppression and also suggest an additional way for p53 regulation.

  6. Ribosomal protein S7 as a novel modulator of p53-MDM2 interaction: binding to MDM2, stabilization of p53 protein, and activation of p53 function.

    Science.gov (United States)

    Chen, D; Zhang, Z; Li, M; Wang, W; Li, Y; Rayburn, E R; Hill, D L; Wang, H; Zhang, R

    2007-08-01

    As a major negative regulator of p53, the MDM2 oncogene plays an important role in carcinogenesis and tumor progression. MDM2 promotes p53 proteasomal degradation and negatively regulates p53 function. The mechanisms by which the MDM2-p53 interaction is regulated are not fully understood, although several MDM2-interacting molecules have recently been identified. To search for novel MDM2-binding partners, we screened a human prostate cDNA library by the yeast two-hybrid assay using full-length MDM2 protein as the bait. Among the candidate proteins, ribosomal protein S7 was identified and confirmed as a novel MDM2-interacting protein. Herein, we demonstrate that S7 binds to MDM2, in vitro and in vivo, and that the interaction between MDM2 and S7 leads to modulation of MDM2-p53 binding by forming a ternary complex among MDM2, p53 and S7. This results in the stabilization of p53 protein through abrogation of MDM2-mediated p53 ubiquitination. Consequently, S7 overexpression increases p53 transactivational activities, induces apoptosis, and inhibits cell proliferation. The identification of S7 as a novel MDM2-interacting partner contributes to elucidation of the complex regulation of the MDM2-p53 interaction and has implications in cancer prevention and therapy.

  7. Probing the functional impact of sequence variation on p53-DNA interactions using a novel microsphere assay for protein-DNA binding with human cell extracts.

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    Maher A Noureddine

    2009-05-01

    Full Text Available The p53 tumor suppressor regulates its target genes through sequence-specific binding to DNA response elements (REs. Although numerous p53 REs are established, the thousands more identified by bioinformatics are not easily subjected to comparative functional evaluation. To examine the relationship between RE sequence variation -- including polymorphisms -- and p53 binding, we have developed a multiplex format microsphere assay of protein-DNA binding (MAPD for p53 in nuclear extracts. Using MAPD we measured sequence-specific p53 binding of doxorubicin-activated or transiently expressed p53 to REs from established p53 target genes and p53 consensus REs. To assess the sensitivity and scalability of the assay, we tested 16 variants of the p21 target sequence and a 62-multiplex set of single nucleotide (nt variants of the p53 consensus sequence and found many changes in p53 binding that are not captured by current computational binding models. A group of eight single nucleotide polymorphisms (SNPs was examined and binding profiles closely matched transactivation capability tested in luciferase constructs. The in vitro binding characteristics of p53 in nuclear extracts recapitulated the cellular in vivo transactivation capabilities for eight well-established human REs measured by luciferase assay. Using a set of 26 bona fide REs, we observed distinct binding patterns characteristic of transiently expressed wild type and mutant p53s. This microsphere assay system utilizes biologically meaningful cell extracts in a multiplexed, quantitative, in vitro format that provides a powerful experimental tool for elucidating the functional impact of sequence polymorphism and protein variation on protein/DNA binding in transcriptional networks.

  8. Selective toxicity of MKT-077 to cancer cells is mediated by its binding to the hsp70 family protein mot-2 and reactivation of p53 function.

    Science.gov (United States)

    Wadhwa, R; Sugihara, T; Yoshida, A; Nomura, H; Reddel, R R; Simpson, R; Maruta, H; Kaul, S C

    2000-12-15

    MKT-077, a cationic rhodacyanine dye analogue has been under preclinical cancer therapeutical trials because of its selective toxicity to cancer cells. Its cellular targets and mechanism of action remain poorly understood. Here we report that MKT-077 binds to an hsp70 family member, mortalin (mot-2), and abrogates its interactions with the tumor suppressor protein, p53. In cancer cells, but not in normal cells, MKT-077 induced release of wild-type p53 from cytoplasmically sequestered p53-mot-2 complexes and rescued its transcriptional activation function. Thus, MKT-077 may be particularly useful for therapy of cancers with wild-type p53.

  9. Dominant effects of Δ40p53 on p53 function and melanoma cell fate

    OpenAIRE

    2013-01-01

    The p53 gene encodes 12 distinct isoforms some of which can alter p53 activity in the absence of genomic alteration. Endogenous p53 isoforms have been identified in cancers; however, the function of these isoforms remains unclear. In melanoma, the frequency of p53 mutations is relatively low compared to other cancers suggesting that these isoforms may play a larger role in regulating p53 activity. We hypothesized that p53 function and therefore cell fate might be altered by the presence of Δ4...

  10. Human Immunodeficiency Virus Type 1 Nef Binds to Tumor Suppressor p53 and Protects Cells against p53-Mediated Apoptosis

    OpenAIRE

    2002-01-01

    The nef gene product of human immunodeficiency virus type 1 (HIV-1) is important for the induction of AIDS, and key to its function is its ability to manipulate T-cell function by targeting cellular signal transduction proteins. We reported that Nef coprecipitates a multiprotein complex from cells which contains tumor suppressor protein p53. We now show that Nef interacts directly with p53. Binding assays showed that an N-terminal, 57-residue fragment of Nef (Nef 1-57) contains the p53-bindin...

  11. An N-terminal Region of Mot-2 Binds to p53 In Vitro

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    Sunil C. Kaul

    2001-01-01

    Full Text Available The mouse mot-2 protein was earlier shown to bind to the tumor suppressor protein, p53. The mot-2 binding site of p53 was mapped to C-terminal amino acid residues 312–352, which includes the cytoplasmic sequestration domain. In the present study, we have found that both mot-1 and mot-2 bind to p53 in vitro. By using His-tagged deletion mutant proteins, the p53-binding domain of mot-2 was mapped to its Nterminal amino acid residues 253–282, which are identical in mot-1 and mot-2 proteins. Some peptides containing the p53-binding region of mot-2 were able to compete with the full-length protein for p53 binding. The data provided rationale for in vitro binding of mot-1 and mot-2 proteins to p53 and supported the conclusion that inability of mot-1 protein to bind p53 in vivo depends on secondary structure or its binding to other cellular factors. Most interestingly, the p53-binding region of mot-2 was common to its MKT-077, a cationic dye that exhibits antitumor activity, binding region. Therefore it is most likely that MKT-077-induced nuclear translocation and restoration of wild-type p53 function in transformed cells takes place by a competitional mechanism.

  12. Emerging Non-Canonical Functions and Regulation by p53: p53 and Stemness.

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    Olivos, David J; Mayo, Lindsey D

    2016-11-26

    Since its discovery nearly 40 years ago, p53 has ascended to the forefront of investigated genes and proteins across diverse research disciplines and is recognized most exclusively for its role in cancer as a tumor suppressor. Levine and Oren (2009) reviewed the evolution of p53 detailing the significant discoveries of each decade since its first report in 1979. In this review, we will highlight the emerging non-canonical functions and regulation of p53 in stem cells. We will focus on general themes shared among p53's functions in non-malignant stem cells and cancer stem-like cells (CSCs) and the influence of p53 on the microenvironment and CSC niche. We will also examine p53 gain of function (GOF) roles in stemness. Mutant p53 (mutp53) GOFs that lead to survival, drug resistance and colonization are reviewed in the context of the acquisition of advantageous transformation processes, such as differentiation and dedifferentiation, epithelial-to-mesenchymal transition (EMT) and stem cell senescence and quiescence. Finally, we will conclude with therapeutic strategies that restore wild-type p53 (wtp53) function in cancer and CSCs, including RING finger E3 ligases and CSC maintenance. The mechanisms by which wtp53 and mutp53 influence stemness in non-malignant stem cells and CSCs or tumor-initiating cells (TICs) are poorly understood thus far. Further elucidation of p53's effects on stemness could lead to novel therapeutic strategies in cancer research.

  13. Spodoptera frugiperda FKBP-46 is a consensus p53 motif binding protein.

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    Mohareer, Krishnaveni; Sahdev, Sudhir; Hasnain, Seyed E

    2013-04-01

    p53 protein, the central molecule of the apoptosis pathway, is mutated in 50% of the human cancers. Of late, p53 homologues have been identified from different invertebrates including Drosophila melanogaster, Caenorhabditis elegans, Squid, and Clams. We report the identification of a p53-like protein in Spodoptera frugiperda (Sf9) insect cells, which is activated during oxidative stress, caused by exposure to UV-B or H(2) O(2) , and binds to p53 consensus DNA binding motifs as well as other p53 cognate motifs. Sf9 p53 motif-binding protein is similar to murine and Drosophila p53 in terms of molecular size, which is around 50-60 kDa, as evident from UV cross-linking, and displays DNA binding characteristics similar to both insect and vertebrate p53 as seen from electrophoretic mobility shift assays. The N-terminal sequencing of the purified Sf9 p53 motif-binding protein reveals extensive homology to the pro-apoptotic FK-506 binding protein (FKBP-46), earlier identified in Sf9 cells as a factor which interacts with murine casein kinase. FKBP, an evolutionarily conserved protein of mammalian origin functions as a pro-apoptotic factor. Identification of FKBP-46 as a novel p53 motif-binding protein in insect cells adds a new facet to our understanding of the mechanisms of apoptosis under oxidative stress in the absence of a typical p53 homologue.

  14. p53 Cellular Localization and Function in Neuroblastoma

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    Tweddle, Deborah A.; Malcolm, Archie J.; Cole, Michael; Pearson, Andrew D.J.; Lunec, John

    2001-01-01

    This study investigated the hypothesis that p53 accumulation in neuroblastoma, in the absence of mutation, is associated with functional inactivation, which interferes with downstream mediators of p53 function. To test this hypothesis, p53 expression, location, and functional integrity was examined in neuroblastoma by irradiating 6 neuroblastoma cell lines and studying the effects on p53 transcriptional function, cell cycle arrest, and induction of apoptosis, together with the transcriptional function of p53 after irradiation in three ex vivo primary, untreated neuroblastoma tumors. p53 sequencing showed five neuroblastoma cell lines, two of which were MYCN-amplified, and that all of the tumors were wild-type for p53. p53 was found to be predominantly nuclear before and after irradiation and to up-regulate the p53 responsive genes WAF1 and MDM2 in wild-type p53 cell lines and a poorly-differentiated neuroblastoma, but not a differentiating neuroblastoma or the ganglioneuroblastoma part of a nodular ganglioneuroblastoma in short term culture. This suggests intact p53 transcriptional activity in proliferating neuroblastoma. Irradiation of wild-type p53 neuroblastoma cell lines led to G1 cell cycle arrest in cell lines without MYCN amplification, but not in those with MYCN amplification, despite induction of WAF1. This suggests MYCN amplification may alter downstream mediators of p53 function in neuroblastoma. PMID:11395384

  15. Modulation of p53's transcriptional function by small molecules

    OpenAIRE

    2011-01-01

    p53 tumour suppressor is a transcriptional factor which induces apoptosis or growth arrest in response to stress thus eliminating damaged cells. p53 function is frequently abrogated in tumours either via inactivation mutations in the TP53 gene or by elevated activity of p53 negative regulators HDM2 and HDMX. Therefore application of small molecules that reactivate p53 function is a promising strategy for anti-cancer therapy. In addition, small molecules can serve as valuable research tool to ...

  16. Iron Metabolism Regulates p53 Signaling through Direct Heme-p53 Interaction and Modulation of p53 Localization, Stability, and Function

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    Jia Shen

    2014-04-01

    Full Text Available Iron excess is closely associated with tumorigenesis in multiple types of human cancers, with underlying mechanisms yet unclear. Recently, iron deprivation has emerged as a major strategy for chemotherapy, but it exerts tumor suppression only on select human malignancies. Here, we report that the tumor suppressor protein p53 is downregulated during iron excess. Strikingly, the iron polyporphyrin heme binds to p53 protein, interferes with p53-DNA interactions, and triggers both nuclear export and cytosolic degradation of p53. Moreover, in a tumorigenicity assay, iron deprivation suppressed wild-type p53-dependent tumor growth, suggesting that upregulation of wild-type p53 signaling underlies the selective efficacy of iron deprivation. Our findings thus identify a direct link between iron/heme homeostasis and the regulation of p53 signaling, which not only provides mechanistic insights into iron-excess-associated tumorigenesis but may also help predict and improve outcomes in iron-deprivation-based chemotherapy.

  17. Interaction of hepatitis B virus with tumor suppressor gene p53: its significance and biological function

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The mechanism of the interaction of hepatitis B virus (HBV) with tumor suppressor p53 and its role in the hepatocarcinogenesis have been studied by PCR-directed sequencing, gel shift assays and in situ ultraviolet cross-linking assay. The biological function of the interaction of HBV with p53 gene was investigated by co-transfection of chloramphenicol acetyltransferase (CAT) reporter gene, p53 and HBV DNA, and quantitative PCR. Among the 16 primary hepatocellular carcinoma (PHC) samples, 13 were HBV-DNA positive,10 HBxAg positive and 9 p53 protein positive. The p53 gene point mutation was found in 5 samples, one of which had a G to T substitution located at codon 249. After analyzing the HBV genome by a computer program, a p53 response element binding sequence was found in HBV genome at upstream of enhancer I, from 1047 to 1059 nucleotides. This sequence could specifically bind to p53 protein, increase p53 protein accumulation in the PHC cells and stimulate the transactivating activity of p53 and HBV replication .The results also revealed that HBxAg could combine with p53 protein to form a complex in the cells and enhance CAT expression. Immunocytochemical staining showed that p53 protein complex was located in the cytoplasm and the process of p53 entry to nuclei was, in part, blocked. From our results, we conclude that the mutation of p53 gene at codon 249 is infrequent in HBV-associated PHC, the DNA-protein binding between HBV and p53, and the protein-protein binding between HBxAg and p53 might lead to the reduction or inactivation of p53 protein, which in turn resulting in HBV-associated hepatocarcinogenesis.

  18. Iron Metabolism Regulates p53 Signaling through Direct Heme-p53 Interaction and Modulation of p53 Localization, Stability, and Function

    OpenAIRE

    2014-01-01

    SUMMARY Iron excess is closely associated with tumorigenesis in multiple types of human cancers, with underlying mechanisms yet unclear. Recently, iron deprivation has emerged as a major strategy for chemotherapy, but it exerts tumor suppression only on select human malignancies. Here, we report that the tumor suppressor protein p53 is downregulated during iron excess. Strikingly, the iron polyporphyrin heme binds to p53 protein, interferes with p53-DNA interactions, and triggers both nuclear...

  19. Divergent evolution of human p53 binding sites: cell cycle versus apoptosis.

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    Monica M Horvath

    2007-07-01

    Full Text Available The p53 tumor suppressor is a sequence-specific pleiotropic transcription factor that coordinates cellular responses to DNA damage and stress, initiating cell-cycle arrest or triggering apoptosis. Although the human p53 binding site sequence (or response element [RE] is well characterized, some genes have consensus-poor REs that are nevertheless both necessary and sufficient for transactivation by p53. Identification of new functional gene regulatory elements under these conditions is problematic, and evolutionary conservation is often employed. We evaluated the comparative genomics approach for assessing evolutionary conservation of putative binding sites by examining conservation of 83 experimentally validated human p53 REs against mouse, rat, rabbit, and dog genomes and detected pronounced conservation differences among p53 REs and p53-regulated pathways. Bona fide NRF2 (nuclear factor [erythroid-derived 2]-like 2 nuclear factor and NFkappaB (nuclear factor of kappa light chain gene enhancer in B cells binding sites, which direct oxidative stress and innate immunity responses, were used as controls, and both exhibited high interspecific conservation. Surprisingly, the average p53 RE was not significantly more conserved than background genomic sequence, and p53 REs in apoptosis genes as a group showed very little conservation. The common bioinformatics practice of filtering RE predictions by 80% rodent sequence identity would not only give a false positive rate of approximately 19%, but miss up to 57% of true p53 REs. Examination of interspecific DNA base substitutions as a function of position in the p53 consensus sequence reveals an unexpected excess of diversity in apoptosis-regulating REs versus cell-cycle controlling REs (rodent comparisons: p < 1.0 e-12. While some p53 REs show relatively high levels of conservation, REs in many genes such as BAX, FAS, PCNA, CASP6, SIVA1, and P53AIP1 show little if any homology to rodent sequences. This

  20. Impact of Alu repeats on the evolution of human p53 binding sites

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    Sirotin Michael V

    2011-01-01

    Full Text Available Abstract Background The p53 tumor suppressor protein is involved in a complicated regulatory network, mediating expression of ~1000 human genes. Recent studies have shown that many p53 in vivo binding sites (BSs reside in transposable repeats. The relationship between these BSs and functional p53 response elements (REs remains unknown, however. We sought to understand whether the p53 REs also reside in transposable elements and particularly in the most-abundant Alu repeats. Results We have analyzed ~160 functional p53 REs identified so far and found that 24 of them occur in repeats. More than half of these repeat-associated REs reside in Alu elements. In addition, using a position weight matrix approach, we found ~400,000 potential p53 BSs in Alu elements genome-wide. Importantly, these putative BSs are located in the same regions of Alu repeats as the functional p53 REs - namely, in the vicinity of Boxes A/A' and B of the internal RNA polymerase III promoter. Earlier nucleosome-mapping experiments showed that the Boxes A/A' and B have a different chromatin environment, which is critical for the binding of p53 to DNA. Here, we compare the Alu-residing p53 sites with the corresponding Alu consensus sequences and conclude that the p53 sites likely evolved through two different mechanisms - the sites overlapping with the Boxes A/A' were generated by CG → TG mutations; the other sites apparently pre-existed in the progenitors of several Alu subfamilies, such as AluJo and AluSq. The binding affinity of p53 to the Alu-residing sites generally correlates with the age of Alu subfamilies, so that the strongest sites are embedded in the 'relatively young' Alu repeats. Conclusions The primate-specific Alu repeats play an important role in shaping the p53 regulatory network in the context of chromatin. One of the selective factors responsible for the frequent occurrence of Alu repeats in introns may be related to the p53-mediated regulation of Alu

  1. Conservation of DNA-binding specificity and oligomerisation properties within the p53 family

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    Joerger Andreas C

    2009-12-01

    Full Text Available Abstract Background Transcription factors activate their target genes by binding to specific response elements. Many transcription factor families evolved from a common ancestor by gene duplication and subsequent divergent evolution. Members of the p53 family, which play key roles in cell-cycle control and development, share conserved DNA binding and oligomerisation domains but exhibit distinct functions. In this study, the molecular basis of the functional divergence of related transcription factors was investigated. Results We characterised the DNA-binding specificity and oligomerisation properties of human p53, p63 and p73, as well as p53 from other organisms using novel biophysical approaches. All p53 family members bound DNA cooperatively as tetramers with high affinity. Despite structural differences in the oligomerisation domain, the dissociation constants of the tetramers was in the low nanomolar range for all family members, indicating that the strength of tetramerisation was evolutionarily conserved. However, small differences in the oligomerisation properties were observed, which may play a regulatory role. Intriguingly, the DNA-binding specificity of p53 family members was highly conserved even for evolutionarily distant species. Additionally, DNA recognition was only weakly affected by CpG methylation. Prediction of p53/p63/p73 binding sites in the genome showed almost complete overlap between the different homologs. Conclusion Diversity of biological function of p53 family members is not reflected in differences in sequence-specific DNA binding. Hence, additional specificity factors must exist, which allowed the acquisition of novel functions during evolution while preserving original roles.

  2. p53 DNA Binding Cooperativity Is Essential for Apoptosis and Tumor Suppression In Vivo

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    Oleg Timofeev

    2013-05-01

    Full Text Available Four molecules of the tumor suppressor p53 assemble to cooperatively bind proapoptotic target genes. The structural basis for cooperativity consists of interactions between adjacent DNA binding domains. Mutations at the interaction interface that compromise cooperativity were identified in cancer patients, suggesting a requirement of cooperativity for tumor suppression. We report on an analysis of cooperativity mutant p53E177R mice. Apoptotic functions of p53 triggered by DNA damage and oncogenes were abolished in these mice, whereas functions in cell-cycle control, senescence, metabolism, and antioxidant defense were retained and were sufficient to suppress development of spontaneous T cell lymphoma. Cooperativity mutant mice are nevertheless highly cancer prone and susceptible to different oncogene-induced tumors. Our data underscore the relevance of DNA binding cooperativity for p53-dependent apoptosis and tumor suppression and highlight cooperativity mutations as a class of p53 mutations that result in a selective loss of apoptotic functions due to an altered quaternary structure of the p53 tetramer.

  3. Ensemble-based computational approach discriminates functional activity of p53 cancer and rescue mutants.

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    Özlem Demir

    2011-10-01

    Full Text Available The tumor suppressor protein p53 can lose its function upon single-point missense mutations in the core DNA-binding domain ("cancer mutants". Activity can be restored by second-site suppressor mutations ("rescue mutants". This paper relates the functional activity of p53 cancer and rescue mutants to their overall molecular dynamics (MD, without focusing on local structural details. A novel global measure of protein flexibility for the p53 core DNA-binding domain, the number of clusters at a certain RMSD cutoff, was computed by clustering over 0.7 µs of explicitly solvated all-atom MD simulations. For wild-type p53 and a sample of p53 cancer or rescue mutants, the number of clusters was a good predictor of in vivo p53 functional activity in cell-based assays. This number-of-clusters (NOC metric was strongly correlated (r(2 = 0.77 with reported values of experimentally measured ΔΔG protein thermodynamic stability. Interpreting the number of clusters as a measure of protein flexibility: (i p53 cancer mutants were more flexible than wild-type protein, (ii second-site rescue mutations decreased the flexibility of cancer mutants, and (iii negative controls of non-rescue second-site mutants did not. This new method reflects the overall stability of the p53 core domain and can discriminate which second-site mutations restore activity to p53 cancer mutants.

  4. Regulation of transcription functions of the p53 tumor suppressor by the mdm-2 oncogene.

    OpenAIRE

    1995-01-01

    BACKGROUND: Mdm-2, a zinc finger protein, negatively regulates the p53 tumor suppressor gene product by binding to it and preventing transcriptional activation (16). MATERIALS AND METHODS: Assays for p53 mediated transcription, repression and activation by mutant and wild-type p53 proteins were used to measure the ability of mdm-2 to block each activity. RESULTS: Mdm-2 was able to inhibit all three functions of the wild-type and mutant p53 activities; transcriptional activation by the wild-ty...

  5. p53 binds human telomeric G-quadruplex in vitro.

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    Adámik, Matej; Kejnovská, Iva; Bažantová, Pavla; Petr, Marek; Renčiuk, Daniel; Vorlíčková, Michaela; Brázdová, Marie

    2016-01-01

    The tumor suppressor protein p53 is a key factor in genome stability and one of the most studied of DNA binding proteins. This is the first study on the interaction of wild-type p53 with guanine quadruplexes formed by the human telomere sequence. Using electromobility shift assay and ELISA, we show that p53 binding to telomeric G-quadruplexes increases with the number of telomeric repeats. Further, p53 strongly favors G-quadruplexes folded in potassium over those formed in sodium, thus indicating the telomeric G-quadruplex conformational selectivity of p53. The presence of the quadruplex-stabilizing ligand, N-methyl mesoporphyrin IX (NMM), increases p53 recognition of G-quadruplexes in potassium. Using deletion mutants and selective p53 core domain oxidation, both p53 DNA binding domains are shown to be crucial for telomeric G-quadruplex recognition.

  6. VHL missense mutations in the p53 binding domain show different effects on p53 signaling and HIFα degradation in clear cell renal cell carcinoma.

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    Razafinjatovo, Caroline Fanja; Stiehl, Daniel; Deininger, Eva; Rechsteiner, Markus; Moch, Holger; Schraml, Peter

    2017-02-07

    Clear cell Renal Cell Carcinoma (ccRCC) formation is connected to functional loss of the von Hippel-Lindau (VHL) gene. Recent data identified its gene product, pVHL, as a multifunctional adaptor protein which interacts with HIFα subunits but also with the tumor suppressor p53. p53 is hardly expressed and rarely mutated in most ccRCC. We showed that low and absent p53 expression correlated with the severity of VHL mutations in 262 analyzed ccRCC tissues. In contrast to nonsense and frameshift mutations which abrogate virtually all pVHL functions, missense mutations may rather influence one or few functions. Therefore, we focused on four VHL missense mutations, which affect the overlapping pVHL binding sites of p53 and Elongin C, by investigating their impact on HIFα degradation, p53 expression and signaling, as well as on cellular behavior using ccRCC cell lines and tissues. TP53 mRNA and its effector targets p21, Bax and Noxa, were altered both in engineered cell lines and in tumor tissues which carried the same missense mutations. Two of these mutations were not able to degrade HIFα whereas the remaining two mutations led to HIFα downregulation, suggesting the latter are p53 binding site-specific. The selected VHL missense mutations further enhanced tumor cell survival, but had no effects on cell proliferation. Whereas Sunitinib was able to efficiently reduce cell proliferation, Camptothecin was additionally able to increase apoptotic activity of the tumor cells. It is concluded that systematic characterization of the VHL mutation status may help optimizing targeted therapy for patients with metastatic ccRCC.

  7. In vitro binding properties of tumor suppressor p53 with PUMA and NOXA.

    Science.gov (United States)

    Park, So Young; Jeong, Mi Suk; Jang, Se Bok

    2012-04-06

    The p53-upregulated modulator of apoptosis (Puma) and Noxa, are direct targets in p53-mediated apoptosis localized to the mitochondria. Tumor suppressor p53 induces apoptosis by transcriptional induction of Puma and Noxa, which encode proapoptotic BH3-only member Bcl-1 family proteins. However, at a molecular level, the mechanism of action of Puma and Noxa proteins remain poorly defined. In addition, there have been no reports on whether or not p53 directly interacts with Puma and Noxa, in vitro. Here, we provide evidence indicating that the DNA binding domain (DBD) of p53 directly interacted with the BH3 domains of human PUMA and NOXA. Our studies revealed that PUMA has a weak affinity for p53, but NOXA has significant affinity for p53. In this study, we developed a molecular docking model using homology modeling based on the structures of truncated p53, PUMA and NOXA. In addition, we investigated whether or not six mutants of p53 (K101A, T102A, L111A, D186A, G199A and S227A) were able to bind to PUMA and NOXA. Four structure-based mutations (T102A, L111A, D186A and G199A) disrupted the p53-PUMA/NOXA interaction. Our study suggested that these four mutations lowered the stability of the p53 DBD domain and induced aggregation of structurally destabilized p53, and thus disrupted the p53-PUMA/NOXA interaction.

  8. Gain-of-function p53 mutants co-opt chromatin pathways to drive cancer growth.

    Science.gov (United States)

    Zhu, Jiajun; Sammons, Morgan A; Donahue, Greg; Dou, Zhixun; Vedadi, Masoud; Getlik, Matthäus; Barsyte-Lovejoy, Dalia; Al-awar, Rima; Katona, Bryson W; Shilatifard, Ali; Huang, Jing; Hua, Xianxin; Arrowsmith, Cheryl H; Berger, Shelley L

    2015-09-10

    TP53 (which encodes p53 protein) is the most frequently mutated gene among all human cancers. Prevalent p53 missense mutations abrogate its tumour suppressive function and lead to a 'gain-of-function' (GOF) that promotes cancer. Here we show that p53 GOF mutants bind to and upregulate chromatin regulatory genes, including the methyltransferases MLL1 (also known as KMT2A), MLL2 (also known as KMT2D), and acetyltransferase MOZ (also known as KAT6A or MYST3), resulting in genome-wide increases of histone methylation and acetylation. Analysis of The Cancer Genome Atlas shows specific upregulation of MLL1, MLL2, and MOZ in p53 GOF patient-derived tumours, but not in wild-type p53 or p53 null tumours. Cancer cell proliferation is markedly lowered by genetic knockdown of MLL1 or by pharmacological inhibition of the MLL1 methyltransferase complex. Our study reveals a novel chromatin mechanism underlying the progression of tumours with GOF p53, and suggests new possibilities for designing combinatorial chromatin-based therapies for treating individual cancers driven by prevalent GOF p53 mutations.

  9. Combining intracellular antibodies to restore function of mutated p53 in cancer.

    Science.gov (United States)

    Chan, Grace; Jordaan, Gwen; Nishimura, Robert N; Weisbart, Richard H

    2016-01-01

    TP53 is a tumor suppressor gene that is mutated in 50% of cancers, and its function is tightly regulated by the E3 ligase, Mdm2. Both p53 and Mdm2 are localized in the cell nucleus, a site that is impervious to therapeutic regulation by most antibodies. We identified a cell-penetrating lupus monoclonal anti-DNA antibody, mAb 3E10, that targets the nucleus, and we engineered mAb 3E10 to function as an intranuclear transport system to deliver therapeutic antibodies into the nucleus as bispecific single chain Fv (scFv) fragments. Bispecific scFvs composed of 3E10 include PAb421 (3E10-PAb421) that binds p53 and restores the function of mutated p53, and 3G5 (3E10-3G5) that binds Mdm2 and prevents destruction of p53 by Mdm2. We documented the therapeutic efficacy of these bispecific scFvs separately in previous studies. In this study, we show that combination therapy with 3E10-PAb421 and 3E10-3G5 augments growth inhibition of cells with p53 mutations compared to the effect of either antibody alone. By contrast, no enhanced response was observed in cells with wild-type p53 or in cells homozygous null for p53.

  10. The in vitro phosphorylation of p53 by calcium-dependent protein kinase C--characterization of a protein-kinase-C-binding site on p53.

    Science.gov (United States)

    Delphin, C; Huang, K P; Scotto, C; Chapel, A; Vincon, M; Chambaz, E; Garin, J; Baudier, J

    1997-05-01

    We show that, in vitro, Ca2+-dependent protein kinase C (PKC) phosphorylates recombinant murine p53 protein on several residues contained within a conserved basic region of 25 amino acids, located in the C-terminal part of the protein. Accordingly, synthetic p53-(357-381)-peptide is phosphorylated by PKC at multiple Ser and Thr residues, including Ser360, Thr365, Ser370 and Thr377. We also establish that p53-(357-381)-peptide at micromolar concentrations has the ability to stimulate sequence-specific DNA binding by p53. That stimulation is lost upon phosphorylation by PKC. To further characterise the mechanisms that regulate PKC-dependent phosphorylation of p53-(357-381)-peptide, the phosphorylation of recombinant p53 and p53-(357-381)-peptide by PKC were compared. The results suggest that phosphorylation of full-length p53 on the C-terminal PKC sites is highly dependent on the accessibility of the phosphorylation sites and that a domain on p53 distinct from p53-(357-381)-peptide is involved in binding PKC. Accordingly, we have identified a conserved 27-amino-acid peptide, p53-(320-346)-peptide, within the C-terminal region of p53 and adjacent to residues 357-381 that interacts with PKC in vitro. The interaction between p53-(320-346)-peptide and PKC inhibits PKC autophosphorylation and the phosphorylation of substrates, including p53-(357-381)-peptide, neurogranin and histone H1. Conventional Ca2+-dependent PKC alpha, beta and gamma and the catalytic fragment of PKC (PKM) were nearly equally susceptible to inhibition by p53-(320-346)-peptide. The Ca2+-independent PKC delta was much less sensitive to inhibition. The significance of these findings for understanding the in vivo phosphorylation of p53 by PKC are discussed.

  11. The contrived mutant p53 oncogene – beyond loss of functions

    Directory of Open Access Journals (Sweden)

    Kanaga eSabapathy

    2015-12-01

    Full Text Available Mutations in p53 are almost synonymous with cancer - be it susceptibility to the disease or response to treatment - and therefore, are a critical determinant of overall survival. As most of these mutations occur in the DNA-binding domain of p53, many of the clinical correlations with mutant p53 have been initially relegated to the loss of its transcription-dependent activities as a tumor suppressor. However, significant efforts over the last two decades have led to the vast knowledge on the potential functions of the mutated p53 protein, that have been attributed to the physical presence of the mutant protein rather than the loss of its wild-type functions. Beyond the inhibitory effects of mutant p53 on the remaining wild-type protein that leads to the dominant-negative effect in the heterozygous state, mutant p53’s presence has also been significantly attributed to novel gain-of-functions that lead to addiction of cancer cells to its presence for survival, as well as for their ability to invade and metastasize, elevating it to a contrived oncogene that drives the cancer cells forward. This review will summarize the functional consequences of the presence of mutant p53 protein on cellular and organismal physiology.

  12. A Novel Protein Interaction between Nucleotide Binding Domain of Hsp70 and p53 Motif

    Directory of Open Access Journals (Sweden)

    Asita Elengoe

    2015-01-01

    Full Text Available Currently, protein interaction of Homo sapiens nucleotide binding domain (NBD of heat shock 70 kDa protein (PDB: 1HJO with p53 motif remains to be elucidated. The NBD-p53 motif complex enhances the p53 stabilization, thereby increasing the tumor suppression activity in cancer treatment. Therefore, we identified the interaction between NBD and p53 using STRING version 9.1 program. Then, we modeled the three-dimensional structure of p53 motif through homology modeling and determined the binding affinity and stability of NBD-p53 motif complex structure via molecular docking and dynamics (MD simulation. Human DNA binding domain of p53 motif (SCMGGMNR retrieved from UniProt (UniProtKB: P04637 was docked with the NBD protein, using the Autodock version 4.2 program. The binding energy and intermolecular energy for the NBD-p53 motif complex were −0.44 Kcal/mol and −9.90 Kcal/mol, respectively. Moreover, RMSD, RMSF, hydrogen bonds, salt bridge, and secondary structure analyses revealed that the NBD protein had a strong bond with p53 motif and the protein-ligand complex was stable. Thus, the current data would be highly encouraging for designing Hsp70 structure based drug in cancer therapy.

  13. Functional characterization of p53 pathway components in the ancient metazoan Trichoplax adhaerens

    Science.gov (United States)

    Siau, Jia Wei; Coffill, Cynthia R.; Zhang, Weiyun Villien; Tan, Yaw Sing; Hundt, Juliane; Lane, David; Verma, Chandra; Ghadessy, Farid

    2016-09-01

    The identification of genes encoding a p53 family member and an Mdm2 ortholog in the ancient placozoan Trichoplax adhaerens advocates for the evolutionary conservation of a pivotal stress-response pathway observed in all higher eukaryotes. Here, we recapitulate several key functionalities ascribed to this known interacting protein pair by analysis of the placozoan proteins (Tap53 and TaMdm2) using both in vitro and cellular assays. In addition to interacting with each other, the Tap53 and TaMdm2 proteins are also able to respectively bind human Mdm2 and p53, providing strong evidence for functional conservation. The key p53-degrading function of Mdm2 is also conserved in TaMdm2. Tap53 retained DNA binding associated with p53 transcription activation function. However, it lacked transactivation function in reporter genes assays using a heterologous cell line, suggesting a cofactor incompatibility. Overall, the data supports functional roles for TaMdm2 and Tap53, and further defines the p53 pathway as an evolutionary conserved fulcrum mediating cellular response to stress.

  14. p53 Requires an Intact C-Terminal Domain for DNA Binding and Transactivation

    OpenAIRE

    2011-01-01

    The p53 tumor suppressor plays a critical role in mediating cellular response to a wide range of environmental stresses. p53 regulates these processes mainly by acting as a short-lived DNA binding protein that stimulates transcription from numerous genes involved in cell cycle arrest, programmed cell death, and other processes. To investigate the importance of C-terminal domain of p53, we generated a series of deletion and point mutations in this region and analyzed their effects on p53 trans...

  15. The DNA Binding Activity of p53 Displays Reaction-Diffusion Kinetics

    Science.gov (United States)

    Hinow, Peter; Rogers, Carl E.; Barbieri, Christopher E.; Pietenpol, Jennifer A.; Kenworthy, Anne K.; DiBenedetto, Emmanuele

    2006-01-01

    The tumor suppressor protein p53 plays a key role in maintaining the genomic stability of mammalian cells and preventing malignant transformation. In this study, we investigated the intracellular diffusion of a p53-GFP fusion protein using confocal fluorescence recovery after photobleaching. We show that the diffusion of p53-GFP within the nucleus is well described by a mathematical model for diffusion of particles that bind temporarily to a spatially homogeneous immobile structure with binding and release rates k1 and k2, respectively. The diffusion constant of p53-GFP was estimated to be Dp53-GFP = 15.4 μm2 s−1, significantly slower than that of GFP alone, DGFP = 41.6 μm2 s−1. The reaction rates of the binding and unbinding of p53-GFP were estimated as k1 = 0.3 s−1 and k2 = 0.4 s−1, respectively, values suggestive of nonspecific binding. Consistent with this finding, the diffusional mobilities of tumor-derived sequence-specific DNA binding mutants of p53 were indistinguishable from that of the wild-type protein. These data are consistent with a model in which, under steady-state conditions, p53 is latent and continuously scans DNA, requiring activation for sequence-specific DNA binding. PMID:16603489

  16. The Machado-Joseph Disease Deubiquitinase Ataxin-3 Regulates the Stability and Apoptotic Function of p53.

    Science.gov (United States)

    Liu, Hongmei; Li, Xiaoling; Ning, Guozhu; Zhu, Shu; Ma, Xiaolu; Liu, Xiuli; Liu, Chunying; Huang, Min; Schmitt, Ina; Wüllner, Ullrich; Niu, Yamei; Guo, Caixia; Wang, Qiang; Tang, Tie-Shan

    2016-11-01

    As a deubiquitinating enzyme (DUB), the physiological substrates of ataxin-3 (ATX-3) remain elusive, which limits our understanding of its normal cellular function and that of pathogenic mechanism of spinocerebellar ataxia type 3 (SCA3). Here, we identify p53 to be a novel substrate of ATX-3. ATX-3 binds to native and polyubiquitinated p53 and deubiquitinates and stabilizes p53 by repressing its degradation through the ubiquitin (Ub)-proteasome pathway. ATX-3 deletion destabilizes p53, resulting in deficiency of p53 activity and functions, whereas ectopic expression of ATX-3 induces selective transcription/expression of p53 target genes and promotes p53-dependent apoptosis in both mammalian cells and the central nervous system of zebrafish. Furthermore, the polyglutamine (polyQ)-expanded ATX-3 retains enhanced interaction and deubiquitination catalytic activity to p53 and causes more severe p53-dependent neurodegeneration in zebrafish brains and in the substantia nigra pars compacta (SNpc) or striatum of a transgenic SCA3 mouse model. Our findings identify a novel molecular link between ATX-3 and p53-mediated cell death and provide an explanation for the direct involvement of p53 in SCA3 disease pathogenesis.

  17. Gain of cellular adaptation due to prolonged p53 impairment leads to functional switchover from p53 to p73 during DNA damage in acute myeloid leukemia cells.

    Science.gov (United States)

    Chakraborty, Juni; Banerjee, Shuvomoy; Ray, Pallab; Hossain, Dewan Md Sakib; Bhattacharyya, Sankar; Adhikary, Arghya; Chattopadhyay, Sreya; Das, Tanya; Sa, Gaurisankar

    2010-10-22

    Tumor suppressor p53 plays the central role in regulating apoptosis in response to genotoxic stress. From an evolutionary perspective, the activity of p53 has to be backed up by other protein(s) in case of any functional impairment of this protein, to trigger DNA damage-induced apoptosis in cancer cells. We adopted multiple experimental approaches to demonstrate that in p53-impaired cancer cells, DNA damage caused accumulation of p53 paralogue p73 via Chk-1 that strongly impacted Bax expression and p53-independent apoptosis. On the contrary, when p53 function was restored by ectopic expression, Chk-2 induced p53 accumulation that in turn overshadowed p73 activity, suggesting an antagonistic interaction between p53 family members. To understand such interaction better, p53-expressing cells were impaired differentially for p53 activity. In wild-type p53-expressing cancer cells that were silenced for p53 for several generations, p73 was activated, whereas no such trend was observed when p53 was transiently silenced. Prolonged p53 interference, even in functional p53 settings, therefore, leads to the "gain of cellular adaptation" in a way that alters the cellular microenvironment in favor of p73 activation by altering p73-regulatory proteins, e.g. Chk1 activation and dominant negative p73 down-regulation. These findings not only unveil a hitherto unexplained mechanism underlying the functional switchover from p53 to p73, but also validate p73 as a promising and potential target for cancer therapy in the absence of functional p53.

  18. Oxidized DJ-1 Inhibits p53 by Sequestering p53 from Promoters in a DNA-Binding Affinity-Dependent Manner

    Science.gov (United States)

    Kato, Izumi; Maita, Hiroshi; Takahashi-Niki, Kazuko; Saito, Yoshiro; Noguchi, Noriko; Iguchi-Ariga, Sanae M. M.

    2013-01-01

    DJ-1 is an oncogene and the causative gene for familial Parkinson's disease. Although the oxidative status of DJ-1 at cysteine 106 (C106) is thought to affect all of the activities of DJ-1 and excess oxidation leads to the onset of various diseases, the precise molecular mechanisms underlying the effects of oxidation of DJ-1 on protein-protein interactions of DJ-1 remain unclear. In this study, we found that DJ-1 bound to the DNA-binding region of p53 in a manner dependent on the oxidation of C106. Of the p53 target genes, the expression level and promoter activity of the DUSP1 gene, but not those of the p21 gene, were increased in H2O2-treated DJ-1−/− cells and were decreased in wild-type DJ-1- but not C106S DJ-1-transfected H1299 cells through sequestration of p53 from the DUSP1 promoter by DJ-1. DUSP1 downregulated by oxidized DJ-1 activated extracellular signal-regulated kinase (ERK) and decreased apoptosis. The DUSP1 and p21 promoters harbor nonconsensus and consensus p53 recognition sequences, respectively, which have low affinity and high affinity for p53. However, DJ-1 inhibited p21 promoter activity exhibited by p53 mutants harboring low DNA-binding affinity but not by wild-type p53. These results indicate that DJ-1 inhibits the expression of p53 target genes and depend on p53 DNA-binding affinity and oxidation of DJ-1 C106. PMID:23149933

  19. Reactivating p53 functions by suppressing its novel inhibitor iASPP: a potential therapeutic opportunity in p53 wild-type tumors

    Science.gov (United States)

    Dong, Peixin; Ihira, Kei; Hamada, Junichi; Watari, Hidemichi; Yamada, Takahiro; Hosaka, Masayoshi; Hanley, Sharon J.B.; Kudo, Masataka; Sakuragi, Noriaki

    2015-01-01

    Although mutational inactivation of p53 is found in 50% of all human tumors, a subset of tumors display defective p53 function, but retain wild-type (WT) p53. Here, direct and indirect mechanisms leading to the loss of WT p53 activities are discussed. We summarize the oncogenic roles of iASPP, an inhibitor of WT p53, in promoting proliferation, invasion, drug or radiation-resistance and metastasis. From the therapeutic view, we highlight promising perspectives of microRNA-124, peptide and small molecules that reduce or block iASPP for the treatment of cancer. High iASPP expression enhances proliferation, aggressive behavior, the resistance to radiation/chemotherapy and correlates with poor prognosis in a range of human tumors. Overexpression of iASPP accelerates tumorigenesis and invasion through p53-dependent and p53-independent mechanisms. MicroRNA-124 directly targets iASPP and represses the growth and invasiveness of cancer cells. The disruption of iASPP-p53 interaction by a p53-derived peptide A34 restores p53 function in cancer cells. The inhibition of iASPP phosphorylation with small molecules induces p53-dependent apoptosis and growth suppression. The mechanisms underlying aberrant expression of iASPP in human tumors should be further investigated. Reactivating WT p53 functions by targeting its novel inhibitor iASPP holds promise for potential therapeutic interventions in the treatment of WT p53-containing tumors. PMID:26343523

  20. Human neuroblastoma cells with acquired resistance to the p53 activator RITA retain functional p53 and sensitivity to other p53 activating agents

    NARCIS (Netherlands)

    Michaelis, M.; Rothweiler, F.; Agha, B.; Barth, S.; Voges, Y.; Loeschmann, N.; von Deimling, A.; Breitling, R.; Doerr, H. Wilhelm; Roedel, F.; Speidel, D.; Cinatl, J.; Cinatl Jr., J.; Stephanou, A.

    2012-01-01

    Adaptation of wild-type p53 expressing UKF-NB-3 cancer cells to the murine double minute 2 inhibitor nutlin-3 causes de novo p53 mutations at high frequency (13/20) and multi-drug resistance. Here, we show that the same cells respond very differently when adapted to RITA, a drug that, like nutlin-3,

  1. Structural Basis for p53 Lys120-Acetylation-Dependent DNA-Binding Mode.

    Science.gov (United States)

    Vainer, Radion; Cohen, Sarit; Shahar, Anat; Zarivach, Raz; Arbely, Eyal

    2016-07-31

    Normal cellular homeostasis depends on tight regulation of gene expression, which requires the modulation of transcription factors' DNA-binding specificity. That said, the mechanisms that allow transcription factors to distinguish between closely related response elements following different cellular signals are not fully understood. In the tumor suppressor protein p53, acetylation of loop L1 residue Lys120 within the DNA-binding domain has been shown to promote the transcription of proapoptotic genes such as bax. Here, we report the crystal structures of Lys120-acetylated p53 DNA-binding domain in complex with a consensus response element and with the natural BAX response element. Our structural analyses reveal that Lys120 acetylation expands the conformational space of loop L1 in the DNA-bound state. Loop L1 flexibility is known to increase p53's DNA-binding specificity, and Lys120-acetylation-dependent conformational changes in loop L1 enable the formation of sequence-dependent DNA-binding modes for p53. Furthermore, binding to the natural BAX response element is accompanied by global conformational changes, deformation of the DNA helical structure, and formation of an asymmetric tetrameric complex. Based on these findings, we suggest a model for p53's Lys120 acetylation-dependent DNA-binding mode. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Wild-type p53 binds to MYC promoter G-quadruplex

    Science.gov (United States)

    Petr, Marek; Helma, Robert; Polášková, Alena; Krejčí, Aneta; Dvořáková, Zuzana; Kejnovská, Iva; Navrátilová, Lucie; Adámik, Matej; Vorlíčková, Michaela; Brázdová, Marie

    2016-01-01

    G-quadruplexes are four-stranded nucleic acid structures that are implicated in the regulation of transcription, translation and replication. Genome regions enriched in putative G-quadruplex motifs include telomeres and gene promoters. Tumour suppressor p53 plays a critical role in regulatory pathways leading to cell cycle arrest, DNA repair and apoptosis. In addition to transcriptional regulation mediated via sequence-specific DNA binding, p53 can selectively bind various non-B DNA structures. In the present study, wild-type p53 (wtp53) binding to G-quadruplex formed by MYC promoter nuclease hypersensitive element (NHE) III1 region was investigated. Wtp53 binding to MYC G-quadruplex is comparable to interaction with specific p53 consensus sequence (p53CON). Apart from the full-length wtp53, its isolated C-terminal region (aa 320–393) as well, is capable of high-affinity MYC G-quadruplex binding, suggesting its critical role in this type of interaction. Moreover, wtp53 binds to MYC promoter region containing putative G-quadruplex motif in two wtp53-expressing cell lines. The results suggest that wtp53 binding to G-quadruplexes can take part in transcriptional regulation of its target genes. PMID:27634752

  3. Wild-type p53 binds to MYC promoter G-quadruplex.

    Science.gov (United States)

    Petr, Marek; Helma, Robert; Polášková, Alena; Krejčí, Aneta; Dvořáková, Zuzana; Kejnovská, Iva; Navrátilová, Lucie; Adámik, Matej; Vorlíčková, Michaela; Brázdová, Marie

    2016-10-01

    G-quadruplexes are four-stranded nucleic acid structures that are implicated in the regulation of transcription, translation and replication. Genome regions enriched in putative G-quadruplex motifs include telomeres and gene promoters. Tumour suppressor p53 plays a critical role in regulatory pathways leading to cell cycle arrest, DNA repair and apoptosis. In addition to transcriptional regulation mediated via sequence-specific DNA binding, p53 can selectively bind various non-B DNA structures. In the present study, wild-type p53 (wtp53) binding to G-quadruplex formed by MYC promoter nuclease hypersensitive element (NHE) III1 region was investigated. Wtp53 binding to MYC G-quadruplex is comparable to interaction with specific p53 consensus sequence (p53CON). Apart from the full-length wtp53, its isolated C-terminal region (aa 320-393) as well, is capable of high-affinity MYC G-quadruplex binding, suggesting its critical role in this type of interaction. Moreover, wtp53 binds to MYC promoter region containing putative G-quadruplex motif in two wtp53-expressing cell lines. The results suggest that wtp53 binding to G-quadruplexes can take part in transcriptional regulation of its target genes.

  4. Illuminating p53 function in cancer with genetically engineered mouse models

    OpenAIRE

    2014-01-01

    The key role of the p53 protein in tumor suppression is highlighted by its frequent mutation in human cancers and by the completely penetrant cancer predisposition of p53 null mice. Beyond providing definitive evidence for the critical function of p53 in tumor suppression, genetically engineered mouse models have offered numerous additional insights into p53 function. p53 knock-in mice expressing tumor-derived p53 mutants have revealed that these mutants display gain-of-function activities th...

  5. Long non-coding RNA NEAT1 is a transcriptional target of p53 and modulates p53-induced transactivation and tumor-suppressor function.

    Science.gov (United States)

    Idogawa, Masashi; Ohashi, Tomoko; Sasaki, Yasushi; Nakase, Hiroshi; Tokino, Takashi

    2017-03-14

    p53 is one of the most important tumor suppressor genes and the direct transcriptional targets of p53 must be explored to elucidate its functional mechanisms. Thus far, the p53 targets that have been primarily studied are protein-coding genes. Our previous study revealed that several long non-coding RNAs (lncRNAs) are direct transcriptional targets of p53, and knockdown of specific lncRNAs modulates p53-induced apoptosis. In this study, analysis of next-generation chromatin immunoprecipitation-sequencing (ChIP-seq) data for p53 revealed that the lncRNA NEAT1 is a direct transcriptional target of p53. The suppression of NEAT1 induction by p53 attenuates the inhibitory effect of p53 on cancer cell growth and also modulates gene transactivation, including that of many lncRNAs. Furthermore, low expression of NEAT1 is related to poor prognosis in several cancers. These results indicate that the induction of NEAT1 expression contributes to the tumor-suppressor function of p53 and suggest that p53 and NEAT1 constitute a transcriptional network contributing to various biological functions and tumor suppression. This article is protected by copyright. All rights reserved.

  6. Roscovitine-induced apoptosis of H1299 cells depends on functional status of p53.

    Science.gov (United States)

    Slovackova, J; Smarda, J; Smardova, J

    2012-01-01

    Roscovitine, an inhibitor of cyclin-dependent kinases, is promising anticancer agent. Its antiproliferative and cytotoxic effects can be mediated by the p53 signaling pathway. To define the role of p53 in roscovitine-induced cell response, we prepared H1299/p53 cell lines inducibly expressing specific variants of p53 (p53wt and hotspot R175H, temperature-dependent P98A, A159V, S215G, Y220C, Y234C mutants). In the presence of roscovitine, each cell line variant behaved in specific way reflecting activity of the p53 protein. Roscovitine decreased production of the cell cycle inhibitor p21 and induced apoptosis. This effect was the most efficient in cells expressing p53wt protein with full activity. The cell expressing partially and conditionally active p53 mutants responded to roscovitine less efficiently. The cells expressing p53 mutants A159V and Y234C were very sensitive to roscovitine but their response was clearly temperature-dependent. The cells expressing P98A, S215G and Y220C p53 mutants exhibited only weak sensitivity to roscovitine and underwent apoptosis in low frequency. In principle, each td p53 mutant responded to roscovitine in distinct way. We showed clearly that the impact of roscovitine on H1299 cells depends on functional status of p53 they produce. This suggests that patients with tumors exhibiting specific p53 variants can benefit from the roscovitine therapy.

  7. Interactions of chromatin context, binding site sequence content, and sequence evolution in stress-induced p53 occupancy and transactivation.

    Directory of Open Access Journals (Sweden)

    Dan Su

    2015-01-01

    Full Text Available Cellular stresses activate the tumor suppressor p53 protein leading to selective binding to DNA response elements (REs and gene transactivation from a large pool of potential p53 REs (p53REs. To elucidate how p53RE sequences and local chromatin context interact to affect p53 binding and gene transactivation, we mapped genome-wide binding localizations of p53 and H3K4me3 in untreated and doxorubicin (DXR-treated human lymphoblastoid cells. We examined the relationships among p53 occupancy, gene expression, H3K4me3, chromatin accessibility (DNase 1 hypersensitivity, DHS, ENCODE chromatin states, p53RE sequence, and evolutionary conservation. We observed that the inducible expression of p53-regulated genes was associated with the steady-state chromatin status of the cell. Most highly inducible p53-regulated genes were suppressed at baseline and marked by repressive histone modifications or displayed CTCF binding. Comparison of p53RE sequences residing in different chromatin contexts demonstrated that weaker p53REs resided in open promoters, while stronger p53REs were located within enhancers and repressed chromatin. p53 occupancy was strongly correlated with similarity of the target DNA sequences to the p53RE consensus, but surprisingly, inversely correlated with pre-existing nucleosome accessibility (DHS and evolutionary conservation at the p53RE. Occupancy by p53 of REs that overlapped transposable element (TE repeats was significantly higher (p<10-7 and correlated with stronger p53RE sequences (p<10-110 relative to nonTE-associated p53REs, particularly for MLT1H, LTR10B, and Mer61 TEs. However, binding at these elements was generally not associated with transactivation of adjacent genes. Occupied p53REs located in L2-like TEs were unique in displaying highly negative PhyloP scores (predicted fast-evolving and being associated with altered H3K4me3 and DHS levels. These results underscore the systematic interaction between chromatin status and p53

  8. The PTTG1-binding factor (PBF/PTTG1IP) regulates p53 activity in thyroid cells.

    Science.gov (United States)

    Read, Martin L; Seed, Robert I; Fong, Jim C W; Modasia, Bhavika; Ryan, Gavin A; Watkins, Rachel J; Gagliano, Teresa; Smith, Vicki E; Stratford, Anna L; Kwan, Perkin K; Sharma, Neil; Dixon, Olivia M; Watkinson, John C; Boelaert, Kristien; Franklyn, Jayne A; Turnell, Andrew S; McCabe, Christopher J

    2014-04-01

    The PTTG1-binding factor (PBF/PTTG1IP) has an emerging repertoire of roles, especially in thyroid biology, and functions as a protooncogene. High PBF expression is independently associated with poor prognosis and lower disease-specific survival in human thyroid cancer. However, the precise role of PBF in thyroid tumorigenesis is unclear. Here, we present extensive evidence demonstrating that PBF is a novel regulator of p53, a tumor suppressor protein with a key role in maintaining genetic stability, which is infrequently mutated in differentiated thyroid cancer. By coimmunoprecipitation and proximity-ligation assays, we show that PBF binds specifically to p53 in thyroid cells and significantly represses transactivation of responsive promoters. Further, we identify that PBF decreases p53 stability by enhancing ubiquitination, which appears dependent on the E3 ligase activity of Mdm2. Impaired p53 function was evident in a transgenic mouse model with thyroid-specific PBF overexpression (transgenic PBF mice), which had significantly increased genetic instability as indicated by fluorescent inter simple sequence repeat-PCR analysis. Consistent with this, approximately 40% of all DNA repair genes examined were repressed in transgenic PBF primary cultures, including genes with critical roles in maintaining genomic integrity such as Mgmt, Rad51, and Xrcc3. Our data also revealed that PBF induction resulted in up-regulation of the E2 enzyme Rad6 in murine thyrocytes and was associated with Rad6 expression in human thyroid tumors. Overall, this work provides novel insights into the role of the protooncogene PBF as a negative regulator of p53 function in thyroid tumorigenesis, in which PBF is generally overexpressed and p53 mutations are rare compared with other tumor types.

  9. Gain of Cellular Adaptation Due to Prolonged p53 Impairment Leads to Functional Switchover from p53 to p73 during DNA Damage in Acute Myeloid Leukemia Cells*

    OpenAIRE

    2010-01-01

    Tumor suppressor p53 plays the central role in regulating apoptosis in response to genotoxic stress. From an evolutionary perspective, the activity of p53 has to be backed up by other protein(s) in case of any functional impairment of this protein, to trigger DNA damage-induced apoptosis in cancer cells. We adopted multiple experimental approaches to demonstrate that in p53-impaired cancer cells, DNA damage caused accumulation of p53 paralogue p73 via Chk-1 that strongly impacted Bax expressi...

  10. Immunomodulatory Function of the Tumor Suppressor p53 in Host Immune Response and the Tumor Microenvironment.

    Science.gov (United States)

    Cui, Yan; Guo, Gang

    2016-11-19

    The tumor suppressor p53 is the most frequently mutated gene in human cancers. Most of the mutations are missense leading to loss of p53 function in inducing apoptosis and senescence. In addition to these autonomous effects of p53 inactivation/dysfunction on tumorigenesis, compelling evidence suggests that p53 mutation/inactivation also leads to gain-of-function or activation of non-autonomous pathways, which either directly or indirectly promote tumorigenesis. Experimental and clinical results suggest that p53 dysfunction fuels pro-tumor inflammation and serves as an immunological gain-of-function driver of tumorigenesis via skewing immune landscape of the tumor microenvironment (TME). It is now increasingly appreciated that p53 dysfunction in various cellular compartments of the TME leads to immunosuppression and immune evasion. Although our understanding of the cellular and molecular processes that link p53 activity to host immune regulation is still incomplete, it is clear that activating/reactivating the p53 pathway in the TME also represents a compelling immunological strategy to reverse immunosuppression and enhance antitumor immunity. Here, we review our current understanding of the potential cellular and molecular mechanisms by which p53 participates in immune regulation and discuss how targeting the p53 pathway can be exploited to alter the immunological landscape of tumors for maximizing therapeutic outcome.

  11. Immunomodulatory Function of the Tumor Suppressor p53 in Host Immune Response and the Tumor Microenvironment

    Directory of Open Access Journals (Sweden)

    Yan Cui

    2016-11-01

    Full Text Available The tumor suppressor p53 is the most frequently mutated gene in human cancers. Most of the mutations are missense leading to loss of p53 function in inducing apoptosis and senescence. In addition to these autonomous effects of p53 inactivation/dysfunction on tumorigenesis, compelling evidence suggests that p53 mutation/inactivation also leads to gain-of-function or activation of non-autonomous pathways, which either directly or indirectly promote tumorigenesis. Experimental and clinical results suggest that p53 dysfunction fuels pro-tumor inflammation and serves as an immunological gain-of-function driver of tumorigenesis via skewing immune landscape of the tumor microenvironment (TME. It is now increasingly appreciated that p53 dysfunction in various cellular compartments of the TME leads to immunosuppression and immune evasion. Although our understanding of the cellular and molecular processes that link p53 activity to host immune regulation is still incomplete, it is clear that activating/reactivating the p53 pathway in the TME also represents a compelling immunological strategy to reverse immunosuppression and enhance antitumor immunity. Here, we review our current understanding of the potential cellular and molecular mechanisms by which p53 participates in immune regulation and discuss how targeting the p53 pathway can be exploited to alter the immunological landscape of tumors for maximizing therapeutic outcome.

  12. Immunomodulatory Function of the Tumor Suppressor p53 in Host Immune Response and the Tumor Microenvironment

    Science.gov (United States)

    Cui, Yan; Guo, Gang

    2016-01-01

    The tumor suppressor p53 is the most frequently mutated gene in human cancers. Most of the mutations are missense leading to loss of p53 function in inducing apoptosis and senescence. In addition to these autonomous effects of p53 inactivation/dysfunction on tumorigenesis, compelling evidence suggests that p53 mutation/inactivation also leads to gain-of-function or activation of non-autonomous pathways, which either directly or indirectly promote tumorigenesis. Experimental and clinical results suggest that p53 dysfunction fuels pro-tumor inflammation and serves as an immunological gain-of-function driver of tumorigenesis via skewing immune landscape of the tumor microenvironment (TME). It is now increasingly appreciated that p53 dysfunction in various cellular compartments of the TME leads to immunosuppression and immune evasion. Although our understanding of the cellular and molecular processes that link p53 activity to host immune regulation is still incomplete, it is clear that activating/reactivating the p53 pathway in the TME also represents a compelling immunological strategy to reverse immunosuppression and enhance antitumor immunity. Here, we review our current understanding of the potential cellular and molecular mechanisms by which p53 participates in immune regulation and discuss how targeting the p53 pathway can be exploited to alter the immunological landscape of tumors for maximizing therapeutic outcome. PMID:27869779

  13. Functions of MDMX in the Modulation of the p53-Response

    Directory of Open Access Journals (Sweden)

    Kristiaan Lenos

    2011-01-01

    Full Text Available The MDM family proteins MDM2 and MDMX are two critical regulators of the p53 tumor suppressor protein. Expression of both proteins is necessary for allowing the embryonal development by keeping the activity of p53 in check. Upon stresses that need to activate p53 to perform its function as guardian of the genome, p53 has to be liberated from these two inhibitors. In this review, we will discuss the various mechanisms by which MDMX protein levels are downregulated upon various types of stress, including posttranslational modifications of the MDMX protein and the regulation of mdmx mRNA expression, including alternative splicing. In addition, the putative function(s of the described MDMX splice variants, particularly in tumor development, will be discussed. Lastly, in contrast to common belief, we have recently shown the existence of a p53-MDMX feedback loop, which is important for dampening the p53-response at later phases after genotoxic stress.

  14. Identification of p53 regulators by genome-wide functional analysis

    Science.gov (United States)

    Huang, Qihong; Raya, Angel; DeJesus, Paul; Chao, Sheng-Hao; Quon, Kim C.; Caldwell, Jeremy S.; Chanda, Sumit K.; Izpisua-Belmonte, Juan C.; Schultz, Peter G.

    2004-01-01

    The p53 tumor-suppressor protein is a critical mediator of cellular growth arrest and the induction of apoptosis. To identify proteins involved in the modulation of p53 transcriptional activity, a gain-of-function cellular screen was carried out with an arrayed matrix of ≈20,000 cDNAs. Nine genes previously unknown to be involved in regulating p53 activity were identified. Overexpression of seven of these genes (Hey1, Hes1, TFAP4, Osr1, NR2F2, SFRS10, and FLJ11339) resulted in up-regulation of p53 activity; overexpression of two genes (M17S2 and cathepsin B) resulted in down-regulation of p53 activity in mammalian cells. HES1, HEY1, and TFAP4, which are members of the basic helix–loop–helix transcription family, and OSR1 were shown to activate p53 through repression of HDM2 transcription. Ectopic expression of these basic helix–loop–helix transcription factors in both zebrafish and avian developmental systems activated p53 and induced apoptosis in vivo, resulting in a phenotype similar to that of p53 overexpression. Furthermore, ras- and myc-mediated transformation of mouse embryonic fibroblasts was abrogated by expression of HEY1 in a p53-dependent manner. These results suggest that these transcription factors are members of an evolutionarily conserved network that governs p53 function. PMID:14990790

  15. Yes-associated protein and p53-binding protein-2 interact through their WW and SH3 domains.

    Science.gov (United States)

    Espanel, X; Sudol, M

    2001-04-27

    To understand the role of the Yes-associated protein (YAP), binding partners of its WW1 domain were isolated by a yeast two-hybrid screen. One of the interacting proteins was identified as p53-binding protein-2 (p53BP-2). YAP and p53BP-2 interacted in vitro and in vivo using their WW1 and SH3 domains, respectively. The YAP WW1 domain bound to the YPPPPY motif of p53BP-2, whereas the p53BP-2 SH3 domain interacted with the VPMRLR sequence of YAP, which is different from other known SH3 domain-binding motifs. By mutagenesis, we showed that this unusual SH3 domain interaction was due to the presence of three consecutive tryptophans located within the betaC strand of the SH3 domain. A point mutation within this triplet, W976R, restored the binding selectivity to the general consensus sequence for SH3 domains, the PXXP motif. A constitutively active form of c-Yes was observed to decrease the binding affinity between YAP and p53BP-2 using chloramphenicol acetyltransferase/enzyme-linked immunosorbent assay, whereas the overexpression of c-Yes did not modify this interaction. Since overexpression of an activated form of c-Yes resulted in tyrosine phosphorylation of p53BP-2, we propose that the p53BP-2 phosphorylation, possibly in the WW1 domain-binding motif, might negatively regulate the YAP.p53BP-2 complex.

  16. Systems-level analysis of the regulation and function of p53 dynamics in cancer

    Science.gov (United States)

    Batchelor, Eric

    Living cells use complex signaling pathways to detect environmental stimuli and generate appropriate responses. As methods for quantifying intracellular signaling have improved, several signaling pathways have been found to transmit information using signals that pulse in time. The transcription factor p53 is a key tumor suppressor and stress-response regulator that exhibits pulsatile dynamics. In response to DNA double-strand breaks, the concentration of p53 in the cell nucleus increases in pulses with a fixed amplitude, duration, and period; the mean number of pulses increases with DNA damage. p53 regulates the expression of over 100 target genes involved in a range of cellular stress responses including apoptosis, cell cycle arrest, and changes in metabolism. p53 pulsing directly impacts p53 function: altering p53 dynamics by pharmacologically inhibiting p53 degradation changes patterns of target gene expression and cell fate. While p53 pulsing serves an important signaling function, it is less clear what it accomplishes mechanistically. Here we will describe our recent efforts to determine the impact of p53 pulsing on the dynamics and coordination of target gene expression.

  17. Serum p53 antibody detection in patients with impaired lung function

    Directory of Open Access Journals (Sweden)

    Mattioni Manlio

    2013-02-01

    Full Text Available Abstract Background TP53 gene mutations can lead to the expression of a dysfunctional protein that in turn may enable genetically unstable cells to survive and change into malignant cells. Mutant p53 accumulates early in cells and can precociously induce circulating anti-p53 antibodies (p53Abs; in fact, p53 overexpression has been observed in pre-neoplastic lesions, such as bronchial dysplasia, and p53Abs have been found in patients with Chronic Obstructive Pulmonary Disease, before the diagnosis of lung and other tobacco-related tumors. Methods A large prospective study was carried out, enrolling non-smokers, ex-smokers and smokers with or without the impairment of lung function, to analyze the incidence of serum p53Abs and the correlation with clinicopathologic features, in particular smoking habits and impairment of lung function, in order to investigate their possible role as early markers of the onset of lung cancer or other cancers. The p53Ab levels were evaluated by a specific ELISA in 675 subjects. Results Data showed that significant levels of serum p53Abs were present in 35 subjects (5.2%; no difference was observed in the presence of p53Abs with regard to age and gender, while p53Abs correlated with the number of cigarettes smoked per day and packs-year. Furthermore, serum p53Abs were associated with the worst lung function impairment. The median p53Ab level in positive subjects was 3.5 units/ml (range 1.2 to 65.3 units/ml. Only fifteen positive subjects participated in the follow-up, again resulting positive for serum p53Abs, and no evidence of cancer was found in these patients. Conclusion The presence of serum p53Abs was found to be associated with smoking level and lung function impairment, both risk factors of cancer development. However, in our study we have not observed the occurrence of lung cancer or other cancers in the follow-up of positive subjects, therefore we cannot directly correlate the presence of serum p53Abs with

  18. Rb and p53 Liver Functions Are Essential for Xenobiotic Metabolism and Tumor Suppression

    NARCIS (Netherlands)

    Nantasanti, Sathidpak; Toussaint, Mathilda J. M.; Youssef, Sameh A.; Tooten, Peter C. J.; de Bruin, Alain

    2016-01-01

    The tumor suppressors Retinoblastoma (Rb) and p53 are frequently inactivated in liver diseases, such as hepatocellular carcinomas (HCC) or infections with Hepatitis B or C viruses. Here, we discovered a novel role for Rb and p53 in xenobiotic metabolism, which represent a key function of the liver f

  19. APE1/Ref-1 enhances DNA binding activity of mutant p53 in a redox-dependent manner.

    Science.gov (United States)

    Cun, Yanping; Dai, Nan; Li, Mengxia; Xiong, Chengjie; Zhang, Qinhong; Sui, Jiangdong; Qian, Chengyuan; Wang, Dong

    2014-02-01

    Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a dual function protein; in addition to its DNA repair activity, it can stimulate DNA binding activity of numerous transcription factors as a reduction-oxidation (redox) factor. APE1/Ref-1 has been found to be a potent activator of wild-type p53 (wtp53) DNA binding in vitro and in vivo. Although p53 is mutated in most types of human cancer including hepatocellular carcinoma (HCC), little is known about whether APE1/Ref-1 can regulate mutant p53 (mutp53). Herein, we reported the increased APE1/Ref-1 protein and accumulation of mutp53 in HCC by immunohistochemistry. Of note, it was observed that APE1/Ref-1 high-expression and mutp53 expression were associated with carcinogenesis and progression of HCC. To determine whether APE1/Ref-1 regulates DNA binding of mutp53, we performed electromobility shift assays (EMSAs) and quantitative chromatin immunoprecipitation (ChIP) assays in HCC cell lines. In contrast to sequence-specific and DNA structure-dependent binding of wtp53, reduced mutp53 efficiently bound to nonlinear DNA, but not to linear DNA. Notably, overexpression of APE1/Ref-1 resulted in increased DNA binding activity of mutp53, while downregulation of APE1/Ref-1 caused a marked decrease of mutp53 DNA binding. In addition, APE1/Ref-1 could not potentiate the accumulation of p21 mRNA and protein in mutp53 cells. These data indicate that APE1/Ref-1 can stimulate mutp53 DNA binding in a redox-dependent manner.

  20. Functional evolution of the p53 regulatory network through its target response elements

    Science.gov (United States)

    Jegga, Anil G.; Inga, Alberto; Menendez, Daniel; Aronow, Bruce J.; Resnick, Michael A.

    2008-01-01

    Transcriptional network evolution is central to the development of complex biological systems. Networks can evolve through variation of master regulators and/or by changes in regulation of genes within networks. To gain insight into meaningful evolutionary differences in large networks, it is essential to address the functional consequences of sequence differences in response elements (REs) targeted by transcription factors. Using a combination of custom bioinformatics and multispecies alignment of promoter regions, we investigated the functional evolution of REs in terms of responsiveness to the sequence-specific transcription factor p53, a tumor suppressor and master regulator of stress responses. We identified REs orthologous to known p53 targets in human and rodent cells or alternatively REs related to the established p53 consensus. The orthologous REs were assigned p53 transactivation capabilities based on rules determined from model systems, and a functional heat map was developed to visually summarize conservation of sequence and relative level of responsiveness to p53 for 47 REs in 14 species. Individual REs exhibited marked differences in transactivation potentials and widespread evolutionary turnover. Functional differences were often not predicted from consensus sequence evaluations. Of the established human p53 REs analyzed, 91% had sequence conservation in at least one nonprimate species compared with 67.5% for functional conservation. Surprisingly, there was almost no conservation of functional REs for genes involved in DNA metabolism or repair between humans and rodents, suggesting important differences in p53 stress responses and cancer development. PMID:18187580

  1. Nuclear Localization Signal and p53 Binding Site in MAP/ERK Kinase Kinase 1 (MEKK1)

    Science.gov (United States)

    Chipps, Elizabeth; Protzman, April; Muhi, M. Zubayed; Ando, Shoko; Calvet, James P.; Islam, M. Rafiq

    2015-01-01

    Previously, we showed that Mekk1 translocates to the nucleus, interacts with tumor suppressor protein p53 and co-represses PKD1 transcription via an atypical p53 binding site on the minimal PKD1 promoter (JBC 285:38818-38831, 2010). In this study, we report the mechanisms of Mekk1 nuclear transport and p53 binding. Using GFP-linked constitutively active-Mekk1 (CA-Mekk1) and a deletion strategy, we identified a nuclear localization signal (HRDVK) located at amino acid (aa) residues 1349–1353 in the C-terminal Mekk1 catalytic domain. Deletion of this sequence in CA-Mekk1 and full-length Mekk1 significantly reduced their nuclear translocation in both HEK293T and COS-1 cells. Using co-immunoprecipitation we identified an adjacent sequence (GANLID, aa 1354–1360) in Mekk1 responsible for p53 binding. Deletion of this sequence markedly reduced the interaction of Mekk1 with p53. Mekk1 does not appear to affect phosphorylation of Ser15, located in the Mdm2 interaction site, or other Ser residues in p53. However, Mekk1 mediates p53 protein stability in the presence of Mdm2 and reduces p53 ubiquitination, suggesting an interference with Mdm2-mediated degradation of p53 by the ubiquitin-proteasome pathway. PMID:26018553

  2. ARF functions as a melanoma tumor suppressor by inducing p53-independent senescence

    Science.gov (United States)

    Ha, Linan; Ichikawa, Takeshi; Anver, Miriam; Dickins, Ross; Lowe, Scott; Sharpless, Norman E.; Krimpenfort, Paul; DePinho, Ronald A.; Bennett, Dorothy C.; Sviderskaya, Elena V.; Merlino, Glenn

    2007-01-01

    Inactivation of the p53 pathway represents the most common molecular defect of human cancer. But in the setting of melanoma, a highly aggressive and invariably fatal malignancy in its advanced disseminated form, mutation/deletion of p53 is relatively rare, whereas its positive regulator ARF is often lost. Here, we show that genetic deficiency in Arf but not p53 facilitates rapid development of melanoma in a genetically engineered mouse model. This difference is accounted for, at least in part, by the unanticipated observation that, unlike fibroblasts, senescence control in melanocytes is strongly regulated by Arf and not p53. Moreover, oncogenic NRAS collaborates with deficiency in Arf, but not p53, to fully transform melanocytes. Our data demonstrate that ARF and p53, although linked in a common pathway, suppress tumorigenesis through distinct, lineage-dependent mechanisms and suggest that ARF helps restrict melanoma progression by executing the oncogene-induced senescence program in benign nevi. Thus, therapeutics designed to restore wild-type p53 function may be insufficient to counter melanoma and other malignancies in which ARF holds p53-independent tumor suppressor activity. PMID:17576930

  3. The tumor suppressors pRB and p53 as regulators of adipocyte differentiation and function

    DEFF Research Database (Denmark)

    Hallenborg, Philip; Feddersen, Søren; Madsen, Lise

    2009-01-01

    BACKGROUND: The retinoblastoma protein (pRB) and p53 are crucial members of regulatory networks controlling the cell cycle and apoptosis, and a hallmark of virtually all cancers is dysregulation of expression or function of pRB or p53. Although they are best known for their role in cancer develop...... of energy metabolism and homeostasis. RESULTS/CONCLUSIONS: pRB is required for adipose conversion and also involved in determining its mitochondrial capacity. p53 inhibits adipogenesis and results suggest that it is involved in maintaining function of adipose tissue.......BACKGROUND: The retinoblastoma protein (pRB) and p53 are crucial members of regulatory networks controlling the cell cycle and apoptosis, and a hallmark of virtually all cancers is dysregulation of expression or function of pRB or p53. Although they are best known for their role in cancer...... development, it is now evident that both are implicated in metabolism and cellular development. OBJECTIVE/METHODS: To review the role of pRB and p53 in adipocyte differentiation and function emphasizing that pRB and p53, via their effects on adipocyte development and function, play a role in the regulation...

  4. Gain-of-function of mutant p53: mutant p53 enhances cancer progression by inhibiting KLF17 expression in invasive breast carcinoma cells.

    Science.gov (United States)

    Ali, Amjad; Shah, Abdus Saboor; Ahmad, Ayaz

    2014-11-01

    Kruppel-like-factor 17 (KLF17) is a negative regulator of metastasis and epithelial-mesenchymal-transition (EMT). However, its expression is downregulated in metastatic breast cancer that contains p53 mutations. Here, we show that mutant-p53 plays a key role to suppress KLF17 and thereby enhances cancer progression, which defines novel gain-of-function (GOF) of mutant-p53. Mutant-p53 interacts with KLF17 and antagonizes KLF17 mediated EMT genes transcription. Depletion of KLF17 promotes cell viability, decreases apoptosis and induces drug resistance in metastatic breast cancer cells. KLF17 suppresses cell migration and invasion by decreasing CD44, PAI-1 and Cyclin-D1 expressions. Taken together, our results show that KLF17 is important for the suppression of metastasis and could be a potential therapeutic target during chemotherapy.

  5. BACH1 Promotes Temozolomide Resistance in Glioblastoma through Antagonizing the Function of p53

    Science.gov (United States)

    Nie, Er; Jin, Xin; Wu, Weining; Yu, Tianfu; Zhou, Xu; Zhi, Tongle; Shi, Zhumei; Zhang, Junxia; Liu, Ning; You, Yongping

    2016-01-01

    The acquisition of drug resistance is a persistent clinical problem limiting the successful treatment of glioblastoma (GBM). However, the molecular mechanisms by which initially chemoresponsive tumors develop therapeutic resistance remain poorly understood. In this study, we report that BACH1, a heme-binding protein that participates in transcriptional repression or activation, was significantly upregulated in glioblastoma tissues. Overexpression of BACH1 in GBM cells conferred resistance to temozolomide, whereas its inhibition markedly sensitized resistant cells to temozolomide in vitro and in vivo. Further investigation revealed that BACH1 activation significantly enhanced the expression of MGMT, and depletion of p53 disrupted the effects of BACH1 on MGMT and temozolomide resistance. P53 sequesters SP1 to prevent its binding to the MGMT promoter region and thus inhibits MGMT expression. Moreover, BACH1 overexpression impaired the association between p53 and SP1 via competitive binding p53, and antagonized the impact of p53 on MGMT expression. Finally, we found that BACH1 low expression correlated with better prognosis in GBM patients undergoing temozolomide therapy, especially in patients with wild-type TP53. Collectively, our findings identify a potential mechanism by which wild-type TP53 GBM cells develop resistance to temozolomide and suggest that targeting this pathway may be beneficial for overcoming resistance. PMID:28000777

  6. mRNA display selection of an optimized MDM2-binding peptide that potently inhibits MDM2-p53 interaction.

    Directory of Open Access Journals (Sweden)

    Hirokazu Shiheido

    Full Text Available p53 is a tumor suppressor protein that prevents tumorigenesis through cell cycle arrest or apoptosis of cells in response to cellular stress such as DNA damage. Because the oncoprotein MDM2 interacts with p53 and inhibits its activity, MDM2-p53 interaction has been a major target for the development of anticancer drugs. While previous studies have used phage display to identify peptides (such as DI that inhibit the MDM2-p53 interaction, these peptides were not sufficiently optimized because the size of the phage-displayed random peptide libraries did not cover all of the possible sequences. In this study, we performed selection of MDM2-binding peptides from large random peptide libraries in two stages using mRNA display. We identified an optimal peptide named MIP that inhibited the MDM2-p53 and MDMX-p53 interactions 29- and 13-fold more effectively than DI, respectively. Expression of MIP fused to the thioredoxin scaffold protein in living cells by adenovirus caused stabilization of p53 through its interaction with MDM2, resulting in activation of the p53 pathway. Furthermore, expression of MIP also inhibited tumor cell proliferation in a p53-dependent manner more potently than DI. These results show that two-stage, mRNA-displayed peptide selection is useful for the rapid identification of potent peptides that target oncoproteins.

  7. Rb and p53 Liver Functions Are Essential for Xenobiotic Metabolism and Tumor Suppression.

    Directory of Open Access Journals (Sweden)

    Sathidpak Nantasanti

    Full Text Available The tumor suppressors Retinoblastoma (Rb and p53 are frequently inactivated in liver diseases, such as hepatocellular carcinomas (HCC or infections with Hepatitis B or C viruses. Here, we discovered a novel role for Rb and p53 in xenobiotic metabolism, which represent a key function of the liver for metabolizing therapeutic drugs or toxins. We demonstrate that Rb and p53 cooperate to metabolize the xenobiotic 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC. DDC is metabolized mainly by cytochrome P450 (Cyp3a enzymes resulting in inhibition of heme synthesis and accumulation of protoporphyrin, an intermediate of heme pathway. Protoporphyrin accumulation causes bile injury and ductular reaction. We show that loss of Rb and p53 resulted in reduced Cyp3a expression decreased accumulation of protoporphyrin and consequently less ductular reaction in livers of mice fed with DDC for 3 weeks. These findings provide strong evidence that synergistic functions of Rb and p53 are essential for metabolism of DDC. Because Rb and p53 functions are frequently disabled in liver diseases, our results suggest that liver patients might have altered ability to remove toxins or properly metabolize therapeutic drugs. Strikingly the reduced biliary injury towards the oxidative stress inducer DCC was accompanied by enhanced hepatocellular injury and formation of HCCs in Rb and p53 deficient livers. The increase in hepatocellular injury might be related to reduce protoporphyrin accumulation, because protoporphrin is well known for its anti-oxidative activity. Furthermore our results indicate that Rb and p53 not only function as tumor suppressors in response to carcinogenic injury, but also in response to non-carcinogenic injury such as DDC.

  8. Reversible inactivation of the transcriptional function of P53 protein by farnesylation

    Directory of Open Access Journals (Sweden)

    Berg Danièle

    2006-05-01

    Full Text Available Abstract Background The use of integrating viral vectors in Gene therapy clinical trials has pointed out the problem of the deleterous effect of the integration of the ectopic gene to the cellular genome and the safety of this strategy. We proposed here a way to induce the death of gene modified cells upon request by acting on a pro-apoptotic protein cellular localization and on the activation of its apoptotic function. Results We constructed an adenoviral vector coding a chimeric p53 protein by fusing p53 sequence with the 21 COOH term amino acids sequence of H-Ras. Indeed, the translation products of Ras genes are cytosolic proteins that become secondarily associated with membranes through a series of post-translational modifications initiated by a CAAX motif present at the C terminus of Ras proteins. The chimeric p53HRCaax protein was farnesylated efficiently in transduced human osteosarcoma p53-/- cell line. The farnesylated form of p53 resided mainly in the cytosol, where it is non-functional. Farnesyl transferase inhibitors (FTIs specifically inhibited farnesyl isoprenoid lipid modification of proteins. Following treatment of the cells with an FTI, p53HRCaax underwent translocation into the nucleus where it retained transcription factor activity. Shifting p53 into the nucleus resulted in the induction of p21waf1/CIP1 and Bax transcription, cell growth arrest, caspase activation and apoptosis. Conclusion Artificial protein farnesylation impaired the transcriptional activity of p53. This could be prevented by Farnesyl transferase inhibition. These data highlight the fact that the artificial prenylation of proteins provides a novel system for controlling the function of a transactivating factor.

  9. Functional domains of wild-type and mutant p53 proteins involved in transcriptional regulation, transdominant inhibition, and transformation suppression.

    OpenAIRE

    1993-01-01

    The wild-type (wt) p53 protein has transcriptional activation functions which may be linked to its tumor suppressor activity. Many mutant p53 proteins expressed in cancers have lost the ability to function as transcriptional activators and furthermore may inhibit wt p53 function. To study the mechanisms by which mutant forms of p53 have lost their transactivation function and can act in a dominant negative manner, a structure-function analysis of both mutant and engineered truncated forms of ...

  10. Lack of p53 Augments Antitumor Functions in Cytolytic T Cells.

    Science.gov (United States)

    Banerjee, Anirban; Thyagarajan, Krishnamurthy; Chatterjee, Shilpak; Chakraborty, Paramita; Kesarwani, Pravin; Soloshchenko, Myroslawa; Al-Hommrani, Mazen; Andrijauskaite, Kristina; Moxley, Kelly; Janakiraman, Harinarayanan; Scheffel, Matthew J; Helke, Kristi; Armenson, Kent; Palanisamy, Viswanathan; Rubinstein, Mark P; Mayer, Elizabeth-Garrett; Cole, David J; Paulos, Chrystal M; Voelkel-Johnson, Christina; Nishimura, Michael I; Mehrotra, Shikhar

    2016-09-15

    Repetitive stimulation of T-cell receptor (TCR) with cognate antigen results in robust proliferation and expansion of the T cells, and also imprints them with replicative senescence signatures. Our previous studies have shown that life-span and antitumor function of T cells can be enhanced by inhibiting reactive oxygen species (ROS) or intervening with ROS-dependent JNK activation that leads to its activation-induced cell death. Because tumor suppressor protein p53 is also a redox active transcription factor that regulates cellular ROS generation that triggers downstream factor-mediating apoptosis, we determined if p53 levels could influence persistence and function of tumor-reactive T cells. Using h3T TCR transgenic mice, with human tyrosinase epitope-reactive T cells developed on p53 knockout (KO) background, we determined its role in regulating antitumor T-cell function. Our data show that as compared with h3T cells, h3T-p53 KO T cells exhibited enhanced glycolytic commitment that correlated with increased proliferation, IFNγ secretion, cytolytic capacity, expression of stemness gene signature, and decreased TGF-β signaling. This increased effector function correlated to the improved control of subcutaneously established murine melanoma after adoptive transfer of p53-KO T cells. Pharmacological inhibition of human TCR-transduced T cells using a combination of p53 inhibitors also potentiated the T-cell effector function and improved persistence. Thus, our data highlight the key role of p53 in regulating the tumor-reactive T-cell response and that targeting this pathway could have potential translational significance in adoptive T-cell therapy. Cancer Res; 76(18); 5229-40. ©2016 AACR.

  11. Oncogenomic Approaches in Exploring Gain of Function of Mutant p53

    Science.gov (United States)

    Donzelli, Sara; Biagioni, Francesca; Fausti, Francesca; Strano, Sabrina; Fontemaggi, Giulia; Blandino, Giovanni

    2008-01-01

    Cancer is caused by the spatial and temporal accumulation of alterations in the genome of a given cell. This leads to the deregulation of key signalling pathways that play a pivotal role in the control of cell proliferation and cell fate. The p53 tumor suppressor gene is the most frequent target in genetic alterations in human cancers. The primary selective advantage of such mutations is the elimination of cellular wild type p53 activity. In addition, many evidences in vitro and in vivo have demonstrated that at least certain mutant forms of p53 may possess a gain of function, whereby they contribute positively to cancer progression. The fine mapping and deciphering of specific cancer phenotypes is taking advantage of molecular-profiling studies based on genome-wide approaches. Currently, high-throughput methods such as array-based comparative genomic hybridization (CGH array), single nucleotide polymorphism array (SNP array), expression arrays and ChIP-on-chip arrays are available to study mutant p53-associated alterations in human cancers. Here we will mainly focus on the integration of the results raised through oncogenomic platforms that aim to shed light on the molecular mechanisms underlying mutant p53 gain of function activities and to provide useful information on the molecular stratification of tumor patients. PMID:19440517

  12. Histone modifications and p53 binding poise the p21 promoter for activation in human embryonic stem cells.

    Science.gov (United States)

    Itahana, Yoko; Zhang, Jinqiu; Göke, Jonathan; Vardy, Leah A; Han, Rachel; Iwamoto, Kozue; Cukuroglu, Engin; Robson, Paul; Pouladi, Mahmoud A; Colman, Alan; Itahana, Koji

    2016-06-27

    The high proliferation rate of embryonic stem cells (ESCs) is thought to arise partly from very low expression of p21. However, how p21 is suppressed in ESCs has been unclear. We found that p53 binds to the p21 promoter in human ESCs (hESCs) as efficiently as in differentiated human mesenchymal stem cells, however it does not promote p21 transcription in hESCs. We observed an enrichment for both the repressive histone H3K27me3 and activating histone H3K4me3 chromatin marks at the p21 locus in hESCs, suggesting it is a suppressed, bivalent domain which overrides activation by p53. Reducing H3K27me3 methylation in hESCs rescued p21 expression, and ectopic expression of p21 in hESCs triggered their differentiation. Further, we uncovered a subset of bivalent promoters bound by p53 in hESCs that are similarly induced upon differentiation in a p53-dependent manner, whereas p53 promotes the transcription of other target genes which do not show an enrichment of H3K27me3 in ESCs. Our studies reveal a unique epigenetic strategy used by ESCs to poise undesired p53 target genes, thus balancing the maintenance of pluripotency in the undifferentiated state with a robust response to differentiation signals, while utilizing p53 activity to maintain genomic stability and homeostasis in ESCs.

  13. Structure of the p53 binding domain of HAUSP/USP7 bound to Epstein-Barr nuclear antigen 1 implications for EBV-mediated immortalization.

    Science.gov (United States)

    Saridakis, Vivian; Sheng, Yi; Sarkari, Feroz; Holowaty, Melissa N; Shire, Kathy; Nguyen, Tin; Zhang, Rongguang G; Liao, Jack; Lee, Weontae; Edwards, Aled M; Arrowsmith, Cheryl H; Frappier, Lori

    2005-04-01

    USP7/HAUSP is a key regulator of p53 and Mdm2 and is targeted by the Epstein-Barr nuclear antigen 1 (EBNA1) protein of Epstein-Barr virus (EBV). We have determined the crystal structure of the p53 binding domain of USP7 alone and bound to an EBNA1 peptide. This domain is an eight-stranded beta sandwich similar to the TRAF-C domains of TNF-receptor associated factors, although the mode of peptide binding differs significantly from previously observed TRAF-peptide interactions in the sequence (DPGEGPS) and the conformation of the bound peptide. NMR chemical shift analyses of USP7 bound by EBNA1 and p53 indicated that p53 binds the same pocket as EBNA1 but makes less extensive contacts with USP7. Functional studies indicated that EBNA1 binding to USP7 can protect cells from apoptotic challenge by lowering p53 levels. The data provide a structural and conceptual framework for understanding how EBNA1 might contribute to the survival of Epstein-Barr virus-infected cells.

  14. Chlamydia infection depends on a functional MDM2-p53 axis.

    Science.gov (United States)

    González, Erik; Rother, Marion; Kerr, Markus C; Al-Zeer, Munir A; Abu-Lubad, Mohammad; Kessler, Mirjana; Brinkmann, Volker; Loewer, Alexander; Meyer, Thomas F

    2014-11-13

    Chlamydia, a major human bacterial pathogen, assumes effective strategies to protect infected cells against death-inducing stimuli, thereby ensuring completion of its developmental cycle. Paired with its capacity to cause extensive host DNA damage, this poses a potential risk of malignant transformation, consistent with circumstantial epidemiological evidence. Here we reveal a dramatic depletion of p53, a tumor suppressor deregulated in many cancers, during Chlamydia infection. Using biochemical approaches and live imaging of individual cells, we demonstrate that p53 diminution requires phosphorylation of Murine Double Minute 2 (MDM2; a ubiquitin ligase) and subsequent interaction of phospho-MDM2 with p53 before induced proteasomal degradation. Strikingly, inhibition of the p53-MDM2 interaction is sufficient to disrupt intracellular development of Chlamydia and interferes with the pathogen's anti-apoptotic effect on host cells. This highlights the dependency of the pathogen on a functional MDM2-p53 axis and lends support to a potentially pro-carcinogenic effect of chlamydial infection.

  15. Actin polymerization negatively regulates p53 function by impairing its nuclear import in response to DNA damage.

    Directory of Open Access Journals (Sweden)

    Ling Wang

    Full Text Available Actin, one of the most evolutionarily conservative proteins in eukaryotes, is distributed both in the cytoplasm and the nucleus, and its dynamics plays important roles in numerous cellular processes. Previous evidence has shown that actin interacts with p53 and this interaction increases in the process of p53 responding to DNA damage, but the physiological significance of their interaction remains elusive. Here, we show that DNA damage induces both actin polymerization and p53 accumulation. To further understand the implication of actin polymerization in p53 function, cells were treated with actin aggregation agent. We find that the protein level of p53 decrease. The change in p53 is a consequence of the polymeric actin anchoring p53 in the cytoplasm, thus impairing p53 nuclear import. Analysis of phosphorylation and ubiquitination of p53 reveals that actin polymerization promotes the p53 phosphorylation at Ser315 and reduces the stabilization of p53 by recruiting Aurora kinase A. Taken together, our results suggest that the actin polymerization serves as a negative modulator leading to the impairment of nuclear import and destabilization of p53. On the basis of our results, we propose that actin polymerization might be a factor participating in the process of orchestrating p53 function in response to DNA damage.

  16. Development of functionalized nanodiamond fluorescence detection platform: Analysis the specific promoter regulated by p53

    Science.gov (United States)

    Wu, Diansyue; Chu, Hsueh-Liang; Chuang, Hung; Lu, Yu-Ning; Ho, Li-Ping; Li, Hsing-Yuan; Hsu, Ming-Hua; Chang, Chia-Ching

    2014-03-01

    Nanodiamond (ND) is one of the biocompatible nanomaterials with large tunable surface for chemical modification. It possesses unique mechanical, spectroscopy, and thermal properties. It is an excellent molecular vehicle to deliver specific molecules in biological system. The green fluorescent protein (GFP) is a protein that emits strong green fluorescence when it is excited by ultra-violet to blue light. It makes GFP a good indicator. By combining ND-GFP, a visible biocompatible delivery system will be developed. p53 is a tumor suppressor protein encoded by the TP53 gene. P53 plays an important role in apoptosis, genomic stability, and inhibition of angiogenesis by interacting with specific DNA sequence of promoter of related genes. In this study, a p53 functionalized ND-GFP will be developed. This complex can recognize the specific DNA sequence of promoter and the intermolecular interactions can be monitored directly by fluorescence and Raman spectroscopy both in vivo and in vitro.

  17. Identification and design of p53-derived HLA-A2-binding peptides with increased CTL immunogenicity

    DEFF Research Database (Denmark)

    Petersen, T R; Buus, S; Brunak, S;

    2001-01-01

    of peptide binding to HLA-A2 molecules, we identified three p53 protein-derived nonamer peptides with intermediate binding owing to suboptimal amino acids in the P2 anchor position. These peptides were synthesized along with the corresponding analogs, where the natural P2 residue had been replaced...

  18. P53与端粒重复序列结合蛋白质1的体外相互作用%The molecular interaction between P53 and telomeric repeat binding protein 1 in vitro

    Institute of Scientific and Technical Information of China (English)

    李玲; 张波; 邹万忠; 郑杰

    2004-01-01

    目的:通过分析端粒主要结合蛋白中端粒重复序列结合蛋白质1(Telomeric repeat binding protein 1,TRBP1)与P53的体外结合,探讨P53通过端粒途径调节细胞增殖、衰老和凋亡的分子机制.方法:谷胱甘肽S转移酶(glutathione S-transferase,GST)和人P53-GST融合蛋白经大肠杆菌表达、谷胱甘肽-SepharoseTM4B纯化后,和人乳腺癌细胞MCF-7细胞蛋白进行体外结合反应(pull down),Western blot检测反应物中P53和TRBP1的结合.融合蛋白中人P53包括野生型(1~393)、C端缺失体P53 N5(2~293)、N端缺失体P53 2C(95~393)、175单个氨基酸突变体P53 R175H(R→H).结果:聚丙烯酰胺凝胶电泳和考马斯亮蓝R250染色显示,纯化的GST和4种P53-GST蛋白纯度在90%以上,且分子量与预计的完全一致.TRBP1的Western blot显示,野生型P53P53-R175H均能沉淀MCF-7中的TRBP1,且结合力相似,而单独的GST则无沉淀TRBP1的作用.与野生型P53P53 R175H相比,P53 2C与TRBP1的结合力明显增加,P53 N5与TRBP1的结合力明显减弱.结论:P53和TRBP1可以直接体外结合,P53的C端(293~393)是与TRBP1结合的结构域.P53和TRBP1结构域依赖性的结合可能与端粒动态变化所诱导的细胞活动有关.

  19. Loss of Geminin induces rereplication in the presence of functional p53

    DEFF Research Database (Denmark)

    Melixetian, Marina; Ballabeni, Andrea; Masiero, Laura

    2004-01-01

    nuclear foci. Abrogation of the checkpoint leads to abortive mitosis and death of rereplicated cells. In addition, we demonstrate that the induction of rereplication is dependent on the replication initiation factors CDT1 and CDC6, and independent of the functional status of p53. These data show...

  20. Comprehensive Expression Profiling and Functional Network Analysis of p53-Regulated MicroRNAs in HepG2 Cells Treated with Doxorubicin.

    Directory of Open Access Journals (Sweden)

    Yalan Yang

    Full Text Available Acting as a sequence-specific transcription factor, p53 tumor suppressor involves in a variety of biological processes after being activated by cellular stresses such as DNA damage. In recent years, microRNAs (miRNAs have been confirmed to be regulated by p53 in several cancer types. However, it is still unclear how miRNAs orchestrate their regulation and function in p53 network after p53 activation in hepatocellular carcinoma (HCC. In this study, we used small RNA sequencing and systematic bioinformatic analysis to characterize the regulatory networks of differentially expressed miRNAs after the p53 activation in HepG2. Here, 33 miRNAs significantly regulated by p53 (12 up-regulated and 21 down-regulated were detected between the doxorubicin-treated and untreated HepG2 cells in two biological replicates for small RNA sequencing and 8 miRNAs have been reported previously to be associated with HCC. Gene ontology (GO and KEGG pathway enrichment analysis showed that 87.9% (29 out of 33 and 90.9% (30 out of 33 p53-regulated miRNAs were involved in p53-related biological processes and pathways with significantly low p-value, respectively. Remarkably, 18 out of 33 p53-regulated miRNAs were identified to contain p53 binding sites around their transcription start sites (TSSs. Finally, comprehensive p53-miRNA regulatory networks were constructed and analyzed. These observations provide a new insight into p53-miRNA co-regulatory network in the context of HCC.

  1. Prosurvival long noncoding RNA PINCR regulates a subset of p53 targets in human colorectal cancer cells by binding to Matrin 3

    Science.gov (United States)

    Chaudhary, Ritu; Gryder, Berkley; Woods, Wendy S; Subramanian, Murugan; Jones, Matthew F; Li, Xiao Ling; Jenkins, Lisa M; Shabalina, Svetlana A; Mo, Min; Dasso, Mary; Yang, Yuan; Wakefield, Lalage M; Zhu, Yuelin; Frier, Susan M; Moriarity, Branden S; Prasanth, Kannanganattu V; Perez-Pinera, Pablo; Lal, Ashish

    2017-01-01

    Thousands of long noncoding RNAs (lncRNAs) have been discovered, yet the function of the vast majority remains unclear. Here, we show that a p53-regulated lncRNA which we named PINCR (p53-induced noncoding RNA), is induced ~100-fold after DNA damage and exerts a prosurvival function in human colorectal cancer cells (CRC) in vitro and tumor growth in vivo. Targeted deletion of PINCR in CRC cells significantly impaired G1 arrest and induced hypersensitivity to chemotherapeutic drugs. PINCR regulates the induction of a subset of p53 targets involved in G1 arrest and apoptosis, including BTG2, RRM2B and GPX1. Using a novel RNA pulldown approach that utilized endogenous S1-tagged PINCR, we show that PINCR associates with the enhancer region of these genes by binding to RNA-binding protein Matrin 3 that, in turn, associates with p53. Our findings uncover a critical prosurvival function of a p53/PINCR/Matrin 3 axis in response to DNA damage in CRC cells. DOI: http://dx.doi.org/10.7554/eLife.23244.001 PMID:28580901

  2. Screening of p53 Promoter Binding Proteins by Phage Display in Liver Cells%筛选肝细胞p53启动子结合蛋白的噬菌体表面展示技术

    Institute of Scientific and Technical Information of China (English)

    吴顺华; 钟彦伟; 成军; 郑玉建

    2011-01-01

    fingers family 2 (DPF2) ;Homo sapiens PAI-1 mRNA-binding protein (PAl-l); H.sapiens mRNA for tyrosine aminotransferase;Homo sapiens requiem,apoptosis response zinc finger gene (REQ) gene;Homo sapiens nuclear ubiquitous casein kinase and cyclin-dependent kinase (NUCK/CDK);Homo sapiens glutathione peroxidase 7 (GPX7);Homo sapiens transmembrane protein 2 (TMEM2);Human 28S ribosomal ;Homo sapiens HIRA interacting protein3 (HIRIP3); Homo sapiens v-erb-b2 erythroblastic leukemia viral oncogene homolog 2, neuro/glioblastoma derived oncogene homolog (avian) (ERBB2) ;Homo sapiens ataxia telangiectasia mutated (includes complementatio groups A, C and D) (ATM) gene et al. The screened proteins with different function associated with extracellular matrix, cell growth and metabolization, cell cycle regulation and proliferation, tumor suppression,blood coagulation,apoptosis,signaltransduction regulation and oncogene including 2 novel protein. Conclusion Many proteins with different functions could bind with p53 gene and affect its activity.

  3. Inhibition of NAMPT pathway by FK866 activates the function of p53 in HEK293T cells

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Basant Kumar, E-mail: thakur.basant@mh-hannover.de [Department of Pediatrics, Hematology and Oncology, Hannover Medical School, Carl Neuberg Str-1, 30625 Hannover (Germany); Department of Molecular Hematopoiesis, Hannover Medical School, Carl Neuberg Str-1, 30625 Hannover (Germany); Dittrich, Tino [Department of Pediatrics, Hematology and Oncology, Hannover Medical School, Carl Neuberg Str-1, 30625 Hannover (Germany); Department of Molecular Hematopoiesis, Hannover Medical School, Carl Neuberg Str-1, 30625 Hannover (Germany); Chandra, Prakash [Frankfurt University Medical School, Molecular Biology, Building 57, Theodor-Stern-Kai-7, 60590 Frankfurt (Germany); Becker, Annette [Department of Biology, Technical University of Darmstadt, 64287 Darmstadt (Germany); Lippka, Yannick [Department of Molecular Hematopoiesis, Hannover Medical School, Carl Neuberg Str-1, 30625 Hannover (Germany); Selvakumar, Divakarvel [Department of Molecular Hematopoiesis, Hannover Medical School, Carl Neuberg Str-1, 30625 Hannover (Germany); Rutgers, The State University of New Jersey, NJ 08901 (United States); Klusmann, Jan-Henning; Reinhardt, Dirk [Department of Pediatrics, Hematology and Oncology, Hannover Medical School, Carl Neuberg Str-1, 30625 Hannover (Germany); Welte, Karl, E-mail: Welte.Karl.H@mh-hannover.de [Department of Molecular Hematopoiesis, Hannover Medical School, Carl Neuberg Str-1, 30625 Hannover (Germany)

    2012-08-03

    Highlights: Black-Right-Pointing-Pointer In 293T cells, p53 is considered to be inactive due to its interaction with the large T-antigen. Black-Right-Pointing-Pointer Acetylation of p53 at lysine 382 is important for its functional activation. Black-Right-Pointing-Pointer First evidence to document the presence of a functional p53 in 293T cells. Black-Right-Pointing-Pointer Inhibition of NAMPT/SIRT pathway by FK866 in 293T cells increases the functional activity of p53. Black-Right-Pointing-Pointer This activation of p53 involves reversible acetylation of p53 at lysine 382. -- Abstract: Inactivation of p53 protein by endogenous and exogenous carcinogens is involved in the pathogenesis of different human malignancies. In cancer associated with SV-40 DNA tumor virus, p53 is considered to be non-functional mainly due to its interaction with the large T-antigen. Using the 293T cell line (HEK293 cells transformed with large T antigen) as a model, we provide evidence that p53 is one of the critical downstream targets involved in FK866-mediated killing of 293T cells. A reduced rate of apoptosis and an increased number of cells in S-phase was accompanied after knockdown of p53 in these cells. Inhibition of NAMPT by FK866, or inhibition of SIRT by nicotinamide decreased proliferation and triggered death of 293T cells involving the p53 acetylation pathway. Additionally, knockdown of p53 attenuated the effect of FK866 on cell proliferation, apoptosis, and cell cycle arrest. The data presented here shed light on two important facts: (1) that p53 in 293T cells is active in the presence of FK866, an inhibitor of NAMPT pathway; (2) the apoptosis induced by FK866 in 293T cells is associated with increased acetylation of p53 at Lys382, which is required for the functional activity of p53.

  4. Drug-dependent functionalization of wild-type and mutant p53 in cisplatin-resistant human ovarian tumor cells.

    Science.gov (United States)

    Bhatt, Michelle; Ivan, Cristina; Xie, Xiaolei; Siddik, Zahid H

    2016-12-26

    Cisplatin (cis-Pt) resistance in tumor cells from p53 dysfunction is a significant clinical problem. Although mutation can inhibit p53 function, >60% of p53 mutants retain normal function according to literature reports. Therefore, we examined the status of p53 in cisplatin-resistant ovarian tumor models and its functional response to cis-Pt and the mechanistically-distinct non-cross-resistant oxaliplatin (oxali-Pt). Relative to sensitive A2780 cells harboring wild-type p53, the 2780CP/Cl-16, OVCAR-10, Hey and OVCA-433 cell lines were 10- to 30-fold resistant to cis-Pt, but was substantially circumvented by oxali-Pt. Mutant p53 in 2780CP/Cl-16 (p53V172F) and OVCAR-10 (p53V172F and p53G266R) cells, predicted as non-functional in p53 database, displayed attenuated response to cis-Pt, as did the polymorphic p53P72R (functionally equivalent to wild-type p53) in HEY and OVCA-433 cell lines. However, p53 was robustly activated by oxali-Pt in all cell lines, with resultant drug potency confirmed as p53-dependent by p53 knockout using CRISPR/Cas9 system. This p53 activation by oxali-Pt was associated with phosphorylation at Ser20 by MEK1/2 based on inhibitor and kinase studies. Cis-Pt, however, failed to phosphorylate Ser20 due to downregulated Chk2, and its clinical impact validated by reduced overall survival of ovarian cancer patients according to TCGA database. In conclusion, cis-Pt resistance occurs in both wild-type and mutant p53 ovarian cancer cells, but is associated with loss of Ser20 phosphorylation. However, these mutant p53, like polymorphic p53, are functional and activated by oxali-Pt-induced Ser20 phosphorylation. Thus, the potential exists for repurposing oxali-Pt or similar drugs against refractory cancers harboring wild-type or specific mutant p53.

  5. Mutations of the p53 gene in human functional adrenal neoplasms

    Energy Technology Data Exchange (ETDEWEB)

    Shiu-Ru Lin; Yau-Jiunn Lee; Juei-Hsiung Tsai [Kaohsiung Medical College, Taiwan (China)

    1994-02-01

    To clarify gene alterations in functional human adrenal tumors, the authors performed molecular analysis for p53 abnormalities in 23 cases with adrenal neoplasms. The immunohistochemical study with anti-p53 monoclonal antibody pAb1801 demonstrated that 10 of 23 (43.5%) cases overexpressed p53 protein in the tumor cells. Using a polymerase chain reaction-single strand conformation polymorphism study, 5 of 6 (83.3%) pheochromocytoma tissues (1 malignant and 5 benign) and 11 of 15 (73.3%) adrenocortical adenomas (2 with Cushing`s syndrome and 13 with primary aldosteronism, all benign) showed an apparent electrophoretic mobility shift between the tumor and its paired adjacent normal adrenal tissue. Such differences were detected in exon 4 (12 cases), exon 5 (2 cases), and exon 7 (3 cases). The types of these mutations in exon 4 were a substitution from threonine (ACC) to isoleucine (ATC) at codon 102 in 5 cases, from glutamine (CAG) to histidine (CAC) at codon 104 in 1 case, from glycine (GGG) to alanine (CGG) at codon 117 in 1 case, from glutamate (GAG) to glutamine (CAG) at codon 68 in 1 case, and single base changes resulting in a premature stop codon at codon 100 in 2 cases. A 2-basepair deletion at codon 175 in exon 5 resulting in a frame shift was identified in 1 case. A single point mutation was identified, resulting in the substitution of glutamine (CAG) for arginine (CGG) at codon 248 of exon 7 in 1 case. A single basepair deletion at codon 249 resulted in a frame shift in 2 cases. There was 1 case with malignant pheochromocytoma that combined a single point mutation in exon 4 and a single base deletion in exon 7. Only 2 of 23 cases showed a loss of a normal allele encoding in the p53 gene. Northern blot analysis with 1.8-kilobase p53 cDNA revealed that p53 mRNA was overexpressed in 6 cases. The results indicate that high frequencies of p53 gene mutation, especially in exon 4, exist in functional adrenal tumors. 39 refs., 6 figs., 4 tabs.

  6. Patterns of Proteins that Associate with p53 or with p53 Binding Sites Present in the Ribosomal Gene Cluster and MDM2 (P2) Promoter

    Science.gov (United States)

    2000-08-01

    factor receptor (efr) (Ludes-Meyers, et al., 1996), proliferating cell nuclear antigen (pCna) (Deb et al., 1992), the multi drug resistant gene (mdr-1...by the HlV -LTR (Subler et al., 1994; Gualberto and Baldwin, 1995). 4 Mutant p53 proteins may activate transcription of the HIV-LTR by cooperation

  7. Co-operative intra-protein structural response due to protein-protein complexation revealed through thermodynamic quantification: study of MDM2-p53 binding

    Science.gov (United States)

    Samanta, Sudipta; Mukherjee, Sanchita

    2017-09-01

    The p53 protein activation protects the organism from propagation of cells with damaged DNA having oncogenic mutations. In normal cells, activity of p53 is controlled by interaction with MDM2. The well understood p53-MDM2 interaction facilitates design of ligands that could potentially disrupt or prevent the complexation owing to its emergence as an important objective for cancer therapy. However, thermodynamic quantification of the p53-peptide induced structural changes of the MDM2-protein remains an area to be explored. This study attempts to understand the conformational free energy and entropy costs due to this complex formation from the histograms of dihedral angles generated from molecular dynamics simulations. Residue-specific quantification illustrates that, hydrophobic residues of the protein contribute maximum to the conformational thermodynamic changes. Thermodynamic quantification of structural changes of the protein unfold the fact that, p53 binding provides a source of inter-element cooperativity among the protein secondary structural elements, where the highest affected structural elements (α2 and α4) found at the binding site of the protein affects faraway structural elements (β1 and Loop1) of the protein. The communication perhaps involves water mediated hydrogen bonded network formation. Further, we infer that in inhibitory F19A mutation of P53, though Phe19 is important in the recognition process, it has less prominent contribution in the stability of the complex. Collectively, this study provides vivid microscopic understanding of the interaction within the protein complex along with exploring mutation sites, which will contribute further to engineer the protein function and binding affinity.

  8. The p53 cofactor Strap exhibits an unexpected TPR motif and oligonucleotide-binding (OB)-fold structure.

    Science.gov (United States)

    Adams, Cassandra J; Pike, Ashley C W; Maniam, Sandra; Sharpe, Timothy D; Coutts, Amanda S; Knapp, Stefan; La Thangue, Nicholas B; Bullock, Alex N

    2012-03-01

    Activation of p53 target genes for tumor suppression depends on the stress-specific regulation of transcriptional coactivator complexes. Strap (stress-responsive activator of p300) is activated upon DNA damage by ataxia telangiectasia mutated (ATM) and Chk2 kinases and is a key regulator of the p53 response. In addition to antagonizing Mdm2, Strap facilitates the recruitment of p53 coactivators, including JMY and p300. Strap is a predicted TPR-repeat protein, but shows only limited sequence identity with any protein of known structure. To address this and to elucidate the molecular mechanism of Strap activity we determined the crystal structure of the full-length protein at 2.05 Å resolution. The structure of Strap reveals an atypical six tetratricopeptide repeat (TPR) protein that also contains an unexpected oligonucleotide/oligosaccharide-binding (OB)-fold domain. This previously unseen domain organization provides an extended superhelical scaffold allowing for protein-protein as well as protein-DNA interaction. We show that both of the TPR and OB-fold domains localize to the chromatin of p53 target genes and exhibit intrinsic regulatory activity necessary for the Strap-dependent p53 response.

  9. Functional ribosome biogenesis is a prerequisite for p53 destabilization: impact of chemotherapy on nucleolar functions and RNA metabolism.

    Science.gov (United States)

    Burger, Kaspar; Eick, Dirk

    2013-09-01

    The production and processing of ribosomal RNA is a complex and well-coordinated nucleolar process for ribosome biogenesis. Progress in understanding nucleolar structure and function has lead to the unexpected discovery of the nucleolus as a highly sensitive sensor of cellular stress and an important regulator of the tumor suppressor p53. Inhibition of ribosomal RNA metabolism has been shown to activate a signaling pathway for p53 induction. This review elucidates the potential of classical and recently developed chemotherapeutic drugs to stabilize p53 by inhibiting nucleolar functions.

  10. p53 Regulates the neuronal intrinsic and extrinsic responses affecting the recovery of motor function following spinal cord injury.

    Science.gov (United States)

    Floriddia, Elisa M; Rathore, Khizr I; Tedeschi, Andrea; Quadrato, Giorgia; Wuttke, Anja; Lueckmann, Jan-Matthis; Kigerl, Kristina A; Popovich, Phillip G; Di Giovanni, Simone

    2012-10-01

    Following spinal trauma, the limited physiological axonal sprouting that contributes to partial recovery of function is dependent upon the intrinsic properties of neurons as well as the inhibitory glial environment. The transcription factor p53 is involved in DNA repair, cell cycle, cell survival, and axonal outgrowth, suggesting p53 as key modifier of axonal and glial responses influencing functional recovery following spinal injury. Indeed, in a spinal cord dorsal hemisection injury model, we observed a significant impairment in locomotor recovery in p53(-/-) versus wild-type mice. p53(-/-) spinal cords showed an increased number of activated microglia/macrophages and a larger scar at the lesion site. Loss- and gain-of-function experiments suggested p53 as a direct regulator of microglia/macrophages proliferation. At the axonal level, p53(-/-) mice showed a more pronounced dieback of the corticospinal tract (CST) and a decreased sprouting capacity of both CST and spinal serotoninergic fibers. In vivo expression of p53 in the sensorimotor cortex rescued and enhanced the sprouting potential of the CST in p53(-/-) mice, while, similarly, p53 expression in p53(-/-) cultured cortical neurons rescued a defect in neurite outgrowth, suggesting a direct role for p53 in regulating the intrinsic sprouting ability of CNS neurons. In conclusion, we show that p53 plays an important regulatory role at both extrinsic and intrinsic levels affecting the recovery of motor function following spinal cord injury. Therefore, we propose p53 as a novel potential multilevel therapeutic target for spinal cord injury.

  11. Induction of Cullin 7 by DNA damage attenuates p53 function

    OpenAIRE

    2007-01-01

    The p53 tumor suppressor gene encodes a transcription factor, which is translationally and posttranslationally activated after DNA damage. In a proteomic screen for p53 interactors, we found that the cullin protein Cul7 efficiently associates with p53. After DNA damage, the level of Cul7 protein increased in a caffeine-sensitive, but p53-independent, manner. Down-regulation of Cul7 by conditional microRNA expression augmented p53-mediated inhibition of cell cycle progression. Ectopic expressi...

  12. Tumor suppressor p53 and its gain-of-function mutants in cancer

    OpenAIRE

    2013-01-01

    Tumor suppressor p53 plays a pivotal role in tumor suppression. p53 is the most frequently mutated gene in cancer. As a transcription factor, p53 mainly exerts its role in tumor suppression through transcriptional regulation of its downstream target genes. Thus, p53 and its target genes form a complex p53 signaling pathway to regulate a wide variety of biological processes to prevent tumorigenesis. Recent studies have revealed that in addition to apoptosis, cell cycle arrest and senescence, p...

  13. Skp2B overexpression alters a prohibitin-p53 axis and the transcription of PAPP-A, the protease of insulin-like growth factor binding protein 4.

    Directory of Open Access Journals (Sweden)

    Harish Chander

    Full Text Available BACKGROUND: We previously reported that the degradation of prohibitin by the SCF(Skp2B ubiquitin ligase results in a defect in the activity of p53. We also reported that MMTV-Skp2B transgenic mice develop mammary gland tumors that are characterized by an increased proteolytic cleavage of the insulin-like growth factor binding protein 4 (IGFBP-4, an inhibitor of IGF signaling. However, whether a link exists between a defect in p53 activity and proteolysis of IGFBP-4 was not established. METHODS AND RESULTS: We analyzed the levels of pregnancy-associated plasma protein A (PAPP-A, the protease of IGFBP-4, in MMTV-Skp2B transgenic mice and found that PAPP-A levels are elevated. Further, we found a p53 binding site in intron 1 of the PAPP-A gene and that both wild type and mutant p53 bind to this site. However, binding of wild type p53 results in the transcriptional repression of PAPP-A, while binding of mutant p53 results in the transcriptional activation of PAPP-A. Since MMTV-Skp2B mice express wild type p53 and yet show elevated levels of PAPP-A, at first, these observations appeared contradictory. However, further analysis revealed that the defect in p53 activity in Skp2B overexpressing cells does not only abolish the activity of wild type of p53 but actually mimics that of mutant p53. Our results suggest that in absence of prohibitin, the half-life of p53 is increased and like mutant p53, the conformation of p53 is denatured. CONCLUSIONS: These observations revealed a novel function of prohibitin as a chaperone of p53. Further, they suggest that binding of denatured p53 in intron 1 causes an enhancer effect and increases the transcription of PAPP-A. Therefore, these findings indicate that the defect in p53 function and the increased proteolysis of IGFBP-4, we had observed, represent two components of the same pathway, which contributes to the oncogenic function of Skp2B.

  14. Mapping the Binding Site of P53 on UBC9 by NMR Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    林东海

    2002-01-01

    Human UBCP9 is a member of the E2 family of proteins.However,instead of conjugating to ubiquitin,it conjugates to a ubiquitin bomologue SUMO-1(also known as UBL1,GMP1,SMTP3,PICT-1 and sentrin).The SUMO-1 conjugation pathway is very similar to that of ubiquin with regard to the primary sequences of the ubiquitin activating enzymes(E1),the three-dimensional structures of the ubiquitin conjugating enzymes(E2),and the chemistry of the overall conjugation pathway.The interactiov of p53 and UBC9,the E2 of the SUMO-1 pathway,has heen studied by nuclear magnetic resonance spectroscopy.A peptide corresponding to the nuclear localization domain of p53 specifically interacts with UBC9 and this interaction is likely to be important for conjugation of p53 with SUMO-1.The largest chemical shift changes on UBC9 occur at residues94 and 129-135.This region is adjacent to the active site and has slgniflcant dynamic behavior on the μs-ms and ps-ns timescales.Correlation of chemical shift changes and mobility of these residues further suggest the importance of these residues in substrate recognition.

  15. Mapping the Binding Site of P53 on UBC9 by NMR Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    LIN,Dong-Hai(林东海)

    2002-01-01

    Human UBC9 is a member of the E2 family of proteins. However, instead of conjugating to ubiquitin, it conjugates to a ubiquitin homologue SUMO-1 (also known as UBL1, GMP1,SMTP3, PICT-1 and sentrin). The SUMO-1 conjugation pathway is very similar to that of ubiquitin with regard to the primary sequences of the ubiquitin activating enzymes (E1), the three-dimensional structures of the ubiquitin conjugating enzymes (E2), and the chemistry of the overall conjugation pathway. The interaction of p53 and UBC9, the E2 of the SUMO-1 pathway, has been studied by nuclear magnetic resonance spectroscopy. A peptide corresponding to the nuclear localization domain of p53 specifically interacts with UBC9 and this interaction is likely to be important for conjugation of p53 with SUMO-1. The largest chenical shift changes on UBC9 occur at residues 94 and 129-135. Tnis region is adjacent to the active site and has significant dynamic behavior on the μs-ms and ps-ns timescales. Correlation of chemical shift changes and mobility of these residues further suggest the importance of these residues in substrate recognition.

  16. Immediate-early gene product ICP22 inhibits the trans-transcription activating function of P53-mdm-2

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    As a product of HSVI immediate-early gene, ICP22 is capable of interacting with various cellular tran-scriptive and regulatory molecules during viral infection so as to impact the normal cellular molecular mechanism. ICP22 expressed in transfected cells can push the cells’ entering into S phase with binding to mdm-1 promoter region and impact its trans-transcription activating effect by P53. Consequently, the MDM-2 binds to P53, and the degradation effects by the ubiquitous pathway are decreased, improving indirectly the P53 levels in cells and making the cells progress into the S phase.

  17. Immediate-early gene product ICP22 inhibits the trans-transcription activating function of P53-mdm-2

    Institute of Scientific and Technical Information of China (English)

    GUO HongXiong; CUN Wei; LIU LongDing; WANG LiChun; ZHAO HongLing; DONG ChengHong; LI QiHan

    2007-01-01

    As a product of HSVI immediate-early gene, ICP22 is capable of interacting with various cellular transcriptive and regulatory molecules during viral infection so as to impact the normal cellular molecular mechanism. ICP22 expressed in transfected cells can push the cells' entering into S phase with binding to mdm-1 promoter region and impact its trans-transcription activating effect by P53. Consequently, the MDM-2 binds to P53, and the degradation effects by the ubiquitous pathway are decreased, improving indirectly the P53 levels in cells and making the cells progress into the S phase.

  18. Mapping the structural and dynamical features of multiple p53 DNA binding domains: insights into loop 1 intrinsic dynamics.

    Directory of Open Access Journals (Sweden)

    Suryani Lukman

    Full Text Available The transcription factor p53 regulates cellular integrity in response to stress. p53 is mutated in more than half of cancerous cells, with a majority of the mutations localized to the DNA binding domain (DBD. In order to map the structural and dynamical features of the DBD, we carried out multiple copy molecular dynamics simulations (totaling 0.8 μs. Simulations show the loop 1 to be the most dynamic element among the DNA-contacting loops (loops 1-3. Loop 1 occupies two major conformational states: extended and recessed; the former but not the latter displays correlations in atomic fluctuations with those of loop 2 (~24 Å apart. Since loop 1 binds to the major groove whereas loop 2 binds to the minor groove of DNA, our results begin to provide some insight into the possible mechanism underpinning the cooperative nature of DBD binding to DNA. We propose (1 a novel mechanism underlying the dynamics of loop 1 and the possible tread-milling of p53 on DNA and (2 possible mutations on loop 1 residues to restore the transcriptional activity of an oncogenic mutation at a distant site.

  19. Research progress on the structure and function of the P53 gene%P53基因与肿瘤的研究进展

    Institute of Scientific and Technical Information of China (English)

    田云鹏

    2013-01-01

    编码P53蛋白的P53基因是最重要的肿瘤抑制基因之一.人类的大多数肿瘤都存在着P53途径的失活.变异的P53不仅不具备肿瘤抑制子的功能,还可能发挥促进肿瘤发生、发展的作用.P53的基本功能是对细胞应激的应答.因此,我们就P53基因的结构和功能做一综述.

  20. A Novel Naphthalimide Compound Restores p53 Function in Non-small Cell Lung Cancer by Reorganizing the Bak·Bcl-xl Complex and Triggering Transcriptional Regulation.

    Science.gov (United States)

    Zhang, Guohai; An, Yunfeng; Lu, Xing; Zhong, Hui; Zhu, Yanhong; Wu, Yiming; Ma, Feng'e; Yang, Jingmei; Liu, Yancheng; Zhou, Zuping; Peng, Yan; Chen, Zhenfeng

    2016-02-19

    p53 inactivation is a hallmark in non-small-cell lung cancer (NSCLC). It is therefore highly desirable to develop tumor-specific treatment for NSCLC therapy by restoring p53 function. Herein, a novel naphthalimide compound, NA-17, was identified as a promising drug candidate in view of both its anticancer activity and mechanism of action. NA-17 exhibited strong anticancer activity on a broad range of cancer cell lines but showed low toxicity to normal cell lines, such as HL-7702 and WI-38. Moreover, NA-17 showed p53-dependent inhibition selectivity in different NSCLC cell lines due to the activation state of endogenous p53 in the background level. Further studies revealed that NA-17 caused cell cycle arrest at the G1 phase, changed cell size, and induced apoptosis and cell death by increasing the proportion of sub-G1 cells. Molecular mechanism studies suggested that targeted accumulation of phospho-p53 in mitochondria and nuclei induced by NA-17 resulted in activation of Bak and direct binding of phospho-p53 to the target DNA sequences, thereby evoking cell apoptosis and cell cycle arrest and eventually leading to irreversible cancer cell inhibition. This work provided new insights into the molecular interactions and anticancer mechanisms of phospho-p53-dependent naphthalimide compounds.

  1. Impact of cadmium on hOGG1 and APE1 as a function of the cellular p53 status

    Energy Technology Data Exchange (ETDEWEB)

    Hamann, Ingrit [Institut fuer Angewandte Biowissenschaften, Abteilung Lebensmittelchemie und Toxikologie, Karlsruher Institut fuer Technologie (KIT), 76131 Karlsruhe (Germany); Fachgebiet Lebensmittelchemie und Toxikologie, Institut fuer Lebensmitteltechnologie und Lebensmittelchemie, Technische Universitaet Berlin, 13355 Berlin (Germany); Faculty for Pharmacy and Pharmaceutical Sciences, University of Alberta, 3126 Dentistry/Pharmacy Centre, Edmonton, Alberta, Canada T6G 2N8 (Canada); Koenig, Charlotte; Richter, Constanze [Fachgebiet Lebensmittelchemie und Toxikologie, Institut fuer Lebensmitteltechnologie und Lebensmittelchemie, Technische Universitaet Berlin, 13355 Berlin (Germany); Jahnke, Gunnar [Institut fuer Angewandte Biowissenschaften, Abteilung Lebensmittelchemie und Toxikologie, Karlsruher Institut fuer Technologie (KIT), 76131 Karlsruhe (Germany); Fachgebiet Lebensmittelchemie und Toxikologie, Institut fuer Lebensmitteltechnologie und Lebensmittelchemie, Technische Universitaet Berlin, 13355 Berlin (Germany); Hartwig, Andrea, E-mail: andrea.hartwig@kit.edu [Institut fuer Angewandte Biowissenschaften, Abteilung Lebensmittelchemie und Toxikologie, Karlsruher Institut fuer Technologie (KIT), 76131 Karlsruhe (Germany); Fachgebiet Lebensmittelchemie und Toxikologie, Institut fuer Lebensmitteltechnologie und Lebensmittelchemie, Technische Universitaet Berlin, 13355 Berlin (Germany)

    2012-08-01

    The tumor suppressor protein p53, often called the guardian of the genome, is involved in important cellular processes, such as cell cycle control, apoptosis and DNA repair. With respect to BER, p53 might physically interact with and affect the transcription of different BER proteins such as hOGG1, APE1 or Pol{beta}. In studies in HCT116 p53{sup -/-} cells previously published, activity and mRNA expression of hOGG1 were found to be significantly decreased, while down-regulation of APE1 mRNA and protein levels in response to genotoxic stress were only described in HCT116 p53{sup +/+} cells, but not in the isogenic p53 knockout cell line. The predominantly indirect genotoxic carcinogen cadmium inhibits the BER pathway and potentially interferes with zinc binding proteins such as p53. Therefore, this study was accomplished to investigate whether p53 is involved in the cadmium-induced inhibition of BER activity. To address this issue we applied a non-radioactive cleavage test system based on a Cy5-labeled oligonucleotide. We present evidence that p53 is not essential for hOGG1 and APE1 gene expression as well as OGG and APE activity in unstressed HCT116 cells; however, it plays an important role in the cellular response to cadmium treatment. Here, a direct involvement of p53 was only observed with respect to APE1 gene expression contributing to an altered APE activity, while OGG activity was presumably affected indirectly due to a stronger accumulation of cadmium in HCT116 p53{sup +/+} cells. In summary, p53 indeed affects the BER pathway directly and indirectly in response to cadmium treatment.

  2. Genotoxic exposure: novel cause of selection for a functional ΔN-p53 isoform

    NARCIS (Netherlands)

    Melis, J.P.M.; Hoogervorst, E.M.; van Oostrom, C.T.M.; Zwart, E.; Breit, T.M.; Pennings, J.L.A.; de Vries, A.; van Steeg, H.

    2011-01-01

    The p53 gene is frequently mutated in cancers and it is vital for cell cycle control, homeostasis and carcinogenesis. We describe a novel p53 mutational spectrum, different to those generally observed in human and murine tumors. Our study shows a high prevalence of nonsense mutations in the p53 N te

  3. p53功能失活在食管鳞癌中的表达及意义%Significance of Functional Inactivation of p53 in Esophageal Squamous Cell Carcinoma

    Institute of Scientific and Technical Information of China (English)

    李小东; 戎铁华; 傅剑华; 龙浩

    2001-01-01

    目的:建立一种评价肿瘤生物学特性的新方法棗p53功能失活检测法,并探讨p53功能失活与食管鳞癌TNM分期(tumor,nodes,metastasisstaging)和组织学分级的关系。方法:采用p53功能测定法对45例新鲜食管鳞癌组织和正常食管组织进行p53功能检测(p53基因突变检测作为对照),将检测结果与患者的TNM分期和组织学分级进行统计学分析。结果:p53功能失活率为64%,明显高于p53基因突变率49%。p53功能失活和食管鳞癌的TNM分期有关,分期越高,p53功能失活率越高;p53功能失活和食管鳞癌的组织学分级有关,分级越高,p53功能失活率越高。结论:p53功能失活有望成为一种评价食管鳞癌生物学特性的新指标;p53功能失活与食管鳞癌的TNM分期和组织学分级有关。%Objective: The current study was designed to establish a new method to evaluate biological activity of carcinoma— functional status of p53, and investigate the relationship between functional inactivation of p53 and the TNM(tumor,nodes,metastasis) staging or histological classification of squamous cell carcinoma of esophagus. Methods: A total of 45 samples of fresh esophageal tissues of squamous cell carcinoma and normal esophageal tissues were examined for functional inactivation of p53 by detection of functional inactivation of p53 ( comparison with detection of p53 gene mutation ) . Then the analyses of detected results and the TNM stagings or the histological classifications of the carcinoma were statistically analyzed in SPSS. Results: The rate of functional inactivation of p53 (64% ) seemed to be obviously higher than that of p53 gene mutation (49% ) with a significant difference (P=0.046). There was a significant relationship between functional inactivation of p53 and the TNM staging of esophageal squamous cell carcinoma. Its rate tended to be increased with the advance of the TNM staging; there was a significant

  4. INMAP overexpression inhibits cell proliferation, induces genomic instability and functions through p53/p21 pathways.

    Directory of Open Access Journals (Sweden)

    Yan Zhu

    Full Text Available INMAP is a spindle protein that plays essential role for mitosis, by ensuring spindle and centromere integrality. The aim of this study was to investigate the relevant functions of INMAP for genomic stability and its functional pathway. We overexpressed INMAP in HeLa cells, resulting in growth inhibition in monolayer cell cultures, anchorage-independent growth in soft agar and xenograft growth in nude mice. In this system caused micronuclei (MNi formation, chromosome distortion and γH2AX expression upregulation, suggesting DNA damage induction and genomic stability impairment. As a tumour biochemical marker, lactate dehydrogenase (LDH isoenzymes were detected to evaluate cell metabolic activity, the results confirming that total activity of LDH, as well as that of its LDH5 isoform, is significantly decreased in INMAP-overexpressing HeLa cells. The levels of p53 and p21 were upregulated, and however, that of PCNA and Bcl-2, downregulated. Indirect immunofluorescence (IIF and coimmunoprecipitation (CoIP analyses revealed the interaction between INMAP and p21. These results suggest that INMAP might function through p53/p21 pathways.

  5. ΔNp73α regulates MDR1 expression by inhibiting p53 function

    Science.gov (United States)

    Vilgelm, A; Wei, JX; Piazuelo, MB; Washington, MK; Prassolov, V; El-Rifai, W; Zaika, A

    2014-01-01

    The p73 protein is a transcription factor and member of the p53 protein family that expresses as a complex variety of isoforms. ΔNp73α is an N-terminally truncated isoform of p73. We found that ΔNp73 protein is upregulated in human gastric carcinoma suggesting that ΔNp73 may play an oncogenic role in these tumors. Although it has been shown that ΔNp73α inhibits apoptosis and counteracts the effect of chemotherapeutic drugs, the underlying mechanism by which this p73 isoform contributes to chemotherapeutic drug response remains to be explored. We found that ΔNp73α upregulates MDR1 mRNA and p-glycoprotein (p-gp), which is involved in chemotherapeutic drug transport. This p-gp upregulation was accompanied by increased p-gp functional activity in gastric cancer cells. Our data suggest that upregulation of MDR1 by ΔNp73α is mediated by interaction with p53 at the MDR1 promoter. PMID:17952118

  6. DeltaNp73alpha regulates MDR1 expression by inhibiting p53 function.

    Science.gov (United States)

    Vilgelm, A; Wei, J X; Piazuelo, M B; Washington, M K; Prassolov, V; El-Rifai, W; Zaika, A

    2008-04-01

    The p73 protein is a transcription factor and member of the p53 protein family that expresses as a complex variety of isoforms. DeltaNp73alpha is an N-terminally truncated isoform of p73. We found that DeltaNp73 protein is upregulated in human gastric carcinoma suggesting that DeltaNp73 may play an oncogenic role in these tumors. Although it has been shown that DeltaNp73alpha inhibits apoptosis and counteracts the effect of chemotherapeutic drugs, the underlying mechanism by which this p73 isoform contributes to chemotherapeutic drug response remains to be explored. We found that DeltaNp73alpha upregulates MDR1 mRNA and p-glycoprotein (p-gp), which is involved in chemotherapeutic drug transport. This p-gp upregulation was accompanied by increased p-gp functional activity in gastric cancer cells. Our data suggest that upregulation of MDR1 by DeltaNp73alpha is mediated by interaction with p53 at the MDR1 promoter.

  7. The pro-survival function of p53 in HeLa cells

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Kyu; Kang, Mi Young; Jang, Eun Yeong; Kim, Jin Hong [Korea Atomic Energy Research Institute, Advanced Radiation Technology Institute, Jeongeup (Korea, Republic of)

    2014-11-15

    The rate of apoptosis and autophagy was variable with different p53 status after IR treatment of cells. The influence of p53 status on cell fate suggests a role of p53 in two fundamentally important cell biological pathways: autophagy and apoptosis. p53 coordinates cell cycle arrest and apoptosis to govern cell fate. This study was done to identify p53-mediated regulation of cell's fate. Autophagy induced by IR may prevent cells from undergoing apoptosis, implying an interlink modulation between autophagy and apoptosis. The rate of apoptosis and autophagy was determined with different p53 status after IR treatment of HeLa cells in this study. Our research on IR-induced cellular responses may provide new information about fate decision between the processes of apoptosis and autophagy.

  8. ARF functions as a melanoma tumor suppressor by inducing p53-independent senescence

    OpenAIRE

    Ha, Linan; Ichikawa, Takeshi; Anver, Miriam; Dickins, Ross; Lowe, Scott; Sharpless, Norman E.; Krimpenfort, Paul; DePinho, Ronald A.; Bennett, Dorothy C.; Sviderskaya, Elena V.; Merlino, Glenn

    2007-01-01

    Inactivation of the p53 pathway represents the most common molecular defect of human cancer. But in the setting of melanoma, a highly aggressive and invariably fatal malignancy in its advanced disseminated form, mutation/deletion of p53 is relatively rare, whereas its positive regulator ARF is often lost. Here, we show that genetic deficiency in Arf but not p53 facilitates rapid development of melanoma in a genetically engineered mouse model. This difference is accounted for, at least in part...

  9. p53 regulates the cardiac transcriptome

    Science.gov (United States)

    Mak, Tak W.; Hauck, Ludger; Grothe, Daniela; Billia, Filio

    2017-01-01

    The tumor suppressor Trp53 (p53) inhibits cell growth after acute stress by regulating gene transcription. The mammalian genome contains hundreds of p53-binding sites. However, whether p53 participates in the regulation of cardiac tissue homeostasis under normal conditions is not known. To examine the physiologic role of p53 in adult cardiomyocytes in vivo, Cre-loxP–mediated conditional gene targeting in adult mice was used. Genome-wide transcriptome analyses of conditional heart-specific p53 knockout mice were performed. Genome-wide annotation and pathway analyses of >5,000 differentially expressed transcripts identified many p53-regulated gene clusters. Correlative analyses identified >20 gene sets containing more than 1,000 genes relevant to cardiac architecture and function. These transcriptomic changes orchestrate cardiac architecture, excitation-contraction coupling, mitochondrial biogenesis, and oxidative phosphorylation capacity. Interestingly, the gene expression signature in p53-deficient hearts confers resistance to acute biomechanical stress. The data presented here demonstrate a role for p53, a previously unrecognized master regulator of the cardiac transcriptome. The complex contributions of p53 define a biological paradigm for the p53 regulator network in the heart under physiological conditions. PMID:28193895

  10. p53 functions as a cell cycle control protein in osteosarcomas.

    Science.gov (United States)

    Diller, L; Kassel, J; Nelson, C E; Gryka, M A; Litwak, G; Gebhardt, M; Bressac, B; Ozturk, M; Baker, S J; Vogelstein, B

    1990-11-01

    Mutations in the p53 gene have been associated with a wide range of human tumors, including osteosarcomas. Although it has been shown that wild-type p53 can block the ability of E1a and ras to cotransform primary rodent cells, it is poorly understood why inactivation of the p53 gene is important for tumor formation. We show that overexpression of the gene encoding wild-type p53 blocks the growth of osteosarcoma cells. The growth arrest was determined to be due to an inability of the transfected cells to progress into S phase. This suggests that the role of the p53 gene as an antioncogene may be in controlling the cell cycle in a fashion analogous to the check-point control genes in Saccharomyces cerevisiae.

  11. Interaction Between P53 and TRF1、TRF2 and Analysis of Binding Domain of P53 in vitro%P53与TRF1、TRF2的体外结合及P53结合功能区的分析

    Institute of Scientific and Technical Information of China (English)

    李玲; 张波; 邹万忠; 郑杰; 刘俊平

    2005-01-01

    通过分析端粒结合蛋白TRF1、TRF2与P53的体外结合,探讨P53-端粒途径调节细胞生命活动的分子机制.GST和4种人P53-GST融合蛋白经大肠杆菌表达、谷胱甘肽-SepharoseTM4B纯化后,进行SDS-PAGE和考马斯亮篮染色.人P53包括野生型(1~393)、C端缺失体P53 N5(2~293)、N端缺失体P53 2C(95~393)、单个氨基酸突变体P53 R175H(175 R→H).各纯化蛋白的分子量与预计的完全一致,且纯化率达90%以上.将纯化的GST和P53-GST融合蛋白与人乳腺癌细胞MCF-7细胞蛋白进行体外结合反应,Western印迹检测反应物中P53和TRF1、TRF2的结合.野生型P53P53-R175H均能沉淀MCF-7中的TRF1、TRF2,且结合力相似,而单独的GST则无沉淀TRF1、TRF2的作用.与野生型P53P53 R175H相比,P53 2C与TRF1、TRF2的结合力明显增加,P53 N5与TRF1、TRF2的结合力大大减弱.表明P53和TRF1、TRF2可以进行直接而特异的体外结合,且它们的结合为P53 C端(293~393)结构域依赖性.P53和TRF1、TRF2这种结构域依赖性的结合可能与端粒动态变化所诱导的细胞活动有关.

  12. Mutual interactions between P53 and growth factors in cancer

    NARCIS (Netherlands)

    Asschert, JGW; Vellenga, E; De Jong, S; De Vries, EGE

    1998-01-01

    The function of p53 armour suppressor protein is determined by various intrinsic properties of the protein. The effect of p53 DNA-binding, and platein-protein interactions are determined by the conformation of the protein. Thus p53 fulfils its role in cell cycle control and the onset of apoptotic ce

  13. SV40 large T-p53 complex: evidence for the presence of two immunologically distinct forms of p53

    Energy Technology Data Exchange (ETDEWEB)

    Milner, J.; Gamble, J.

    1985-11-01

    The transforming protein of SV40 is the large T antigen. Large T binds a cellular protein, p53, which is potentially oncogenic by virtue of its functional involvement in the control of cell proliferation. This raises the possibility that p53 may mediate, in part, the transforming function of SV40 large T. Two immunologically distinct forms of p53 have been identified in normal cells: the forms are cell-cycle dependent, one being restricted to nondividing cells (p53-Go) and the second to dividing cells (p53-G divided by). The authors have now dissociated and probed the multimeric complex of SV40 large T-p53 for the presence of immunologically distinct forms of p53. Here they present evidence for the presence of p53-Go and p53-G divided by complexed with SV40 large T.

  14. TATA-binding protein (TBP)-like protein is required for p53-dependent transcriptional activation of upstream promoter of p21Waf1/Cip1 gene.

    Science.gov (United States)

    Suzuki, Hidefumi; Ito, Ryo; Ikeda, Kaori; Tamura, Taka-Aki

    2012-06-01

    TATA-binding protein-like protein (TLP) is involved in development, checkpoint, and apoptosis through potentiation of gene expression. TLP-overexpressing human cells, especially p53-containing cells, exhibited a decreased growth rate and increased proportion of G(1) phase cells. TLP stimulated expression of several growth-related genes including p21 (p21(Waf1/Cip1)). TLP-mediated activation of the p21 upstream promoter in cells was shown by a promoter-luciferase reporter assay. The p53-binding sequence located in the p21 upstream promoter and p53 itself are required for TLP-mediated transcriptional activation. TLP and p53 bound to each other and synergistically enhanced activity of the upstream promoter. TLP specifically activated transcription from the endogenous upstream promoter, and p53 was required for this activation. Etoposide treatment also resulted in activation of the upstream promoter as well as nuclear accumulation of TLP and p53. Moreover, the upstream promoter was associated with endogenous p53 and TLP, and the p53 recruitment was enhanced by TLP. The results of the present study suggest that TLP mediates p53-governed transcriptional activation of the p21 upstream promoter.

  15. p53 DNA结合域与抗癌多肽的拉伸分子动力学研究%Steered Molecular Dynamics of an Anticancer Peptide Interacting With The p53 DNA-binding Domain

    Institute of Scientific and Technical Information of China (English)

    许先进; 苏计国; 陈慰祖; 王存新; CANNISTRARO Salvatore; BIZZARRI Anna-Rita

    2014-01-01

    The p28 peptide,derived from the blue copper protein azurin,is known to enhance the anticancer capabilities of the tumor suppressor p53 likely binding to its DNA-binding domain (DBD).The p28-p53 DBD complex has been investigated by steered molecular dynamics in order to characterize the unbinding process at atomic resolution.We found that the unbinding of the complex follows a candidate pathway with a well-defined detaching sequence between the partners.The analysis of the unbinding force and the calculation of the irreversible work done along several unbinding paths have allowed us to extract information on the energy landscape regulating the unbinding process.%研究发现,取自蓝铜蛋白azur的一段多肽p28能够进入癌细胞,结合到肿瘤抑制因子p53的DNA结合域上,进而增加p53的抗癌能力.本工作中,通过拉伸分子动力学方法,在原子尺度上研究了p28-p53 DBD复合物的解离过程.分析结果显示复合物的解离过程遵循着一定的分离顺序.对解离力的分析以及对沿着解离路径的不可逆做功的计算,使我们能够从复合物的能量地貌中提取有用的信息,而这些信息也决定了复合物的解离过程.

  16. Assessment of p53 and ATM functionality in chronic lymphocytic leukemia by multiplex ligation-dependent probe amplification.

    Science.gov (United States)

    te Raa, G D; Moerland, P D; Leeksma, A C; Derks, I A; Yigittop, H; Laddach, N; Loden-van Straaten, M; Navrkalova, V; Trbusek, M; Luijks, D M; Zenz, T; Skowronska, A; Hoogendoorn, M; Stankovic, T; van Oers, M H; Eldering, E; Kater, A P

    2015-08-06

    The ATM-p53 DNA-damage response (DDR) pathway has a crucial role in chemoresistance in CLL, as indicated by the adverse prognostic impact of genetic aberrations of TP53 and ATM. Identifying and distinguishing TP53 and ATM functional defects has become relevant as epigenetic and posttranscriptional dysregulation of the ATM/p53 axis is increasingly being recognized as the underlying cause of chemoresistance. Also, specific treatments sensitizing TP53- or ATM-deficient CLL cells are emerging. We therefore developed a new ATM-p53 functional assay with the aim to (i) identify and (ii) distinguish abnormalities of TP53 versus ATM and (iii) enable the identification of additional defects in the ATM-p53 pathway. Reversed transcriptase multiplex ligation-dependent probe amplification (RT-MLPA) was used to measure ATM and/or p53-dependent genes at the RNA level following DNA damage using irradiation. Here, we showed that this assay is able to identify and distinguish three subgroups of CLL tumors (i.e., TP53-defective, ATM-defective and WT) and is also able to detect additional samples with a defective DDR, without molecular aberrations in TP53 and/or ATM. These findings make the ATM-p53 RT-MLPA functional assay a promising prognostic tool for predicting treatment responses in CLL.

  17. Involvement of 53BP1, a p53 Binding Protein, in Chk2 Phosphyorylation of p53 and DNA Damage Cell Cycle Checkpoints

    Science.gov (United States)

    2006-05-01

    20:4859-69. 24. Cote J, Utley RT, Workman JL. Basic analysis of transcription factor binding to nucleo - somes. Methods Mol Gen 1995; 6:108-27. 25...47755 (2001). 18. D. Cortez , Y. Wang, J. Qin, S. J. Elledge, Science 286, 1162 (1999). 19. R. DiTullio, T. Halazonetis, personal communication. 20. A...Cancer Res. 83, 209 (2001). 23. Antibodies to Chk2T68P provided by J. Chen; 53BP1, T. D. Halazonetis; and -H2AX, W. M. Bonner. 24. We thank D. Cortez

  18. TBP-like Protein (TLP) Disrupts the p53-MDM2 Interaction and Induces Long-lasting p53 Activation.

    Science.gov (United States)

    Maeda, Ryo; Tamashiro, Hiroyuki; Takano, Kazunori; Takahashi, Hiro; Suzuki, Hidefumi; Saito, Shinta; Kojima, Waka; Adachi, Noritaka; Ura, Kiyoe; Endo, Takeshi; Tamura, Taka-Aki

    2017-02-24

    Stress-induced activation of p53 is an essential cellular response to prevent aberrant cell proliferation and cancer development. The ubiquitin ligase MDM2 promotes p53 degradation and limits the duration of p53 activation. It remains unclear, however, how p53 persistently escapes MDM2-mediated negative control for making appropriate cell fate decisions. Here we report that TBP-like protein (TLP), a member of the TBP family, is a new regulatory factor for the p53-MDM2 interplay and thus for p53 activation. We found that TLP acts to stabilize p53 protein to ensure long-lasting p53 activation, leading to potentiation of p53-induced apoptosis and senescence after genotoxic stress. Mechanistically, TLP interferes with MDM2 binding and ubiquitination of p53. Moreover, single cell imaging analysis shows that TLP depletion accelerates MDM2-mediated nuclear export of p53. We further show that a cervical cancer-derived TLP mutant has less p53 binding ability and lacks a proliferation-repressive function. Our findings uncover a role of TLP as a competitive MDM2 blocker, proposing a novel mechanism by which p53 escapes the p53-MDM2 negative feedback loop to modulate cell fate decisions.

  19. p53 isoforms change p53 paradigm

    OpenAIRE

    2014-01-01

    Although p53 defines cellular responses to cancer treatment it is not clear how p53 can be used to control cell fate outcome. Data demonstrate that so-called p53 does not exist as a single protein, but is in fact a group of p53 protein isoforms whose expression can be manipulated to control the cellular response to treatment.

  20. Expression of Androgen Receptor Is Negatively Regulated By p53

    Directory of Open Access Journals (Sweden)

    Fatouma Alimirah

    2007-12-01

    Full Text Available Increased expression of androgen receptor (AR in prostate cancer (PC is associated with transition to androgen independence. Because the progression of PC to advanced stages is often associated with the loss of p53 function, we tested whether the p53 could regulate the expression of AR gene. Here we report that p53 negatively regulates the expression of AR in prostate epithelial cells (PrECs. We found that in LNCaP human prostate cancer cells that express the wild-type p53 and AR and in human normal PrECs, the activation of p53 by genotoxic stress or by inhibition of p53 nuclear export downregulated the expression of AR. Furthermore, forced expression of p53 in LNCaP cells decreased the expression of AR. Conversely, knockdown of p53 expression in LNCaP cells increased the AR expression. Consistent with the negative regulation of AR expression by p53, the p53-null HCT116 cells expressed higher levels of AR compared with the isogenic HCT116 cells that express the wildtype p53. Moreover, we noted that in etoposide treated LNCaP cells p53 bound to the promoter region of the AR gene, which contains a potential p53 DNA-binding consensus sequence, in chromatin immunoprecipitation assays. Together, our observations provide support for the idea that the loss of p53 function in prostate cancer cells contributes to increased expression of AR.

  1. MicroRNA-128-2 targets the transcriptional repressor E2F5 enhancing mutant p53 gain of function

    Science.gov (United States)

    Donzelli, S; Fontemaggi, G; Fazi, F; Di Agostino, S; Padula, F; Biagioni, F; Muti, P; Strano, S; Blandino, G

    2012-01-01

    p53 mutations have profound effects on non-small-cell lung cancer (NSCLC) resistance to chemotherapeutic treatments. Mutant p53 proteins are usually expressed at high levels in tumors, where they exert oncogenic functions. Here we show that p53R175H, a hotspot p53 mutant, induces microRNA (miRNA)-128-2 expression. Mutant p53 binds to the putative promoter of miR128-2 host gene, ARPP21, determining a concomitant induction of ARPP21 mRNA and miR-128-2. miR-128-2 expression in lung cancer cells inhibits apoptosis and confers increased resistance to cisplatin, doxorubicin and 5-fluorouracyl treatments. At the molecular level, miR-128-2 post-transcriptionally targets E2F5 and leads to the abrogation of its repressive activity on p21waf1 transcription. p21waf1 protein localizes to the cytoplasmic compartment, where it exerts an anti-apoptotic effect by preventing pro-caspase-3 cleavage. This study emphasizes miRNA-128-2 role as a master regulator in NSCLC chemoresistance. PMID:22193543

  2. Distinct p53, p53:LANA, and LANA Complexes in Kaposi's Sarcoma-Associated Herpesvirus Lymphomas▿

    OpenAIRE

    Chen, Wuguo; Hilton, Isaac B.; Staudt, Michelle R; Burd, Christin E.; Dittmer, Dirk P

    2010-01-01

    The role of p53 in primary effusion lymphoma (PEL) is complicated. The latency-associated nuclear antigen (LANA) of Kaposi's sarcoma-associated herpesvirus (KSHV) binds p53. Despite this interaction, we had found that p53 was functional in PEL, i.e., able to induce apoptosis in response to DNA damage (C. E. Petre, S. H. Sin, and D. P. Dittmer, J. Virol. 81:1912-1922, 2007), and that hdm2 was overexpressed. To further elucidate the relationship between LANA, p53, and hdm2, we purified LANA com...

  3. p16(INK4A) enhances the transcriptional and the apoptotic functions of p53 through DNA-dependent interaction.

    Science.gov (United States)

    Al-Khalaf, Huda H; Nallar, Shreeram C; Kalvakolanu, Dhananjaya V; Aboussekhra, Abdelilah

    2017-02-20

    p16(INK4A) and p53 are two important tumor suppressor proteins that play essential roles during cell proliferation and aging through regulating the expression of several genes. Here, we report that p16(INK4A) and p53 co-regulate a plethora of transcripts. Furthermore, both proteins colocalize in the nucleus of human primary skin fibroblasts and breast luminal cells, and form a heteromer whose level increases in response to genotoxic stress as well as aging of human fibroblasts and various mouse organs. CDK4 is also present in this heteromeric complex, which is formed only in the presence of DNA both in vitro using pure recombinant proteins and in vivo. We have also shown that p16(INK4A) enhances the binding efficiency of p53 to its cognate sequence presents in the CDKN1A promoter in vitro, and both proteins are present at the promoters of CDKN1A and BAX in vivo. Importantly, the fourth ankyrin repeat of p16(INK4A) and the C-terminal domain of p53 were necessary for the physical association between these two proteins. The physiologic importance of this association was revealed by the inability of cancer-associated p16(INK4A) mutants to interact with p53 and to transactivate the expression of its major targets CDKN1A and BAX in the p16-defective U2OS cells expressing either wild-type or mutated p16(INK4A) . Furthermore, the association between p16(INK4A) and p53 was capital for their nuclear colocalization, the X-ray-dependent induction of p21 and Bax proteins as well as the induction of apoptosis in various types of cells. Together, these results show DNA-dependent physical interaction between p16(INK4A) and p53.

  4. Nitric oxide as a carcinogen. Analysis by yeast functional assay of inactivating p53 mutations induced by nitric oxide

    Energy Technology Data Exchange (ETDEWEB)

    Murata, Jun-Ichi; Tada, Mitsuhiro; Sawamura, Yutaka; Shinohe, Yumiko; Abe, Hiroshi [Laboratory for Molecular Brain Research, Department of Neurosurgery, Hokkaido University School of Medicine, Sapporo (Japan); Iggo, Richard D. [Oncogene group, Swiss Institute for Experimental Cancer Research ISREC, Epalinges (Switzerland)

    1997-10-06

    We have used a yeast p53 functional assay to study induction of mutations in the p53 tumor suppressor gene by nitric oxide and cytosine methylation. The yeast assay identifies only biologically important p53 mutations. p53 cDNA was treated with the nitric oxide donor sydnonimine, PCR-amplified and transfected into yeast. Sydnonimine produced a significant, dose-dependent increase in C:G->A:T transversions. Many important p53 mutational hotspots are postulated to arise by deamination of methylCpG in tumors. We therefore examined nitric oxide induction of mutations in p53 cDNA methylated by PCR-mediated substitution of 5-methylcytosine for cytosine or by treatment with the SssI CpG methylase. Both methylation procedures increased the baseline mutation rate, and nitric oxide treatment produced a further increase in mutation yield. Sequence analysis showed that methylation alone led to C:G->T:A transitions, whereas nitric oxide treatment simply produced more C:G->A:T transversions. Thus the most important factor in C:G->T:A transition at CpG sites identified in this experimental system is cytosine methylation, consistent with spontaneous conversion of 5-methylcytosine to thymine by deamination

  5. A combined atomic force microscopy imaging and docking study to investigate the complex between p53 DNA binding domain and Azurin.

    Science.gov (United States)

    Bizzarri, Anna Rita; Di Agostino, Silvia; Andolfi, Laura; Cannistraro, Salvatore

    2009-01-01

    The tumor suppressor p53 interacts with the redox copper protein Azurin (AZ) forming a complex which is of some relevance in biomedicine and cancer therapy. To obtain information on the spatial organization of this complex when it is immobilized on a substrate, we have used tapping mode-atomic force microscopy (TM-AFM) imaging combined with computational docking. The vertical dimension and the bearing volume of the DNA binding domain (DBD) of p53, anchored to functionalized gold substrate through exposed lysine residues, alone and after deposing AZ, have been measured by TM-AFM. By a computational docking approach, a three-dimensional model for the DBD of p53, before and after addition of AZ, have been predicted. Then we have calculated the possible arrangements of these biomolecular systems on gold substrate by finding a good agreement with the related experimental distribution of the height. The potentiality of the approach combining TM-AFM imaging and computational docking for the study of biomolecular complexes immobilized on substrates is briefly discussed.

  6. Mdm2 RING mutation enhances p53 transcriptional activity and p53-p300 interaction.

    Directory of Open Access Journals (Sweden)

    Hilary V Clegg

    Full Text Available The p53 transcription factor and tumor suppressor is regulated primarily by the E3 ubiquitin ligase Mdm2, which ubiquitinates p53 to target it for proteasomal degradation. Aside from its ubiquitin ligase function, Mdm2 has been believed to be capable of suppressing p53's transcriptional activity by binding with and masking the transactivation domain of p53. The ability of Mdm2 to restrain p53 activity by binding alone, without ubiquitination, was challenged by a 2007 study using a knockin mouse harboring a single cysteine-to-alanine point mutation (C462A in Mdm2's RING domain. Mouse embryonic fibroblasts with this mutation, which abrogates Mdm2's E3 ubiquitin ligase activity without affecting its ability to bind with p53, were unable to suppress p53 activity. In this study, we utilized the Mdm2(C462A mouse model to characterize in further detail the role of Mdm2's RING domain in the control of p53. Here, we show in vivo that the Mdm2(C462A protein not only fails to suppress p53, but compared to the complete absence of Mdm2, Mdm2(C462A actually enhances p53 transcriptional activity toward p53 target genes p21/CDKN1A, MDM2, BAX, NOXA, and 14-3-3σ. In addition, we found that Mdm2(C462A facilitates the interaction between p53 and the acetyltransferase CBP/p300, and it fails to heterodimerize with its homolog and sister regulator of p53, Mdmx, suggesting that a fully intact RING domain is required for Mdm2's inhibition of the p300-p53 interaction and for its interaction with Mdmx. These findings help us to better understand the complex regulation of the Mdm2-p53 pathway and have important implications for chemotherapeutic agents targeting Mdm2, as they suggest that inhibition of Mdm2's E3 ubiquitin ligase activity may be sufficient for increasing p53 activity in vivo, without the need to block Mdm2-p53 binding.

  7. OTUD5 regulates p53 stability by deubiquitinating p53.

    Directory of Open Access Journals (Sweden)

    Judong Luo

    Full Text Available BACKGROUND: The p53 tumour suppressor protein is a transcription factor that prevents oncogenic progression by activating the expression of apoptosis and cell-cycle arrest genes in stressed cells. The stability of p53 is tightly regulated by ubiquitin-dependent degradation, driven mainly by its negative regulators ubiquitin ligase MDM2. PRINCIPAL FINDINGS: In this study, we have identified OTUD5 as a DUB that interacts with and deubiquitinates p53. OTUD5 forms a direct complex with p53 and controls level of ubiquitination. The function of OTUD5 is required to allow the rapid activation of p53-dependent transcription and a p53-dependent apoptosis in response to DNA damage stress. CONCLUSIONS: As a novel deubiquitinating enzyme for p53, OTUD5 is required for the stabilization and the activation of a p53 response.

  8. Structure of p53 binding to the BAX response element reveals DNA unwinding and compression to accommodate base-pair insertion

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.; Zhang, X.; Dantas Machado, A. C.; Ding, Y.; Chen, Z.; Qin, P. Z.; Rohs, R.; Chen, L.

    2013-07-08

    The p53 core domain binds to response elements (REs) that contain two continuous half-sites as a cooperative tetramer, but how p53 recognizes discontinuous REs is not well understood. Here we describe the crystal structure of the p53 core domain bound to a naturally occurring RE located at the promoter of the Bcl-2-associated X protein (BAX) gene, which contains a one base-pair insertion between the two half-sites. Surprisingly, p53 forms a tetramer on the BAX-RE that is nearly identical to what has been reported on other REs with a 0-bp spacer. Each p53 dimer of the tetramer binds in register to a half-site and maintains the same protein–DNA interactions as previously observed, and the two dimers retain all the protein–protein contacts without undergoing rotation or translation. To accommodate the additional base pair, the DNA is deformed and partially disordered around the spacer region, resulting in an apparent unwinding and compression, such that the interactions between the dimers are maintained. Furthermore, DNA deformation within the p53-bound BAX-RE is confirmed in solution by site-directed spin labeling measurements. Our results provide a structural insight into the mechanism by which p53 binds to discontinuous sites with one base-pair spacer.

  9. Altered-function p53 missense mutations identified in breast cancers can have subtle effects on transactivation

    Science.gov (United States)

    Jordan, Jennifer J.; Inga, Alberto; Conway, Kathleen; Edmiston, Sharon; Carey, Lisa A.; Wu, Lin; Resnick, Michael A.

    2010-01-01

    Mutations of the sequence-specific master regulator p53 that alter transactivation function from promoter response elements (REs) could result in changes in the strength of gene activation or spectra of genes regulated. Such mutations in this tumor suppressor might lead to dramatic phenotypic changes and diversification of cell responses to stress. We have determined “functional fingerprints” of sporadic breast cancer-related p53 mutants many of which are also associated with familial cancer proneness such as the Li-Fraumeni Syndrome and germline BRCA1/2 mutant-associated cancers. The ability of p53, wild type and mutants, to transactivate from 11 human target REs has been assessed at variable expression levels using a cellular, isogenomic yeast model system that allows for the rapid analysis of p53 function using a qualitative and a quantitative reporter. Among 50 missense mutants, 29 were classified as loss-of-function. The remaining 21 retained transactivation towards at least one RE. At high levels of galactose induced p53 expression, 12/21 mutants that retain transactivation appeared similar to WT. When the level of galactose was reduced, transactivation defects could be revealed suggesting that some breast cancer related mutants can have subtle changes in transcription. These findings have been compared with clinical data from an ongoing neoadjuvant chemotherapy treatment trial for locally advanced breast tumors. The functional and nonfunctional missense mutations may distinguish tumors in terms of demographics, appearance and relapse, implying that heterogeneity in the functionality of specific p53 mutations could impact clinical behavior and outcome. PMID:20407015

  10. Lack of p53 function promotes radiation-induced mitotic catastrophe in mouse embryonic fibroblast cells

    Directory of Open Access Journals (Sweden)

    Phillips Stacia L

    2006-04-01

    Full Text Available Abstract Background We have demonstrated that in some human cancer cells both chronic mild heat and ionizing radiation exposures induce a transient block in S and G2 phases of the cell cycle. During this delay, cyclin B1 protein accumulates to supranormal levels, cyclin B1-dependent kinase is activated, and abrogation of the G2/M checkpoint control occurs resulting in mitotic catastrophe (MC. Results Using syngenic mouse embryonic fibroblasts (MEF with wild-type or mutant p53, we now show that, while both cell lines exhibit delays in S/G2 phase post-irradiation, the mutant p53 cells show elevated levels of cyclin B1 followed by MC, while the wild-type p53 cells present both a lower accumulation of cyclin B1 and a lower frequency of MC. Conclusion These results are in line with studies reporting the role of p53 as a post-transcriptional regulator of cyclin B1 protein and confirm that dysregulation of cyclin B1 promote radiation-induced MC. These findings might be exploited to design strategies to augment the yield of MC in tumor cells that are resistant to radiation-induced apoptosis.

  11. Reactivation of mutant p53 by capsaicin, the major constituent of peppers

    OpenAIRE

    2016-01-01

    Background Mutations in the p53 oncosuppressor gene are highly frequent in human cancers. These alterations are mainly point mutations in the DNA binding domain of p53 and disable p53 from transactivating target genes devoted to anticancer activity. Mutant p53 proteins are usually more stable than wild-type p53 and may not only impair wild-type p53 activity but also acquire pro-oncogenic functions. Therefore, targeting mutant p53 to clear the hyperstable proteins or change p53 conformation to...

  12. The fold recognition of CP2 transcription factors gives new insights into the function and evolution of tumor suppressor protein p53.

    Science.gov (United States)

    Kokoszynska, Katarzyna; Ostrowski, Jerzy; Rychlewski, Leszek; Wyrwicz, Lucjan S

    2008-09-15

    The CP2 transcription factor (TFCP2) is a critical regulator of erythroid gene expression. Apart from the involvement in the transcriptional switch of globin gene promoters it activates an array of cellular and viral gene promoters. A number of homologous proteins was identified in genomes of Metazoa, with additional five homologues encoded by the human genome (TFCP2L1, UBP1, GRHL1, GRHL2, GRHL3). Although several experimental studies have already been published, the knowledge on the molecular mechanism of activity of this transcription factors remains very limited. Here we present the application of fold recognition and protein structure prediction in drafting the structure-to-function relationship of the CP2 family. The employed procedure clearly shows that the family adopts a DNA binding immunoglobulin fold homologous to the p53 (TP53) core domain, and a novel type of ubiquitin-like domain and a sterile alpha motif (SAM) form oligomerization modules. With a traceable evolution of CP2 family throughout the Metazoa group this protein family is highly likely to represent an ancestor of the critical cell cycle regulator p53. Based on this observation several functional hypotheses on structure-to-function relationship of p53 were drawn. The DNA motif recognized by p53 is a result of further specialization of the CP2 DNA-binding module. The analysis also shows the critical role of protein oligomerization for the function of this protein superfamily. Finally, the identification of distant homologs of TP53 allowed performing a phylogenetic footprinting analysis explaining the role of the specific amino acids important for both - the protein folding and the binding of DNA.

  13. The Establishment of a Hyperactive Structure Allows the Tumour Suppressor Protein p53 to Function through P-TEFb during Limited CDK9 Kinase Inhibition.

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    Thomas K Albert

    Full Text Available CDK9 is the catalytic subunit of positive elongation factor b (P-TEFb that controls the transition of RNA polymerase II (RNAPII into elongation. CDK9 inhibitors block mRNA synthesis and trigger activation of the stress-sensitive p53 protein. This in turn induces transcription of CDKN1A (p21 and other cell cycle control genes. It is presently unclear if and how p53 circumvents a general P-TEFb-requirement when it activates its target genes. Our investigations using a panel of specific inhibitors reason for a critical role of CDK9 also in the case of direct inhibition of the kinase. At the prototypic p21 gene, the activator p53 initially accumulates at the pre-bound upstream enhancer followed-with significant delay-by de novo binding to a secondary enhancer site within the first intron of p21. This is accompanied by recruitment of the RNAPII initiation machinery to both elements. ChIP and functional analyses reason for a prominent role of CDK9 itself and elongation factor complexes PAF1c and SEC involved in pause and elongation control. It appears that the strong activation potential of p53 facilitates gene activation in the situation of global repression of RNAPII transcription. The data further underline the fundamental importance of CDK9 for class II gene transcription.

  14. A p53-dependent response limits epidermal stem cell functionality and organismal size in mice with short telomeres.

    Directory of Open Access Journals (Sweden)

    Ignacio Flores

    Full Text Available Telomere maintenance is essential to ensure proper size and function of organs with a high turnover. In particular, a dwarf phenotype as well as phenotypes associated to premature loss of tissue regeneration, including the skin (hair loss, hair graying, decreased wound healing, are found in mice deficient for telomerase, the enzyme responsible for maintaining telomere length. Coincidental with the appearance of these phenotypes, p53 is found activated in several tissues from these mice, where is thought to trigger cellular senescence and/or apoptotic responses. Here, we show that p53 abrogation rescues both the small size phenotype and restitutes the functionality of epidermal stem cells (ESC of telomerase-deficient mice with dysfunctional telomeres. In particular, p53 ablation restores hair growth, skin renewal and wound healing responses upon mitogenic induction, as well as rescues ESCmobilization defects in vivo and defective ESC clonogenic activity in vitro. This recovery of ESC functions is accompanied by a downregulation of senescence markers and an increased proliferation in the skin and kidney of telomerase-deficient mice with critically short telomeres without changes in apoptosis rates. Together, these findings indicate the existence of a p53-dependent senescence response acting on stem/progenitor cells with dysfunctional telomeres that is actively limiting their contribution to tissue regeneration, thereby impinging on tissue fitness.

  15. Modeling of arylamide helix mimetics in the p53 peptide binding site of hDM2 suggests parallel and anti-parallel conformations are both stable.

    Directory of Open Access Journals (Sweden)

    Jonathan C Fuller

    Full Text Available The design of novel α-helix mimetic inhibitors of protein-protein interactions is of interest to pharmaceuticals and chemical genetics researchers as these inhibitors provide a chemical scaffold presenting side chains in the same geometry as an α-helix. This conformational arrangement allows the design of high affinity inhibitors mimicking known peptide sequences binding specific protein substrates. We show that GAFF and AutoDock potentials do not properly capture the conformational preferences of α-helix mimetics based on arylamide oligomers and identify alternate parameters matching solution NMR data and suitable for molecular dynamics simulation of arylamide compounds. Results from both docking and molecular dynamics simulations are consistent with the arylamides binding in the p53 peptide binding pocket. Simulations of arylamides in the p53 binding pocket of hDM2 are consistent with binding, exhibiting similar structural dynamics in the pocket as simulations of known hDM2 binders Nutlin-2 and a benzodiazepinedione compound. Arylamide conformations converge towards the same region of the binding pocket on the 20 ns time scale, and most, though not all dihedrals in the binding pocket are well sampled on this timescale. We show that there are two putative classes of binding modes for arylamide compounds supported equally by the modeling evidence. In the first, the arylamide compound lies parallel to the observed p53 helix. In the second class, not previously identified or proposed, the arylamide compound lies anti-parallel to the p53 helix.

  16. Somatotropinomas, but not nonfunctioning pituitary adenomas, maintain a functional apoptotic RET/Pit1/ARF/p53 pathway that is blocked by excess GDNF.

    Science.gov (United States)

    Diaz-Rodriguez, Esther; Garcia-Rendueles, Angela R; Ibáñez-Costa, Alejandro; Gutierrez-Pascual, Ester; Garcia-Lavandeira, Montserrat; Leal, Alfonso; Japon, Miguel A; Soto, Alfonso; Venegas, Eva; Tinahones, Francisco J; Garcia-Arnes, Juan A; Benito, Pedro; Angeles Galvez, Maria; Jimenez-Reina, Luis; Bernabeu, Ignacio; Dieguez, Carlos; Luque, Raul M; Castaño, Justo P; Alvarez, Clara V

    2014-11-01

    Acromegaly is caused by somatotroph cell adenomas (somatotropinomas [ACROs]), which secrete GH. Human and rodent somatotroph cells express the RET receptor. In rodents, when normal somatotrophs are deprived of the RET ligand, GDNF (Glial Cell Derived Neurotrophic Factor), RET is processed intracellularly to induce overexpression of Pit1 [Transcription factor (gene : POUF1) essential for transcription of Pituitary hormones GH, PRL and TSHb], which in turn leads to p19Arf/p53-dependent apoptosis. Our purpose was to ascertain whether human ACROs maintain the RET/Pit1/p14ARF/p53/apoptosis pathway, relative to nonfunctioning pituitary adenomas (NFPAs). Apoptosis in the absence and presence of GDNF was studied in primary cultures of 8 ACROs and 3 NFPAs. Parallel protein extracts were analyzed for expression of RET, Pit1, p19Arf, p53, and phospho-Akt. When GDNF deprived, ACRO cells, but not NFPAs, presented marked level of apoptosis that was prevented in the presence of GDNF. Apoptosis was accompanied by RET processing, Pit1 accumulation, and p14ARF and p53 induction. GDNF prevented all these effects via activation of phospho-AKT. Overexpression of human Pit1 (hPit1) directly induced p19Arf/p53 and apoptosis in a pituitary cell line. Using in silico studies, 2 CCAAT/enhancer binding protein alpha (cEBPα) consensus-binding sites were found to be 100% conserved in mouse, rat, and hPit1 promoters. Deletion of 1 cEBPα site prevented the RET-induced increase in hPit1 promoter expression. TaqMan qRT-PCR (real time RT-PCR) for RET, Pit1, Arf, TP53, GDNF, steroidogenic factor 1, and GH was performed in RNA from whole ACRO and NFPA tumors. ACRO but not NFPA adenomas express RET and Pit1. GDNF expression in the tumors was positively correlated with RET and negatively correlated with p53. In conclusion, ACROs maintain an active RET/Pit1/p14Arf/p53/apoptosis pathway that is inhibited by GDNF. Disruption of GDNF's survival function might constitute a new therapeutic route in

  17. p53 and NF-κB: different strategies for responding to stress lead to a functional antagonism.

    Science.gov (United States)

    Ak, Prashanth; Levine, Arnold J

    2010-10-01

    The p53 transcription factor responds to a variety of intrinsic stresses, such as DNA damage, hypoxia, and even oncogene activation. NF-κB responds to a large number of extrinsic stresses such as cytokine activation and infectious diseases. The p53 tumor suppressor limits the consequences of stress by initiating cell death, senescence, or cell cycle arrest and promotes metabolic patterns in the cell to favor oxidative phosphorylation. NF-κB, the oncogene, promotes cell division, which initiates the innate and adaptive immune responses utilizing large amounts of glucose in aerobic glycolysis, resulting in the synthesis of substrates for cell division. Thus these two transcription factors, both of which have evolved to respond to different types of stress, have adopted opposite strategies and cannot function in the same cell at the same time. On activation of one of these transcription factors, the other is inactivated. This is achieved at several places in the p53 and NF-κB pathways where regulatory proteins act on both p53 and NF-κB with opposite functional consequences. These internodal sites create core regulatory circuits essential for integrating two central pathways in cells.

  18. p53 binding protein 1 foci as a biomarker of DNA double strand breaks induced by ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ng, C.K.M.; Wong, M.Y.P.; Lam, R.K.K.; Ho, J.P.Y. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Chiu, S.K. [Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Yu, K.N., E-mail: peter.yu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); State Key Laboratory in Marine Pollution, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)

    2011-12-21

    Foci of p53 binding protein 1 (53 BP1) have been used as a biomarker of DNA double-strand breaks (DSBs) in cells induced by ionizing radiations. 53 BP1 was shown to relocalize into foci shortly after irradiation, with the number of foci closely paralleling the number of DNA DSBs. However, consensus on criteria in terms of the numbers of 53 BP1 foci to define cells damaged by direct irradiation or by bystander signals has not been reached, which is partly due to the presence of 53 BP1 also in normal cells. The objective of the present work was to study the changes in the distribution of cells with different numbers of 53 BP1 foci in a cell population after low-dose ionizing irradiation (<0.1 Gy) provided by alpha particles, with a view to propose feasible criteria for defining cells damaged by direct irradiation or by bystander signals. It was proposed that the change in the percentage of cells with 1-3 foci should be used for such purposes. The underlying reasons were discussed.

  19. Transcriptional profiling in C. elegans suggests DNA damage dependent apoptosis as an ancient function of the p53 family

    Directory of Open Access Journals (Sweden)

    Rothblatt Jonathan

    2008-07-01

    Full Text Available Abstract Background In contrast to the three mammalian p53 family members, p53, which is generally involved in DNA damage responses, and p63 and p73 which are primarily needed for developmental regulation, cep-1 encodes for the single C. elegans p53-like gene. cep-1 acts as a transcription activator in a primordial p53 pathway that involves CEP-1 activation and the CEP-1 dependent transcriptional induction of the worm BH3 only domain encoding genes egl-1 and ced-13 to induce germ cell apoptosis. EGL-1 and CED-13 proteins inactivate Bcl-2 like CED-9 to trigger CED-4 and CED-3 caspase dependent germ cell apoptosis. To address the function of p53 in global transcriptional regulation we investigate genome-wide transcriptional responses upon DNA damage and cep-1 deficiency. Results Examining C. elegans expression profiles using whole genome Affymetrix GeneChip arrays, we found that 83 genes were induced more than two fold upon ionizing radiation (IR. None of these genes, with exception of an ATP ribosylase homolog, encode for known DNA repair genes. Using two independent cep-1 loss of function alleles we did not find genes regulated by cep-1 in the absence of IR. Among the IR-induced genes only three are dependent on cep-1, namely egl-1, ced-13 and a novel C. elegans specific gene. The majority of IR-induced genes appear to be involved in general stress responses, and qRT-PCR experiments indicate that they are mainly expressed in somatic tissues. Interestingly, we reveal an extensive overlap of gene expression changes occurring in response to DNA damage and in response to bacterial infection. Furthermore, many genes induced by IR are also transcriptionally regulated in longevity mutants suggesting that DNA damage and aging induce an overlapping stress response. Conclusion We performed genome-wide gene expression analyses which indicate that only a surprisingly small number of genes are regulated by CEP-1 and that DNA damage induced apoptosis via the

  20. Urodele p53 tolerates amino acid changes found in p53 variants linked to human cancer

    Directory of Open Access Journals (Sweden)

    Villiard Éric

    2007-09-01

    , other significant changes in the axolotl proteins may play more subtle roles on p53 functions, including DNA binding and promoter specificity and could represent useful adaptations to ensure p53 activity and tumor suppression in animals able to regenerate or subject to large variations in oxygen levels or temperature.

  1. Negative Regulation of Tumor Suppressor p53 by microRNA miR-504

    OpenAIRE

    2010-01-01

    Tumor suppressor p53 plays a central role in tumor prevention. p53 protein levels and activity are under a tight and complex regulation in cells to maintain the proper function of p53. microRNAs play a key role in the regulation of gene expression. Here we report the regulation of p53 through microRNA miR-504. miR-504 acts as a negative regulator of human p53 through its direct binding to two sites in p53 3′-UTR. Overexpression of miR-504 decreases p53 protein levels and functions in cells, i...

  2. Paracrine Apoptotic Effect of p53 Mediated by Tumor Suppressor Par-4

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    Ravshan Burikhanov

    2014-01-01

    Full Text Available The guardian of the genome, p53, is often mutated in cancer and may contribute to therapeutic resistance. Given that p53 is intact and functional in normal tissues, we harnessed its potential to inhibit the growth of p53-deficient cancer cells. Specific activation of p53 in normal fibroblasts selectively induced apoptosis in p53-deficient cancer cells. This paracrine effect was mediated by p53-dependent secretion of the tumor suppressor Par-4. Accordingly, the activation of p53 in normal mice, but not p53−/− or Par-4−/− mice, caused systemic elevation of Par-4, which induced apoptosis of p53-deficient tumor cells. Mechanistically, p53 induced Par-4 secretion by suppressing the expression of its binding partner, UACA, which sequesters Par-4. Thus, normal cells can be empowered by p53 activation to induce Par-4 secretion for the inhibition of therapy-resistant tumors.

  3. Intrinsic Differences in Backbone Dynamics between Wild Type and DNA-Contact Mutants of the p53 DNA Binding Domain Revealed by Nuclear Magnetic Resonance Spectroscopy.

    Science.gov (United States)

    Rasquinha, Juhi A; Bej, Aritra; Dutta, Shraboni; Mukherjee, Sujoy

    2017-09-07

    Mutations in p53's DNA binding domain (p53DBD) are associated with 50% of all cancers, making it an essential system to investigate and understand the genesis and progression of cancer. In this work, we studied the changes in the structure and dynamics of wild type p53DBD in comparison with two of its "hot-spot" DNA-contact mutants, R248Q and R273H, by analysis of backbone amide chemical shift perturbations and (15)N spin relaxation measurements. The results of amide chemical shift changes indicated significantly more perturbations in the R273H mutant than in wild type and R248Q p53DBD. Analysis of (15)N spin relaxation rates and the resulting nuclear magnetic resonance order parameters suggests that for most parts, the R248Q mutant exhibits limited conformational flexibility and is similar to the wild type protein. In contrast, R273H showed significant backbone dynamics extending up to its β-sandwich scaffold in addition to motions along the DNA binding interface. Furthermore, comparison of rotational correlation times between the mutants suggests that the R273H mutant, with a higher correlation time, forms an enlarged structural fold in comparison to the R248Q mutant and wild type p53DBD. Finally, we identify three regions in these proteins that show conformational flexibility to varying degrees, which suggests that the R273H mutant, in addition to being a DNA-contact mutation, exhibits properties of a conformational mutant.

  4. Integration of Genomic, Biologic, and Chemical Approaches to Target p53 Loss and Gain-of-Function in Triple Negative Breast Cancer

    Science.gov (United States)

    2014-09-01

    Approaches to Target p53 Loss and Gain-of-Function in Triple Negative Breast Cancer PRINCIPAL INVESTIGATOR: Jennifer A. Pietenpol, Ph.D...Biologic, and Chemical Approaches to Target p53 Loss and Gain-of-Function in Triple Negative Breast Cancer 5a. CONTRACT NUMBER...states resulting from alterations in the p53 signaling pathway in triple negative breast cancer (TNBC). Development of therapies for TNBC is a

  5. Structural visualization of the p53/RNA polymerase II assembly.

    Science.gov (United States)

    Singh, Sameer K; Qiao, Zhen; Song, Lihua; Jani, Vijay; Rice, William; Eng, Edward; Coleman, Robert A; Liu, Wei-Li

    2016-11-15

    The master tumor suppressor p53 activates transcription in response to various cellular stresses in part by facilitating recruitment of the transcription machinery to DNA. Recent studies have documented a direct yet poorly characterized interaction between p53 and RNA polymerase II (Pol II). Therefore, we dissected the human p53/Pol II interaction via single-particle cryo-electron microscopy, structural docking, and biochemical analyses. This study reveals that p53 binds Pol II via the Rpb1 and Rpb2 subunits, bridging the DNA-binding cleft of Pol II proximal to the upstream DNA entry site. In addition, the key DNA-binding surface of p53, frequently disrupted in various cancers, remains exposed within the assembly. Furthermore, the p53/Pol II cocomplex displays a closed conformation as defined by the position of the Pol II clamp domain. Notably, the interaction of p53 and Pol II leads to increased Pol II elongation activity. These findings indicate that p53 may structurally regulate DNA-binding functions of Pol II via the clamp domain, thereby providing insights into p53-regulated Pol II transcription.

  6. Recognition of Local DNA Structures by p53 Protein.

    Science.gov (United States)

    Brázda, Václav; Coufal, Jan

    2017-02-10

    p53 plays critical roles in regulating cell cycle, apoptosis, senescence and metabolism and is commonly mutated in human cancer. These roles are achieved by interaction with other proteins, but particularly by interaction with DNA. As a transcription factor, p53 is well known to bind consensus target sequences in linear B-DNA. Recent findings indicate that p53 binds with higher affinity to target sequences that form cruciform DNA structure. Moreover, p53 binds very tightly to non-B DNA structures and local DNA structures are increasingly recognized to influence the activity of wild-type and mutant p53. Apart from cruciform structures, p53 binds to quadruplex DNA, triplex DNA, DNA loops, bulged DNA and hemicatenane DNA. In this review, we describe local DNA structures and summarize information about interactions of p53 with these structural DNA motifs. These recent data provide important insights into the complexity of the p53 pathway and the functional consequences of wild-type and mutant p53 activation in normal and tumor cells.

  7. Senescence-Associated Secretory Phenotypes Reveal Cell-Nonautonomous Functions of Oncogenic RAS and the p53 Tumor Suppressor

    Energy Technology Data Exchange (ETDEWEB)

    Copp& #233; , Jean-Philippe; Patil, Christopher; Rodier, Francis; Sun, Yu; Munoz, Denise; Goldstein, Joshua; Nelson, Peter; Desprez, Pierre-Yves; Campisi, Judith

    2008-10-24

    Cellular senescence suppresses cancer by arresting cell proliferation, essentially permanently, in response to oncogenic stimuli, including genotoxic stress. We modified the use of antibody arrays to provide a quantitative assessment of factors secreted by senescent cells. We show that human cells induced to senesce by genotoxic stress secrete myriad factors associated with inflammation and malignancy. This senescence-associated secretory phenotype (SASP) developed slowly over several days and only after DNA damage of sufficient magnitude to induce senescence. Remarkably similar SASPs developed in normal fibroblasts, normal epithelial cells, and epithelial tumor cells after genotoxic stress in culture, and in epithelial tumor cells in vivo after treatment of prostate cancer patients with DNA-damaging chemotherapy. In cultured premalignant epithelial cells, SASPs induced an epithelial-mesenchyme transition and invasiveness, hallmarks of malignancy, by a paracrine mechanism that depended largely on the SASP factors interleukin (IL)-6 and IL-8. Strikingly, two manipulations markedly amplified, and accelerated development of, the SASPs: oncogenic RAS expression, which causes genotoxic stress and senescence in normal cells, and functional loss of the p53 tumor suppressor protein. Both loss of p53 and gain of oncogenic RAS also exacerbated the promalignant paracrine activities of the SASPs. Our findings define a central feature of genotoxic stress-induced senescence. Moreover, they suggest a cell-nonautonomous mechanism by which p53 can restrain, and oncogenic RAS can promote, the development of age-related cancer by altering the tissue microenvironment.

  8. Senescence-associated secretory phenotypes reveal cell-nonautonomous functions of oncogenic RAS and the p53 tumor suppressor.

    Directory of Open Access Journals (Sweden)

    Jean-Philippe Coppé

    2008-12-01

    Full Text Available Cellular senescence suppresses cancer by arresting cell proliferation, essentially permanently, in response to oncogenic stimuli, including genotoxic stress. We modified the use of antibody arrays to provide a quantitative assessment of factors secreted by senescent cells. We show that human cells induced to senesce by genotoxic stress secrete myriad factors associated with inflammation and malignancy. This senescence-associated secretory phenotype (SASP developed slowly over several days and only after DNA damage of sufficient magnitude to induce senescence. Remarkably similar SASPs developed in normal fibroblasts, normal epithelial cells, and epithelial tumor cells after genotoxic stress in culture, and in epithelial tumor cells in vivo after treatment of prostate cancer patients with DNA-damaging chemotherapy. In cultured premalignant epithelial cells, SASPs induced an epithelial-mesenchyme transition and invasiveness, hallmarks of malignancy, by a paracrine mechanism that depended largely on the SASP factors interleukin (IL-6 and IL-8. Strikingly, two manipulations markedly amplified, and accelerated development of, the SASPs: oncogenic RAS expression, which causes genotoxic stress and senescence in normal cells, and functional loss of the p53 tumor suppressor protein. Both loss of p53 and gain of oncogenic RAS also exacerbated the promalignant paracrine activities of the SASPs. Our findings define a central feature of genotoxic stress-induced senescence. Moreover, they suggest a cell-nonautonomous mechanism by which p53 can restrain, and oncogenic RAS can promote, the development of age-related cancer by altering the tissue microenvironment.

  9. Functionalized Graphene Oxide as a Nanocarrier in a Multienzyme Labeling Amplification Strategy for Ultrasensitive Electrochemical Immunoassay of Phosphorylated p53 (S392)

    Energy Technology Data Exchange (ETDEWEB)

    Du, Dan; Wang, Limin; Shao, Yuyan; Wang, Jun; Engelhard, Mark H.; Lin, Yuehe

    2011-01-06

    P53 phosphorylation plays an important role in many biological processes and might be used as a potential biomarker in clinical diagnoses. We report a new electrochemical immunosensor for ultrasensitive detection of phosphorylated p53 at Ser392 (phospho-p53-392) based on graphene oxide (GO) as a nanocarrier in multienzymes amplification strategy. Greatly enhanced sensitivity was achieved by using the bioconjugates featuring horseradish peroxidase (HRP) and p53392 signal antibody (p53Ab2) linked to functionalized GO (HRP-p53Ab2-GO) at high ratio of HRP/p53Ab2. After a sandwich immunoreaction, the HRP-p53Ab2-GO captured onto the electrode surface produced an amplified electrocatalytic response by the reduction of enzymatically oxidized thionine in the presence of hydrogen peroxide. The increase of response current was proportional to the phospho-p53 concentration in the range of 0.02 to 2 nM with the detection limit of 0.01 nM, which was 10-fold lower than that of traditional sandwich electrochemical measurement for p53. The amplified immunoassay developed in this work shows acceptable stability and reproducibility and the assay results for phospho-p53 spiked in human plasma also show good recovery (92%~103.8%). This simple and low-cost immunosensor shows great promise for detection of other phosphorylated proteins and clinical applications.

  10. The structure formed by inverted repeats in p53 response elements determines the transactivation activity of p53 protein.

    Science.gov (United States)

    Brázda, Václav; Čechová, Jana; Battistin, Michele; Coufal, Jan; Jagelská, Eva B; Raimondi, Ivan; Inga, Alberto

    2017-01-29

    The TP53 gene is the most frequently mutated gene in human cancer and p53 protein plays a crucial role in gene expression and cancer protection. Its role is manifested by interactions with other proteins and DNA. p53 is a transcription factor that binds to DNA response elements (REs). Due to the palindromic nature of the consensus binding site, several p53-REs have the potential to form cruciform structures. However, the influence of cruciform formation on the activity of p53-REs has not been evaluated. Therefore, we prepared sets of p53-REs with identical theoretical binding affinity in their linear state, but different probabilities to form extra helical structures, for in vitro and in vivo analyses. Then we evaluated the presence of cruciform structures when inserted into plasmid DNA and employed a yeast-based assay to measure transactivation potential of these p53-REs cloned at a chromosomal locus in isogenic strains. We show that transactivation in vivo correlated more with relative propensity of an RE to form cruciforms than to its predicted in vitro DNA binding affinity for wild type p53. Structural features of p53-REs could therefore be an important determinant of p53 transactivation function.

  11. A família do p53: aspectos estruturais e funcionais do p73 e do p63 The p53 family: structural and functional aspects of p73 and p63

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    Alfredo Ribeiro-Silva

    2003-06-01

    Full Text Available O p53 é um gene regulador chave do ciclo celular que, quando sofre mutações, leva ao desenvolvimento de neoplasias, atuando, portanto, como um gene supressor tumoral em condições normais. Recentemente foram identificados genes homólogos ao p53 denominados p73 e p63, provavelmente oriundos de um gene ancestral comum. Apesar da grande homologia estrutural, os membros da família do p53 possuem diferenças funcionais entre si. O presente artigo tem por finalidade discorrer sobre os principais aspectos estruturais e funcionais do p73 e do p63, ressaltando seus papéis na tumorigênese humana. O p73 ativa vários genes responsivos ao p53 e, quando superexpresso, inibe a ação do p53. Raramente encontra-se mutado em neoplasias, e seu papel na tumorigênese humana ainda é motivo de controvérsias. O p63 não é um gene supressor tumoral clássico, sendo essencial para a manutenção de uma população de células precursoras (células-tronco em vários tecidos epiteliais. O p63 marca as células basais de vários órgãos epiteliais, como a pele e a próstata, podendo ser considerado um marcador de indiferenciação celular. O p63 é um marcador recentemente descrito e ainda requer maior investigação para determinar seu papel no desenvolvimento de neoplasias em humanos.The p53 gene has a key role in the cell cycle control. When mutated, it promotes the development of neoplasms, acting in so far as a tumor suppressor gene in normal conditions. Recently, genes homologue to p53 were identified, named p73 e p63, probably originated from a common ancestral gene. Despite the great structural homology, the members of p53 family have functional differences. This article aims to discourse about the major structural and functional aspects of p73 and p63, reinforcing their role in human tumorigenesis. P73 activates several p53 responsive genes and, when overexpressed, inhibits the p53 action. It is rarely mutated in neoplasms and its role in human

  12. Cross-regulation of protein stability by p53 and nuclear receptor SHP.

    Directory of Open Access Journals (Sweden)

    Zhihong Yang

    Full Text Available We report here a novel interplay between tumor suppressor p53 and nuclear receptor SHP that controls p53 and SHP stability. Overexpression of p53 causes rapid SHP protein degradation, which does not require the presence of Mdm2 and is mediated by the proteosome pathway. Overexpressing SHP alone does not affect p53 stability. However, SHP destabilizes p53 by augmentation of Mdm2 ubiquitin ligase activity toward p53. The single amino acid substitution in the SHP protein SHPK170R increases SHP binding to p53 relative to SHP wild-type, whereas SHPG171A variant shows a diminished p53 binding. As a result of the cross-regulation, the tumor suppressor function of p53 and SHP in inhibition of colon cancer growth is compromised. Our findings reveal a unique scenario for a cross-inhibition between two tumor suppressors to keep their expression and function in check.

  13. p53 in stem cells

    Institute of Scientific and Technical Information of China (English)

    Valeriya; Solozobova; Christine; Blattner

    2011-01-01

    p53 is well known as a "guardian of the genome" for differentiated cells,in which it induces cell cycle arrest and cell death after DNA damage and thus contributes to the maintenance of genomic stability.In addition to this tumor suppressor function for differentiated cells,p53 also plays an important role in stem cells.In this cell type,p53 not only ensures genomic integrity after genotoxic insults but also controls their proliferation and differentiation.Additionally,p53 provides an effective barrier for the generation of pluripotent stem celllike cells from terminally differentiated cells.In this review,we summarize our current knowledge about p53 activities in embryonic,adult and induced pluripotent stem cells.

  14. p53 isoform Δ113p53/Δ133p53 promotes DNA double-strand break repair to protect cell from death and senescence in response to DNA damage.

    Science.gov (United States)

    Gong, Lu; Gong, Hongjian; Pan, Xiao; Chang, Changqing; Ou, Zhao; Ye, Shengfan; Yin, Le; Yang, Lina; Tao, Ting; Zhang, Zhenhai; Liu, Cong; Lane, David P; Peng, Jinrong; Chen, Jun

    2015-03-01

    The inhibitory role of p53 in DNA double-strand break (DSB) repair seems contradictory to its tumor-suppressing property. The p53 isoform Δ113p53/Δ133p53 is a p53 target gene that antagonizes p53 apoptotic activity. However, information on its functions in DNA damage repair is lacking. Here we report that Δ113p53 expression is strongly induced by γ-irradiation, but not by UV-irradiation or heat shock treatment. Strikingly, Δ113p53 promotes DNA DSB repair pathways, including homologous recombination, non-homologous end joining and single-strand annealing. To study the biological significance of Δ113p53 in promoting DNA DSB repair, we generated a zebrafish Δ113p53(M/M) mutant via the transcription activator-like effector nuclease technique and found that the mutant is more sensitive to γ-irradiation. The human ortholog, Δ133p53, is also only induced by γ-irradiation and functions to promote DNA DSB repair. Δ133p53-knockdown cells were arrested at the G2 phase at the later stage in response to γ-irradiation due to a high level of unrepaired DNA DSBs, which finally led to cell senescence. Furthermore, Δ113p53/Δ133p53 promotes DNA DSB repair via upregulating the transcription of repair genes rad51, lig4 and rad52 by binding to a novel type of p53-responsive element in their promoters. Our results demonstrate that Δ113p53/Δ133p53 is an evolutionally conserved pro-survival factor for DNA damage stress by preventing apoptosis and promoting DNA DSB repair to inhibit cell senescence. Our data also suggest that the induction of Δ133p53 expression in normal cells or tissues provides an important tolerance marker for cancer patients to radiotherapy.

  15. Effects of temperature on the p53-DNA binding interactions and their dynamical behavior: comparing the wild type to the R248Q mutant.

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    Khaled Barakat

    Full Text Available BACKGROUND: The protein p53 plays an active role in the regulation of cell cycle. In about half of human cancers, the protein is inactivated by mutations located primarily in its DNA-binding domain. Interestingly, a number of these mutations possess temperature-induced DNA-binding characteristics. A striking example is the mutation of Arg248 into glutamine or tryptophan. These mutants are defective for binding to DNA at 310 K although they have been shown to bind specifically to several p53 response elements at sub-physiological temperatures (298-306 K. METHODOLOGY/PRINCIPAL FINDINGS: This important experimental finding motivated us to examine the effects of temperature on the structure and configuration of R248Q mutant and compare it to the wild type protein. Our aim is to determine how and where structural changes of mutant variants take place due to temperature changes. To answer these questions, we compared the mutant to the wild-type proteins from two different aspects. First, we investigated the systems at the atomistic level through their DNA-binding affinity, hydrogen bond networks and spatial distribution of water molecules. Next, we assessed changes in their long-lived conformational motions at the coarse-grained level through the collective dynamics of their side-chain and backbone atoms separately. CONCLUSIONS: The experimentally observed effect of temperature on the DNA-binding properties of p53 is reproduced. Analysis of atomistic and coarse-grained data reveal that changes in binding are determined by a few key residues and provide a rationale for the mutant-loss of binding at physiological temperatures. The findings can potentially enable a rescue strategy for the mutant structure.

  16. Reactivating mutant p53 using small molecules as zinc metallochaperones: awakening a sleeping giant in cancer.

    Science.gov (United States)

    Blanden, Adam R; Yu, Xin; Loh, Stewart N; Levine, Arnold J; Carpizo, Darren R

    2015-11-01

    Tumor protein p53 (TP53) is the most commonly mutated gene in human cancer. The majority of mutations are missense, and generate a defective protein that is druggable. Yet, for decades, the small-molecule restoration of wild-type (WT) p53 function in mutant p53 tumors (so-called p53 mutant 'reactivation') has been elusive to researchers. The p53 protein requires the binding of a single zinc ion for proper folding, and impairing zinc binding is a major mechanism for loss of function in missense mutant p53. Here, we describe recent work defining a new class of drugs termed zinc metallochaperones that restore WT p53 structure and function by restoring Zn(2+) to Zn(2+)-deficient mutant p53.

  17. Long Noncoding RNA MEG3 Interacts with p53 Protein and Regulates Partial p53 Target Genes in Hepatoma Cells.

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    Juanjuan Zhu

    Full Text Available Maternally Expressed Gene 3 (MEG3 encodes a lncRNA which is suggested to function as a tumor suppressor. Previous studies suggested that MEG3 functioned through activation of p53, however, the functional properties of MEG3 remain obscure and their relevance to human diseases is under continuous investigation. Here, we try to illuminate the relationship of MEG3 and p53, and the consequence in hepatoma cells. We find that transfection of expression construct of MEG3 enhances stability and transcriptional activity of p53. Deletion analysis of MEG3 confirms that full length and intact structure of MEG3 are critical for it to activate p53-mediated transactivation. Interestingly, our results demonstrate for the first time that MEG3 can interact with p53 DNA binding domain and various p53 target genes are deregulated after overexpression of MEG3 in hepatoma cells. Furthermore, results of qRT-PCR have shown that MEG3 RNA is lost or reduced in the majority of HCC samples compared with adjacent non-tumorous samples. Ectopic expression of MEG3 in hepatoma cells significantly inhibits proliferation and induces apoptosis. In conclusion, our data demonstrates that MEG3 functions as a tumor suppressor in hepatoma cells through interacting with p53 protein to activate p53-mediated transcriptional activity and influence the expression of partial p53 target genes.

  18. p53 Amino-terminus region (1-125 stabilizes and restores heat denatured p53 wild phenotype.

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    Anuj Kumar Sharma

    Full Text Available BACKGROUND: The intrinsically disordered N-ter domain (NTD of p53 encompasses approximately hundred amino acids that contain a transactivation domain (1-73 and a proline-rich domain (64-92 and is responsible for transactivation function and apoptosis. It also possesses an auto-inhibitory function as its removal results in remarkable reduction in dissociation of p53 from DNA. PRINCIPAL FINDINGS/METHODOLOGY: In this report, we have discovered that p53-NTD spanning amino acid residues 1-125 (NTD125 interacted with WT p53 and stabilized its wild type conformation under physiological and elevated temperatures, both in vitro and in cellular systems. NTD125 prevented irreversible thermal aggregation of heat denatured p53, enhanced p21-5'-DBS binding and further restored DBS binding activity of heat-denatured p53, in vitro, in a dose-dependent manner. In vivo ELISA and immunoprecipitation analysis of NTD125-transfected cells revealed that NTD125 shifted equilibrium from p53 mutant to wild type under heat stress conditions. Further, NTD125 initiated nuclear translocation of cytoplasmic p53 in transcriptionally active state in order to activate p53 downstream genes such as p21, Bax, PUMA, Noxa and SUMO. CONCLUSION/SIGNIFICANCE: Here, we showed that a novel chaperone-like activity resides in p53-N-ter region. This study might have significance in understanding the role of p53-NTD in p53 stabilization, conformational activation and apoptosis under heat-stress conditions.

  19. Abrogation of p53-induced apoptosis by the hepatitis B virus X gene.

    NARCIS (Netherlands)

    X.W. Wang (Xin Wei); M.K. Gibson (Michael); W. Vermeulen (Wim); H. Yeh; K. Forrester; H.-W. Stürzbecher; J.H.J. Hoeijmakers (Jan); C.C. Harris

    1996-01-01

    textabstractThe p53 tumor suppressor gene product is a transcriptional transactivator and a potent apoptotic inducer. The fact that many of the DNA tumor virus oncoproteins bind to p53 and affect these p53 functions indicates that this interaction is an important step in oncogenic transformation. We

  20. Avian Reovirus Protein p17 Functions as a Nucleoporin Tpr Suppressor Leading to Activation of p53, p21 and PTEN and Inactivation of PI3K/AKT/mTOR and ERK Signaling Pathways.

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    Wei-Ru Huang

    Full Text Available Avian reovirus (ARV protein p17 has been shown to regulate cell cycle and autophagy by activation of p53/PTEN pathway; nevertheless, it is still unclear how p53 and PTEN are activated by p17. Here, we report for the first time that p17 functions as a nucleoporin Tpr suppressor that leads to p53 nuclear accumulation and consequently activates p53, p21, and PTEN. The nuclear localization signal (119IAAKRGRQLD128 of p17 has been identified for Tpr binding. This study has shown that Tpr suppression occurs by p17 interacting with Tpr and by reducing the transcription level of Tpr, which together inhibit Tpr function. In addition to upregulation of PTEN by activation of p53 pathway, this study also suggests that ARV protein p17 acts as a positive regulator of PTEN. ARV p17 stabilizes PTEN by stimulating phosphorylation of cytoplasmic PTEN and by elevating Rak-PTEN association to prevent it from E3 ligase NEDD4-1 targeting. To activate PTEN, p17 is able to promote β-arrestin-mediated PTEN translocation from the cytoplasm to the plasma membrane via a Rock-1-dependent manner. The accumulation of p53 in the nucleus induces the PTEN- and p21-mediated downregulation of cyclin D1 and CDK4. Furthermore, Tpr and CDK4 knockdown increased virus production in contrast to depletion of p53, PTEN, and LC3 reducing virus yield. Taken together, our data suggest that p17-mediated Tpr suppression positively regulates p53, PTEN, and p21 and negatively regulates PI3K/AKT/mTOR and ERK signaling pathways, both of which are beneficial for virus replication.

  1. Avian Reovirus Protein p17 Functions as a Nucleoporin Tpr Suppressor Leading to Activation of p53, p21 and PTEN and Inactivation of PI3K/AKT/mTOR and ERK Signaling Pathways.

    Science.gov (United States)

    Huang, Wei-Ru; Chiu, Hung-Chuan; Liao, Tsai-Ling; Chuang, Kuo-Pin; Shih, Wing-Ling; Liu, Hung-Jen

    2015-01-01

    Avian reovirus (ARV) protein p17 has been shown to regulate cell cycle and autophagy by activation of p53/PTEN pathway; nevertheless, it is still unclear how p53 and PTEN are activated by p17. Here, we report for the first time that p17 functions as a nucleoporin Tpr suppressor that leads to p53 nuclear accumulation and consequently activates p53, p21, and PTEN. The nuclear localization signal (119IAAKRGRQLD128) of p17 has been identified for Tpr binding. This study has shown that Tpr suppression occurs by p17 interacting with Tpr and by reducing the transcription level of Tpr, which together inhibit Tpr function. In addition to upregulation of PTEN by activation of p53 pathway, this study also suggests that ARV protein p17 acts as a positive regulator of PTEN. ARV p17 stabilizes PTEN by stimulating phosphorylation of cytoplasmic PTEN and by elevating Rak-PTEN association to prevent it from E3 ligase NEDD4-1 targeting. To activate PTEN, p17 is able to promote β-arrestin-mediated PTEN translocation from the cytoplasm to the plasma membrane via a Rock-1-dependent manner. The accumulation of p53 in the nucleus induces the PTEN- and p21-mediated downregulation of cyclin D1 and CDK4. Furthermore, Tpr and CDK4 knockdown increased virus production in contrast to depletion of p53, PTEN, and LC3 reducing virus yield. Taken together, our data suggest that p17-mediated Tpr suppression positively regulates p53, PTEN, and p21 and negatively regulates PI3K/AKT/mTOR and ERK signaling pathways, both of which are beneficial for virus replication.

  2. MicroRNA Control of p53.

    Science.gov (United States)

    Liu, Juan; Zhang, Cen; Zhao, Yuhan; Feng, Zhaohui

    2017-01-01

    Tumor suppressor p53 plays a central role in tumor suppression. As a transcription factor, p53 mainly exerts its tumor suppressive function through transcriptional regulation of many target genes. To maintain the proper function of p53, p53 protein level and activity are exquisitely controlled by a group of positive and negative regulators in cells. Thus, p53, its regulators, and regulated genes form a complicated p53 signaling network. microRNAs (miRNAs) are a group of endogenous small non-coding RNA molecules. miRNAs play an important role in regulation of gene expression by blocking translational protein synthesis and/or degrading target mRNAs. Recent studies have demonstrated that p53 and its network are regulated by miRNAs at multiple levels. Some miRNAs regulate the level and function of p53 through directly targeting p53, whereas some other miRNAs target regulators of p53, such as MDM2 and MDM4, to indirectly regulate the activity and function of p53. On the other hand, p53 also regulates the transcriptional expression and the biogenesis of a group of miRNAs, which contributes to the tumor suppressive function of p53. p53 is the most frequently mutated gene in human cancer. Many tumor-associated mutant p53, which have "gain-of-function" activities in tumorigenesis independently of wild type p53, can regulate the expression of different miRNAs and modulate the biogenesis of specific miRNAs to promote tumorigenesis. These findings have demonstrated that miRNAs are important regulators and mediators of p53 and its signaling pathway, which highlights a pivotal role of miRNAs in the p53 network and cancer. J. Cell. Biochem. 118: 7-14, 2017. © 2016 Wiley Periodicals, Inc.

  3. Spiro-oxindole derivative 5-chloro-4',5'-diphenyl-3'-(4-(2-(piperidin-1-yl) ethoxy) benzoyl) spiro[indoline-3,2'-pyrrolidin]-2-one triggers apoptosis in breast cancer cells via restoration of p53 function.

    Science.gov (United States)

    Saxena, Ruchi; Gupta, Garima; Manohar, Murli; Debnath, Utsab; Popli, Pooja; Prabhakar, Yenamandra S; Konwar, Rituraj; Kumar, Sandeep; Kumar, Atul; Dwivedi, Anila

    2016-01-01

    Breast cancer remains a significant health problem due to the involvement of multiple aberrant and redundant signaling pathways in tumorigenesis and the development of resistance to the existing therapeutic agents. Therefore, the search for novel chemotherapeutic agents for effective management of breast cancer is still warranted. In an effort to develop new anti-breast cancer agents, we have synthesized and identified novel spiro-oxindole derivative G613 i.e. 5-chloro-4',5'-diphenyl-3'-(4-(2-(piperidin-1-yl) ethoxy) benzoyl) spiro[indoline-3,2'-pyrrolidin]-2-one, which has shown growth inhibitory activity in breast cancer cells. The present study was aimed to explore the mechanism of anti-tumorigenic action of this newly identified spiro-oxindole compound. Compound G613 inhibited the Mdm2-p53 interaction in breast cancer cells and tumor xenograft. It caused restoration of p53 function by activating its promoter activity, triggering its nuclear accumulation and preventing its ubiquitination and proteasomal degradation. Supportively, molecular docking studies revealed considerable homology in the docking mode of G613 and the known Mdm2 inhibitor Nutlin-3, to p53 binding pocket of Mdm2. The activation of p53 led to upregulation of p53 dependent pro-apoptotic proteins, Bax, Pumaα and Noxa and enhanced interaction of p53 with bcl2 member proteins thus triggering both transcription-dependent and transcription-independent apoptosis, respectively. Additionally, the compound decreased estrogen receptor activity through sequestration of estrogen receptor α by p53 thereby causing a decreased transcriptional activation and expression of proliferation markers. In conclusion, G613 represents a potent small-molecule inhibitor of the Mdm2-p53 interaction and can serve as a promising lead for developing a new class of anti-cancer therapy for breast cancer patients.

  4. TRIM65 negatively regulates p53 through ubiquitination

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yang [Department of Respiration, The First Hospital of Jilin University, Changchun 130021 (China); Ma, Chengyuan [Department of Neurosurgery, The First Hospital of Jilin University, Changchun 130021 (China); Zhou, Tong [Department of Endocrinology, The First Hospital of Jilin University, Changchun 130021 (China); Liu, Ying [Department of Respiration, The First Hospital of Jilin University, Changchun 130021 (China); Sun, Luyao [Department of Infectious Diseases, The First Hospital of Jilin University, Changchun 130021 (China); Yu, Zhenxiang, E-mail: zhenxiangyu2015@gmail.com [Department of Respiration, The First Hospital of Jilin University, Changchun 130021 (China)

    2016-04-22

    Tripartite-motif protein family member 65 (TRIM65) is an important protein involved in white matter lesion. However, the role of TRIM65 in human cancer remains less understood. Through the Cancer Genome Atlas (TCGA) gene alteration database, we found that TRIM65 is upregulated in a significant portion of non-small cell lung carcinoma (NSCLC) patients. Our cell growth assay revealed that TRIM65 overexpression promotes cell proliferation, while knockdown of TRIM65 displays opposite effect. Mechanistically, TRIM65 binds to p53, one of the most critical tumor suppressors, and serves as an E3 ligase toward p53. Consequently, TRIM65 inactivates p53 through facilitating p53 poly-ubiquitination and proteasome-mediated degradation. Notably, chemotherapeutic reagent cisplatin induction of p53 is markedly attenuated in response to ectopic expression of TRIM65. Cell growth inhibition by TRIM65 knockdown is more significant in p53 positive H460 than p53 negative H1299 cells, and knockdown of p53 in H460 cells also shows compromised cell growth inhibition by TRIM65 knockdown, indicating that p53 is required, at least in part, for TRIM65 function. Our findings demonstrate TRIM65 as a potential oncogenic protein, highly likely through p53 inactivation, and provide insight into development of novel approaches targeting TRIM65 for NSCLC treatment, and also overcoming chemotherapy resistance. - Highlights: • TRIM65 expression is elevated in NSCLC. • TRIM65 inactivates p53 through mediating p53 ubiquitination and degradation. • TRIM65 attenuates the response of NSCLC cells to cisplatin.

  5. miR-30 functions as an oncomiR in gastric cancer cells through regulation of P53-mediated mitochondrial apoptotic pathway.

    Science.gov (United States)

    Wang, Jianjun; Jiao, Yang; Cui, Lunmeng; Jiang, Lili

    2017-01-01

    The present study was designed to investigate the role of miR-30 in the development of Gastric cancer (GC). miR-30 expression was increased in GC tissues and cell lines. Downregulation of miR-30 inhibited cell proliferation and promoted apoptosis in HGC-27 cells. Upregulation of miR-30 enhanced the proliferation and inhibited apoptosis. P53 expression was decreased in GC tissues. P53 expression was correlated with miR-30 expression. Downregulation of miR-30 increased P53 expression. Knockdown of P53 inhibited miR-30-inhibitor-induced suppression of cell proliferation and increase of apoptosis. Downregulation of miR-30 increased ROS generation which was inhibited by shP53. miR-30 inhibitors induced a decrease in mitochondrial oxygen consumption, cytoplasmic release of cytochrome c, and activation of Caspase 3 and 9, activating mitochondrial apoptotic pathway. Downregulation of P53 and N-acetyl-cysteine suppressed miR-30 inhibitors-activated mitochondrial dysfunction and apoptotic events. In conclusion, we identified that miR-30 functioned as a potential oncomiR through P53/ROS-mediated regulation of mitochondrial apoptotic pathway.

  6. p53 Acetylation: Regulation and Consequences

    Directory of Open Access Journals (Sweden)

    Sara M. Reed

    2014-12-01

    Full Text Available Post-translational modifications of p53 are critical in modulating its tumor suppressive functions. Ubiquitylation, for example, plays a major role in dictating p53 stability, subcellular localization and transcriptional vs. non-transcriptional activities. Less is known about p53 acetylation. It has been shown to govern p53 transcriptional activity, selection of growth inhibitory vs. apoptotic gene targets, and biological outcomes in response to diverse cellular insults. Yet recent in vivo evidence from mouse models questions the importance of p53 acetylation (at least at certain sites as well as canonical p53 functions (cell cycle arrest, senescence and apoptosis to tumor suppression. This review discusses the cumulative findings regarding p53 acetylation, with a focus on the acetyltransferases that modify p53 and the mechanisms regulating their activity. We also evaluate what is known regarding the influence of other post-translational modifications of p53 on its acetylation, and conclude with the current outlook on how p53 acetylation affects tumor suppression. Due to redundancies in p53 control and growing understanding that individual modifications largely fine-tune p53 activity rather than switch it on or off, many questions still remain about the physiological importance of p53 acetylation to its role in preventing cancer.

  7. p53 Acetylation: Regulation and Consequences

    Energy Technology Data Exchange (ETDEWEB)

    Reed, Sara M. [Department of Pharmacology, The University of Iowa Carver College of Medicine, Iowa City, IA 52242 (United States); Medical Scientist Training Program, The University of Iowa Carver College of Medicine, Iowa City, IA 52242 (United States); Quelle, Dawn E., E-mail: dawn-quelle@uiowa.edu [Department of Pharmacology, The University of Iowa Carver College of Medicine, Iowa City, IA 52242 (United States); Medical Scientist Training Program, The University of Iowa Carver College of Medicine, Iowa City, IA 52242 (United States); Department of Pathology, The University of Iowa Carver College of Medicine, Iowa City, IA 52242 (United States)

    2014-12-23

    Post-translational modifications of p53 are critical in modulating its tumor suppressive functions. Ubiquitylation, for example, plays a major role in dictating p53 stability, subcellular localization and transcriptional vs. non-transcriptional activities. Less is known about p53 acetylation. It has been shown to govern p53 transcriptional activity, selection of growth inhibitory vs. apoptotic gene targets, and biological outcomes in response to diverse cellular insults. Yet recent in vivo evidence from mouse models questions the importance of p53 acetylation (at least at certain sites) as well as canonical p53 functions (cell cycle arrest, senescence and apoptosis) to tumor suppression. This review discusses the cumulative findings regarding p53 acetylation, with a focus on the acetyltransferases that modify p53 and the mechanisms regulating their activity. We also evaluate what is known regarding the influence of other post-translational modifications of p53 on its acetylation, and conclude with the current outlook on how p53 acetylation affects tumor suppression. Due to redundancies in p53 control and growing understanding that individual modifications largely fine-tune p53 activity rather than switch it on or off, many questions still remain about the physiological importance of p53 acetylation to its role in preventing cancer.

  8. Human p53(264-272) HLA-A2 binding peptide is an immunodominant epitope in DNA-immunized HLA-A2 transgenic mice

    DEFF Research Database (Denmark)

    Petersen, T R; Bregenholta, S; Pedersen, L O;

    1999-01-01

    C57BL/10 mice transgenic for HLA-A2 were immunized with either a full-length DNA-construct of the tumor suppressor p53 or with a minigene encoding the p53-derived immunodominant peptide p53(264)LLGRNSFEV272 (L9V). Vaccination with the full-length p53 construct induced potent cytotoxic activity...

  9. HEXIM1, a New Player in the p53 Pathway

    Directory of Open Access Journals (Sweden)

    Nge Cheong

    2013-07-01

    Full Text Available Hexamethylene bisacetamide-inducible protein 1 (HEXIM1 is best known as the inhibitor of positive transcription elongation factor b (P-TEFb, which controls transcription elongation of RNA polymerase II and Tat transactivation of human immunodeficiency virus. Besides P-TEFb, several proteins have been identified as HEXIM1 binding proteins. It is noteworthy that more than half of the HEXIM1 binding partners are involved in cancers. P53 and two key regulators of the p53 pathway, nucleophosmin (NPM and human double minute-2 protein (HDM2, are among the factors identified. This review will focus on the functional importance of the interactions between HEXIM1 and p53/NPM/HDM2. NPM and the cytoplasmic mutant of NPM, NPMc+, were found to regulate P-TEFb activity and RNA polymerase II transcription through the interaction with HEXIM1. Importantly, more than one-third of acute myeloid leukemia (AML patients carry NPMc+, suggesting the involvement of HEXIM1 in tumorigenesis of AML. HDM2 was found to ubiquitinate HEXIM1. The HDM2-mediated ubiquitination of HEXIM1 did not lead to protein degradation of HEXIM1 but enhanced its inhibitory activity on P-TEFb. Recently, HEXIM1 was identified as a novel positive regulator of p53. HEXIM1 prevented p53 ubiquitination by competing with HDM2 in binding to p53. Taken together, the new evidence suggests a role of HEXIM1 in regulating the p53 pathway and tumorigenesis.

  10. HEXIM1, a New Player in the p53 Pathway

    Energy Technology Data Exchange (ETDEWEB)

    Lew, Qiao Jing; Chu, Kai Ling; Chia, Yi Ling; Cheong, Nge [Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), 20 Biopolis Way, #06-01, Singapore 138668 (Singapore); Chao, Sheng-Hao, E-mail: jimmy_chao@bti.a-star.edu.sg [Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), 20 Biopolis Way, #06-01, Singapore 138668 (Singapore); Department of Microbiology, National University of Singapore, Singapore 117597 (Singapore)

    2013-07-04

    Hexamethylene bisacetamide-inducible protein 1 (HEXIM1) is best known as the inhibitor of positive transcription elongation factor b (P-TEFb), which controls transcription elongation of RNA polymerase II and Tat transactivation of human immunodeficiency virus. Besides P-TEFb, several proteins have been identified as HEXIM1 binding proteins. It is noteworthy that more than half of the HEXIM1 binding partners are involved in cancers. P53 and two key regulators of the p53 pathway, nucleophosmin (NPM) and human double minute-2 protein (HDM2), are among the factors identified. This review will focus on the functional importance of the interactions between HEXIM1 and p53/NPM/HDM2. NPM and the cytoplasmic mutant of NPM, NPMc+, were found to regulate P-TEFb activity and RNA polymerase II transcription through the interaction with HEXIM1. Importantly, more than one-third of acute myeloid leukemia (AML) patients carry NPMc+, suggesting the involvement of HEXIM1 in tumorigenesis of AML. HDM2 was found to ubiquitinate HEXIM1. The HDM2-mediated ubiquitination of HEXIM1 did not lead to protein degradation of HEXIM1 but enhanced its inhibitory activity on P-TEFb. Recently, HEXIM1 was identified as a novel positive regulator of p53. HEXIM1 prevented p53 ubiquitination by competing with HDM2 in binding to p53. Taken together, the new evidence suggests a role of HEXIM1 in regulating the p53 pathway and tumorigenesis.

  11. p53 Acetylation: Regulation and Consequences

    OpenAIRE

    2014-01-01

    Post-translational modifications of p53 are critical in modulating its tumor suppressive functions. Ubiquitylation, for example, plays a major role in dictating p53 stability, subcellular localization and transcriptional vs. non-transcriptional activities. Less is known about p53 acetylation. It has been shown to govern p53 transcriptional activity, selection of growth inhibitory vs. apoptotic gene targets, and biological outcomes in response to diverse cellular insults. Yet recent in vivo ev...

  12. Metabolic regulation by p53 family members.

    Science.gov (United States)

    Berkers, Celia R; Maddocks, Oliver D K; Cheung, Eric C; Mor, Inbal; Vousden, Karen H

    2013-11-05

    The function of p53 is best understood in response to genotoxic stress, but increasing evidence suggests that p53 also plays a key role in the regulation of metabolic homeostasis. p53 and its family members directly influence various metabolic pathways, enabling cells to respond to metabolic stress. These functions are likely to be important for restraining the development of cancer but could also have a profound effect on the development of metabolic diseases, including diabetes. A better understanding of the metabolic functions of p53 family members may aid in the identification of therapeutic targets and reveal novel uses for p53-modulating drugs.

  13. Structure of the E6/E6AP/p53 complex required for HPV-mediated degradation of p53

    Science.gov (United States)

    Martinez-Zapien, Denise; Ruiz, Francesc Xavier; Poirson, Juline; Mitschler, André; Ramirez-Ramos, Juan; Forster, Anne; Cousido-Siah, Alexandra; Masson, Murielle; Pol, Scott Vande; Podjarny, Alberto; Travé, Gilles; Zanier, Katia

    2015-01-01

    Summary The p53 pro-apoptotic tumor suppressor is mutated or functionally altered in most cancers. In epithelial tumors induced by “high-risk” mucosal Human Papillomaviruses (hrm-HPVs), including human cervical carcinoma and a growing number of head-and-neck cancers 1, p53 is degraded by the viral oncoprotein E6 2. In this process, E6 binds to a short LxxLL consensus sequence within the cellular ubiquitin ligase E6AP 3. Subsequently, the E6/E6AP heterodimer recruits and degrades p53 4. Neither E6 nor E6AP are separately able to recruit p53 3,5, and the precise mode of assembly of E6, E6AP and p53 is unknown. Here, we solved the crystal structure of a ternary complex comprising full-length HPV16 E6, the LxxLL motif of E6AP and the core domain of p53. The LxxLL motif of E6AP renders the conformation of E6 competent for interaction with p53 by structuring a p53-binding cleft on E6. Mutagenesis of critical positions at the E6-p53 interface disrupts p53 degradation. The E6-binding site of p53 is distal from previously described DNA- and protein-binding surfaces of the core domain. This suggests that, in principle, E6 may avoid competition with cellular factors by targeting both free and bound p53 molecules. The E6/E6AP/p53 complex represents a prototype of viral hijacking of both the ubiquitin-mediated protein degradation pathway and the p53 tumor suppressor pathway. The present structure provides a framework for the design of inhibitory therapeutic strategies against HPV-mediated oncogenesis. PMID:26789255

  14. Ethylenediamine functionalized-single-walled nanotube (f-SWNT)-assisted in vitro delivery of the oncogene suppressor p53 gene to breast cancer MCF-7 cells.

    Science.gov (United States)

    Karmakar, Alokita; Bratton, Stacie M; Dervishi, Enkeleda; Ghosh, Anindya; Mahmood, Meena; Xu, Yang; Saeed, Lamya Mohammed; Mustafa, Thikra; Casciano, Dan; Radominska-Pandya, Anna; Biris, Alexandru S

    2011-01-01

    A gene delivery concept based on ethylenediamine-functionalized single-walled carbon nanotubes (f-SWCNTs) using the oncogene suppressor p53 gene as a model gene was successfully tested in vitro in MCF-7 breast cancer cells. The f-SWCNTs-p53 complexes were introduced into the cell medium at a concentration of 20 μg mL(-1) and cells were exposed for 24, 48, and 72 hours. Standard ethidium bromide and acridine orange assays were used to detect apoptotic cells and indicated that a significantly larger percentage of the cells (approx 40%) were dead after 72 hours of exposure to f-SWCNTs-p53 as compared to the control cells, which were exposed to only p53 or f-SWCNTs, respectively. To further support the uptake and expression of the genes within the cells, green fluorescent protein-tagged p53, attached to the f-SWCNTs was added to the medium and the complex was observed to be strongly expressed in the cells. Moreover, caspase 3 activity was found to be highly enhanced in cells incubated with the f-SWCNTs-p53 complex, indicating strongly induced apoptosis. This system could be the foundation for novel gene delivery platforms based on the unique structural and morphological properties of multi-functional nanomaterials.

  15. Transcriptional activation of p21(WAF¹/CIP¹) is mediated by increased DNA binding activity and increased interaction between p53 and Sp1 via phosphorylation during replicative senescence of human embryonic fibroblasts.

    Science.gov (United States)

    Kim, Hyun-Seok; Heo, Jee-In; Park, Seong-Hoon; Shin, Jong-Yeon; Kang, Hong-Jun; Kim, Min-Ju; Kim, Sung Chan; Kim, Jaebong; Park, Jae-Bong; Lee, Jae-Yong

    2014-01-01

    Although p21(WAF1/CIP1) is known to be elevated during replicative senescence of human embryonic fibroblasts (HEFs), the mechanism for p21 up-regulation has not been elucidated clearly. In order to explore the mechanism, we analyzed expression of p21 mRNA and protein and luciferase activity of full-length p21 promoter. The result demonstrated that p21 up-regulation was accomplished largely at transcription level. The promoter assay using serially-deleted p21 promoter constructs revealed that p53 binding site was the most important site and Sp1 binding sites were necessary but not sufficient for transcriptional activation of p21. In addition, p53 protein was shown to interact with Sp1 protein. The interaction was increased in aged fibroblasts and was regulated by phosphorylation of p53 and Sp1. DNA binding activity of p53 was significantly elevated in aged fibroblasts but that of Sp1 was not. DNA binding activities of p53 and Sp1 were also regulated by phosphorylation. Phosphorylation of p53 at serine-15 and of Sp1 at serines appears to be involved. Taken together, the result demonstrated that p21 transcription during replicative senescence of HEFs is up-regulated by increase in DNA binding activity and interaction between p53 and Sp1 via phosphorylation.

  16. Monitoring p53 by MDM2 and MDMX is required for endocrine pancreas development and function in a spatio-temporal manner.

    Science.gov (United States)

    Zhang, Yiwei; Zeng, Shelya X; Hao, Qian; Lu, Hua

    2017-03-01

    Although p53 is not essential for normal embryonic development, it plays a pivotal role in many biological and pathological processes, including cell fate determination-dependent and independent events and diseases. The expression and activity of p53 largely depend on its two biological inhibitors, MDM2 and MDMX, which have been shown to form a complex in order to tightly control p53 to an undetectable level during early stages of embryonic development. However, more delicate studies using conditional gene-modification mouse models show that MDM2 and MDMX may function separately or synergistically on p53 regulation during later stages of embryonic development and adulthood in a cell and tissue-specific manner. Here, we report the role of the MDM2/MDMX-p53 pathway in pancreatic islet morphogenesis and functional maintenance, using mouse lines with specific deletion of MDM2 or MDMX in pancreatic endocrine progenitor cells. Interestingly, deletion of MDM2 results in defects of embryonic endocrine pancreas development, followed by neonatal hyperglycemia and lethality, by inducing pancreatic progenitor cell apoptosis and inhibiting cell proliferation. However, unlike MDM2-knockout animals, mice lacking MDMX in endocrine progenitor cells develop normally. But, surprisingly, the survival rate of adult MDMX-knockout mice drastically declines compared to control mice, as blockage of neonatal development of endocrine pancreas by inhibition of cell proliferation and subsequent islet dysfunction and hyperglycemia eventually lead to type 1 diabetes-like disease with advanced diabetic nephropathy. As expected, both MDM2 and MDMX deletion-caused pancreatic defects are completely rescued by loss of p53, verifying the crucial role of the MDM2 and/or MDMX in regulating p53 in a spatio-temporal manner during the development, functional maintenance, and related disease progress of endocrine pancreas. Also, our study suggests a possible mouse model of advanced diabetic nephropathy

  17. Ethylenediamine functionalized-single-walled nanotube (f-SWNT-assisted in vitro delivery of the oncogene suppressor p53 gene to breast cancer MCF-7 cells

    Directory of Open Access Journals (Sweden)

    Karmakar A

    2011-05-01

    Full Text Available Alokita Karmakar2, Stacie M Bratton1, Enkeleda Dervishi2, Anindya Ghosh3, Meena Mahmood2, Yang Xu2, Lamya Mohammed Saeed2, Thikra Mustafa2, Dan Casciano2, Anna Radominska-Pandya1, Alexandru S Biris21Biochemistry Department, University of Arkansas for Medical Sciences; 2Nanotechnology Center, Applied Science Department; 3Department of Chemistry, University of Arkansas, Little Rock, AR, USAAbstract: A gene delivery concept based on ethylenediamine-functionalized single-walled carbon nanotubes (f-SWCNTs using the oncogene suppressor p53 gene as a model gene was successfully tested in vitro in MCF-7 breast cancer cells. The f-SWCNTs-p53 complexes were introduced into the cell medium at a concentration of 20 µg mL-1 and cells were exposed for 24, 48, and 72 hours. Standard ethidium bromide and acridine orange assays were used to detect apoptotic cells and indicated that a significantly larger percentage of the cells (approx 40% were dead after 72 hours of exposure to f-SWCNTs-p53 as compared to the control cells, which were exposed to only p53 or f-SWCNTs, respectively. To further support the uptake and expression of the genes within the cells, green fluorescent protein-tagged p53, attached to the f-SWCNTs was added to the medium and the complex was observed to be strongly expressed in the cells. Moreover, caspase 3 activity was found to be highly enhanced in cells incubated with the f-SWCNTs-p53 complex, indicating strongly induced apoptosis. This system could be the foundation for novel gene delivery platforms based on the unique structural and morphological properties of multi-functional nanomaterials.Keywords: carbon nanotubes, gene delivery, cancer cells, p53 oncogene suppressor

  18. Enhancement of p53 Expression in Keratinocytes by the Bioflavonoid Apigenin Is Associated with RNA-binding Protein HuR

    OpenAIRE

    Tong, Xin; Pelling, Jill C.

    2009-01-01

    We have reported previously that apigenin, a naturally occurring non-mutagenic flavonoid, increased wild type p53 protein expression in the mouse keratinocyte 308 cell line by a mechanism involving p53 protein stabilization. Here we further demonstrated that the increase in p53 protein level induced by apigenin treatment of 308 keratinoyctes was not the result of enhanced transcription, mRNA stabilization or cytoplasmic export of p53 mRNA. Instead, biosynthetic labeling showed that apigenin i...

  19. Transcriptional upregulation of restin by p53

    Institute of Scientific and Technical Information of China (English)

    WANG RuiHua; LU Fan; FU HaiYan; WU YouSheng; YANG GuoDong; ZHAO WenMing; Zhao ZhongLiang

    2007-01-01

    Restin, belonging to the melanoma-associated antigen superfamily, was firstly cloned from the differentiated HL-60 cells when induced by all-trans retinoic acid ( ATRA ) in our lab. Our previous results showed that restin might be correlated to cell cycle arrest. Due to the importance of p53 in the regulation of cell growth and the relationship between p53 and ATRA, we tried to test the relationship between p53 and restin. Firstly, transfection results showed that p53 was able to upregulate the expression of restin at the transcriptional level when p53 was transfected into eukaryotic cells. Secondly, the bioinformatics analysis revealed that the upstream sequence (about 2 kb) from the first ATG of the ORF of restin gene contained a p53 binding site. In order to confirm that p53 was involved in the transcriptional regulation of restin, we cloned the upstream sequence of restin and constructed the promoter luciferase reporter system. From the luciferase activity, we demonstrated that the promoter of restin gene could be induced by ATRA. Then, another two luciferase reporter plasmids driven by the reporter of restin with no (RP△p53-luc) or mutant (mRP-luc) p53 binding site were constructed to see the regulation of restin by p53. Results showed that the transcriptional upregulation of restin gene was not due to the putative p53 binding site on the upstream of restin gene. We proposed that p53 upregulated restin transcription through an indirect way rather than direct interaction with the cis-activating element of the restin promoter.

  20. Transcriptional upregulation of restin by p53

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Restin, belonging to the melanoma-associated antigen superfamily, was firstly cloned from the differentiated HL-60 cells when induced by all-trans retinoic acid ( ATRA ) in our lab. Our previous results showed that restin might be correlated to cell cycle arrest. Due to the importance of p53 in the regulation of cell growth and the relationship between p53 and ATRA, we tried to test the relationship between p53 and restin. Firstly, transfection results showed that p53 was able to upregulate the expression of restin at the transcriptional level when p53 was transfected into eukaryotic cells. Secondly, the bioinformatics analysis revealed that the upstream sequence (about 2 kb) from the first ATG of the ORF of restin gene contained a p53 binding site. In order to confirm that p53 was involved in the transcriptional regulation of restin, we cloned the upstream sequence of restin and constructed the promoter luciferase reporter system. From the luciferase activity, we demonstrated that the promoter of restin gene could be induced by ATRA. Then, another two luciferase reporter plasmids driven by the reporter of restin with no (RP?p53-luc) or mutant (mRP-luc) p53 binding site were constructed to see the regulation of restin by p53. Results showed that the transcriptional upregulation of restin gene was not due to the putative p53 binding site on the upstream of restin gene. We proposed that p53 upregulated restin transcription through an indirect way rather than direct interaction with the cis-activating element of the restin promoter.

  1. The calcium binding protein ALG-2 binds and stabilizes Scotin, a p53-inducible gene product localized at the endoplasmic reticulum membrane

    DEFF Research Database (Denmark)

    Draeby, Ingrid; Woods, Yvonne L; la Cour, Jonas Marstrand

    2007-01-01

    ALG-2 (apoptosis linked gene 2 product) is a calcium binding protein for which no clear cellular function has been established. In this study we identified Scotin as a novel ALG-2 target protein containing 6 PXY and 4 PYP repeats, earlier identified in the ALG-2 binding regions of AIP1/ALIX and TSG......101, respectively. An in vitro synthesized C-terminal fragment of Scotin bound specifically to immobilized recombinant ALG-2 and tagged ALG-2 and Scotin were shown by immunoprecipitation to interact in MCF7 and U2OS cell lines. Furthermore ALG-2 bound to endogenous Scotin in extracts from mouse NIH3T3...

  2. Suppression of p53 activity through the cooperative action of Ski and histone deacetylase SIRT1.

    Science.gov (United States)

    Inoue, Yasumichi; Iemura, Shun-ichiro; Natsume, Tohru; Miyazawa, Keiji; Imamura, Takeshi

    2011-02-25

    Ski was originally identified as an oncogene based on the fact that Ski overexpression transformed chicken and quail embryo fibroblasts. Consistent with these proposed oncogenic roles, Ski is overexpressed in various human tumors. However, whether and how Ski functions in mammalian tumorigenesis has not been fully investigated. Here, we show that Ski interacts with p53 and attenuates the biological functions of p53. Ski overexpression attenuated p53-dependent transactivation, whereas Ski knockdown enhanced the transcriptional activity of p53. Interestingly, Ski bound to the histone deacetylase SIRT1 and stabilized p53-SIRT1 interaction to promote p53 deacetylation, which subsequently decreased the DNA binding activity of p53. Consistent with the ability of Ski to inactivate p53, overexpressing Ski desensitized cells to genotoxic drugs and Nutlin-3, a small-molecule antagonist of Mdm2 that stabilizes p53 and activates the p53 pathway, whereas knocking down Ski increased the cellular sensitivity to these agents. These results indicate that Ski negatively regulates p53 and suggest that the p53-Ski-SIRT1 axis is an attractive target for cancer therapy.

  3. Epigenetic identification of ZNF545 as a functional tumor suppressor in multiple myeloma via activation of p53 signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Yu [Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing (China); Zhan, Qian [The Center for Clinical Molecular Medical Detection, The First Affiliated Hospital of Chongqing Medical University, Chongqing (China); Xu, Hongying [Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing (China); Li, Lili; Li, Chen [Cancer Epigenetics Laboratory, Department of Clinical Oncology, Sir YK Pao Center for Cancer and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong and CUHK Shenzhen Research Institute (Hong Kong); Xiao, Qian; Xiang, Shili; Hui, Tianli [Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing (China); Xiang, Tingxiu, E-mail: larissaxiang@163.com [Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing (China); Ren, Guosheng, E-mail: rengs726@126.com [Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing (China)

    2016-06-10

    The KRAB–zinc-finger protein ZNF545 was recently identified as a potential suppressor gene in several tumors. However, the regulatory mechanisms of ZNF545 in tumorigenesis remain unclear. In this study, we investigated the expression and roles of ZNF545 in multiple myeloma (MM). ZNF545 was frequently downregulated in MM tissues compared with non-tumor bone marrow tissues. ZNF545 expression was silenced by promoter methylation in MM cell lines, and could be restored by demethylation treatment. ZNF545 methylation was detected in 28.3% of MM tissues, compared with 4.3% of normal bone marrow tissues. ZNF545 transcriptionally activated the p53 signaling pathway but had no effect on Akt in MM, whereas ectopic expression of ZNF545 in silenced cells suppressed their proliferation and induced apoptosis. We therefore identified ZNF545 as a novel tumor suppressor inhibiting tumor growth through activation of the p53 pathway in MM. Moreover, tumor-specific methylation of ZNF545 may represent an epigenetic biomarker for MM diagnosis, and a potential target for specific therapy. -- Highlights: •Downregulated ZNF545 in MM tissues and cell lines and ectopic expression of ZNF545 suppresses tumor growth. •Tumor-specific methylation of ZNF545 represents an epigenetic biomarker for MM diagnosis, and a potential target for specific therapy. •ZNF545 exerts its tumor suppressive effects via transcriptional activating p53 pathway.

  4. Genome-wide analysis of the p53 gene regulatory network in the developing mouse kidney.

    Science.gov (United States)

    Li, Yuwen; Liu, Jiao; McLaughlin, Nathan; Bachvarov, Dimcho; Saifudeen, Zubaida; El-Dahr, Samir S

    2013-10-16

    Despite mounting evidence that p53 senses and responds to physiological cues in vivo, existing knowledge regarding p53 function and target genes is largely derived from studies in cancer or stressed cells. Herein we utilize p53 transcriptome and ChIP-Seq (chromatin immunoprecipitation-high throughput sequencing) analyses to identify p53 regulated pathways in the embryonic kidney, an organ that develops via mesenchymal-epithelial interactions. This integrated approach allowed identification of novel genes that are possible direct p53 targets during kidney development. We find the p53-regulated transcriptome in the embryonic kidney is largely composed of genes regulating developmental, morphogenesis, and metabolic pathways. Surprisingly, genes in cell cycle and apoptosis pathways account for kidney lie within proximal promoters of annotated genes compared with 7% in a representative cancer cell line; 25% of the differentially expressed p53-bound genes are present in nephron progenitors and nascent nephrons, including key transcriptional regulators, components of Fgf, Wnt, Bmp, and Notch pathways, and ciliogenesis genes. The results indicate widespread p53 binding to the genome in vivo and context-dependent differences in the p53 regulon between cancer, stress, and development. To our knowledge, this is the first comprehensive analysis of the p53 transcriptome and cistrome in a developing mammalian organ, substantiating the role of p53 as a bona fide developmental regulator. We conclude p53 targets transcriptional networks regulating nephrogenesis and cellular metabolism during kidney development.

  5. Interaction between transactivation domain of p53 and middle part of TBP-like protein (TLP is involved in TLP-stimulated and p53-activated transcription from the p21 upstream promoter.

    Directory of Open Access Journals (Sweden)

    Ryo Maeda

    Full Text Available TBP-like protein (TLP is involved in transcriptional activation of an upstream promoter of the human p21 gene. TLP binds to p53 and facilitates p53-activated transcription from the upstream promoter. In this study, we clarified that in vitro affinity between TLP and p53 is about one-third of that between TBP and p53. Extensive mutation analyses revealed that the TLP-stimulated function resides in transcription activating domain 1 (TAD1 in the N-terminus of p53. Among the mutants, #22.23, which has two amino acid substitutions in TAD1, exhibited a typical mutant phenotype. Moreover, #22.23 exhibited the strongest mutant phenotype for TLP-binding ability. It is thus thought that TLP-stimulated and p53-dependent transcriptional activation is involved in TAD1 binding of TLP. #22.23 had a decreased transcriptional activation function, especially for the upstream promoter of the endogenous p21 gene, compared with wild-type p53. This mutant did not facilitate p53-dependent growth repression and etoposide-mediated cell-death as wild-type p53 does. Moreover, mutation analysis revealed that middle part of TLP, which is requited for p53 binding, is involved in TLP-stimulated and p53-dependent promoter activation and cell growth repression. These results suggest that activation of the p21 upstream promoter is mediated by interaction between specific regions of TLP and p53.

  6. ID4 regulates transcriptional activity of wild type and mutant p53 via K373 acetylation.

    Science.gov (United States)

    Morton, Derrick J; Patel, Divya; Joshi, Jugal; Hunt, Aisha; Knowell, Ashley E; Chaudhary, Jaideep

    2017-01-10

    Given that mutated p53 (50% of all human cancers) is over-expressed in many cancers, restoration of mutant p53 to its wild type biological function has been sought after as cancer therapy. The conformational flexibility has allowed to restore the normal biological function of mutant p53 by short peptides and small molecule compounds. Recently, studies have focused on physiological mechanisms such as acetylation of lysine residues to rescue the wild type activity of mutant p53. Using p53 null prostate cancer cell line we show that ID4 dependent acetylation promotes mutant p53 DNA-binding capabilities to its wild type consensus sequence, thus regulating p53-dependent target genes leading to subsequent cell cycle arrest and apoptosis. Specifically, by using wild type, mutant (P223L, V274F, R175H, R273H), acetylation mimics (K320Q and K373Q) and non-acetylation mimics (K320R and K373R) of p53, we identify that ID4 promotes acetylation of K373 and to a lesser extent K320, in turn restoring p53-dependent biological activities. Together, our data provides a molecular understanding of ID4 dependent acetylation that suggests a strategy of enhancing p53 acetylation at sites K373 and K320 that may serve as a viable mechanism of physiological restoration of mutant p53 to its wild type biological function.

  7. The function of apoptosis and protein expression of bcl-2, p53 and C-myc inthe development of gastric cancer

    Institute of Scientific and Technical Information of China (English)

    An Gao Xu; Shao Guang Li; Ji Hong Liu; Ai Hua Gan

    2000-01-01

    AIM To understand the rule and possible function of apoptosis and protein expression of bcl-2, p53 and C-myc in chronic gastritis, gastric ulcer, non-classic proliferation of gastric mucosa and gastric cancer.METHODS Apoptosis was detected by using in situ terminal labelling (TUNEL). The protein expression ofbcl-2, p53 and C-myc was detected by immunohistochemical method.RESULTS The indexes of apoptosis in chronic active gastritis, gastric ulcer, mild and severe non-classicproliferation of gastric mucosa, early and progressive gastric cancer were 16.8%±12.3%, 24.1%±20.0%,19.3%±16.4%, 15.7%±15.2%, 10.1%±9.1% and 6.3%±6.0%, respectively. The index of progressivegastric cancer was lower than that of early gastric cancer and non-classic proliferation of gastric mucosa(P<0.05). The positive rate of bcl-2 protein was 9.4%, 27.6%, 52.9%, 75.0%, 83.3% and 46.7%,respectively. The positive rate of bcl-2 of early gastric cancer was higher than that of progressive gastriccancer. The positive rates of p53 protein of severe non-classic proliferation, early and progressive gastriccancer were 25.0%, 33.3% and 63.3%, respectively. The positive rate of p53 of progressive gastric cancerwas higher than that of early gastric cancer and non-classic proliferation (P<0.05). In Lauren types, theindex of apoptosis, protein expression rates of bcl-2, p53 and C-myc of intestinal type were 8.3%±7.2%,38.9%, 77.7% and 56.6%, while that of diffuse type were 5.1%±4.9%, 58.3%, 50.0% and 8.3%,respectively. All markers had statistical difference between two types (P<0.05).CONCLUSION Apoptosis was inhibited stepwise in the development of non-classic proliferation of gastricmucosa to early gastric cancer and then to progressive gastric cancer. The high expression of bcl-2, p53 andC-myc was related to the development of gastric cancer, bcl-2 might play an important role in early gastriccancer while p53 and C-myc act mostly in middle and late stage gastric cancer. The Lauren typing of

  8. Interplay among p53, MDM2, and MDMX and Progress in Related Studies%p53与MDM2及MDMX 的相互作用和研究进展

    Institute of Scientific and Technical Information of China (English)

    李小龙

    2012-01-01

    p53是重要的抑癌基因,在细胞周期阻滞、DNA损伤修复及细胞凋亡等生物过程中发挥重要作用,并已成为潜在的肿瘤治疗靶点.MDM2(Mdm2 p53 binding protein homolog)及MDMX(Mdm4 p53 binding protein homolog)是p53的主要抑制因子,两者相互协同并通过不同的信号途径抑制p53的活性.MDM2是p53的E3连接酶,介导p53的泛素化从而降低p53的稳定性.MDMX则主要通过与p53的转录活性区结合,抑制p53对其下游基因的转录活性,但并不介导p53的降解.MDM2与MDMX通过不同机制协同对p53产生抑制作用,其具体分子过程及作用机制繁多且复杂.本文就p53、MDM2及MDMX的相互作用及各蛋白的功能进行综述.%P53 is one of the most important tumor suppressors. The resukts from functional analysis revealed that p53 is a potent stress responder that regulates cell-cycle arrest, DNA repair, cell senescence, and apoptosis. P53 is also recognized as a potential therapy target. MDM2 and MDMX are two major p53 suppressors, which can both inhibit p53 activity via different mechanisms. MDM2 is an E3 ligase of p53, which can promote p53 ubiquitination and can regulate p53 degradation and stabilization. MDMX does not have E3 ligase activity, but can directly bind to the N terminus of p53 and can inhibit p53 transactivation. Studies have shown that MDM2 and MDMX could work together to regulate p53 activity in a more complicated mechanism. The present work reviews the interplay among p53, MDM2, and MDMX.

  9. Translocation of p53 to Mitochondria Is Regulated by Its Lipid Binding Property to Anionic Phospholipids and It Participates in Cell Death Control

    Directory of Open Access Journals (Sweden)

    Ching-Hao Li

    2010-02-01

    Full Text Available p53, can regulate cell apoptosis in both transcription-dependent and -independent manners. The transcription-independent pathway was demonstrated by the translocation of p53 to mitochondria. Our study showed that p53 mitochondrial translocation was found in mitomycin C (MMC-treated HepG2. The p53 C-terminal domain is clustered with potential nuclear leading sequences and showed strong electrostatic ion-ion interactions with cardiolipin, phosphatidylglycerol and phosphatidic acid in vitro. Disruption of cardiolipin biosynthesis by phosphatidylglycero-phosphate synthase (PGS or CDP-diacylglycerol synthase 2 (CDS-2 short hairpin RNA (shRNA transfection eliminated the MMC-induced translocation of mitochondrial p53. The elimination of mitochondrial p53 translocation also reduced Bcl-xL and Bcl-2 mitochondrial distribution. In HEK 293T models with saturated p53 expression, the mitochondrial partition of p53, Bcl-xL, and Bcl-2 obviously decreased in their PGS shRNA- or CDS-2 shRNA-expressing stable clones. In p53-null H1299 models, both the mitochondrial partitions of Bcl-xL and Bcl-2 were strongly reduced in relation to the HEK 293T models. The Bcl-xL mitochondrial partition was elevated in H1299 models expressing pCEP4-p53wt suggesting the direct carrier role of p53 in transporting Bcl-xL to the mitochondria. We also found that the cytosolic pool of Bcl-xL and Bcl-2 remained unaffected in the low-dose MMC treatment but decreased in the high-dose MMC treatment. The cytosolic pool of Bcl-2 and Bcl-xL directly regulated their amounts in p53-dependent mitochondrial distribution. In the low-dose MMC treatment, the increased mitochondrial p53, Bcl-xL, and Bcl-2 could attenuate apoptosis. However, in the high-dose MMC treatment, only the p53 translocated to the mitochondria and resulted in apoptosis progression. On the basis of this study, we thought mitochondrial p53 might regulate apoptosis in a biphasic manner.

  10. p63 expression confers significantly better survival outcomes in high-risk diffuse large B-cell lymphoma and demonstrates p53-like and p53-independent tumor suppressor function

    DEFF Research Database (Denmark)

    Xu-Monette, Zijun Y; Zhang, Shanxiang; Li, Xin

    2016-01-01

    The role of p53 family member p63 in oncogenesis is the subject of controversy. Limited research has been done on the clinical implications of p63 expression in diffuse large B-cell lymphoma (DLBCL). In this study, we assessed p63 expression in de novo DLBCL samples (n=795) by immunohistochemistr...

  11. p63 expression confers significantly better survival outcomes in high-risk diffuse large B-cell lymphoma and demonstrates p53-like and p53-independent tumor suppressor function

    DEFF Research Database (Denmark)

    Xu-Monette, Zijun Y; Zhang, Shanxiang; Li, Xin;

    2016-01-01

    The role of p53 family member p63 in oncogenesis is the subject of controversy. Limited research has been done on the clinical implications of p63 expression in diffuse large B-cell lymphoma (DLBCL). In this study, we assessed p63 expression in de novo DLBCL samples (n=795) by immunohistochemistr...

  12. Mutant p53: multiple mechanisms define biologic activity in cancer

    Directory of Open Access Journals (Sweden)

    Michael Paul Kim

    2015-11-01

    Full Text Available The functional importance of p53 as a tumor suppressor gene is evident through its pervasiveness in cancer biology. The p53 gene is the most commonly altered gene in human cancer; however, not all genetic alterations are biologically equivalent. The majority of p53 alterations involve missense mutations that result in the production of mutant p53 proteins. Such mutant p53 proteins lack normal p53 function and may acquire novel functions, often with deleterious effects. Here, we review characterized mechanisms of mutant p53 gain of function in multiple model systems. In addition, we review mutant p53 addiction as emerging evidence suggests that tumors may depend on sustained mutant p53 activity for continued growth. We also discuss the role of p53 in stromal elements and their contribution to tumor initiation and progression. Lastly, current genetic mouse models of mutant p53 are reviewed and their limitations discussed.

  13. Effect of hydroxyurea on the promoter occupancy profiles of tumor suppressor p53 and p73

    OpenAIRE

    2009-01-01

    Abstract Background The p53 tumor suppressor and its related protein, p73, share a homologous DNA binding domain, and mouse genetics studies have suggested that they have overlapping as well as distinct biological functions. Both p53 and p73 are activated by genotoxic stress to regulate an array of cellular responses. Previous studies have suggested that p53 and p73 independently activate the cellular apoptotic program in response to cytotoxic drugs. The goal of this study was to compare the ...

  14. Noncanonical DNA motifs as transactivation targets by wild type and mutant p53.

    Directory of Open Access Journals (Sweden)

    Jennifer J Jordan

    2008-06-01

    Full Text Available Sequence-specific binding by the human p53 master regulator is critical to its tumor suppressor activity in response to environmental stresses. p53 binds as a tetramer to two decameric half-sites separated by 0-13 nucleotides (nt, originally defined by the consensus RRRCWWGYYY (n = 0-13 RRRCWWGYYY. To better understand the role of sequence, organization, and level of p53 on transactivation at target response elements (REs by wild type (WT and mutant p53, we deconstructed the functional p53 canonical consensus sequence using budding yeast and human cell systems. Contrary to early reports on binding in vitro, small increases in distance between decamer half-sites greatly reduces p53 transactivation, as demonstrated for the natural TIGER RE. This was confirmed with human cell extracts using a newly developed, semi-in vitro microsphere binding assay. These results contrast with the synergistic increase in transactivation from a pair of weak, full-site REs in the MDM2 promoter that are separated by an evolutionary conserved 17 bp spacer. Surprisingly, there can be substantial transactivation at noncanonical (1/2-(a single decamer and (3/4-sites, some of which were originally classified as biologically relevant canonical consensus sequences including PIDD and Apaf-1. p53 family members p63 and p73 yielded similar results. Efficient transactivation from noncanonical elements requires tetrameric p53, and the presence of the carboxy terminal, non-specific DNA binding domain enhanced transactivation from noncanonical sequences. Our findings demonstrate that RE sequence, organization, and level of p53 can strongly impact p53-mediated transactivation, thereby changing the view of what constitutes a functional p53 target. Importantly, inclusion of (1/2- and (3/4-site REs greatly expands the p53 master regulatory network.

  15. Noncanonical DNA motifs as transactivation targets by wild type and mutant p53.

    Directory of Open Access Journals (Sweden)

    Jennifer J Jordan

    2008-06-01

    Full Text Available Sequence-specific binding by the human p53 master regulator is critical to its tumor suppressor activity in response to environmental stresses. p53 binds as a tetramer to two decameric half-sites separated by 0-13 nucleotides (nt, originally defined by the consensus RRRCWWGYYY (n = 0-13 RRRCWWGYYY. To better understand the role of sequence, organization, and level of p53 on transactivation at target response elements (REs by wild type (WT and mutant p53, we deconstructed the functional p53 canonical consensus sequence using budding yeast and human cell systems. Contrary to early reports on binding in vitro, small increases in distance between decamer half-sites greatly reduces p53 transactivation, as demonstrated for the natural TIGER RE. This was confirmed with human cell extracts using a newly developed, semi-in vitro microsphere binding assay. These results contrast with the synergistic increase in transactivation from a pair of weak, full-site REs in the MDM2 promoter that are separated by an evolutionary conserved 17 bp spacer. Surprisingly, there can be substantial transactivation at noncanonical (1/2-(a single decamer and (3/4-sites, some of which were originally classified as biologically relevant canonical consensus sequences including PIDD and Apaf-1. p53 family members p63 and p73 yielded similar results. Efficient transactivation from noncanonical elements requires tetrameric p53, and the presence of the carboxy terminal, non-specific DNA binding domain enhanced transactivation from noncanonical sequences. Our findings demonstrate that RE sequence, organization, and level of p53 can strongly impact p53-mediated transactivation, thereby changing the view of what constitutes a functional p53 target. Importantly, inclusion of (1/2- and (3/4-site REs greatly expands the p53 master regulatory network.

  16. Noncanonical DNA Motifs as Transactivation Targets by Wild Type and Mutant p53

    Science.gov (United States)

    Jordan, Jennifer J.; Menendez, Daniel; Inga, Alberto; Nourredine, Maher; Bell, Douglas; Resnick, Michael A.

    2008-01-01

    Sequence-specific binding by the human p53 master regulator is critical to its tumor suppressor activity in response to environmental stresses. p53 binds as a tetramer to two decameric half-sites separated by 0–13 nucleotides (nt), originally defined by the consensus RRRCWWGYYY (n = 0–13) RRRCWWGYYY. To better understand the role of sequence, organization, and level of p53 on transactivation at target response elements (REs) by wild type (WT) and mutant p53, we deconstructed the functional p53 canonical consensus sequence using budding yeast and human cell systems. Contrary to early reports on binding in vitro, small increases in distance between decamer half-sites greatly reduces p53 transactivation, as demonstrated for the natural TIGER RE. This was confirmed with human cell extracts using a newly developed, semi–in vitro microsphere binding assay. These results contrast with the synergistic increase in transactivation from a pair of weak, full-site REs in the MDM2 promoter that are separated by an evolutionary conserved 17 bp spacer. Surprisingly, there can be substantial transactivation at noncanonical ½-(a single decamer) and ¾-sites, some of which were originally classified as biologically relevant canonical consensus sequences including PIDD and Apaf-1. p53 family members p63 and p73 yielded similar results. Efficient transactivation from noncanonical elements requires tetrameric p53, and the presence of the carboxy terminal, non-specific DNA binding domain enhanced transactivation from noncanonical sequences. Our findings demonstrate that RE sequence, organization, and level of p53 can strongly impact p53-mediated transactivation, thereby changing the view of what constitutes a functional p53 target. Importantly, inclusion of ½- and ¾-site REs greatly expands the p53 master regulatory network. PMID:18714371

  17. p53 mutant breast cancer patients expressing p53γ have as good a prognosis as wild-type p53 breast cancer patients.

    OpenAIRE

    2011-01-01

    International audience; INTRODUCTION: Normal function of the p53 network is lost in most cancers, often through p53 mutation. The clinical impact of p53 mutations in breast cancer remains uncertain, especially where p53 isoforms may modify the effects of these p53 mutations. METHODS: Expression of p53β and p53γ isoforms, the isoforms identified in normal breast tissue, was detected by reverse transcription polymerase chain reaction from a cohort of 127 primary breast tumours. Expression of p5...

  18. Arginine methylation regulates the p53 response

    DEFF Research Database (Denmark)

    Jansson, Martin; Durant, Stephen T; Cho, Er-Chieh;

    2008-01-01

    Activation of the p53 tumour suppressor protein in response to DNA damage leads to apoptosis or cell-cycle arrest. Enzymatic modifications are widely believed to affect and regulate p53 activity. We describe here a level of post-translational control that has an important functional consequence o...

  19. An MDM2 antagonist (MI-319 restores p53 functions and increases the life span of orally treated follicular lymphoma bearing animals

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    Yang Dajun

    2009-12-01

    Full Text Available Abstract Background MI-319 is a synthetic small molecule designed to target the MDM2-P53 interaction. It is closely related to MDM2 antagonists MI-219 and Nutlin-3 in terms of the expected working mechanisms. The purpose of this study was to evaluate anti-lymphoma activity of MI-319 in WSU-FSCCL, a B-cell follicular lymphoma line. For comparison purpose, MI-319, MI-219 and Nutlin-3 were assessed side by side against FSCCL and three other B-cell hematological tumor cell lines in growth inhibition and gene expression profiling experiments. Results MI-319 was shown to bind to MDM2 protein with an affinity slightly higher than that of MI-219 and Nutlin-3. Nevertheless, cell growth inhibition and gene expression profiling experiments revealed that the three compounds have quite similar potency against the tumor cell lines tested in this study. In vitro, MI-319 exhibited the strongest anti-proliferation activity against FSCCL and four patient cells, which all have wild-type p53. Data obtained from Western blotting, cell cycle and apoptosis analysis experiments indicated that FSCCL exhibited strong cell cycle arrest and significant apoptotic cell death; cells with mutant p53 did not show significant apoptotic cell death with drug concentrations up to 10 μM, but displayed weaker and differential cell cycle responses. In our systemic mouse model for FSCCL, MI-319 was tolerated well by the animals, displayed effectiveness against FSCCL-lymphoma cells in blood, brain and bone marrow, and achieved significant therapeutic impact (p 28% (%ILS, 14.4 days increase in median survival days. Conclusion Overall, MI-319 probably has an anti-lymphoma potency equal to that of MI-219 and Nutlin-3. It is a potent agent against FSCCL in vitro and in vivo and holds the promises to be developed further for the treatment of follicular lymphoma that retains wild-type p53.

  20. The p53R172H Mutant Does Not Enhance Hepatocellular Carcinoma Development and Progression

    Science.gov (United States)

    Ahronian, Leanne G.; Driscoll, David R.; Klimstra, David S.; Lewis, Brian C.

    2015-01-01

    Hepatocellular carcinoma is a highly deadly malignancy, accounting for approximately 800,000 deaths worldwide every year. Mutation of the p53 tumor suppressor gene is a common genetic change in HCC, present in 30% of cases. p53R175H (corresponding to p53R172H in mice) is a hotspot for mutation that demonstrates “prometastatic” gain-of-function in other cancer models. Since the frequency of p53 mutation increases with tumor grade in HCC, we hypothesized that p53R172H is a gain-of-function mutation in HCC that contributes to a decrease in tumor-free survival and an increase in metastasis. In an HCC mouse model, we found that p53R172H/flox mice do not have decreased survival, increased tumor incidence, or increased metastasis, relative to p53flox/flox littermates. Analysis of cell lines derived from both genotypes indicated that there are no differences in anchorage-independent growth and cell migration. However, shRNA-mediated knockdown of mutant p53 in p53R172H-expressing HCC cell lines resulted in decreased cell migration and anchorage-independent growth. Thus, although p53 mutant-expressing cells and tumors do not have enhanced properties relative to their p53 null counterparts, p53R172H-expressing HCC cells depend on this mutant for their transformation. p53 mutants have been previously shown to bind and inhibit the p53 family proteins p63 and p73. Interestingly, we find that the levels of p63 and p73 target genes are similar in p53 mutant and p53 null HCC cells. These data suggest that pathways regulated by these p53 family members are similarly impacted by p53R172H in mutant expressing cells, and by alternate mechanisms in p53 null cells, resulting in equivalent phenotypes. Consistent with this, we find that p53 null HCC cell lines display lower levels of the TA isoforms of p63 and p73 and higher levels of ΔNp63. Taken together these data point to the importance of p63 and p73 in constraining HCC progression. PMID:25885474

  1. Disrupted p53 function as predictor of treatment failure and poor prognosis in B- and T-cell non-Hodgkin's lymphoma

    DEFF Research Database (Denmark)

    Møller, Michael Boe; Gerdes, A M; Skjødt, K;

    1999-01-01

    Mutation of the p53 gene has been associated with treatment failure and poor outcome in various malignancies. It has been suggested that immunohistochemical analysis of p53 and p21Waf1, a downstream target, can be used to screen for p53 gene mutations. We determined the value of immunohistochemical...... screening for p53 gene mutations as a prognostic marker in a population-based group of B- and T-cell non-Hodgkin's lymphomas (NHLs). On the basis of p53 gene mutation status and immunohistochemically detected p53 and p21Waf1 expression in 34 lymphomas, we established an immunophenotype (delta p53......) correlating with p53 gene mutation. The immunohistochemical analysis was extended to encompass 199 lymphomas from a population-based registry and was correlated with clinical parameters. Delta p53 showed 100% concordance with p53 gene mutation and was detected in 42 cases (21%). Multivariate analysis...

  2. Tumor suppressor WWOX and p53 alterations and drug resistance in glioblastomas

    Directory of Open Access Journals (Sweden)

    Ming-Fu eChiang

    2013-03-01

    Full Text Available Tumor suppressor p53 are frequently mutated in glioblastomas (GBMs and appears to contribute, in part, to resistance to temozolomide and therapeutic drugs. WW domain-containing oxidoreductase WWOX (FOR or WOX1 is a proapoptotic protein and is considered as a tumor suppressor. Loss of WWOX gene expression is frequently seen in malignant cancer cells due to promoter hypermethylation, genetic alterations, and translational blockade. Intriguingly, ectopic expression of wild type WWOX preferentially induces apoptosis in human glioblastoma cells harboring mutant p53. WWOX is known to physically bind and stabilize wild type p53. Here, we provide an overview for the updated knowledge in p53 and WWOX, and postulate a potential scenarios that wild type and mutant p53, or isoforms, modulate the apoptotic function of WWOX. We propose that triggering WWOX activation by therapeutic drugs under p53 functional deficiency is needed to overcome TMZ resistance and induce GBM cell death.

  3. Upregulated, 7q21-22 amplicon candidate gene SHFM1 confers oncogenic advantage by suppressing p53 function in gastric cancer.

    Science.gov (United States)

    Tamilzhalagan, Sembulingam; Muthuswami, Muthulakshmi; Periasamy, Jayaprakash; Lee, Ming Hui; Rha, Sun Young; Tan, Patrick; Ganesan, Kumaresan

    2015-06-01

    Chromosomal aberrations are hallmarks of cancers and the locus of frequent genomic amplifications often harbors key cancer driver genes. Many genomic amplicons remain larger with hundreds of genes and the key drivers remain to be identified by an amplification-wide systematic analysis. The 7q21.12-q22.3 genomic amplification is frequent in gastric cancers which occur in ~10% of the patients and multiple cell lines. This 7q21.12-q22.3 amplicon has not yet been completely analyzed towards identifying the driver genes and their functional contribution in oncogenesis. The amplitude and prevalence indicate the important role conferred by this amplicon in gastric cancers. Among the 159 genes of this amplicon, 12 genes are found over-expressed in primary gastric tumors and cell lines. Many of the over-expressed genes show negative association with p53 transcriptional activity. RNAi based functional screening of the genes reveal, SHFM1 as key gastric cancer driver gene. SHFM1 confers cell cycle progression and resistance to p53 stabilizing drugs in gastric cancer cells. SHFM1 also activates Src, MAPK/ERK and PI3K/Akt signaling pathways. This is the first integrative genomic investigation of 7q21.12-q22.3 amplicon revealing the potential oncogenic candidacy of 12 genes. The oncogenic contribution of SHFM1, mediated by the p53 suppressive feature has been demonstrated in gastric cancer cells.

  4. Mammary-specific inactivation of E-cadherin and p53 impairs functional gland development and leads to pleomorphic invasive lobular carcinoma in mice

    Directory of Open Access Journals (Sweden)

    Patrick W. B. Derksen

    2011-05-01

    Breast cancer is the most common malignancy in women of the Western world. Even though a large percentage of breast cancer patients show pathological complete remission after standard treatment regimes, approximately 30–40% are non-responsive and ultimately develop metastatic disease. To generate a good preclinical model of invasive breast cancer, we have taken a tissue-specific approach to somatically inactivate p53 and E-cadherin, the cardinal cell-cell adhesion receptor that is strongly associated with tumor invasiveness. In breast cancer, E-cadherin is found mutated or otherwise functionally silenced in invasive lobular carcinoma (ILC, which accounts for 10–15% of all breast cancers. We show that mammary-specific stochastic inactivation of conditional E-cadherin and p53 results in impaired mammary gland function during pregnancy through the induction of anoikis resistance of mammary epithelium, resulting in loss of epithelial organization and a dysfunctional mammary gland. Moreover, combined inactivation of E-cadherin and p53 induced lactation-independent development of invasive and metastatic mammary carcinomas, which showed strong resemblance to human pleomorphic ILC. Dissemination patterns of mouse ILC mimic the human malignancy, showing metastasis to the gastrointestinal tract, peritoneum, lung, lymph nodes and bone. Our results confirm that loss of E-cadherin contributes to both mammary tumor initiation and metastasis, and establish a preclinical mouse model of human ILC that can be used for the development of novel intervention strategies to treat invasive breast cancer.

  5. The p53 target Wig-1 regulates p53 mRNA stability through an AU-rich element

    DEFF Research Database (Denmark)

    Vilborg, Anna; Glahder, Jacob-Andreas Harald; Wilhelm, Margareta T

    2009-01-01

    The p53 target gene Wig-1 encodes a double-stranded-RNA-binding zinc finger protein. We show here that Wig-1 binds to p53 mRNA and stabilizes it through an AU-rich element (ARE) in the 3' UTR of the p53 mRNA. This effect is mirrored by enhanced p53 protein levels in both unstressed cells and cells...... exposed to p53-activating stress agents. Thus, the p53 target Wig-1 is a previously undescribed ARE-regulating protein that acts as a positive feedback regulator of p53, with implications both for the steady-state levels of p53 and for the p53 stress response. Our data reveal a previously undescribed link...

  6. SUMOylation of p53 mediates interferon activities

    Science.gov (United States)

    Marcos-Villar, Laura; Pérez-Girón, José V; Vilas, Jéssica M; Soto, Atenea; de la Cruz-Hererra, Carlos F; Lang, Valerie; Collado, Manuel; Vidal, Anxo; Rodríguez, Manuel S; Muñoz-Fontela, César; Rivas, Carmen

    2013-01-01

    There is growing evidence that many host proteins involved in innate and intrinsic immunity are regulated by SUMOylation, and that SUMO contributes to the regulatory process that governs the initiation of the type I interferon (IFN) response. The tumor suppressor p53 is a modulator of the IFN response that plays a role in virus-induced apoptosis and in IFN-induced senescence. Here we demonstrate that IFN treatment increases the levels of SUMOylated p53 and induces cellular senescence through a process that is partially dependent upon SUMOylation of p53. Similarly, we show that vesicular stomatitis virus (VSV) infection induces p53 SUMOylation, and that this modification favors the control of VSV replication. Thus, our study provides evidence that IFN signaling induces p53 SUMOylation, which results in the activation of a cellular senescence program and contributes to the antiviral functions of interferon. PMID:23966171

  7. Characterization of highly frequent epitope-specific CD45RA+/CCR7+/- T lymphocyte responses against p53-binding domains of the human polyomavirus BK large tumor antigen in HLA-A*0201+ BKV-seropositive donors

    Directory of Open Access Journals (Sweden)

    Zajac Paul

    2006-11-01

    Full Text Available Abstract Human polyomavirus BK (BKV has been implicated in oncogenic transformation. Its ability to replicate is determined by the binding of its large tumor antigen (LTag to products of tumor-suppressor genes regulating cell cycle, as specifically p53. We investigated CD8+ T immune responses to BKV LTag portions involved in p53 binding in HLA-A*0201+ BKV LTag experienced individuals. Peptides selected from either p53-binding region (LTag351–450 and LTag533–626 by current algorithms and capacity to bind HLA-A*0201 molecule were used to stimulate CD8+ T responses, as assessed by IFN-γ gene expression ex vivo and detected by cytotoxicity assays following in vitro culture. We observed epitope-specific immune responses in all HLA-A*0201+ BKV LTag experienced individuals tested. At least one epitope, LTag579–587; LLLIWFRPV, was naturally processed in non professional antigen presenting cells and induced cytotoxic responses with CTL precursor frequencies in the order of 1/20'000. Antigen specific CD8+ T cells were only detectable in the CD45RA+ subset, in both CCR7+ and CCR7- subpopulations. These data indicate that widespread cellular immune responses against epitopes within BKV LTag-p53 binding regions exist and question their roles in immunosurveillance against tumors possibly associated with BKV infection.

  8. Mutant p53 accumulation in human breast cancer is not an intrinsic property or dependent on structural or functional disruption but is regulated by exogenous stress and receptor status.

    Science.gov (United States)

    Bouchalova, Pavla; Nenutil, Rudolf; Muller, Petr; Hrstka, Roman; Appleyard, M Virginia; Murray, Karen; Jordan, Lee B; Purdie, Colin A; Quinlan, Philip; Thompson, Alastair M; Vojtesek, Borivoj; Coates, Philip J

    2014-07-01

    Many human cancers contain missense TP53 mutations that result in p53 protein accumulation. Although generally considered as a single class of mutations that abrogate wild-type function, individual TP53 mutations may have specific properties and prognostic effects. Tumours that contain missense TP53 mutations show variable p53 stabilization patterns, which may reflect the specific mutation and/or aspects of tumour biology. We used immunohistochemistry on cell lines and human breast cancers with known TP53 missense mutations and assessed the effects of each mutation with four structure-function prediction methods. Cell lines with missense TP53 mutations show variable percentages of cells with p53 stabilization under normal growth conditions, ranging from approximately 50% to almost 100%. Stabilization is not related to structural or functional disruption, but agents that stabilize wild-type p53 increase the percentages of cells showing missense mutant p53 accumulation in cell lines with heterogeneous stabilization. The same heterogeneity of p53 stabilization occurs in primary breast cancers, independent of the effect of the mutation on structural properties or functional disruption. Heterogeneous accumulation is more common in steroid receptor-positive or HER2-positive breast cancers and cell lines than in triple-negative samples. Immunohistochemcal staining patterns associate with Mdm2 levels, proliferation, grade and overall survival, whilst the type of mutation reflects downstream target activity. Inhibiting Mdm2 activity increases the extent of p53 stabilization in some, but not all, breast cancer cell lines. The data indicate that missense mutant p53 stabilization is a complex and variable process in human breast cancers that associates with disease characteristics but is unrelated to structural or functional properties. That agents which stabilize wild-type p53 also stabilize mutant p53 has implications for patients with heterogeneous mutant p53 accumulation

  9. The expanding regulatory universe of p53 in gastrointestinal cancer.

    Science.gov (United States)

    Fesler, Andrew; Zhang, Ning; Ju, Jingfang

    2016-01-01

    Tumor suppresser gene TP53 is one of the most frequently deleted or mutated genes in gastrointestinal cancers. As a transcription factor, p53 regulates a number of important protein coding genes to control cell cycle, cell death, DNA damage/repair, stemness, differentiation and other key cellular functions. In addition, p53 is also able to activate the expression of a number of small non-coding microRNAs (miRNAs) through direct binding to the promoter region of these miRNAs.  Many miRNAs have been identified to be potential tumor suppressors by regulating key effecter target mRNAs. Our understanding of the regulatory network of p53 has recently expanded to include long non-coding RNAs (lncRNAs). Like miRNA, lncRNAs have been found to play important roles in cancer biology.  With our increased understanding of the important functions of these non-coding RNAs and their relationship with p53, we are gaining exciting new insights into the biology and function of cells in response to various growth environment changes. In this review we summarize the current understanding of the ever expanding involvement of non-coding RNAs in the p53 regulatory network and its implications for our understanding of gastrointestinal cancer.

  10. Interactions of the p53 protein family in cellular stress response in gastrointestinal tumors.

    Science.gov (United States)

    Vilgelm, Anna E; Washington, Mary K; Wei, Jinxiong; Chen, Heidi; Prassolov, Vladimir S; Zaika, Alexander I

    2010-03-01

    p53, p63, and p73 are members of the p53 protein family involved in regulation of cell cycle, apoptosis, differentiation, and other critical cellular processes. Here, we investigated the contribution of the entire p53 family in chemotherapeutic drug response in gastrointestinal tumors. Real-time PCR and immunohistochemistry revealed complexity and variability of expression profiles of the p53 protein family. Using colon and esophageal cancer cells, we found that the integral transcription activity of the entire p53 family, as measured by the reporter analysis, associated with response to drug treatment in studied cells. We also found that p53 and p73, as well as p63 and p73, bind simultaneously to the promoters of p53 target genes. Taken together, our results support the view that the p53 protein family functions as an interacting network of proteins and show that cellular responses to chemotherapeutic drug treatment are determined by the total activity of the entire p53 family rather than p53 alone.

  11. Targeting the p53 Pathway in Ewing Sarcoma

    OpenAIRE

    Neilsen, Paul M.; Pishas, Kathleen I.; Callen, David F; Thomas, David M.

    2011-01-01

    The p53 tumour suppressor plays a pivotal role in the prevention of oncogenic transformation. Cancers frequently evade the potent antitumour surveillance mechanisms of p53 through mutation of the TP53 gene, with approximately 50% of all human malignancies expressing dysfunctional, mutated p53 proteins. Interestingly, genetic lesions in the TP53 gene are only observed in 10% of Ewing Sarcomas, with the majority of these sarcomas expressing a functional wild-type p53. In addition, the p53 downs...

  12. 鼠双微体基因2与p53在子宫颈癌发生中的作用%The Function in Cervix Carcinogenesis of Murine Double Minute 2 and p53

    Institute of Scientific and Technical Information of China (English)

    张鸿瑞; 何春年

    2008-01-01

    鼠双微体2(murine double minute 2,mdm2)基因是从一个含有鼠双微体(marine double minut,DM)自发转化的BALB/3T3DM细胞中克隆出来的高度扩增的基因.高表达时呈现癌基因功能.子宫颈鳞状上皮由CIN转变为癌有许多因素参与,其中mdm2和p53在宫颈感染人乳头状瘤病毒(human papillomavirus,HPV)情况下相互作用,可促进宫颈上皮的恶性转变,是导致子宫颈癌的发生的因素之一,本文对其进行综述.

  13. p53 in the game of transposons.

    Science.gov (United States)

    Wylie, Annika; Jones, Amanda E; Abrams, John M

    2016-11-01

    Throughout the animal kingdom, p53 genes function to restrain mobile elements and recent observations indicate that transposons become derepressed in human cancers. Together, these emerging lines of evidence suggest that cancers driven by p53 mutations could represent "transpospoathies," i.e. disease states linked to eruptions of mobile elements. The transposopathy hypothesis predicts that p53 acts through conserved mechanisms to contain transposon movement, and in this way, prevents tumor formation. How transposon eruptions provoke neoplasias is not well understood but, from a broader perspective, this hypothesis also provides an attractive framework to explore unrestrained mobile elements as inciters of late-onset idiopathic disease. Also see the video abstract here.

  14. THE HEPARIN-BINDING DOMAIN AND V REGION OF FIBRONECTIN REGULATE APOPTOSIS BY SUPPRESSION OF P53 AND C-MYC IN HUMAN PRIMARY CELLS

    Science.gov (United States)

    In apoptosis the tumor suppressor p53 and oncogene c-myc, are usually upregulated. However, we report here an alternate pathway of regulation that is triggered by inflammatory-associated matrix fragments of fibronectin (FN) and leads to apoptosis. It is mediated by transcriptio...

  15. Low p53 Binding Protein 1 (53BP1) Expression Is Associated With Increased Local Recurrence in Breast Cancer Patients Treated With Breast-Conserving Surgery and Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Neboori, Hanmanth J.R. [Department of Radiation Oncology, Cancer Institute of New Jersey and University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ (United States); Haffty, Bruce G., E-mail: hafftybg@umdnj.edu [Department of Radiation Oncology, The Cancer Institute of New Jersey and University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ (United States); Wu Hao [Department of Radiation Oncology, Cancer Institute of New Jersey and University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ (United States); Yang Qifeng [Department of Breast Surgery, Qilu Hospital, Shandong University, Ji' nan (China); Aly, Amal [Division of Medical Oncology, The Cancer Institute of New Jersey and University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ (United States); Goyal, Sharad; Schiff, Devora [Department of Radiation Oncology, Cancer Institute of New Jersey and University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ (United States); Moran, Meena S. [Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT (United States); Golhar, Ryan [Department of Radiation Oncology, Cancer Institute of New Jersey and University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ (United States); Chen Chunxia; Moore, Dirk [Department of Biostatistics, The Cancer Institute of New Jersey and University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ (United States); and others

    2012-08-01

    Purpose: To investigate whether the expression of p53 binding protein 1 (53BP1) has prognostic significance in a cohort of early-stage breast cancer patients treated with breast-conserving surgery and radiotherapy (BCS+RT). Methods and Materials: A tissue microarray of early-stage breast cancer treated with BCS+RT from a cohort of 514 women was assayed for 53BP1, estrogen receptor, progesterone receptor, and HER2 expression by immunohistochemistry. Through log-rank tests and univariate and multivariate models, the staining profile of each tumor was correlated with clinical endpoints, including ipsilateral breast recurrence-free survival (IBRFS), distant metastasis-free survival (DMFS), cause-specific survival (CSS), recurrence-free survival (RFS), and overall survival (OS). Results: Of the 477 (93%) evaluable tumors, 63 (13%) were scored as low. Low expression of 53BP1 was associated with worse outcomes for all endpoints studied, including 10-year IBRFS (76.8% vs. 90.5%; P=.01), OS (66.4% vs. 81.7%; P=.02), CSS (66.0% vs. 87.4%; P<.01), DMFS (55.9% vs. 87.0%; P<.01), and RFS (45.2% vs. 80.6%; P<.01). Multivariate analysis incorporating various clinico-pathologic markers and 53BP1 expression found that 53BP1 expression was again an independent predictor of all endpoints (IBRFS: P=.0254; OS: P=.0094; CSS: P=.0033; DMFS: P=.0006; RFS: P=.0002). Low 53BP1 expression was also found to correlate with triple-negative (TN) phenotype (P<.01). Furthermore, in subset analysis of all TN breast cancer, negative 53BP1 expression trended for lower IBRFS (72.3% vs. 93.9%; P=.0361) and was significant for worse DMFS (48.2% vs. 86.8%; P=.0035) and RFS (37.8% vs. 83.7%; P=.0014). Conclusion: Our data indicate that low 53BP1 expression is an independent prognostic indicator for local relapse among other endpoints in early-stage breast cancer and TN breast cancer patients treated with BCS+RT. These results should be verified in larger cohorts of patients to validate their clinical

  16. N-methylpurine DNA glycosylase inhibits p53-mediated cell cycle arrest and coordinates with p53 to determine sensitivity to alkylating agents

    Institute of Scientific and Technical Information of China (English)

    Shanshan Song; Guichun Xing; Lin Yuan; Jian Wang; Shan Wang; Yuxin Yin; Chunyan Tian; Fuchu He; Lingqiang Zhang

    2012-01-01

    Alkylating agents induce genome-wide base damage,which is repaired mainly by N-methylpurine DNA glycosylase (MPG).An elevated expression of MPG in certain types of tumor cells confers higher sensitivity to alkylation agents because MPG-induced apurinic/apyrimidic (AP) sites trigger more strand breaks.However,the determinant of drug sensitivity or insensitivity still remains unclear.Here,we report that the p53 status coordinates with MPG to play a pivotal role in such process.MPG expression is positive in breast,lung and colon cancers (38.7%,43.4% and 25.3%,respectively) but negative in all adjacent normal tissues.MPG directly binds to the tumor suppressor p53 and represses p53 activity in unstressed cells.The overexpression of MPG reduced,whereas depletion of MPG increased,the expression levels of pro-arrest gene downstream of p53 including p21,14-3-3σ and Gadd45 but not pro-apoptotic ones.The N-terminal region of MPG was specifically required for the interaction with the DNA binding domain of p53.Upon DNA alkylation stress,in p53 wild-type tumor cells,p53 dissociated from MPG and induced cell growth arrest.Then,AP sites were repaired efficiently,which led to insensitivity to alkylating agents.By contrast,in p53-mutated cells,the AP sites were repaired with low efficacy.To our knowledge,this is the first direct evidence to show that a DNA repair enzyme functions as a selective regulator of p53,and these findings provide new insights into the functional linkage between MPG and p53 in cancer therapy.

  17. p53 protein aggregation promotes platinum resistance in ovarian cancer.

    Science.gov (United States)

    Yang-Hartwich, Y; Soteras, M G; Lin, Z P; Holmberg, J; Sumi, N; Craveiro, V; Liang, M; Romanoff, E; Bingham, J; Garofalo, F; Alvero, A; Mor, G

    2015-07-01

    High-grade serous ovarian carcinoma (HGSOC), the most lethal gynecological cancer, often leads to chemoresistant diseases. The p53 protein is a key transcriptional factor regulating cellular homeostasis. A majority of HGSOCs have inactive p53 because of genetic mutations. However, genetic mutation is not the only cause of p53 inactivation. The aggregation of p53 protein has been discovered in different types of cancers and may be responsible for impairing the normal transcriptional activation and pro-apoptotic functions of p53. We demonstrated that in a unique population of HGSOC cancer cells with cancer stem cell properties, p53 protein aggregation is associated with p53 inactivation and platinum resistance. When these cancer stem cells differentiated into their chemosensitive progeny, they lost tumor-initiating capacity and p53 aggregates. In addition to the association of p53 aggregation and chemoresistance in HGSOC cells, we further demonstrated that the overexpression of a p53-positive regulator, p14ARF, inhibited MDM2-mediated p53 degradation and led to the imbalance of p53 turnover that promoted the formation of p53 aggregates. With in vitro and in vivo models, we demonstrated that the inhibition of p14ARF could suppress p53 aggregation and sensitize cancer cells to platinum treatment. Moreover, by two-dimensional gel electrophoresis and mass spectrometry we discovered that the aggregated p53 may function uniquely by interacting with proteins that are critical for cancer cell survival and tumor progression. Our findings help us understand the poor chemoresponse of a subset of HGSOC patients and suggest p53 aggregation as a new marker for chemoresistance. Our findings also suggest that inhibiting p53 aggregation can reactivate p53 pro-apoptotic function. Therefore, p53 aggregation is a potential therapeutic target for reversing chemoresistance. This is paramount for improving ovarian cancer patients' responses to chemotherapy, and thus increasing their

  18. Escape, or Vanish: Control the Fate of p53 through MDM2-Mediated Ubiquitination.

    Science.gov (United States)

    Wei, Jinlian; Yang, Yingrui; Lu, Mengchen; Xu, Lili; Liu, Fang; Yuan, Zhenwei; Bao, Qichao; Jiang, Zhengyu; Xu, Xiaoli; Guo, Xiaoke; Zhang, Xiaojin; You, Qidong; Sun, Haopeng

    2015-01-01

    p53 protein is a prominent tumor suppressor to induce cell cycle arrest, apoptosis and senescence, which attracts significant interest to cancer treatment. Therefore, it would be particularly important to restore the wild-type p53 that retains latent functions in the approximately 50% of tumors. MDM2 (murine double minute 2), the principal cellular antagonist of p53, has long been believed to suppress p53 activity through two main mechanisms: promoting degradation via its E3 ligase activity and masking p53 transcriptional activation by direct binding. Targeting MDM2 E3 ligase activity is becoming a potential antitumor strategy resulting from MDM2's decisive role in controlling the fate of p53: p53 is going to degradation when entrapped into MDM2-mediated ubiquitination, where p53 can escape by abrogating MDM2 E3 ligase activity using regulators. The intensive focus on regulating MDM2 ubiquitin E3 ligase activity has led to the rapid progress of its inhibitors, which may be possible to help p53 escape from degradation and restore its function to control tumor growth. This review summarizes the current inhibitors of MDM2 E3 ligase in cancer therapy based on the understanding the regulation of MDM2 E3 ubiquitin ligase activity, including post-translational modification, interactions between MDM2 and its cofactors, and regulation of MDM2 stability.

  19. The translation initiation factor DAP5 promotes IRES-driven translation of p53 mRNA.

    Science.gov (United States)

    Weingarten-Gabbay, S; Khan, D; Liberman, N; Yoffe, Y; Bialik, S; Das, S; Oren, M; Kimchi, A

    2014-01-30

    Translational regulation of the p53 mRNA can determine the ratio between p53 and its N-terminal truncated isoforms and therefore has a significant role in determining p53-regulated signaling pathways. Although its importance in cell fate decisions has been demonstrated repeatedly, little is known about the regulatory mechanisms that determine this ratio. Two internal ribosome entry sites (IRESs) residing within the 5'UTR and the coding sequence of p53 mRNA drive the translation of full-length p53 and Δ40p53 isoform, respectively. Here, we report that DAP5, a translation initiation factor shown to positively regulate the translation of various IRES containing mRNAs, promotes IRES-driven translation of p53 mRNA. Upon DAP5 depletion, p53 and Δ40p53 protein levels were decreased, with a greater effect on the N-terminal truncated isoform. Functional analysis using bicistronic vectors driving the expression of a reporter gene from each of these two IRESs indicated that DAP5 preferentially promotes translation from the second IRES residing in the coding sequence. Furthermore, p53 mRNA expressed from a plasmid carrying this second IRES was selectively shifted to lighter polysomes upon DAP5 knockdown. Consequently, Δ40p53 protein levels and the subsequent transcriptional activation of the 14-3-3σ gene, a known target of Δ40p53, were strongly reduced. In addition, we show here that DAP5 interacts with p53 IRES elements in in vitro and in vivo binding studies, proving for the first time that DAP5 directly binds a target mRNA. Thus, through its ability to regulate IRES-dependent translation of the p53 mRNA, DAP5 may control the ratio between different p53 isoforms encoded by a single mRNA.

  20. RNF38 encodes a nuclear ubiquitin protein ligase that modifies p53

    Energy Technology Data Exchange (ETDEWEB)

    Sheren, Jamie E. [Department of Pathology, The University of Colorado Anschutz Medical Campus, Aurora, CO 80045 (United States); Kassenbrock, C. Kenneth, E-mail: ken.kassenbrock@ucdenver.edu [Department of Pathology, The University of Colorado Anschutz Medical Campus, Aurora, CO 80045 (United States); Department of Biology, Colorado State University, Fort Collins, CO 80523-1878 (United States)

    2013-11-01

    Highlights: •RNF38 is shown to be a nuclear protein with a bipartite nuclear localization signal. •RNF38 protein is purified and shown to have ubiquitin protein ligase (E3) activity. •We show that RNF38 binds p53 and can ubiquitinate p53 in vitro. •Overexpression of RNF38 increases p53 ubiquitination in HEK293T cells. •Overexpression of RNF38 in HEK293T cells alters p53 localization. -- Abstract: The RNF38 gene encodes a RING finger protein of unknown function. Here we demonstrate that RNF38 is a functional ubiquitin protein ligase (E3). We show that RNF38 isoform 1 is localized to the nucleus by a bipartite nuclear localization sequence (NLS). We confirm that RNF38 is a binding partner of p53 and demonstrate that RNF38 can ubiquitinate p53 in vitro and in vivo. Finally, we show that overexpression of RNF38 in HEK293T cells results in relocalization of p53 to discrete foci associated with PML nuclear bodies. These results suggest RNF38 is an E3 ubiquitin ligase that may play a role in regulating p53.

  1. Cellular adaptation to hypoxia and p53 transcription regulation

    Institute of Scientific and Technical Information of China (English)

    Yang ZHAO; Xue-qun CHEN; Ji-zeng DU

    2009-01-01

    Tumor suppressor p53 is the most frequently mutated gene in human tumors. Meanwhile, under stress conditions, p53 also acts as a transcription factor, regulating the expression of a series of target genes to maintain the integrity of genome. The target genes of p53 can be classified into genes regulating cell cycle arrest, genes involved in apoptosis, and genes inhibiting angiogenesis. p53 protein contains a transactivation domain, a sequence-specific DNA binding domain, a tetramerization domain, a non-specific DNA binding domain that recognizes damaged DNA, and a later identified proline-rich domain. Under stress, p53 proteins accumulate and are activated through two mechanisms. One, involving ataxia telangiectasia-mutated protein (ATM), is that the interaction between p53 and its down-regulation factor murine double minute 2 (MDM2) decreases, leading to p53 phosphorylation on Ser15, as determined by the post-translational mechanism; the other holds that p53 increases and is activated through the binding of ribosomal protein L26 (RPL26) or nucleolin to p53 mRNA 5' untranslated region (UTR), regulating p53 translation. Under hypoxia, p53 decreases transactivation and increases transrepression. The mutations outside the DNA binding domain of p53 also contribute to tumor progress, so further studies on p53 should also be focused on this direction. The subterranean blind mole rat Spalax in Israel is a good model for hypoxia-adaptation. The p53 of Spalax mutated in residue 172 and residue 207 from arginine to lysine, conferring it the ability to survive hypoxic conditions. This model indicates that p53 acts as a master gene of diversity formation during evolution.

  2. P53 Mdm2 Inhibitors

    NARCIS (Netherlands)

    Khoury, Kareem; Doemling, Alex

    2012-01-01

    The protein-protein interaction (PPI) between p53 and its negative regulator MDM2 comprises one of the most important and intensely studied PPI's involved in preventing the initiation of cancer. The interaction between p53 and MDM2 is conformation-based and is tightly regulated on multiple levels. D

  3. p53 mediates the suppression of cancer cell invasion by inducing LIMA1/EPLIN.

    Science.gov (United States)

    Ohashi, Tomoko; Idogawa, Masashi; Sasaki, Yasushi; Tokino, Takashi

    2017-04-01

    The tumor suppressor gene p53 is frequently mutated in human cancer. p53 executes various functions, such as apoptosis induction and cell cycle arrest, by modulating transcriptional regulation. In this study, LIM domain and Actin-binding protein 1 (LIMA1) was identified as a target of the p53 family using a cDNA microarray. We also evaluated genome-wide occupancy of the p53 protein by performing chromatin immunoprecipitation-sequencing (ChIP-seq) and identified two p53 response elements in the LIMA1 gene. LIMA1 protein levels were increased by treatment with nutlin-3a, a small molecule that activates endogenous p53. In addition, LIMA1 expression was significantly downregulated in cancers compared with normal tissues. Knockdown of LIMA1 significantly enhanced cancer cell invasion and partially inhibited p53-induced suppression of cell invasion. Furthermore, low expression of LIMA1 in cancer patients correlated with decreased survival and poor prognosis. Thus, p53-induced LIMA1 inhibits cell invasion, and the downregulation of LIMA1 caused by p53 mutation results in decreased survival in cancer patients. Collectively, this study reveals the molecular mechanism of LIMA1 downregulation in various cancers and suggests that LIMA1 may be a novel prognostic predictor and a therapeutic target for cancer.

  4. Autophagy induced by p53-reactivating molecules protects pancreatic cancer cells from apoptosis.

    Science.gov (United States)

    Fiorini, Claudia; Menegazzi, Marta; Padroni, Chiara; Dando, Ilaria; Dalla Pozza, Elisa; Gregorelli, Alex; Costanzo, Chiara; Palmieri, Marta; Donadelli, Massimo

    2013-03-01

    TP53 mutations compromising p53 transcriptional function occur in more than 50 % of human cancers, including pancreatic adenocarcinoma, and render cancer cells more resistant to conventional therapy. In the last few years, many efforts have been addressed to identify p53-reactivating molecules able to restore the wild-type transcriptionally competent conformation of the mutated proteins. Here, we show that two of these compounds, CP-31398 and RITA, induce cell growth inhibition, apoptosis, and autophagy by activating p53/DNA binding and p53 phosphorylation (Ser15), without affecting the total p53 amount. These effects occur in both wild-type and mutant p53 pancreatic adenocarcinoma cell lines, whereas they are much less pronounced in normal human primary fibroblasts. Furthermore, CP-31398 and RITA regulate the axis SESN1-2/AMPK/mTOR by inducing AMPK phosphorylation on Thr172, which has a crucial role in the autophagic response. The protective role of autophagy in cell growth inhibition by CP-31398 and RITA is supported by the finding that the AMPK inhibitor compound C or the autophagy inhibitors chloroquine or 3-methyladenine sensitize both pancreatic adenocarcinoma cell lines to the apoptotic response induced by p53-reactivating molecules. Our results demonstrate for the first time a survival role for autophagy induced by p53-reactivating molecules, supporting the development of an anti-cancer therapy based on autophagy inhibition associated to p53 activation.

  5. hSSB1 regulates both the stability and the transcriptional activity of p53

    Institute of Scientific and Technical Information of China (English)

    Shuangbing Xu; Yuanzhong Wu; Qiong Chen; Jingying Cao; Kaishun Hu; Jianjun Tang; Yi Sang

    2013-01-01

    The tumor suppressor p53 is essential for several cellular processes that are involved in the response to diverse genotoxic stress,including cell cycle arrest,DNA repair,apoptosis and senescence.Studies of the regulation of p53 have mostly focused on its stability and transactivation; however,new regulatory molecules for p53 have also been frequently identified.Here,we report that human ssDNA binding protein SSB1 (hSSB1),a novel DNA damageassociated protein,can interact with p53 and protect p53 from ubiquitin-mediated degradation.Furthermore,hSSB1 also associates with the acetyltransferase p300 and is required for efficient transcriptional activation of the p53 target gene p21 by affecting the acetylation of p53 at lysine382.Functionally,the hSSB1 knockdown-induced abrogation of the G2/M checkpoint is partially dependent on p53 or p300.Collectively,our results indicate that hSSB1 may regulate DNA damage checkpoints by positively modulating p53 and its downstream target p21.

  6. Degradation of phosphorylated p53 by viral protein-ECS E3 ligase complex.

    Directory of Open Access Journals (Sweden)

    Yoshitaka Sato

    2009-07-01

    Full Text Available p53-signaling is modulated by viruses to establish a host cellular environment advantageous for their propagation. The Epstein-Barr virus (EBV lytic program induces phosphorylation of p53, which prevents interaction with MDM2. Here, we show that induction of EBV lytic program leads to degradation of p53 via an ubiquitin-proteasome pathway independent of MDM2. The BZLF1 protein directly functions as an adaptor component of the ECS (Elongin B/C-Cul2/5-SOCS-box protein ubiquitin ligase complex targeting p53 for degradation. Intringuingly, C-terminal phosphorylation of p53 resulting from activated DNA damage response by viral lytic replication enhances its binding to BZLF1 protein. Purified BZLF1 protein-associated ECS could be shown to catalyze ubiquitination of phospho-mimetic p53 more efficiently than the wild-type in vitro. The compensation of p53 at middle and late stages of the lytic infection inhibits viral DNA replication and production during lytic infection, suggesting that the degradation of p53 is required for efficient viral propagation. Taken together, these findings demonstrate a role for the BZLF1 protein-associated ECS ligase complex in regulation of p53 phosphorylated by activated DNA damage signaling during viral lytic infection.

  7. Dynamically regulated sumoylation of HDAC2 controls p53 deacetylation and restricts apoptosis following genotoxic stress

    Institute of Scientific and Technical Information of China (English)

    André Brandl; Tobias Wagner; Katharina M. Uhlig; Shirley K. Knauer; Roland H. Stauber; Frauke Melchior; Günter Schneider; Thorsten Heinzel; Oliver H. Kr(a)mer

    2012-01-01

    Histone deacetylase 2 (HDAC2) is relevant for homeostasis and plays a critical role in gastrointestinal cancers.Here,we report that post-translational modification of endogenous HDAC2 with small ubiquitin-related modifier 1 (SUMO1) is a new regulatory switch for the tumor suppressor p53.Sumoylation of HDAC2 at lysine 462 allows binding of HDAC2 to p53.Moreover,sumoylated HDAC2 is a previously not recognized biologically relevant site-specific deacetylase for p53.Deacetylation of p53 at lysine 320 by sumoylated HDAC2 blocks recruitment of p53 into promoter-associated complexes and p53-dependent expression of genes for cell cycle control and apoptosis.Thereby,catalytically active sumoylated HDAC2 restricts p53 functions and attenuates DNA damage-induced apoptosis.Genotoxic stress evokes desumoylation of HDAC2,enabling p53-dependent gene expression,Our data show a new molecular mechanism involving a dynamically controlled HDAC2-sumoylation/p53-acetylation switch that regulates cell fate decisions following genotoxic stress.

  8. USP11通过去泛素化p53调控p53稳定性%USP11 regulates p53 stability by deubiquitinating p53

    Institute of Scientific and Technical Information of China (English)

    Jia-ying KE; Cong-jie DAI; Wen-lin WU; Jin-hua GAO; Ai-juan XIA; Guang-ping LIU; Kao-sheng LV; Chun-lin WU

    2014-01-01

    The p53 tumor suppressor protein coordinates the celular responses to a broad range of celular stresses, leading to DNA repair, cel cycle arrest or apoptosis. The stability of p53 is essential for its tumor suppressor function, which is tightly controlled by ubiquitin-dependent degradation primarily through its negative regulator murine double minute 2 (Mdm2). To better understand the regulation of p53, we tested the interaction between p53 and USP11 using co-immunoprecipitation. The results show that USP11, an ubiquitin-specific protease, forms specific complexes with p53 and stabilizes p53 by deubiquitinating it. Moreover, down-regulation of USP11 dramaticaly attenuated p53 in-duction in response to DNA damage stress. These findings reveal that USP11 is a novel regulator of p53, which is required for p53 activation in response to DNA damage.

  9. Anticancer Effects of a New SIRT Inhibitor, MHY2256, against Human Breast Cancer MCF-7 Cells via Regulation of MDM2-p53 Binding.

    Science.gov (United States)

    Park, Eun Young; Woo, Youngwoo; Kim, Seong Jin; Kim, Do Hyun; Lee, Eui Kyung; De, Umasankar; Kim, Kyeong Seok; Lee, Jaewon; Jung, Jee H; Ha, Ki-Tae; Choi, Wahn Soo; Kim, In Su; Lee, Byung Mu; Yoon, Sungpil; Moon, Hyung Ryong; Kim, Hyung Sik

    2016-01-01

    The sirtuins (SIRTs), a family of NAD(+)-dependent class III histone deacetylase, are involved in various biological processes including cell survival, division, senescence, and metabolism via activation of the stress-response pathway. Recently, inhibition of SIRTs has been considered a promising anticancer strategy, but their precise mechanisms of action are not well understood. In particular, the relevance of p53 to SIRT-induced effects has not been fully elucidated. We investigated the anticancer effects of a novel SIRT inhibitor, MHY2256, and its efficacy was compared to that of salermide in MCF-7 (wild-type p53) and SKOV-3 (null-type p53) cells. Cell viability, SIRT1 enzyme activity, cell cycle regulation, apoptosis, and autophagic cell death were measured. We compared sensitivity to cytotoxicity in MCF-7 and SKOV-3 cells. MHY2256 significantly decreased the viability of MCF-7 (IC50, 4.8 μM) and SKOV-3 (IC50, 5.6 μM) cells after a 48 h treatment period. MHY2256 showed potent inhibition (IC50, 0.27 mM) against SIRT1 enzyme activity compared with nicotinamide (IC50, >1 mM). Moreover, expression of SIRT (1, 2, or 3) protein levels was significantly reduced by MHY2256 treatment in both MCF-7 and SKOV-3 cells. Flow cytometry analysis revealed that MHY2256 significantly induced cell cycle arrest in the G1 phase, leading to an effective increase in apoptotic cell death in MCF-7 and SKOV-3 cells. A significant increase in acetylated p53, a target protein of SIRT, was observed in MCF-7 cells after MHY2256 treatment. MHY2256 up-regulated LC3-II and induced autophagic cell death in MCF-7 cells. Furthermore, MHY2256 markedly inhibited tumor growth in a tumor xenograft model of MCF-7 cells. These results suggest that a new SIRT inhibitor, MHY2256, has anticancer activity through p53 acetylation in MCF-7 human breast cancer cells.

  10. CD40-mediated apoptosis in murine B-lymphoma lines containing mutated p53

    DEFF Research Database (Denmark)

    Hollmann, Annette C; Gong, Qiaoke; Owens, Trevor

    2002-01-01

    Crosslinking CD40 induces normal B-cells to proliferate and differentiate but causes many tumor cell lines to undergo apoptosis. As p53 is required for many apoptotic pathways, we analyzed the effects of CD40 ligation and their correlation with p53 function in four murine B-lymphoma lines. A20...... to amino acid substitutions in DNA binding regions, but was unmutated in WEHI231 and WEHI 279. These results suggest that CD40-mediated apoptosis can occur in the absence of functional p53....... was normal. NFkappaB activity was quantitated by reporter and gel shift assays and found to be equivalent in all four cell lines. P53 reporter constructs were activated in WEHI231 but not A20 or M12 cells, suggesting that p53 in the latter two cell lines may be mutated. These data are supported by the lack...

  11. CD40-mediated apoptosis in murine B-lymphoma lines containing mutated p53

    DEFF Research Database (Denmark)

    Hollmann, Annette C; Gong, Qiaoke; Owens, Trevor

    2002-01-01

    Crosslinking CD40 induces normal B-cells to proliferate and differentiate but causes many tumor cell lines to undergo apoptosis. As p53 is required for many apoptotic pathways, we analyzed the effects of CD40 ligation and their correlation with p53 function in four murine B-lymphoma lines. A20...... of detectable p21 mRNA in A20 and M12 cells. P21 mRNA was increased to detectable levels in M12 cells upon CD40 ligation; however, blocking this effect with the p53 inhibitor pifithrin had no effect on CD40-mediated apoptosis. Sequencing showed that p53 in A20 and M12 cells contained point mutations leading...... to amino acid substitutions in DNA binding regions, but was unmutated in WEHI231 and WEHI 279. These results suggest that CD40-mediated apoptosis can occur in the absence of functional p53....

  12. APAF1 is a key transcriptional target for p53 in the regulation of neuronal cell death

    DEFF Research Database (Denmark)

    Fortin, A; Cregan, S P; MacLaurin, J G

    2001-01-01

    of this process have not been identified. In the present study, we demonstrate that p53 directly upregulates Apaf1 transcription as a critical step in the induction of neuronal cell death. Using DNA microarray analysis of total RNA isolated from neurons undergoing p53-induced apoptosis a 5-6-fold upregulation...... of Apaf1 mRNA was detected. Induction of neuronal cell death by camptothecin, a DNA-damaging agent that functions through a p53-dependent mechanism, resulted in increased Apaf1 mRNA in p53-positive, but not p53-deficient neurons. In both in vitro and in vivo neuronal cell death processes of p53-induced...... cell death, Apaf1 protein levels were increased. We addressed whether p53 directly regulates Apaf1 transcription via the two p53 consensus binding sites in the Apaf1 promoter. Electrophoretic mobility shift assays demonstrated p53-DNA binding activity at both p53 consensus binding sequences in extracts...

  13. Knockin mice expressing a chimeric p53 protein reveal mechanistic differences in how p53 triggers apoptosis and senescence

    OpenAIRE

    2008-01-01

    The contribution of transcriptional activation to the p53 effector functions critical for tumor suppression, apoptosis and cellular senescence, remains unclear because of p53's ability to regulate diverse cellular processes in a transactivation-independent manner. Dissociating the importance of transactivation from other p53 functions, including regulating transcriptional repression, DNA replication, homologous recombination, centrosome duplication, and mitochondrial function, has been diffic...

  14. Definition of a major p53 binding site on Ad2E1B58K protein and a possible nuclear localization signal on the Ad12E1B54K protein.

    Science.gov (United States)

    Grand, R J; Parkhill, J; Szestak, T; Rookes, S M; Roberts, S; Gallimore, P H

    1999-01-28

    Previous studies have established that adenovirus 2/5 early region 1B (Ad E1B) 58K protein binds p53 strongly and co-localizes with it to cytoplasmic dense bodies whilst the homologous Ad12E1B54K protein binds only weakly and co-localizes primarily to the nucleus in Ad12E1 transformed cells. We have used these properties of the E1B proteins from different viral serotypes to map the p53 binding site on the Ad2/5 protein. A set of chimaeric genes was constructed containing different proportions of the Ad12 and Ad2E1B DNA. These, together with Ad12E1A and E1B19K DNA, were transfected into baby rat kidney cells and transformed lines isolated. From an examination of the properties of these Ad12/Ad2E1B fusion proteins in co-immunoprecipitation and subcellular localization experiments it has been concluded that the p53 binding site on Ad2E1B58K protein lies between amino acids 216 and 235 and that the homologous region on Ad12E1B54K protein also binds p53. In addition, a unique nuclear localization signal is located on Ad12E1B54K between residues 228 and 239. We suggest that primary structure differences in these regions of the Ad2 and Ad12E1B proteins are responsible for the different subcellular localizations in AdE1 transformants.

  15. Glycogen synthase kinase3 beta phosphorylates serine 33 of p53 and activates p53's transcriptional activity

    Directory of Open Access Journals (Sweden)

    Price Brendan D

    2001-07-01

    Full Text Available Abstract Background The p53 protein is activated by genotoxic stress, oncogene expression and during senescence, p53 transcriptionally activates genes involved in growth arrest and apoptosis. p53 activation is regulated by post-translational modification, including phosphorylation of the N-terminal transactivation domain. Here, we have examined how Glycogen Synthase Kinase (GSK3, a protein kinase involved in tumorigenesis, differentiation and apoptosis, phosphorylates and regulates p53. Results The 2 isoforms of GSK3, GSK3α and GSK3β, phosphorylate the sequence Ser-X-X-X-Ser(P when the C-terminal serine residue is already phosphorylated. Several p53 kinases were examined for their ability to create GSK3 phosphorylation sites on the p53 protein. Our results demonstrate that phosphorylation of serine 37 of p53 by DNA-PK creates a site for GSK3β phosphorylation at serine 33 in vitro. GSK3α did not phosphorylate p53 under any condition. GSK3β increased the transcriptional activity of the p53 protein in vivo. Mutation of either serine 33 or serine 37 of p53 to alanine blocked the ability of GSK3β to regulate p53 transcriptional activity. GSK3β is therefore able to regulate p53 function in vivo. p53's transcriptional activity is commonly increased by DNA damage. However, GSK3β kinase activity was inhibited in response to DNA damage, suggesting that GSK3β regulation of p53 is not involved in the p53-DNA damage response. Conclusions GSK3β can regulate p53's transcriptional activity by phosphorylating serine 33. However, GSK3β does not appear to be part of the p53-DNA damage response pathway. Instead, GSK3β may provide the link between p53 and non-DNA damage mechanisms for p53 activation.

  16. PRIMA-1Met suppresses colorectal cancer independent of p53 by targeting MEK.

    Science.gov (United States)

    Lu, Tao; Zou, Yanmei; Xu, Guogang; Potter, Jane A; Taylor, Garry L; Duan, Qiuhong; Yang, Qin; Xiong, Huihua; Qiu, Hong; Ye, Dawei; Zhang, Peng; Yu, Shiying; Yuan, Xianglin; Zhu, Feng; Wang, Yihua; Xiong, Hua

    2016-12-13

    PRIMA-1Met is the methylated PRIMA-1 (p53 reactivation and induction of massive apoptosis) and could restore tumor suppressor function of mutant p53 and induce p53 dependent apoptosis in cancer cells harboring mutant p53. However, p53 independent activity of PRIMA-1Met remains elusive. Here we reported that PRIMA-1Met attenuated colorectal cancer cell growth irrespective of p53 status. Kinase profiling revealed that mitogen-activated or extracellular signal-related protein kinase (MEK) might be a potential target of PRIMA-1Met. Pull-down binding and ATP competitive assay showed that PRIMA-1Met directly bound MEK in vitro and in cells. Furthermore, the direct binding sites of PRIMA-1Met were explored by using a computational docking model. Treatment of colorectal cancer cells with PRIMA-1Met inhibited p53-independent phosphorylation of MEK, which in turn impaired anchorage-independent cell growth in vitro. Moreover, PRIMA-1Met suppressed colorectal cancer growth in xenograft mouse model by inhibiting MEK1 activity.Taken together, our findings demonstrate a novel p53-independent activity of PRIMA-1Met to inhibit MEK and suppress colorectal cancer growth.

  17. Expression of TP53 isoforms p53β or p53γ enhances chemosensitivity in TP53(null cell lines.

    Directory of Open Access Journals (Sweden)

    Elisabeth Silden

    Full Text Available The carboxy-terminal truncated p53 alternative spliced isoforms, p53β and p53γ, are expressed at disparate levels in cancer and are suggested to influence treatment response and therapy outcome. However, their functional role in cancer remains to be elucidated. We investigated their individual functionality in the p53(null background of cell lines H1299 and SAOS-2 by stable retroviral transduction or transient transfection. Expression status of p53β and p53γ protein was found to correlate with increased response to camptothecin and doxorubicin chemotherapy. Decreased DNA synthesis and clonogenicity in p53β and p53γ congenic H1299 was accompanied by increased p21((CIP1/WAF1, Bax and Mdm2 proteins. Chemotherapy induced p53 isoform degradation, most prominent for p53γ. The proteasome inhibitor bortezomib substantially increased basal p53γ protein level, while the level of p53β protein was unaffected. Treatment with dicoumarol, a putative blocker of the proteasome-related NAD(PH quinone oxidoreductase NQO1, effectively attenuated basal p53γ protein level in spite of bortezomib treatment. Although in vitro proliferation and clonogenicity assays indicated a weak suppressive effect by p53β and p53γ expression, studies of in vivo subcutaneous H1299 tumor growth demonstrated a significantly increased growth by expression of either p53 isoforms. This study suggests that p53β and p53γ share functionality in chemosensitizing and tumor growth enhancement but comprise distinct regulation at the protein level.

  18. Mdm2’s Dilemma: To Degrade or To Translate p53?

    OpenAIRE

    2012-01-01

    In this issue of Cancer Cell, Gajjar et al. provide insight into how Mdm2 can both inhibit and enhance p53 activity. In the basal setting, Mdm2 binds p53 and promotes p53 degradation. Under stress conditions, ATM-dependent phosphorylation of Mdm2 results in its recruitment to p53 mRNA, thereby stimulating p53 translation.

  19. Direct interaction of the hepatitis B virus HBx protein with p53 leads to inhibition by HBx of p53 response element-directed transactivation.

    OpenAIRE

    1995-01-01

    Hepatitis B virus is a major risk factor in human hepatocellular carcinomas. We have used protein affinity chromatography to show that the 17-kDa hepatitis B virus gene product, HBx, binds directly to the human tumor suppressor gene product, p53. Interaction of HBx with p53 did not prevent p53 from specifically binding DNA. Instead, HBx enhanced p53's oligomerization state on a DNA oligonucleotide containing a p53 response element. Optimal binding of HBx to p53 required intact p53, but weaker...

  20. Zn(II)-curc targets p53 in thyroid cancer cells.

    Science.gov (United States)

    Garufi, Alessia; D'Orazi, Valerio; Crispini, Alessandra; D'Orazi, Gabriella

    2015-10-01

    TP53 mutation is a common event in many cancers, including thyroid carcinoma. Defective p53 activity promotes cancer resistance to therapies and a more malignant phenotype, acquiring oncogenic functions. Rescuing the function of mutant p53 (mutp53) protein is an attractive anticancer therapeutic strategy. Zn(II)-curc is a novel small molecule that has been shown to target mutp53 protein in several cancer cells, but its effect in thyroid cancer cells remains unclear. Here, we investigated whether Zn(II)-curc could affect p53 in thyroid cancer cells with both p53 mutation (R273H) and wild-type p53. Zn(II)-curc induced mutp53H273 downregulation and reactivation of wild-type functions, such as binding to canonical target promoters and target gene transactivation. This latter effect was similar to that induced by PRIMA-1. In addition, Zn(II)-curc triggered p53 target gene expression in wild-type p53-carrying cells. In combination treatments, Zn(II)-curc enhanced the antitumor activity of chemotherapeutic drugs, in both mutant and wild-type-carrying cancer cells. Taken together, our data indicate that Zn(II)-curc promotes the reactivation of p53 in thyroid cancer cells, providing in vitro evidence for a potential therapeutic approach in thyroid cancers.

  1. P53 suppresses expression of the 14-3-3gamma oncogene

    Directory of Open Access Journals (Sweden)

    Qi Wenqing

    2011-08-01

    Full Text Available Abstract Background 14-3-3 proteins are a family of highly conserved proteins that are involved in a wide range of cellular processes. Recent evidence indicates that some of these proteins have oncogenic activity and that they may promote tumorigenesis. We previously showed that one of the 14-3-3 family members, 14-3-3gamma, is over expressed in human lung cancers and that it can induce transformation of rodent cells in vitro. Methods qRTPCR and Western blot analysis were performed to examine 14-3-3gamma expression in non-small cell lung cancers (NSCLC. Gene copy number was analyzed by qPCR. P53 mutations were detected by direct sequencing and also by western blot. CHIP and yeast one hybrid assays were used to detect p53 binding to 14-3-3gamma promoter. Results Quantitative rtPCR results showed that the expression level of 14-3-3gamma was elevated in the majority of NSCLC that we examined which was also consistent with protein expression. Further analysis of the expression pattern of 14-3-3gamma in lung tumors showed a correlation with p53 mutations suggesting that p53 might suppress 14-3-3 gamma expression. Analysis of the gamma promoter sequence revealed the presence of a p53 consensus binding motif and in vitro assays demonstrated that wild-type p53 bound to this motif when activated by ionizing radiation. Deletion of the p53 binding motif eliminated p53's ability to suppress 14-3-3gamma expression. Conclusion Increased expression of 14-3-3gamma in lung cancer coincides with loss of functional p53. Hence, we propose that 14-3-3gamma's oncogenic activities cooperate with loss of p53 to promote lung tumorigenesis.

  2. Autoregulatory control of the p53 response by Siah-1L-mediated HIPK2 degradation.

    Science.gov (United States)

    Calzado, Marco A; de la Vega, Laureano; Muñoz, Eduardo; Schmitz, M Lienhard

    2009-10-01

    The different activities of the tumor suppressor p53 are tightly regulated by various negative and positive feedback loops, which allow accurate control of its function. Here we show that the p53-inducible ubiquitin E3 ligase Siah-1L can bind to the p53 phosphorylating kinase HIPK2 and thus allows its ubiquitination and proteasomal elimination. Siah-1L also eliminates the HIPK family member HIPK3, indicating that its activity is not restricted to one member of the HIPK family. The stimulating effect of HIPK2 on p53-triggered transcription is counteracted by Siah-1L, thus showing the occurrence of another negative feedback loop controlling the p53 response.

  3. Mutant p53 protein localized in the cytoplasm inhibits autophagy.

    Science.gov (United States)

    Morselli, Eugenia; Tasdemir, Ezgi; Maiuri, Maria Chiara; Galluzzi, Lorenzo; Kepp, Oliver; Criollo, Alfredo; Vicencio, José Miguel; Soussi, Thierry; Kroemer, Guido

    2008-10-01

    The knockout, knockdown or chemical inhibition of p53 stimulates autophagy. Moreover, autophagy-inducing stimuli such as nutrient depletion, rapamycin or lithium cause the depletion of cytoplasmic p53, which in turn is required for the induction of autophagy. Here, we show that retransfection of p53(-/-) HCT 116 colon carcinoma cells with wild type p53 decreases autophagy down to baseline levels. Surprisingly, one third among a panel of 22 cancer-associated p53 single amino acid mutants also inhibited autophagy when transfected into p53(-/-) cells. Those variants of p53 that preferentially localize to the cytoplasm effectively repressed autophagy, whereas p53 mutants that display a prominently nuclear distribution failed to inhibit autophagy. The investigation of a series of deletion mutants revealed that removal of the DNA-binding domain from p53 fails to interfere with its role in the regulation of autophagy. Altogether, these results identify the cytoplasmic localization of p53 as the most important feature for p53-mediated autophagy inhibition. Moreover, the structural requirements for the two biological activities of extranuclear p53, namely induction of apoptosis and inhibition of autophagy, are manifestly different.

  4. Translational Control Protein 80 Stimulates IRES-Mediated Translation of p53 mRNA in Response to DNA Damage

    Directory of Open Access Journals (Sweden)

    Marie-Jo Halaby

    2015-01-01

    Full Text Available Synthesis of the p53 tumor suppressor increases following DNA damage. This increase and subsequent activation of p53 are essential for the protection of normal cells against tumorigenesis. We previously discovered an internal ribosome entry site (IRES that is located at the 5′-untranslated region (UTR of p53 mRNA and found that the IRES activity increases following DNA damage. However, the mechanism underlying IRES-mediated p53 translation in response to DNA damage is still poorly understood. In this study, we discovered that translational control protein 80 (TCP80 has increased binding to the p53 mRNA in vivo following DNA damage. Overexpression of TCP80 also leads to increased p53 IRES activity in response to DNA damage. TCP80 has increased association with RNA helicase A (RHA following DNA damage and overexpression of TCP80, along with RHA, leads to enhanced expression of p53. Moreover, we found that MCF-7 breast cancer cells with decreased expression of TCP80 and RHA exhibit defective p53 induction following DNA damage and diminished expression of its downstream target PUMA, a proapoptotic protein. Taken together, our discovery of the function of TCP80 and RHA in regulating p53 IRES and p53 induction following DNA damage provides a better understanding of the mechanisms that regulate IRES-mediated p53 translation in response to genotoxic stress.

  5. Mouse modeling of the MDM2/MDMX-p53 signaling axis.

    Science.gov (United States)

    Tackmann, Nicole R; Zhang, Yanping

    2017-01-17

    It is evident that p53 activity is critical for tumor prevention and stress response through its transcriptional activation of genes affecting cellular senescence, apoptosis, cellular metabolism, and DNA repair. The regulation of p53 is highly complex, and MDM2 and MDMX are thought to be critical for deciding the fate of p53, both through inhibitory binding and posttranslational modification. Many mouse models have been generated to study the regulation of p53 in vivo, and they have altered our interpretations of how p53 is regulated by MDM2 and MDMX. Although MDM2 is absolutely required for p53 regulation, certain functions are dispensable under unstressed conditions, including the ability of MDM2 to degrade p53. MDMX, on the other hand, may only be required in select situations, like embryogenesis. These models have also clarified how cellular stress signals modify the p53-inhibiting activities of MDM2 and MDMX in vivo It is clear that more work will need to be performed to further understand the contexts for each of these signals and the requirements of various MDM2 and MDMX functions. Here, we will discuss what we have learned from mouse modeling of MDM2 and MDMX and underscore the ways in which these models could inform future therapies.

  6. Structures of oncogenic, suppressor and rescued p53 core-domain variants: mechanisms of mutant p53 rescue

    Energy Technology Data Exchange (ETDEWEB)

    Wallentine, Brad D.; Wang, Ying; Tretyachenko-Ladokhina, Vira; Tan, Martha; Senear, Donald F. [University of California, Irvine, Irvine, CA 92697 (United States); Luecke, Hartmut, E-mail: hudel@uci.edu [University of California, Irvine, Irvine, CA 92697 (United States); University of California, Irvine, Irvine, CA 92697 (United States); University of California, Irvine, Irvine, CA 92697 (United States); University of California, Irvine, Irvine, CA 92697 (United States); Universidad del Pais Vasco, 48940 Leioa (Spain)

    2013-10-01

    X-ray crystallographic structures of four p53 core-domain variants were determined in order to gain insights into the mechanisms by which certain second-site suppressor mutations rescue the function of a significant number of cancer mutations of the tumor suppressor protein p53. To gain insights into the mechanisms by which certain second-site suppressor mutations rescue the function of a significant number of cancer mutations of the tumor suppressor protein p53, X-ray crystallographic structures of four p53 core-domain variants were determined. These include an oncogenic mutant, V157F, two single-site suppressor mutants, N235K and N239Y, and the rescued cancer mutant V157F/N235K/N239Y. The V157F mutation substitutes a smaller hydrophobic valine with a larger hydrophobic phenylalanine within strand S4 of the hydrophobic core. The structure of this cancer mutant shows no gross structural changes in the overall fold of the p53 core domain, only minor rearrangements of side chains within the hydrophobic core of the protein. Based on biochemical analysis, these small local perturbations induce instability in the protein, increasing the free energy by 3.6 kcal mol{sup −1} (15.1 kJ mol{sup −1}). Further biochemical evidence shows that each suppressor mutation, N235K or N239Y, acts individually to restore thermodynamic stability to V157F and that both together are more effective than either alone. All rescued mutants were found to have wild-type DNA-binding activity when assessed at a permissive temperature, thus pointing to thermodynamic stability as the critical underlying variable. Interestingly, thermodynamic analysis shows that while N239Y demonstrates stabilization of the wild-type p53 core domain, N235K does not. These observations suggest distinct structural mechanisms of rescue. A new salt bridge between Lys235 and Glu198, found in both the N235K and rescued cancer mutant structures, suggests a rescue mechanism that relies on stabilizing the

  7. Gain of oncogenic function of p53 mutants regulates E-cadherin expression uncoupled from cell invasion in colon cancer cells.

    Science.gov (United States)

    Roger, Lauréline; Jullien, Laurent; Gire, Véronique; Roux, Pierre

    2010-04-15

    Mutations in the p53 tumour suppressor gene are associated clinically with tumour progression and metastasis. Downregulation of the E-cadherin cell-cell adhesion molecule is a key event for epithelial to mesenchymal transition (EMT) in tumour progression. Here, we show that wild-type p53 induced to adopt a mutant conformation, and hot-spot p53 mutants, which are both transcriptionally inactive, downregulate E-cadherin expression in the colon carcinoma cell line HCT116. Downregulation of E-cadherin occurred concomitantly with the upregulation of Slug and Zeb-1, transcriptional factors known to repress E-cadherin gene expression. In addition, knockdown of Slug and Zeb-1 expression diminished p53-mediated E-cadherin repression. Knocking down endogenous mutant p53 in MDA-MB-231 and SW620 cancer cell lines lacking E-cadherin protein restored the expression of E-cadherin. Complete loss of E-cadherin expression in HCT116 cells induced morphological alterations along with upregulation of vimentin, a mesenchymal marker. These changes characteristic of the EMT phenotype were, however, not sufficient to confer invasiveness in a three-dimensional matrix. Downregulation of E-cadherin by mutant p53 was not required to promote the invasive phenotype induced by inactivation of p53. These findings indicate that independent control of E-cadherin expression and cell motility could be essential molecular events in p53 mutant-induced invasive phenotypes.

  8. A novel radiation-induced p53 mutation is not implicated in radiation resistance via a dominant-negative effect.

    Directory of Open Access Journals (Sweden)

    Yunguang Sun

    Full Text Available Understanding the mutations that confer radiation resistance is crucial to developing mechanisms to subvert this resistance. Here we describe the creation of a radiation resistant cell line and characterization of a novel p53 mutation. Treatment with 20 Gy radiation was used to induce mutations in the H460 lung cancer cell line; radiation resistance was confirmed by clonogenic assay. Limited sequencing was performed on the resistant cells created and compared to the parent cell line, leading to the identification of a novel mutation (del at the end of the DNA binding domain of p53. Levels of p53, phospho-p53, p21, total caspase 3 and cleaved caspase 3 in radiation resistant cells and the radiation susceptible (parent line were compared, all of which were found to be similar. These patterns held true after analysis of p53 overexpression in H460 cells; however, H1299 cells transfected with mutant p53 did not express p21, whereas those given WT p53 produced a significant amount, as expected. A luciferase assay demonstrated the inability of mutant p53 to bind its consensus elements. An MTS assay using H460 and H1299 cells transfected with WT or mutant p53 showed that the novel mutation did not improve cell survival. In summary, functional characterization of a radiation-induced p53 mutation in the H460 lung cancer cell line does not implicate it in the development of radiation resistance.

  9. Whole-genome cartography of p53 response elements ranked on transactivation potential.

    Science.gov (United States)

    Tebaldi, Toma; Zaccara, Sara; Alessandrini, Federica; Bisio, Alessandra; Ciribilli, Yari; Inga, Alberto

    2015-06-17

    Many recent studies using ChIP-seq approaches cross-referenced to trascriptome data and also to potentially unbiased in vitro DNA binding selection experiments are detailing with increasing precision the p53-directed gene regulatory network that, nevertheless, is still expanding. However, most experiments have been conducted in established cell lines subjected to specific p53-inducing stimuli, both factors potentially biasing the results. We developed p53retriever, a pattern search algorithm that maps p53 response elements (REs) and ranks them according to predicted transactivation potentials in five classes. Besides canonical, full site REs, we developed specific pattern searches for non-canonical half sites and 3/4 sites and show that they can mediate p53-dependent responsiveness of associated coding sequences. Using ENCODE data, we also mapped p53 REs in about 44,000 distant enhancers and identified a 16-fold enrichment for high activity REs within those sites in the comparison with genomic regions near transcriptional start sites (TSS). Predictions from our pattern search were cross-referenced to ChIP-seq, ChIP-exo, expression, and various literature data sources. Based on the mapping of predicted functional REs near TSS, we examined expression changes of thirteen genes as a function of different p53-inducing conditions, providing further evidence for PDE2A, GAS6, E2F7, APOBEC3H, KCTD1, TRIM32, DICER, HRAS, KITLG and TGFA p53-dependent regulation, while MAP2K3, DNAJA1 and potentially YAP1 were identified as new direct p53 target genes. We provide a comprehensive annotation of canonical and non-canonical p53 REs in the human genome, ranked on predicted transactivation potential. We also establish or corroborate direct p53 transcriptional control of thirteen genes. The entire list of identified and functionally classified p53 REs near all UCSC-annotated genes and within ENCODE mapped enhancer elements is provided. Our approach is distinct from, and complementary

  10. The Mechanism of p53 Rescue by SUSP4.

    Science.gov (United States)

    Kim, Do-Hyoung; Lee, Chewook; Lee, Si-Hyung; Kim, Kyung-Tae; Han, Joan J; Cha, Eun-Ji; Lim, Ji-Eun; Cho, Ye-Jin; Hong, Seung-Hee; Han, Kyou-Hoon

    2017-01-24

    p53 is an important tumor-suppressor protein deactivation of which by mdm2 results in cancers. A SUMO-specific protease 4 (SUSP4) was shown to rescue p53 from mdm2-mediated deactivation, but the mechanism is unknown. The discovery by NMR spectroscopy of a "p53 rescue motif" in SUSP4 that disrupts p53-mdm2 binding is presented. This 29-residue motif is pre-populated with two transient helices connected by a hydrophobic linker. The helix at the C-terminus binds to the well-known p53-binding pocket in mdm2 whereas the N-terminal helix serves as an affinity enhancer. The hydrophobic linker binds to a previously unidentified hydrophobic crevice in mdm2. Overall, SUSP4 appears to use two synergizing modules, the p53 rescue motif described here and a globular-structured SUMO-binding catalytic domain, to stabilize p53. A p53 rescue motif peptide exhibits an anti-tumor activity in cancer cell lines expressing wild-type p53. A pre-structures motif in the intrinsically disordered proteins is thus important for target recognition.

  11. Identification of the core promoter of STK11 gene and its transcriptional regulation by p53

    Institute of Scientific and Technical Information of China (English)

    Maojin Yao; Chenjie Li; Yi Chu; Fei Wang; Xiaoliu Shi; Yongjun Wang; Hongwei Shen; Wenfeng Ning; Jianguang Tang; Xiangping Wang; Jie Li; Shiquang Zhou; Xin Yi

    2008-01-01

    Peutz-Jeghers syndrome (PJS) is an autosomal dominant disease characterized by mucocutaneous pigmentation and hamartomatous polyps. Most cases of PJS involve the inactivation of germline mutations in the serine/threonine kinase gene STK11 which is also known as LKB1. The function of STK11 was previously linked to the tumor suppressor p53 and was shown to activate the p53 target p21/ WAF1. Recently, STK11 was reported to be interacting with p53 physically in the nucleus and it can directly or indirectly phosphorylate p53. Here we characterized the 5'-flanking region of human STK11 gene and identified a 161-bp fragment with promoter activity. Sequence analysis, mutagenesis and gel shift studies revealed a binding site of Spl and p53, which affects the promoter activity. Mutation analyses showed that this fragment was required for p53-mediated transcriptional activation. This transcriptional activation was further confirmed by real-time quantitative RT-PCR and Western blot analysis. Transient transfection of p53 expression plasmid into fetal liver cell lines increased STK11 mRNA and protein levels. In conclusion, our results reveal a new role for p53 in elevating STK11 gene expression via a positive feedback pattern.

  12. Prospective virtual screening for novel p53-MDM2 inhibitors using ultrafast shape recognition

    Science.gov (United States)

    Patil, Sachin P.; Ballester, Pedro J.; Kerezsi, Cassidy R.

    2014-02-01

    The p53 protein, known as the guardian of genome, is mutated or deleted in approximately 50 % of human tumors. In the rest of the cancers, p53 is expressed in its wild-type form, but its function is inhibited by direct binding with the murine double minute 2 (MDM2) protein. Therefore, inhibition of the p53-MDM2 interaction, leading to the activation of tumor suppressor p53 protein presents a fundamentally novel therapeutic strategy against several types of cancers. The present study utilized ultrafast shape recognition (USR), a virtual screening technique based on ligand-receptor 3D shape complementarity, to screen DrugBank database for novel p53-MDM2 inhibitors. Specifically, using 3D shape of one of the most potent crystal ligands of MDM2, MI-63, as the query molecule, six compounds were identified as potential p53-MDM2 inhibitors. These six USR hits were then subjected to molecular modeling investigations through flexible receptor docking followed by comparative binding energy analysis. These studies suggested a potential role of the USR-selected molecules as p53-MDM2 inhibitors. This was further supported by experimental tests showing that the treatment of human colon tumor cells with the top USR hit, telmisartan, led to a dose-dependent cell growth inhibition in a p53-dependent manner. It is noteworthy that telmisartan has a long history of safe human use as an approved anti-hypertension drug and thus may present an immediate clinical potential as a cancer therapeutic. Furthermore, it could also serve as a structurally-novel lead molecule for the development of more potent, small-molecule p53-MDM2 inhibitors against variety of cancers. Importantly, the present study demonstrates that the adopted USR-based virtual screening protocol is a useful tool for hit identification in the domain of small molecule p53-MDM2 inhibitors.

  13. P53 mutations and cancer: a tight linkage.

    Science.gov (United States)

    Perri, Francesco; Pisconti, Salvatore; Della Vittoria Scarpati, Giuseppina

    2016-12-01

    P53 is often mutated in solid tumors, in fact, somatic changes involving the gene encoding for p53 (TP53) have been discovered in more than 50% of human malignancies and several data confirmed that p53 mutations represent an early event in cancerogenesis. Main p53 functions consist in cell cycle arrest, DNA repair, senescence and apoptosis induction in response to mutagenic stimuli, and, to exert those functions, p53 acts as transcriptional factor. Recent data have highlighted another very important role of p53, consisting in regulate cell metabolism and cell response to oxidative stress. Majority of tumor suppressor genes, such as adenomatous polyposis coli (APC), retinoblastoma-associated protein (RB) and Von-Hippel-Lindau (VHL) are inactivated by deletion or early truncation mutations in tumors, resulting in the decreased or loss of expression of their proteins. Differently, most p53 mutations in human cancer are missense mutations, which result in the production of full-length mutant p53 proteins. It has been reported that mutant p53 proteins and wild type p53 proteins often regulate same cellular biological processes with opposite effects. So, mutant p53 has been reported to supply the cancer cells of glucose and nutrients, and, to avoid reactive oxygen species (ROS) mediated damage during oxidative stress. These last features are able to render tumor cells resistant to ionizing radiations and chemotherapy. A future therapeutic approach in tumors bearing p53 mutations may be to deplete cancer cells of their energy reserves and antioxidants.

  14. Tumor suppressor p53 meets microRNAs

    OpenAIRE

    2011-01-01

    Tumor suppressor p53 plays a central role in tumor prevention. As a transcription factor, p53 mainly exerts its function through transcription regulation of its target genes to initiate various cellular responses. To maintain its proper function, p53 is tightly regulated by a wide variety of regulators in cells. Thus, p53, its regulators and regulated genes form a complex p53 network which is composed of hundreds of genes and their products. microRNAs (miRNAs) are a class of endogenously expr...

  15. Yes-associated protein (YAP) increases chemosensitivity of hepatocellular carcinoma cells by modulation of p53.

    Science.gov (United States)

    Bai, Nan; Zhang, Chunyan; Liang, Ning; Zhang, Zhuhong; Chang, Antao; Yin, Jing; Li, Zongjin; Luo, Na; Tan, Xiaoyue; Luo, Na; Luo, Yunping; Xiang, Rong; Li, Xiru; Reisfeld, Ralph A; Stupack, Dwayne; Lv, Dan; Liu, Chenghu

    2013-06-01

    The yes-associated protein (YAP) transcription co-activator has been reported either as an oncogene candidate or a tumor suppressor. Liver tissue chips revealed that about 51.4% human hepatocellular carcinoma (HCC) samples express YAP and 32.9% HCC samples express phosphorylated YAP. In this study, we found that chemotherapy increased YAP protein expression and nuclear translocation in HepG2 cells, as well as p53 protein expression and nuclear translocation. However, little is known about YAP functions during chemotherapy. Our results show that overexpression of YAP increases chemosensitivity of HepG2 cells during chemotherapy. Dominant negative transfection of Flag-S94A (TEAD binding domain mutant) or Flag-W1W2 (WW domain mutant) to HepG2 cells decreases p53 expression/ nuclear translocation and chemosensitivity when compared with control HepG2 cells. Furthermore, rescue transfection of Flag-5SA-S94A or Flag-5SA-W1W2, respectively to HepG2 cells regains p53 expression/nuclear translocation and chemosensitivity. These results indicate that YAP promotes chemosensitivity by modulating p53 during chemotherapy and both TEAD and WW binding domains are required for YAP-mediated p53 function. ChIP assay results also indicated that YAP binds directly to the p53 promoter to improve its expression. In addition, p53 could positively feedback YAP expression through binding to the YAP promoter. Taken together, our current data indicate that YAP functions as a tumor suppressor that enhances apoptosis by modulating p53 during chemotherapy.

  16. Chemical Variations on the p53 Reactivation Theme

    Directory of Open Access Journals (Sweden)

    Carlos J. A. Ribeiro

    2016-05-01

    Full Text Available Among the tumor suppressor genes, p53 is one of the most studied. It is widely regarded as the “guardian of the genome”, playing a major role in carcinogenesis. In fact, direct inactivation of the TP53 gene occurs in more than 50% of malignancies, and in tumors that retain wild-type p53 status, its function is usually inactivated by overexpression of negative regulators (e.g., MDM2 and MDMX. Hence, restoring p53 function in cancer cells represents a valuable anticancer approach. In this review, we will present an updated overview of the most relevant small molecules developed to restore p53 function in cancer cells through inhibition of the p53-MDMs interaction, or direct targeting of wild-type p53 or mutated p53. In addition, optimization approaches used for the development of small molecules that have entered clinical trials will be presented.

  17. Necdin, a p53-target gene, is an inhibitor of p53-mediated growth arrest.

    Directory of Open Access Journals (Sweden)

    Julie Lafontaine

    Full Text Available In vitro, cellular immortalization and transformation define a model for multistep carcinogenesis and current ongoing challenges include the identification of specific molecular events associated with steps along this oncogenic pathway. Here, using NIH3T3 cells, we identified transcriptionally related events associated with the expression of Polyomavirus Large-T antigen (PyLT, a potent viral oncogene. We propose that a subset of these alterations in gene expression may be related to the early events that contribute to carcinogenesis. The proposed tumor suppressor Necdin, known to be regulated by p53, was within a group of genes that was consistently upregulated in the presence of PyLT. While Necdin is induced following p53 activation with different genotoxic stresses, Necdin induction by PyLT did not involve p53 activation or the Rb-binding site of PyLT. Necdin depletion by shRNA conferred a proliferative advantage to NIH3T3 and PyLT-expressing NIH3T3 (NIHLT cells. In contrast, our results demonstrate that although overexpression of Necdin induced a growth arrest in NIH3T3 and NIHLT cells, a growing population rapidly emerged from these arrested cells. This population no longer showed significant proliferation defects despite high Necdin expression. Moreover, we established that Necdin is a negative regulator of p53-mediated growth arrest induced by nutlin-3, suggesting that Necdin upregulation could contribute to the bypass of a p53-response in p53 wild type tumors. To support this, we characterized Necdin expression in low malignant potential ovarian cancer (LMP where p53 mutations rarely occur. Elevated levels of Necdin expression were observed in LMP when compared to aggressive serous ovarian cancers. We propose that in some contexts, the constitutive expression of Necdin could contribute to cancer promotion by delaying appropriate p53 responses and potentially promote genomic instability.

  18. Mechanisms of p53-Mediated Apoptosis

    Science.gov (United States)

    2007-03-01

    BD) within residues 364 to 393. AD1 is important for transactivation; this domain contains residues that contact the basal transcriptional machinery...256 IGFBP3, a genomic fragment of the IGFBP3 promoter spanning nucleo - tides (nt) 256 to 72, with 1 being the transcriptional start site, was...BD) bind to the IGFBP3 promoter, but full-length p53 cannot recruit the basal transcriptional machinery due to its association with HDAC activity (Fig

  19. Nitration of the tumor suppressor protein, p53, at tyrosine 327 promotes p53 oligomerization and activation

    Science.gov (United States)

    Yakovlev, Vasily A.; Bayden, Alexander S.; Graves, Paul R.; Kellogg, Glen E.; Mikkelsen, Ross B.

    2010-01-01

    Previous studies demonstrate that nitric oxide (NO) promotes p53 transcriptional activity by a classical DNA-damage-responsive mechanism involving activation of ATM/ATR and phosphorylation of p53. These studies intentionally used high doses of NO-donors to achieve the maximum DNA-damage. However, lower concentrations of NO donors also stimulate rapid and unequivocal nuclear retention of p53, but apparently do not require ATM/ATR-dependent p53 phosphorylation or total p53 protein accumulation. To identify possible mechanisms for p53 activation at low NO levels, the role of Tyr nitration in p53 activation was evaluated. Low concentrations of the NO donor, DETA NONOate (nitrate Tyr327 within the tetramerization domain promoting p53 oligomerization, nuclear accumulation and increased DNA-binding activity without p53 Ser15 phosphorylation. Molecular modeling indicates that nitration of one Tyr327 stabilizes the dimer by about 2.67 kcal mol−1. Significant quantitative and qualitative differences in the patterns of p53-target gene modulation by low (50μM), non DNA-damaging and high (500μM), DNA-damaging NO donor concentrations was shown. These results demonstrate a new post-translational mechanism for modulating p53 transcriptional activity responsive to low NO concentrations and independent of DNA damage signaling. PMID:20499882

  20. Separase loss of function cooperates with the loss of p53 in the initiation and progression of T- and B-cell lymphoma, leukemia and aneuploidy in mice.

    Directory of Open Access Journals (Sweden)

    Malini Mukherjee

    Full Text Available BACKGROUND: Cohesin protease Separase plays a key role in faithful segregation of sister chromatids by cleaving the cohesin complex at the metaphase to anaphase transition. Homozygous deletion of ESPL1 gene that encodes Separase protein results in embryonic lethality in mice and Separase overexpression lead to aneuploidy and tumorigenesis. However, the effect of Separase haploinsufficiency has not been thoroughly investigated. METHODOLOGY/PRINCIPAL FINDINGS: Here we examined the effect of ESPL1 heterozygosity using a hypomorphic mouse model that has reduced germline Separase activity. We report that while ESPL1 mutant (ESPL1 (+/hyp mice have a normal phenotype, in the absence of p53, these mice develop spontaneous T- and B-cell lymphomas, and leukemia with a significantly shortened latency as compared to p53 null mice. The ESPL1 hypomorphic, p53 heterozygous transgenic mice (ESPL1(+/hyp, p53(+/- also show a significantly reduced life span with an altered tumor spectrum of carcinomas and sarcomas compared to p53(+/- mice alone. Furthermore, ESPL1(+/hyp, p53(-/- mice display significantly higher levels of genetic instability and aneuploidy in normal cells, as indicated by the abnormal metaphase counts and SKY analysis of primary splenocytes. CONCLUSIONS/SIGNIFICANCE: Our results indicate that reduced levels of Separase act synergistically with loss of p53 in the initiation and progression of B- and T- cell lymphomas, which is aided by increased chromosomal missegregation and accumulation of genomic instability. ESPL1(+/hyp, p53(-/- mice provide a new animal model for mechanistic study of aggressive lymphoma and also for preclinical evaluation of new agents for its therapy.

  1. Tumor suppressor p53 meets microRNAs

    Institute of Scientific and Technical Information of China (English)

    Zhaohui Feng; Cen Zhang; Rui Wu; Wenwei Hu

    2011-01-01

    Tumor suppressor p53 plays a central role in tumor prevention. As a transcription factor, p53 mainly exerts its function through transcription regulation of its target genes to initiate various cellular responses. To maintain its proper function, p53 is tightly regulated by a wide variety of regulators in cells. Thus, p53, its regulators and regulated genes form a complex p53 network which is composed of hundreds of genes and their products. microRNAs (miRNAs) are a class of endogenously expressed, small non-coding RNA molecules which play a key role in regulation of gene expression at the post-transcriptional level. Recent studies have demonstrated that miRNAs interact with p53 and its network at multiple levels. p53 regulates the transcription expression and the maturation of a group of miRNAs. On the other hand, miRNAs can regulate the activity and function of p53 through direct repression of p53 or its regulators in cells. These findings have demonstrated that miRNAs are important components in the p53 network, and also added another layer of complexity to the p53 network.

  2. Phosphorylation Regulates the Bound Structure of an Intrinsically Disordered Protein: The p53-TAZ2 Case.

    Directory of Open Access Journals (Sweden)

    Raúl Esteban Ithuralde

    Full Text Available Disordered regions and Intrinsically Disordered Proteins (IDPs are involved in critical cellular processes and may acquire a stable three-dimensional structure only upon binding to their partners. IDPs may follow a folding-after-binding process, known as induced folding, or a folding-before-binding process, known as conformational selection. The transcription factor p53 is involved in the regulation of cellular events that arise upon stress or DNA damage. The p53 domain structure is composed of an N-terminal transactivation domain (p53TAD, a DNA Binding Domain and a tetramerization domain. The activity of TAD is tightly regulated by interactions with cofactors, inhibitors and phosphorylation. To initiate transcription, p53TAD binds to the TAZ2 domain of CBP, a co-transcription factor, and undergoes a folding and binding process, as revealed by the recent NMR structure of the complex. The activity of p53 is regulated by phosphorylation at multiple sites on the TAD domain and recent studies have shown that modifications at three residues affect the binding towards TAZ2. However, we still do not know how these phosphorylations affect the structure of the bound state and, therefore, how they regulate the p53 function. In this work, we have used computational simulations to understand how phosphorylation affects the structure of the p53TAD:TAZ2 complex and regulates the recognition mechanism. Phosphorylation has been proposed to enhance binding by direct interaction with the folded protein or by changing the unbound conformation of IDPs, for example by pre-folding the protein favoring the recognition mechanism. Here, we show an interesting turn in the p53 case: phosphorylation mainly affects the bound structure of p53TAD, highlighting the complexity of IDP protein-protein interactions. Our results are in agreement with previous experimental studies, allowing a clear picture of how p53 is regulated by phosphorylation and giving new insights into how

  3. SPATA18, a Spermatogenesis-Associated Gene, Is a Novel Transcriptional Target of p53 and p63▿

    Science.gov (United States)

    Bornstein, Chamutal; Brosh, Ran; Molchadsky, Alina; Madar, Shalom; Kogan-Sakin, Ira; Goldstein, Ido; Chakravarti, Deepavali; Flores, Elsa R.; Goldfinger, Naomi; Sarig, Rachel; Rotter, Varda

    2011-01-01

    The transcription factor p53 functions not only to suppress tumorigenesis but also to maintain normal development and homeostasis. Although p53 was implicated in different aspects of fertility, including spermatogenesis and implantation, the mechanism underlying p53 involvement in spermatogenesis is poorly resolved. In this study we describe the identification of a spermatogenesis-associated gene, SPATA18, as a novel p53 transcriptional target and show that SPATA18 transcription is induced by p53 in a variety of cell types of both human and mouse origin. p53 binds a consensus DNA motif that resides within the first intron of SPATA18. We describe the spatiotemporal expression patterns of SPATA18 in mouse seminiferous tubules and suggest that SPATA18 transcription is regulated in vivo by p53. We also demonstrate the induction of SPATA18 by p63 and suggest that p63 can compensate for the loss of p53 activity in vivo. Our data not only enrich the known collection of p53 targets but may also provide insights on spermatogenesis defects that are associated with p53 deficiency. PMID:21300779

  4. MicroRNA-24 increases hepatocellular carcinoma cell metastasis and invasion by targeting p53: miR-24 targeted p53.

    Science.gov (United States)

    Chen, Li; Luo, Liang; Chen, Wei; Xu, Hong-Xu; Chen, Fan; Chen, Lian-Zhou; Zeng, Wen-Tao; Chen, Jing-Song; Huang, Xiao-Hui

    2016-12-01

    MicroRNA-24 (miR-24), a member of the miRNA family, functions as an oncogene in various types of human cancer. However, the underlying mechanisms of miR-24 involvement in the development and progression of hepatocellular carcinoma (HCC) remain poorly understood. The present study revealed that miRNA-24 down-regulates p53 through binding to the 3'-UTR of p53 mRNA based on a luciferase reporter assay, and that the expression level of miR-24 could affect the invasion of HCC lines via p53. Down-regulation of p53 significantly attenuated the inhibitory effects of miR-24 knockdown on the invasion of HCC cells, suggesting that miR-24 could be a potential target for HCC treatment. Moreover, our results revealed that miR-24 expression was significantly increased in HCC metastatic tumor tissues compared with matched non-metastatic tumor tissues, and that the up-regulation of miR-24 was significantly associated with down-regulation of p53 in the HCC tissues. In conclusion, this study demonstrates that miR-24 functions as an oncogene in HCC, at least partly by promoting cell invasion through down-regulation of p53. Therefore, miR-24 may be a potential therapeutic target for treatment of HCC.

  5. Science Letters: Screen p53 mutations in hepatocellular carcinoma by FASAY: A novel splicing mutation

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-mo; FU Jing-geng; GE Wang-zhong; ZHU Jiang-yan; WANG Jun-yong; ZHANG Wei; QIAN Wei; HUO Ke-ke

    2007-01-01

    Objective: To establish a routine procedure for the detection of p53 mutations in hepatocellular carcinoma (HCC)surgical resections using the FASAY (functional analysis of separated alleles of p53 on yeast) procedure. Methods: p53 status was analyzed by FASAY and cDNA sequencing in 50 cases of HCC. After the extraction of RNA from the frozen tumor and corresponding normal tissues, reverse transcription RT-PCR was carried out using these samples. The assay can detect mutations of p53mRNA between codons 67 and 347 by the DNA-binding activity of the protein and reveal them as red colonies. Results: Of the 50specimens, 29 (58%) were positive (mutant) by FASAY. Sequencing analysis confirmed that all 29 FASAY positive tumors harbored mutations, and that no mutations were detectable in any FASAY negative tumors. In 29 p53 mutations, 22 mutations were point missense mutation, 5 were deletions and 2 were splicing mutations. A novel splice mutation on splice donor of intron 6was reported, which could produce two different mRNAs, respectively using the nearest upstream and downstream recessive splice donor sites. Conclusion: FASAY is a sensitive method for detecting the various types of p53 mutations in HCC, suggesting that the yeast functional assay for the detection of p53 mutations may be essential for elucidating their clinical significance.

  6. p53 as a target for the treatment of cancer.

    Science.gov (United States)

    Duffy, Michael J; Synnott, Naoise C; McGowan, Patricia M; Crown, John; O'Connor, Darran; Gallagher, William M

    2014-12-01

    TP53 (p53) is the most frequently mutated gene in cancer, being altered in approximately 50% of human malignancies. In most, if not all, cancers lacking mutation, wild-type (WT) p53 is inactivated by interaction with cellular (MDM2/MDM4) or viral proteins, leading to its degradation. Because of its near universal alteration in cancer, p53 is an attractive target for the development of new targeted therapies for this disease. However, until recently, p53 was widely regarded as ‘‘undruggable’’. This situation has now changed, as several compounds have become available that can restore wild-type properties to mutant p53 (e.g., PRIMA-1 and PRIMA-1MET). Other compounds are available that prevent the binding of MDM2/MDM4 to WT p53, thereby blocking its degradation (e.g., nutlins). Anti-mutant p53 compounds are potentially most useful in cancers with a high prevalence of p53 mutations. These include difficult-totreat tumors such as high grade serous ovarian cancer, triple-negative breast cancer and squamous lung cancer. MDM2/4 antagonists, on the other hand, are likely to be efficacious in malignancies in which MDM2 or MDM4 is overexpressed such as sarcomas, neuroblastomas and specific childhood leukemias. Presently, early clinical trials are ongoing evaluating the anti-mutant p53 agent, PRIMA-1MET, and specific MDM2–p53 nutlin antagonists.

  7. Using yeast to determine the functional consequences of mutations in the human p53 tumor suppressor gene: An introductory course-based undergraduate research experience in molecular and cell biology.

    Science.gov (United States)

    Hekmat-Scafe, Daria S; Brownell, Sara E; Seawell, Patricia Chandler; Malladi, Shyamala; Imam, Jamie F Conklin; Singla, Veena; Bradon, Nicole; Cyert, Martha S; Stearns, Tim

    2017-03-04

    The opportunity to engage in scientific research is an important, but often neglected, component of undergraduate training in biology. We describe the curriculum for an innovative, course-based undergraduate research experience (CURE) appropriate for a large, introductory cell and molecular biology laboratory class that leverages students' high level of interest in cancer. The course is highly collaborative and emphasizes the analysis and interpretation of original scientific data. During the course, students work in teams to characterize a collection of mutations in the human p53 tumor suppressor gene via expression and analysis in yeast. Initially, student pairs use both qualitative and quantitative assays to assess the ability of their p53 mutant to activate expression of reporter genes, and they localize their mutation within the p53 structure. Through facilitated discussion, students suggest possible molecular explanations for the transactivation defects displayed by their p53 mutants and propose experiments to test these hypotheses that they execute during the second part of the course. They use a western blot to determine whether mutant p53 levels are reduced, a DNA-binding assay to test whether recognition of any of three p53 target sequences is compromised, and fluorescence microscopy to assay nuclear localization. Students studying the same p53 mutant periodically convene to discuss and interpret their combined data. The course culminates in a poster session during which students present their findings to peers, instructors, and the greater biosciences community. Based on our experience, we provide recommendations for the development of similar large introductory lab courses. © 2016 by The International Union of Biochemistry and Molecular Biology, 45(2):161-178, 2017.

  8. The p53-MDM2 network: from oscillations to apoptosis

    Indian Academy of Sciences (India)

    Indrani Bose; Bhaswar Ghosh

    2007-08-01

    The p53 protein is well-known for its tumour suppressor function. The p53-MDM2 negative feedback loop constitutes the core module of a network of regulatory interactions activated under cellular stress. In normal cells, the level of p53 proteins is kept low by MDM2, i.e. MDM2 negatively regulates the activity of p53. In the case of DNA damage, the p53-mediated pathways are activated leading to cell cycle arrest and repair of the DNA. If repair is not possible due to excessive damage, the p53-mediated apoptotic pathway is activated bringing about cell death. In this paper, we give an overview of our studies on the p53-MDM2 module and the associated pathways from a systems biology perspective. We discuss a number of key predictions, related to some specific aspects of cell cycle arrest and cell death, which could be tested in experiments.

  9. Wild type p53 transcriptionally represses the SALL2 transcription factor under genotoxic stress.

    Directory of Open Access Journals (Sweden)

    Carlos Farkas

    Full Text Available SALL2- a member of the Spalt gene family- is a poorly characterized transcription factor found deregulated in various cancers, which suggests it plays a role in the disease. We previously identified SALL2 as a novel interacting protein of neurotrophin receptors and showed that it plays a role in neuronal function, which does not necessarily explain why or how SALL2 is deregulated in cancer. Previous evidences indicate that SALL2 gene is regulated by the WT1 and AP4 transcription factors. Here, we identified SALL2 as a novel downstream target of the p53 tumor suppressor protein. Bioinformatic analysis of the SALL2 gene revealed several putative p53 half sites along the promoter region. Either overexpression of wild-type p53 or induction of the endogenous p53 by the genotoxic agent doxorubicin repressed SALL2 promoter activity in various cell lines. However R175H, R249S, and R248W p53 mutants, frequently found in the tumors of cancer patients, were unable to repress SALL2 promoter activity, suggesting that p53 specific binding to DNA is important for the regulation of SALL2. Electrophoretic mobility shift assay demonstrated binding of p53 to one of the identified p53 half sites in the Sall2 promoter, and chromatin immunoprecipitation analysis confirmed in vivo interaction of p53 with the promoter region of Sall2 containing this half site. Importantly, by using a p53ER (TAM knockin model expressing a variant of p53 that is completely dependent on 4-hydroxy-tamoxifen for its activity, we show that p53 activation diminished SALL2 RNA and protein levels during genotoxic cellular stress in primary mouse embryo fibroblasts (MEFs and radiosensitive tissues in vivo. Thus, our finding indicates that p53 represses SALL2 expression in a context-specific manner, adding knowledge to the understanding of SALL2 gene regulation, and to a potential mechanism for its deregulation in cancer.

  10. A p53-bound enhancer region controls a long intergenic noncoding RNA required for p53 stress response

    NARCIS (Netherlands)

    Melo, C A; Léveillé, N; Rooijers, K; Wijchers, P J; Geeven, G; Tal, A; Melo, S A; de Laat, W; Agami, R

    2016-01-01

    Genome-wide chromatin studies identified the tumor suppressor p53 as both a promoter and an enhancer-binding transcription factor. As an enhancer factor, p53 can induce local production of enhancer RNAs, as well as transcriptional activation of distal neighboring genes. Beyond the regulation of prot

  11. The p53 pathway in breast cancer

    OpenAIRE

    Gasco, Milena; Shami, Shukri; Crook, Tim

    2002-01-01

    p53 mutation remains the most common genetic change identified in human neoplasia. In breast cancer, p53 mutation is associated with more aggressive disease and worse overall survival. The frequency of mutation in p53 is, however, lower in breast cancer than in other solid tumours. Changes, both genetic and epigenetic, have been identified in regulators of p53 activity and in some downstream transcriptional targets of p53 in breast cancers that express wild-type p53. Molecular pathological an...

  12. Autoantibody recognition mechanisms of p53 epitopes

    Science.gov (United States)

    Phillips, J. C.

    2016-06-01

    There is an urgent need for economical blood based, noninvasive molecular biomarkers to assist in the detection and diagnosis of cancers in a cost-effective manner at an early stage, when curative interventions are still possible. Serum autoantibodies are attractive biomarkers for early cancer detection, but their development has been hindered by the punctuated genetic nature of the ten million known cancer mutations. A landmark study of 50,000 patients (Pedersen et al., 2013) showed that a few p53 15-mer epitopes are much more sensitive colon cancer biomarkers than p53, which in turn is a more sensitive cancer biomarker than any other protein. The function of p53 as a nearly universal "tumor suppressor" is well established, because of its strong immunogenicity in terms of not only antibody recruitment, but also stimulation of autoantibodies. Here we examine dimensionally compressed bioinformatic fractal scaling analysis for identifying the few sensitive epitopes from the p53 amino acid sequence, and show how it could be used for early cancer detection (ECD). We trim 15-mers to 7-mers, and identify specific 7-mers from other species that could be more sensitive to aggressive human cancers, such as liver cancer. Our results could provide a roadmap for ECD.

  13. Targeting the p53 Pathway in Ewing Sarcoma

    Directory of Open Access Journals (Sweden)

    Paul M. Neilsen

    2011-01-01

    Full Text Available The p53 tumour suppressor plays a pivotal role in the prevention of oncogenic transformation. Cancers frequently evade the potent antitumour surveillance mechanisms of p53 through mutation of the TP53 gene, with approximately 50% of all human malignancies expressing dysfunctional, mutated p53 proteins. Interestingly, genetic lesions in the TP53 gene are only observed in 10% of Ewing Sarcomas, with the majority of these sarcomas expressing a functional wild-type p53. In addition, the p53 downstream signaling pathways and DNA-damage cell cycle checkpoints remain functionally intact in these sarcomas. This paper summarizes recent insights into the functional capabilities and regulation of p53 in Ewing Sarcoma, with a particular focus on the cross-talk between p53 and the EWS-FLI1 gene rearrangement frequently associated with this disease. The development of several activators of p53 is discussed, with recent evidence demonstrating the potential of small molecule p53 activators as a promising systemic therapeutic approach for the treatment of Ewing Sarcomas with wild-type p53.

  14. The Proteasome Activator PA28γ, a Negative Regulator of p53, Is Transcriptionally Up-Regulated by p53

    Directory of Open Access Journals (Sweden)

    Zhen-Xing Wan

    2014-02-01

    Full Text Available PA28γ (also called REGγ, 11Sγ or PSME3 negatively regulates p53 activity by promoting its nuclear export and/or degradation. Here, using the RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE method, we identified the transcription start site of the PA28γ gene. Assessment with the luciferase assay demonstrated that the sequence −193 to +16 is the basal promoter. Three p53 binding sites were found within the PA28γ promoter utilizing a bioinformatics approach and were confirmed by chromatin immunoprecipitation and biotinylated DNA affinity precipitation experiments. The p53 protein promotes PA28γ transcription, and p53-stimulated transcription of PA28γ can be inhibited by PA28γ itself. Our results suggest that PA28γ and p53 form a negative feedback loop, which maintains the balance of p53 and PA28γ in cells.

  15. The physical interaction of p53 and plakoglobin is necessary for their synergistic inhibition of migration and invasion

    Science.gov (United States)

    Mehrabani, Vahedah; Churchill, Lucas; Pasdar, Manijeh

    2016-01-01

    Plakoglobin (PG) is a paralog of β-catenin with similar adhesive, but contrasting signalling functions. Although β-catenin has well-known oncogenic function, PG generally acts as a tumor/metastasis suppressor by mechanisms that are just beginning to be deciphered. Previously, we showed that PG interacted with wild type (WT) and a number of mutant p53s, and that its tumor/metastasis suppressor activity may be mediated, at least partially, by this interaction. Here, carcinoma cell lines deficient in both p53 and PG (H1299), or expressing mutant p53 in the absence of PG (SCC9), were transfected with expression constructs encoding WT and different fragments and deletions of p53 and PG, individually or in pairs. Transfectants were characterized for their in vitro growth, migratory and invasive properties and for mapping the interacting domain of p53 and PG. We showed that when coexpressed, p53-WT and PG-WT cooperated to decrease growth, and acted synergistically to significantly reduce cell migration and invasion. The DNA-binding domain of p53 and C-terminal domain of PG mediated p53/PG interaction, and furthermore, the C-terminus of PG played a central role in the inhibition of invasion in association with p53. PMID:27058623

  16. P53 family members modulate the expression of PRODH, but not PRODH2, via intronic p53 response elements.

    Directory of Open Access Journals (Sweden)

    Ivan Raimondi

    Full Text Available The tumor suppressor p53 was previously shown to markedly up-regulate the expression of the PRODH gene, encoding the proline dehydrogenase (PRODH enzyme, which catalyzes the first step in proline degradation. Also PRODH2, which degrades 4-hydroxy-L-proline, a product of protein (e.g. collagen catabolism, was recently described as a p53 target. Here, we confirmed p53-dependent induction of endogenous PRODH in response to genotoxic damage in cell lines of different histological origin. We established that over-expression of TAp73β or TAp63β is sufficient to induce PRODH expression in p53-null cells and that PRODH expression parallels the modulation of endogenous p73 by genotoxic drugs in several cell lines. The p53, p63, and p73-dependent transcriptional activation was linked to specific intronic response elements (REs, among those predicted by bioinformatics tools and experimentally validated by a yeast-based transactivation assay. p53 occupancy measurements were validated in HCT116 and MCF7 human cell lines. Conversely, PRODH2 was not responsive to p63 nor p73 and, at best, could be considered a weak p53 target. In fact, minimal levels of PRODH2 transcript induction by genotoxic stress was observed exclusively in one of four p53 wild-type cell lines tested. Consistently, all predicted p53 REs in PRODH2 were poor matches to the p53 RE consensus and showed very weak responsiveness, only to p53, in the functional assay. Taken together, our results highlight that PRODH, but not PRODH2, expression is under the control of p53 family members, specifically p53 and p73. This supports a deeper link between proteins of the p53-family and metabolic pathways, as PRODH modulates the balance of proline and glutamate levels and those of their derivative alpha-keto-glutarate (α-KG under normal and pathological (tumor conditions.

  17. Function of apoptosis and expression of the proteins Bcl-2, p53 and C-myc in the development of gastric cancer

    Institute of Scientific and Technical Information of China (English)

    An Gao Xu; Shao Guang Li; Ji Hong Liu; Ai Hua Gan

    2001-01-01

    @@INTRODUCTION In China ,the incidence and mortality of gastric cancer rank the second among all cancers. Recent development of cancer [1-20].The aim of this study was investigat the insight of apoptosis and bcl-2, p53 and C-myc protein expression in the development of gastric cancer .

  18. Brca1/p53 deficient mouse breast tumor hemodynamics during hyperoxic respiratory challenge monitored by a novel wide-field functional imaging (WiFI) system

    Science.gov (United States)

    Moy, Austin; Kim, Jae G.; Lee, Eva Y. H. P.; Tromberg, Bruce; Cerussi, Albert; Choi, Bernard

    2009-02-01

    Current imaging modalities allow precise visualization of tumors but do not enable quantitative characterization of the tumor metabolic state. Such quantitative information would enhance our understanding of tumor progression and response to treatment, and to our overall understanding of tumor biology. To address this problem, we have developed a wide-field functional imaging (WiFI) instrument which combines two optical imaging modalities, spatially modulated imaging (MI) and laser speckle imaging (LSI). Our current WiFI imaging protocol consists of multispectral imaging in the near infrared (650-980 nm) spectrum, over a wide (7 cm × 5 cm) field of view. Using MI, the spatially-resolved reflectance of sinusoidal patterns projected onto the tissue is assessed, and optical properties of the tissue are estimated using a Monte Carlo model. From the spatial maps of local absorption and reduced scattering coefficients, tissue composition information is extracted in the form of oxy-, deoxy-, and total hemoglobin concentrations, and percentage of lipid and water. Using LSI, the reflectance of a 785 nm laser speckle pattern on the tissue is acquired and analyzed to compute maps of blood perfusion in the tissue. Tissue metabolism state is estimated from the values of blood perfusion, volume and oxygenation state. We currently are employing the WiFI instrument to study tumor development in a BRCA1/p53 deficient mice breast tumor model. The animals are monitored with WiFI during hyperoxic respiratory challenge. At present, four tumors have been measured with WiFI, and preliminary data suggest that tumor metabolic changes during hyperoxic respiratory challenge can be determined.

  19. Protective role of p53 in acetaminophen hepatotoxicity.

    Science.gov (United States)

    Huo, Yazhen; Yin, Shutao; Yan, Mingzhu; Win, Sanda; Aung Than, Tin; Aghajan, Mariam; Hu, Hongbo; Kaplowitz, Neil

    2017-02-11

    p53 is a tumor suppressor with a pro-death role in many conditions. However, in some contexts, evidence supports a pro-survival function. p53 has been shown to be activated in acetaminophen (APAP) toxicity but the impact of this on toxicity is uncertain. In the present study, we have found that p53 plays a protective role in APAP-induced liver injury. We inhibited p53 using three different approaches in mice, pifithrin-α (PFTα), knockdown of p53 expression with antisense oligonucleotide, and p53 knockout. Mice were treated with APAP (300mg/kg) i.p. and after 24h in all three conditions, the liver injury was more severe as reflected in higher ALT levels and great area of necrosis in histology of the liver. Conversely, a p53 activator, nutlin-3a, decreased the liver injury induced by APAP. In the p53 inhibition models, enhanced sustained JNK activation was seen in the early time course, while the JNK was suppressed with the p53 activator. In conclusion, p53 plays a novel protective role in APAP induced liver injury through inhibiting the activation of JNK, a key mediator in APAP-induced oxidative stress.

  20. The p53-p21-DREAM-CDE/CHR pathway regulates G2/M cell cycle genes.

    Science.gov (United States)

    Fischer, Martin; Quaas, Marianne; Steiner, Lydia; Engeland, Kurt

    2016-01-01

    The tumor suppressor p53 functions predominantly as a transcription factor by activating and downregulating gene expression, leading to cell cycle arrest or apoptosis. p53 was shown to indirectly repress transcription of the CCNB2, KIF23 and PLK4 cell cycle genes through the recently discovered p53-p21-DREAM-CDE/CHR pathway. However, it remained unclear whether this pathway is commonly used. Here, we identify genes regulated by p53 through this pathway in a genome-wide computational approach. The bioinformatic analysis is based on genome-wide DREAM complex binding data, p53-depedent mRNA expression data and a genome-wide definition of phylogenetically conserved CHR promoter elements. We find 210 target genes that are expected to be regulated by the p53-p21-DREAM-CDE/CHR pathway. The target gene list was verified by detailed analysis of p53-dependent repression of the cell cycle genes B-MYB (MYBL2), BUB1, CCNA2, CCNB1, CHEK2, MELK, POLD1, RAD18 and RAD54L. Most of the 210 target genes are essential regulators of G2 phase and mitosis. Thus, downregulation of these genes through the p53-p21-DREAM-CDE/CHR pathway appears to be a principal mechanism for G2/M cell cycle arrest by p53.

  1. p53 and its isoforms in cancer

    OpenAIRE

    2007-01-01

    p53, p63 and p73 are members of the p53 gene family involved in development, differentiation and response to cellular stress. p53 gene is a transcription factor essential for the prevention of cancer formation. The p53 pathway is ubiquitously lost in human cancer either by p53 gene mutation (60% of cancers) or by lost of cell signalling upstream and downstream of p53 in the remaining cancers expressing WTp53 gene. As p53 pathway inactivation is a common denominator to all cancers, the underst...

  2. HDAC6 deacetylates p53 at lysines 381/382 and differentially coordinates p53-induced apoptosis.

    Science.gov (United States)

    Ryu, Hyun-Wook; Shin, Dong-Hee; Lee, Dong Hoon; Choi, Junjeong; Han, Gyoonhee; Lee, Kang Young; Kwon, So Hee

    2017-04-10

    HDAC6-selective inhibitors represent promising new cancer therapeutic agents, but their precise mechanisms of action are not well understood. In particular, p53's role in HDAC6 inhibitor-induced effects has not been fully elucidated. In this study, we show that an HDAC6-selective inhibitor, A452, increased wild-type p53 levels by destabilizing MDM2, but decreased mutant p53 by inducing MDM2 and inhibiting Hsp90-mutant p53 complex formation. Interestingly, HDAC6 levels inversely correlated with p53 acetylation at lysines 381/382 associated with p53 functional activation. A452 blocked HDAC6 nuclear localization, resulting in increased levels of acetylated p53 at Lys381/382. HDAC6 bound to the C-terminal region of p53 via its deacetylase domain. A452 disrupted the HDAC6-Hsp90 chaperone machinery via Hsp90 acetylation and degradation. Furthermore, it chemosensitized cancer cells to the Hsp90 inhibitor 17-AAG. Overall, silencing of HDAC6 showed similar effects. These findings suggest that the anticancer action of HDAC6 inhibitors requires p53 and Hsp90 and targeting of HDAC6 may represent a new therapeutic strategy for cancers regardless of p53's mutation status.

  3. Tumor-suppressive p53 Signaling Empowers Metastatic Inhibitor KLF17-dependent Transcription to Overcome Tumorigenesis in Non-small Cell Lung Cancer.

    Science.gov (United States)

    Ali, Amjad; Bhatti, Muhammad Zeeshan; Shah, Abdus Saboor; Duong, Hong-Quan; Alkreathy, Huda Mohammad; Mohammad, Shah Faisal; Khan, Rahmat Ali; Ahmad, Ayaz

    2015-08-28

    Metastasis, which is controlled by concerted action of multiple genes, is a complex process and is an important cause of cancer death. Krüppel-like factor 17 (KLF17) is a negative regulator of metastasis and epithelial-mesenchymal transition (EMT) during cancer progression. However, the underlying molecular mechanism and biological relevance of KLF17 in cancer cells are poorly understood. Here, we show that tumor suppressor protein p53 plays an integral role to induce KLF17 expression in non-small cell lung cancer (NSCLC). p53 is recruited to the KLF17 promoter and results in the formation of p53-DNA complex. p53 enhances binding of p300 and favors histone acetylation on the KLF17 promoter. Mechanistically, p53 physically interacts with KLF17 and thereby enhances the anti-metastatic function of KLF17. p53 empowers KLF17-mediated EMT genes transcription via enhancing physical association of KLF17 with target gene promoters. Nutlin-3 recruits KLF17 to EMT target gene promoters and results in the formation of KLF17-DNA complex via a p53-dependent pathway. p53 depletion abrogates DNA binding affinity of KLF17 to EMT target gene promoters. KLF17 is critical for p53 cellular activities in NSCLC. Importantly, KLF17 enhances p53 transcription to generate a novel positive feedback loop. KLF17 depletion accelerates lung cancer cell growth in response to chemotherapy. Mechanistically, we found that KLF17 increases the expression of tumor suppressor genes p53, p21, and pRB. Functionally, KLF17 required p53 to suppress cancer cell invasion and migration in NSCLC. In conclusion, our study highlights a novel insight into the anti-EMT effect of KLF17 via a p53-dependent pathway in NSCLC, and KLF17 may be a new therapeutic target in NSCLC with p53 status.

  4. INGN 201: Ad-p53, Ad5CMV-p53, Adenoviral p53, INGN 101, p53 gene therapy--Introgen, RPR/INGN 201.

    Science.gov (United States)

    2003-01-01

    undergoing phase I trials for the potential treatment of lung, breast, ovarian, bladder, liver and brain cancers. Introgen and Aventis Pharma had signed a Cooperative Research and Development Agreement (CRADA) with the National Cancer Institute (NCI). NCI will sponsor clinical trials to evaluate and develop RPR/INGN 201 as a potential anticancer agent for these cancer indications. The trials conducted under a NCI-sponsored IND will evaluate RPR/INGN 201 alone and in combination with other anticancer agents. This agreement was originally signed by Rhône-Poulenc Rorer's Gencell. Introgen has completed three phase I clinical trials with INGN 201 in patients with bronchioalveolar cell lung carcinoma, ovarian cancer and recurrent glioblastomas, respectively. Intratumoural injection of RPR/INGN 201 in patients with recurrent glioblastomas was well tolerated and resulted in expression of the p53 protein. Direct administration of RPR/INGN 201 to the lower airways of patients with bronchioalveolar cell lung carcinoma resulted in symptomatic improvement and improved lung function in some patients. In February 2003, Introgen announced that the US Patent and Trademark Office has issued to The Board of Regents of The University of Texas System, patent No. 6,511,847 entitled "Recombinant p53 Adenovirus Methods and Compositions". Introgen Therapeutics is the exclusive licensee of this patent. The patent covers any adenoviral DNA molecules that encode the p53 gene positioned under the control of a promoter. Such a DNA molecule forms the genetic core of Introgen's ADVEXIN cancer therapy. Introgen's ADVEXIN therapy is now covered by up to ten separate US patents relevant to the product including compositions, therapeutic methods of administering the product in virtually any form, alone and in conjunction with the most widely used chemotherapeutic and radiation treatments, as well as its production. Introgen has a number of US patents that relate to the clinical use of ADVEXIN in cancer as

  5. Restoring expression of wild-type p53 suppresses tumor growth but does not cause tumor regression in mice with a p53 missense mutation

    OpenAIRE

    2011-01-01

    The transcription factor p53 is a tumor suppressor. As such, the P53 gene is frequently altered in human cancers. However, over 80% of the P53 mutations found in human cancers are missense mutations that lead to expression of mutant proteins that not only lack p53 transcriptional activity but exhibit new functions as well. Recent studies show that restoration of p53 expression leads to tumor regression in mice carrying p53 deletions. However, the therapeutic efficacy of restoring p53 expressi...

  6. Targeting cancer stem cells with p53 modulators

    Science.gov (United States)

    Hayashi, Ryo; Appella, Ettore; Kopelovich, Levy; DeLeo, Albert B.

    2016-01-01

    Cancer stem cells (CSC) typically over-express aldehyde dehydrogenase (ALDH). Thus, ALDHbright tumor cells represent targets for developing novel cancer prevention/treatment interventions. Loss of p53 function is a common genetic event during cancer development wherein small molecular weight compounds (SMWC) that restore p53 function and reverse tumor growth have been identified. Here, we focused on two widely studied p53 SMWC, CP-31398 and PRIMA-1, to target ALDHbright CSC in human breast, endometrial and pancreas carcinoma cell lines expressing mutant or wild type (WT) p53. CP-31398 and PRIMA-1 significantly reduced CSC content and sphere formation by these cell lines in vitro. In addition, these agents were more effective in vitro against CSC compared to cisplatin and gemcitabine, two often-used chemotherapeutic agents. We also tested a combinatorial treatment in methylcholantrene (MCA)-treated mice consisting of p53 SMWC and p53-based vaccines. Yet using survival end-point analysis, no increased efficacy in the presence of either p53 SMWC alone or with vaccine compared to vaccine alone was observed. These results may be due, in part, to the presence of immune cells, such as activated lymphocytes expressing WT p53 at levels comparable to some tumor cells, wherein further increase of p53 expression by p53 SMWC may alter survival of these immune cells and negatively impact an effective immune response. Continuous exposure of mice to MCA may have also interfered with the action of these p53 SMWC, including potential direct interaction with MCA. Nonetheless, the effect of p53 SMWC on CSC and cancer treatment remains of great interest. PMID:27074569

  7. On p53 revival using system oriented drug dosage design.

    Science.gov (United States)

    Haseeb, Muhammad; Azam, Shumaila; Bhatti, A I; Azam, Rizwan; Ullah, Mukhtar; Fazal, Sahar

    2017-02-21

    We propose a new paradigm in the drug design for the revival of the p53 pathway in cancer cells. It is shown that the current strategy of using small molecule based Mdm2 inhibitors is not enough to adequately revive p53 in cancerous cells, especially when it comes to the extracting pulsating behavior of p53. This fact has come to notice when a novel method for the drug dosage design is introduced using system oriented concepts. As a test case, small molecule drug Mdm2 repressor Nutlin 3a is considered. The proposed method determines the dose of Nutlin to revive p53 pathway functionality. For this purpose, PBK dynamics of Nutlin have also been integrated with p53 pathway model. The p53 pathway is the focus of researchers for the last thirty years for its pivotal role as a frontline cancer suppressant protein due to its effect on cell cycle checkpoints and cell apoptosis in response to a DNA strand break. That is the reason for finding p53 being absent in more than 50% of tumor cancers. Various drugs have been proposed to revive p53 in cancer cells. Small molecule based drugs are at the foremost and are the subject of advanced clinical trials. The dosage design of these drugs is an important issue. We use control systems concepts to develop the drug dosage so that the cancer cells can be treated in appropriate time. We investigate by using a computational model how p53 protein responds to drug Nutlin 3a, an agent that interferes with the MDM2-mediated p53 regulation. The proposed integrated model describes in some detail the regulation network of p53 including the negative feedback loop mediated by MDM2 and the positive feedback loop mediated by Mdm2 mRNA as well as the reversible represses of MDM2 caused by Nutlin. The reported PBK dynamics of Nutlin 3a are also incorporated to see the full effect. It has been reported that p53 response to stresses in two ways. Either it has a sustained (constant) p53 response, or there are oscillations in p53 concentration. The

  8. Structure of the p53 C-terminus bound to 14-3-3: implications for stabilization of the p53 tetramer.

    Science.gov (United States)

    Schumacher, Benjamin; Mondry, Justine; Thiel, Philipp; Weyand, Michael; Ottmann, Christian

    2010-04-16

    The adaptor protein 14-3-3 binds to and stabilizes the tumor suppressor p53 and enhances its anti-tumour activity. In the regulatory C-terminal domain of p53 several 14-3-3 binding motifs have been identified. Here, we report the crystal structure of the extreme C-terminus (residues 385-393, p53pT387) of p53 in complex with 14-3-3sigma at a resolution of 1.28A. p53pT387 is accommodated by 14-3-3 in a yet unrecognized fashion implying a rationale for 14-3-3 binding to the active p53 tetramer. The structure exhibits a potential binding site for small molecules that could stabilize the p53/14-3-3 protein complex suggesting the possibility for therapeutic intervention. Copyright 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  9. Structure and stability insights into tumour suppressor p53 evolutionary related proteins.

    Directory of Open Access Journals (Sweden)

    Bruno Pagano

    Full Text Available The p53 family of genes and their protein products, namely, p53, p63 and p73, have over one billion years of evolutionary history. Advances in computational biology and genomics are enabling studies of the complexities of the molecular evolution of p53 protein family to decipher the underpinnings of key biological conditions spanning from cancer through to various metabolic and developmental disorders and facilitate the design of personalised medicines. However, a complete understanding of the inherent nature of the thermodynamic and structural stability of the p53 protein family is still lacking. This is due, to a degree, to the lack of comprehensive structural information for a large number of homologous proteins and to an incomplete knowledge of the intrinsic factors responsible for their stability and how these might influence function. Here we investigate the thermal stability, secondary structure and folding properties of the DNA-binding domains (DBDs of a range of proteins from the p53 family using biophysical methods. While the N- and the C-terminal domains of the p53 family show sequence diversity and are normally targets for post-translational modifications and alternative splicing, the central DBD is highly conserved. Together with data obtained from Molecular Dynamics simulations in solution and with structure based homology modelling, our results provide further insights into the molecular properties of evolutionary related p53 proteins. We identify some marked structural differences within the p53 family, which could account for the divergence in biological functions as well as the subtleties manifested in the oligomerization properties of this family.

  10. p53 modulation of TFIIH-associated nucleotide excision repair activity

    NARCIS (Netherlands)

    X.W. Wang (Xin Wei); H. Yeh; L. Schaeffer; R. Roy (R.); V. Moncollin; J-M. Egly (Jean-Marc); Z. Wang (Z.); E.C. Friedberg (Errol); M.K. Evans; B.G. Taffe; V.A. Bohr; G. Weeda (Geert); J.H.J. Hoeijmakers (Jan); K. Forrester; C.C. Harris

    1995-01-01

    textabstractp53 has pleiotropic functions including control of genomic plasticity and integrity. Here we report that p53 can bind to several transcription factor IIH−associated factors, including transcription−repair factors, XPD (Rad3) and XPB, as well as CSB involved in strand−specific DNA repair,

  11. INGN 201: Ad-p53, Ad5CMV-p53, adenoviral p53, p53 gene therapy--introgen, RPR/INGN 201.

    Science.gov (United States)

    2007-01-01

    former trial) followed by a combination of chemo- and radiotherapy. In September 2003, INGN 201 was granted designation as a Fast Track Drug Product development programme by the FDA for prolonging survival and delaying time to disease progression in patients with recurrent, unresectable squamous cell carcinoma of the head and neck. Previously, in February 2003, INGN 201 received orphan drug designation from the FDA for head and neck cancer. Phase I trials in the US for the treatment of non-small-cell lung cancer have been completed. Sanofi-aventis (formerly Rhône-Poulenc Rorer Gencell) initiated phase II trials in the US, Europe and Canada for non-small-cell lung cancer. Intratumoral injection of RPR/INGN 201 in patients with recurrent glioblastomas was safe and resulted in expression of the p53 protein. Direct administration of RPR/INGN 201 to the lower airways of patients with bronchioalveolar cell lung carcinoma resulted in symptomatic improvement and improved lung function in some patients. In November 2003, according to a Clinical Trials Agreement between the Division of Cancer Treatment and Diagnosis (DCTD) of the National Cancer Institute (NCI) and Introgen, a 6-month phase I/II study with p53 gene therapy administered in the form of an oral rinse or mouthwash for patients with oral premalignancies has been initiated. This is the first trial to investigate the effect of this treatment on oral lesions that are at high risk for developing into full blown cancers. In September 2006, the EMEA granted orphan drug status to INGN 201 for the treatment of LFS, following Gendux's application for the designation. The company intends to provide the therapy on a compassionate use basis to qualifying patients in Europe.INGN 201 has been successfully used in the treatment of a LFS patient on a compassionate use basis under a protocol authorised by the FDA. Based on these interim findings, Introgen has decided to continue making the therapy available through a compassionate use

  12. p53 and mitochondrial dysfunction: novel insight of neurodegenerative diseases.

    Science.gov (United States)

    Dai, Chun-Qiu; Luo, Ting-Ting; Luo, Shi-Cheng; Wang, Jia-Qi; Wang, Sheng-Ming; Bai, Yun-Hu; Yang, Yan-Ling; Wang, Ya-Yun

    2016-08-01

    Mitochondria are organelles responsible for vital cell functions. p53 is a transcription factor that regulates the DNA stability and cell growth normality. Recent studies revealed that p53 can influence mitochondrial function changing from normal condition to abnormal condition under different stress levels. In normal state, p53 can maintain mitochondrial respiration through transactivation of SCO2. When stress stimuli presents, SCO2 overexpresses and leads to ROS generation. ROS promotes p53 inducing MALM (Mieap-induced accumulation of lysosome-like organelles within mitochondria) to repair dysfunctional mitochondria and MIV (Mieap-induced vacuole) to accomplish damaged mitochondria degradation. If stress or damage is irreversible, p53 will translocate to mitochondria, leading into apoptosis or necrosis. Neurodegenerative diseases including Parkinson's disease, Huntington's disease and Alzheimer's disease are still lack of clear explanations of mechanisms, but more studies have revealed the functional relationship between mitochondria and p53 towards the pathological development of these diseases. In this review, we discuss that p53 plays the vital role in the function of mitochondria in the aspect of pathological change metabolism. We also analyze these diseases with novel targeted treating molecules which are related to p53 and mitochondria, hoping to present novel therapies in future clinic.

  13. MdmX Protects p53 from Mdm2-Mediated Degradation

    OpenAIRE

    2000-01-01

    The p53 tumor suppressor protein is stabilized in response to cellular stress, resulting in activation of genes responsible for either cell cycle arrest or apoptosis. The cellular pathway for releasing normal cells from p53-dependent cell cycle arrest involves the Mdm2 protein. Recently, a p53-binding protein with homology to Mdm2 was identified and called MdmX. Like Mdm2, MdmX is able to bind p53 and inhibit p53 transactivation; however, the ability of MdmX to degrade p53 has yet to be exami...

  14. The p53 pathway in hematopoiesis: lessons from mouse models, implications for humans

    OpenAIRE

    Pant, Vinod; Quintás-Cardama, Alfonso; Lozano, Guillermina

    2012-01-01

    Aberrations in the p53 tumor suppressor pathway are associated with hematologic malignancies. p53-dependent cell cycle control, senescence, and apoptosis functions are actively involved in maintaining hematopoietic homeostasis under normal and stress conditions. Whereas loss of p53 function promotes leukemia and lymphoma development in humans and mice, increased p53 activity inhibits hematopoietic stem cell function and results in myelodysplasia. Thus, exquisite regulation of p53 activity is ...

  15. p53 prevents neurodegeneration by regulating synaptic genes.

    Science.gov (United States)

    Merlo, Paola; Frost, Bess; Peng, Shouyong; Yang, Yawei J; Park, Peter J; Feany, Mel

    2014-12-16

    DNA damage has been implicated in neurodegenerative disorders, including Alzheimer's disease and other tauopathies, but the consequences of genotoxic stress to postmitotic neurons are poorly understood. Here we demonstrate that p53, a key mediator of the DNA damage response, plays a neuroprotective role in a Drosophila model of tauopathy. Further, through a whole-genome ChIP-chip analysis, we identify genes controlled by p53 in postmitotic neurons. We genetically validate a specific pathway, synaptic function, in p53-mediated neuroprotection. We then demonstrate that the control of synaptic genes by p53 is conserved in mammals. Collectively, our results implicate synaptic function as a central target in p53-dependent protection from neurodegeneration.

  16. Lenalidomide inhibits the proliferation of CLL cells via a cereblon/p21(WAF1/Cip1)-dependent mechanism independent of functional p53.

    Science.gov (United States)

    Fecteau, Jessie-F; Corral, Laura G; Ghia, Emanuela M; Gaidarova, Svetlana; Futalan, Diahnn; Bharati, Ila Sri; Cathers, Brian; Schwaederlé, Maria; Cui, Bing; Lopez-Girona, Antonia; Messmer, Davorka; Kipps, Thomas J

    2014-09-04

    Lenalidomide has demonstrated clinical activity in patients with chronic lymphocytic leukemia (CLL), even though it is not cytotoxic for primary CLL cells in vitro. We examined the direct effect of lenalidomide on CLL-cell proliferation induced by CD154-expressing accessory cells in media containing interleukin-4 and -10. Treatment with lenalidomide significantly inhibited CLL-cell proliferation, an effect that was associated with the p53-independent upregulation of the cyclin-dependent kinase inhibitor, p21(WAF1/Cip1) (p21). Silencing p21 with small interfering RNA impaired the capacity of lenalidomide to inhibit CLL-cell proliferation. Silencing cereblon, a known molecular target of lenalidomide, impaired the capacity of lenalidomide to induce expression of p21, inhibit CD154-induced CLL-cell proliferation, or enhance the degradation of Ikaros family zinc finger proteins 1 and 3. We isolated CLL cells from the blood of patients before and after short-term treatment with low-dose lenalidomide (5 mg per day) and found the leukemia cells were also induced to express p21 in vivo. These results indicate that lenalidomide can directly inhibit proliferation of CLL cells in a cereblon/p21-dependent but p53-independent manner, at concentrations achievable in vivo, potentially contributing to the capacity of this drug to inhibit disease-progression in patients with CLL.

  17. Lenalidomide inhibits the proliferation of CLL cells via a cereblon/p21WAF1/Cip1-dependent mechanism independent of functional p53

    Science.gov (United States)

    Fecteau, Jessie-F.; Corral, Laura G.; Ghia, Emanuela M.; Gaidarova, Svetlana; Futalan, Diahnn; Bharati, Ila Sri; Cathers, Brian; Schwaederlé, Maria; Cui, Bing; Lopez-Girona, Antonia; Messmer, Davorka

    2014-01-01

    Lenalidomide has demonstrated clinical activity in patients with chronic lymphocytic leukemia (CLL), even though it is not cytotoxic for primary CLL cells in vitro. We examined the direct effect of lenalidomide on CLL-cell proliferation induced by CD154-expressing accessory cells in media containing interleukin-4 and -10. Treatment with lenalidomide significantly inhibited CLL-cell proliferation, an effect that was associated with the p53-independent upregulation of the cyclin-dependent kinase inhibitor, p21WAF1/Cip1 (p21). Silencing p21 with small interfering RNA impaired the capacity of lenalidomide to inhibit CLL-cell proliferation. Silencing cereblon, a known molecular target of lenalidomide, impaired the capacity of lenalidomide to induce expression of p21, inhibit CD154-induced CLL-cell proliferation, or enhance the degradation of Ikaros family zinc finger proteins 1 and 3. We isolated CLL cells from the blood of patients before and after short-term treatment with low-dose lenalidomide (5 mg per day) and found the leukemia cells were also induced to express p21 in vivo. These results indicate that lenalidomide can directly inhibit proliferation of CLL cells in a cereblon/p21-dependent but p53-independent manner, at concentrations achievable in vivo, potentially contributing to the capacity of this drug to inhibit disease-progression in patients with CLL. PMID:24990888

  18. Adenovirus type 12 E1B 55-kilodalton oncoprotein promotes p53-mediated apoptotic response of ovarian cancer to cisplatin.

    Science.gov (United States)

    Wang, Junnai; Gao, Qinglei; Li, Qiang

    2015-08-01

    The tumor suppressor p53-mediated apoptotic response plays an important role in cisplatin resistant in ovarian cancer. The adenovirus (Ad) type 12 E1B 55-kDa protein binds to p53 and inactivates its transcriptional transactivation function. In this study, we test the hypothesis that Ad12 E1B 55-kDa oncoprotein promotes p53-mediated apoptotic response of ovarian cancer to cisplatin. First, we observed the upregulation protein level of p53 target genes in cisplatin-resistant or cisplatin-sensitive ovarian cancer by Western blotting. Second, after transfection of Ad12 E1b 55-kDa expression plasmid, the expressions of p53 target genes in A2780 cells were further enhanced. Co-IP experiment demonstrated Ad12 E1b 55 kDa associated with p53. MTT assay confirmed that the cell proliferation was enhanced after transfection, as well as the enhanced cell inhibitory rate in the presence of cisplatin. Using flow cytometry, transfection of Ad12 E1B 55-kDa protein induced apoptosis and promoted S-phase transition in proliferation. Finally, results showed that all these changes promoted by Ad12 E1b 55 kDa were attenuated by the exposure of specific inhibitor of p53 signaling, pifithrin-α. Taken together, we concluded that Ad E1B 55-kDa oncoprotein promotes p53-mediated apoptotic response of ovarian cancer to cisplatin.

  19. Pleckstrin homology domain-containing protein PHLDB3 supports cancer growth via a negative feedback loop involving p53

    Science.gov (United States)

    Chao, Tengfei; Zhou, Xiang; Cao, Bo; Liao, Peng; Liu, Hongbing; Chen, Yun; Park, Hee-Won; Zeng, Shelya X.; Lu, Hua

    2016-01-01

    The tumour suppressor p53 transactivates the expression of its target genes to exert its functions. Here, we identify a pleckstrin homology domain-containing protein (PHLDB3)-encoding gene as a p53 target. PHLDB3 overexpression increases proliferation and restrains apoptosis of wild-type p53-harboring cancer cells by reducing p53 protein levels. PHLDB3 binds to MDM2 (mouse double minute 2 homolog) and facilitates MDM2-mediated ubiquitination and degradation of p53. Knockdown of PHLDB3 more efficiently inhibits the growth of mouse xenograft tumours derived from human colon cancer HCT116 cells that contain wild type p53 compared with p53-deficient HCT116 cells, and also sensitizes tumour cells to doxorubicin and 5-Fluorouracil. Analysis of cancer genomic databases reveals that PHLDB3 is amplified and/or highly expressed in numerous human cancers. Altogether, these results demonstrate that PHLDB3 promotes tumour growth by inactivating p53 in a negative feedback fashion and suggest PHLDB3 as a potential therapeutic target in various human cancers. PMID:28008906

  20. HAUSP-nucleolin interaction is regulated by p53-Mdm2 complex in response to DNA damage response.

    Science.gov (United States)

    Lim, Key-Hwan; Park, Jang-Joon; Gu, Bon-Hee; Kim, Jin-Ock; Park, Sang Gyu; Baek, Kwang-Hyun

    2015-08-04

    HAUSP (herpes virus-associated ubiquitin specific protease, known as ubiquitin specific protease 7), one of DUBs, regulates the dynamics of the p53 and Mdm2 network in response to DNA damage by deubiquitinating both p53 and its E3 ubiquitin ligase, Mdm2. Its concerted action increases the level of functional p53 by preventing proteasome-dependent degradation of p53. However, the protein substrates that are targeted by HAUSP to mediate DNA damage responses in the context of the HAUSP-p53-Mdm2 complex are not fully identified. Here, we identified nucleolin as a new substrate for HAUSP by proteomic analysis. Nucleolin has two HAUSP binding sites in its N- and C-terminal regions, and the mutation of HAUSP interacting peptides on nucleolin disrupts their interaction and it leads to the increased level of nucleolin ubiquitination. In addition, HAUSP regulates the stability of nucleolin by removing ubiquitin from nucleolin. Nucleolin exists as a component of the HAUSP-p53-Mdm2 complex, and both Mdm2 and p53 are required for the interaction between HAUSP and nucleolin. Importantly, the irradiation increases the HAUSP-nucleolin interaction, leading to nucleolin stabilization significantly. Taken together, this study reveals a new component of the HAUSP-p53-Mdm2 complex that governs dynamic cellular responses to DNA damage.

  1. A negative regulation loop of long noncoding RNA HOTAIR and p53 in non-small-cell lung cancer

    Directory of Open Access Journals (Sweden)

    Zhai N

    2016-09-01

    Full Text Available Nailiang Zhai,1 Yongfu Xia,1 Rui Yin,2 Jinping Liu,3 Fuquan Gao1 1Department of Respiratory Medicine, Affiliated Hospital of Binzhou Medical University, 2Department of Respiratory Medicine, People’s Hospital of Binzhou City, 3Department of Pharmacology, Binzhou Medical University, Binzhou, Shandong, People’s Republic of China Abstract: Non-small-cell lung cancer (NSCLC is one of the leading causes of cancer-related death worldwide, and the 5-year survival rate is still low despite advances in diagnosis and therapeutics. A long noncoding RNA (lncRNA HOX antisense intergenic RNA (HOTAIR has been revealed to play important roles in NSCLC carcinogenesis but the detailed mechanisms are still unclear. In the current study, we aimed to investigate the regulation between the lncRNA HOTAIR and p53 in the NSCLC patient samples and cell lines. Our results showed that HOTAIR expression was significantly higher in the cancer tissues than that in the adjacent normal tissue, and was negatively correlated with p53 functionality rather than expression. When p53 was overexpressed in A549 cells, the lncRNA HOTAIR expression was downregulated, and the cell proliferation rate and cell invasion capacity decreased as a consequence. We identified two binding sites of p53 on the promoter region of HOTAIR, where the p53 protein would bind to and suppress the HOTAIR mRNA transcription. Inversely, overexpression of lncRNA HOTAIR inhibited the expression of p53 in A549 cells. Mechanistic studies revealed that HOTAIR modified the promoter of p53 and enhanced histone H3 lysine 27 trimethylation (H3K27me3. These studies identified a specific negative regulation loop of lncRNA HOTAIR and p53 in NSCLC cells, which revealed a new understanding of tumorigenesis in p53 dysfunction NSCLC cells. Keywords: NSCLC, LncRNA HOTAIR, p53, negative loop

  2. A platform for interrogating cancer-associated p53 alleles.

    Science.gov (United States)

    D'Brot, A; Kurtz, P; Regan, E; Jakubowski, B; Abrams, J M

    2017-01-12

    p53 is the most frequently mutated gene in human cancer. Compelling evidence argues that full transformation involves loss of growth suppression encoded by wild-type p53 together with poorly understood oncogenic activity encoded by missense mutations. Furthermore, distinguishing disease alleles from natural polymorphisms is an important clinical challenge. To interrogate the genetic activity of human p53 variants, we leveraged the Drosophila model as an in vivo platform. We engineered strains that replace the fly p53 gene with human alleles, producing a collection of stocks that are, in effect, 'humanized' for p53 variants. Like the fly counterpart, human p53 transcriptionally activated a biosensor and induced apoptosis after DNA damage. However, all humanized strains representing common alleles found in cancer patients failed to complement in these assays. Surprisingly, stimulus-dependent activation of hp53 occurred without stabilization, demonstrating that these two processes can be uncoupled. Like its fly counterpart, hp53 formed prominent nuclear foci in germline cells but cancer-associated p53 variants did not. Moreover, these same mutant alleles disrupted hp53 foci and inhibited biosensor activity, suggesting that these properties are functionally linked. Together these findings establish a functional platform for interrogating human p53 alleles and suggest that simple phenotypes could be used to stratify disease variants.

  3. Disruption of estrogen receptor α-p53 interaction in breast tumors: a novel mechanism underlying the anti-tumor effect of radiation therapy

    Science.gov (United States)

    Liu, Wensheng; Ip, Margot M.; Podgorsak, Matthew B.; Das, Gokul M.

    2014-01-01

    Inactivation of tumor suppressor p53 is one of the most frequent events in cancer. Unlike many other cancers, however, p53 gene mutations are infrequent in breast cancers, as about 80% of breast tumors contain wild type p53. The mechanisms underlying functional inactivation of wild type p53 in breast cancer have remained elusive. Besides, how p53 gets activated in breast tumors subjected to radiation therapy remains unknown. We recently reported that in MCF-7 breast cancer cells, estrogen receptor alpha (ERα) directly binds to p53 and represses its function. Furthermore, the ERα-p53 interaction was disrupted by ionizing radiation. These observations have important translational implications especially as there are no reliable cellular or molecular criteria for rational radiotherapy for breast cancer. Here we report our studies towards addressing this important issue, using an MCF-7 breast cancer xenograft model in mice. Radiation effectively inhibits growth of these tumors and stabilizes p53, but has no observable effect on ERα protein level. Importantly, chromatin immunoprecipitation (ChIP) assays demonstrated that ERα interacts with p53 bound to endogenous target gene promoters in tumors in vivo, and this interaction is considerably reduced in response to radiotherapy although p53 level is increased. Concomitant with its effect on ERα-p53 interaction, radiation increases p53-mediated transcriptional activation of several target genes and increases p53-mediated transcriptional repression of survivin. Our studies show that disruption of ERα-p53 interaction in vivo resulting in restoration of functional p53 is a cellular response to radiation. Radiation could be affecting ERα and/or p53 directly or it could be influencing other proteins associated with the ERα-p53 complex. To the best of our knowledge, this is the first report on analysis of DNA–protein–protein interaction occurring on endogenous gene promoters in vivo in breast tumor tissues. These

  4. Disruption of estrogen receptor alpha-p53 interaction in breast tumors: a novel mechanism underlying the anti-tumor effect of radiation therapy.

    Science.gov (United States)

    Liu, Wensheng; Ip, Margot M; Podgorsak, Matthew B; Das, Gokul M

    2009-05-01

    Inactivation of tumor suppressor p53 is one of the most frequent events in cancer. Unlike many other cancers, however, p53 gene mutations are infrequent in breast cancers, as about 80% of breast tumors contain wild type p53. The mechanisms underlying functional inactivation of wild type p53 in breast cancer have remained elusive. Besides, how p53 gets activated in breast tumors subjected to radiation therapy remains unknown. We recently reported that in MCF-7 breast cancer cells, estrogen receptor alpha (ERalpha) directly binds to p53 and represses its function. Furthermore, the ERalpha-p53 interaction was disrupted by ionizing radiation. These observations have important translational implications especially as there are no reliable cellular or molecular criteria for rational radiotherapy for breast cancer. Here we report our studies towards addressing this important issue, using an MCF-7 breast cancer xenograft model in mice. Radiation effectively inhibits growth of these tumors and stabilizes p53, but has no observable effect on ERalpha protein level. Importantly, chromatin immunoprecipitation (ChIP) assays demonstrated that ERalpha interacts with p53 bound to endogenous target gene promoters in tumors in vivo, and this interaction is considerably reduced in response to radiotherapy although p53 level is increased. Concomitant with its effect on ERalpha-p53 interaction, radiation increases p53-mediated transcriptional activation of several target genes and increases p53-mediated transcriptional repression of survivin. Our studies show that disruption of ERalpha-p53 interaction in vivo resulting in restoration of functional p53 is a cellular response to radiation. Radiation could be affecting ERalpha and/or p53 directly or it could be influencing other proteins associated with the ERalpha-p53 complex. To the best of our knowledge, this is the first report on analysis of DNA-protein-protein interaction occurring on endogenous gene promoters in vivo in breast tumor

  5. Evidence for allosteric variants of wild-type p53, a tumour suppressor protein.

    OpenAIRE

    1990-01-01

    A tumour suppressor function for p53 is indicated in human lung cancer and in carcinoma of the colorectum. Loss of suppressor function, by mutation of the p53 gene, is associated with activation of p53 as an oncogene. The suppressor (wild type) and oncogenic (mutant) forms of the murine p53 protein are distinguishable at the molecular level by reactivity with anti-p53 monoclonal antibodies. For example, activated mutant p53 fails to react with PAb246 (p53-246 degrees). We now demonstrate that...

  6. Gene p53 mutations, protein p53, and anti-p53 antibodies as biomarkers of cancer process.

    Science.gov (United States)

    Lutz, Waldemar; Nowakowska-Swirta, Ewa

    2002-01-01

    The finding that gene mutations and changes in their expression form the basis of cancer processes, has prompted molecular epidemiologists to use biomarkers for detecting damaged genes or proteins synthesized under their control in easily available cellular material or systemic liquids. Mutations in the suppressor gen p53 are thought to be essential for cancer development. This gen is one of the most important regulators of transcription, cellular cycle, DNA repair and apoptosis detected till now. Inactivation of gene p53 leads to uncontrolled cell divisions, and further to transformation of normal cells into the carcinous ones. Observations that mutations in gene p53 appear under conditions of occupational and environmental exposures to chemical and physical carcinogens, such as vinyl chloride, radon, or aflatoxin B1, have proved to be of enormous importance for the occupational and environmental health. Changes in expression of gene p53, and also its mutations, cause variations of cellular protein p53 concentration. Higher cellular protein p53 levels are associated with increased protein transfer to the extracellular liquid and to blood. It has been observed that increased blood serum protein p53 concentrations may have a prognostic value in early diagnosis of lung cancer. The results of a number of studies confirm that accumulation of a mutated form of protein p53, and presumably also large quantities of wild forms of that protein in the cells, may be a factor that triggers the production of anti-p53 antibodies. Statistical analysis showed that anti-p53 antibodies can be regarded as a specific biomarker of cancer process. The prevalence of anti-p53 antibodies correlated with the degree of cancer malignancy. The increased incidence of anti-p53 antibodies was also associated with higher frequency of mutations in gene p53. There are some reports confirming that anti-p53 antibodies emerging in blood serum in the subclinical phase of cancer development may be

  7. Concomitant inactivation of the p53- and pRB- functional pathways predicts resistance to DNA damaging drugs in breast cancer in vivo.

    Science.gov (United States)

    Knappskog, Stian; Berge, Elisabet O; Chrisanthar, Ranjan; Geisler, Stephanie; Staalesen, Vidar; Leirvaag, Beryl; Yndestad, Synnøve; de Faveri, Elise; Karlsen, Bård O; Wedge, David C; Akslen, Lars A; Lilleng, Peer K; Løkkevik, Erik; Lundgren, Steinar; Østenstad, Bjørn; Risberg, Terje; Mjaaland, Ingvild; Aas, Turid; Lønning, Per E

    2015-10-01

    Chemoresistance is the main obstacle to cancer cure. Contrasting studies focusing on single gene mutations, we hypothesize chemoresistance to be due to inactivation of key pathways affecting cellular mechanisms such as apoptosis, senescence, or DNA repair. In support of this hypothesis, we have previously shown inactivation of either TP53 or its key activators CHK2 and ATM to predict resistance to DNA damaging drugs in breast cancer better than TP53 mutations alone. Further, we hypothesized that redundant pathway(s) may compensate for loss of p53-pathway signaling and that these are inactivated as well in resistant tumour cells. Here, we assessed genetic alterations of the retinoblastoma gene (RB1) and its key regulators: Cyclin D and E as well as their inhibitors p16 and p27. In an exploratory cohort of 69 patients selected from two prospective studies treated with either doxorubicin monotherapy or 5-FU and mitomycin for locally advanced breast cancers, we found defects in the pRB-pathway to be associated with therapy resistance (p-values ranging from 0.001 to 0.094, depending on the cut-off value applied to p27 expression levels). Although statistically weaker, we observed confirmatory associations in a validation cohort from another prospective study (n = 107 patients treated with neoadjuvant epirubicin monotherapy; p-values ranging from 7.0 × 10(-4) to 0.001 in the combined data sets). Importantly, inactivation of the p53-and the pRB-pathways in concert predicted resistance to therapy more strongly than each of the two pathways assessed individually (exploratory cohort: p-values ranging from 3.9 × 10(-6) to 7.5 × 10(-3) depending on cut-off values applied to ATM and p27 mRNA expression levels). Again, similar findings were confirmed in the validation cohort, with p-values ranging from 6.0 × 10(-7) to 6.5 × 10(-5) in the combined data sets. Our findings strongly indicate that concomitant inactivation of the p53- and pRB- pathways predict

  8. p53 gene mutations, p53 protein accumulation and compartmentalization in colorectal adenocarcinoma.

    OpenAIRE

    1995-01-01

    p53 accumulation may occur in the nucleus and/or cytoplasm of neoplastic cells. Cytoplasmic accumulation has been reported to be an unfavorable, but not established, prognostic indicator in colorectal cancer. Different types of p53 intracellular compartmentalization could depend either on p53 gene mutations or on the interaction with p53 protein ligands. The purposes of our study were (1) to assess whether the different patterns of p53 accumulation are selectively associated with p53 mutation...

  9. p53's choice of myocardial death or survival: Oxygen protects infarct myocardium by recruiting p53 on NOS3 promoter through regulation of p53-Lys(118) acetylation.

    Science.gov (United States)

    Gogna, Rajan; Madan, Esha; Khan, Mahmood; Pati, Uttam; Kuppusamy, Periannan

    2013-11-01

    Myocardial infarction, an irreversible cardiac tissue damage, involves progressive loss of cardiomyocytes due to p53-mediated apoptosis. Oxygenation is known to promote cardiac survival through activation of NOS3 gene. We hypothesized a dual role for p53, which, depending on oxygenation, can elicit apoptotic death signals or NOS3-mediated survival signals in the infarct heart. p53 exhibited a differential DNA-binding, namely, BAX-p53RE in the infarct heart or NOS3-p53RE in the oxygenated heart, which was regulated by oxygen-induced, post-translational modification of p53. In the infarct heart, p53 was heavily acetylated at Lys(118) residue, which was exclusively reversed in the oxygenated heart, apparently regulated by oxygen-dependent expression of TIP60. The inhibition of Lys(118) acetylation promoted the generation of NOS3-promoting prosurvival form of p53. Thus, oxygenation switches p53-DNA interaction by regulating p53 core-domain acetylation, promoting a prosurvival transcription activity of p53. Understanding this novel oxygen-p53 survival pathway will open new avenues in cardioprotection molecular therapy. © 2013 The Authors. Published by John Wiley and Sons, Ltd on behalf of EMBO.

  10. p53's choice of myocardial death or survival: Oxygen protects infarct myocardium by recruiting p53 on NOS3 promoter through regulation of p53-Lys118 acetylation

    Science.gov (United States)

    Gogna, Rajan; Madan, Esha; Khan, Mahmood; Pati, Uttam; Kuppusamy, Periannan

    2013-01-01

    Myocardial infarction, an irreversible cardiac tissue damage, involves progressive loss of cardiomyocytes due to p53-mediated apoptosis. Oxygenation is known to promote cardiac survival through activation of NOS3 gene. We hypothesized a dual role for p53, which, depending on oxygenation, can elicit apoptotic death signals or NOS3-mediated survival signals in the infarct heart. p53 exhibited a differential DNA-binding, namely, BAX-p53RE in the infarct heart or NOS3-p53RE in the oxygenated heart, which was regulated by oxygen-induced, post-translational modification of p53. In the infarct heart, p53 was heavily acetylated at Lys118 residue, which was exclusively reversed in the oxygenated heart, apparently regulated by oxygen-dependent expression of TIP60. The inhibition of Lys118 acetylation promoted the generation of NOS3-promoting prosurvival form of p53. Thus, oxygenation switches p53-DNA interaction by regulating p53 core-domain acetylation, promoting a prosurvival transcription activity of p53. Understanding this novel oxygen-p53 survival pathway will open new avenues in cardioprotection molecular therapy. PMID:24096875

  11. Che-1/AATF: a critical co-factor for both wild type- and mutant-p53 proteins

    Directory of Open Access Journals (Sweden)

    Tiziana eBruno

    2016-02-01

    Full Text Available The p53 protein is a key player in a wide range of protein networks that allow the state of good health of the cell. Not surprisingly, mutations of the p53 gene are one of the most common alterations associated to cancer cells. Mutated forms of p53 (mtp53 not only lose the ability to protect the integrity of the genetic heritage of the cell, but acquire pro-oncogenic functions, behaving like dangerous accelerators of transformation and tumor progression. In recent years, many studies focused on investigating possible strategies aiming to counteract this mutant p53 gain of function but the results have not always been satisfactory. Che-1/AATF is a nuclear protein that binds to RNA polymerase II and plays a role in multiple fundamental processes, including control of transcription, cell cycle regulation, DNA damage response and apoptosis. Several studies showed Che-1/AATF as an important endogenous regulator of p53 expression and activity in a variety of biological processes. Notably, this same regulation was more recently observed also on mtp53. The depletion of Che-1/AATF strongly reduces the expression of mutant p53 in several tumors in vitro and in vivo, making the cells an easier target for chemotherapy treatments. In this mini review, we report an overview of Che-1/AATF functions and discuss a possible role of Che-1/AATF in cancer therapy, with particular regard to its action on p53/mtp53.

  12. A dynamic P53-MDM2 model with time delay

    Energy Technology Data Exchange (ETDEWEB)

    Mihalas, Gh.I. [Department of Biophysics and Medical Informatics, University of Medicine and Pharmacy, Piata Eftimie Murgu, nr. 3, 300041 Timisoara (Romania)]. E-mail: mihalas@medinfo.umft.ro; Neamtu, M. [Department of Forecasting, Economic Analysis, Mathematics and Statistics, West University of Timisoara, Str. Pestalozzi, nr. 14A, 300115 Timisoara (Romania)]. E-mail: mihaela.neamtu@fse.uvt.ro; Opris, D. [Department of Applied Mathematics, West University of Timisoara, Bd. V. Parvan, nr. 4, 300223 Timisoara (Romania)]. E-mail: opris@math.uvt.ro; Horhat, R.F. [Department of Biophysics and Medical Informatics, University of Medicine and Pharmacy, Piata Eftimie Murgu, nr. 3, 300041 Timisoara (Romania)]. E-mail: rhorhat@yahoo.com

    2006-11-15

    Specific activator and repressor transcription factors which bind to specific regulator DNA sequences, play an important role in gene activity control. Interactions between genes coding such transcription factors should explain the different stable or sometimes oscillatory gene activities characteristic for different tissues. Starting with the model P53-MDM2 described into [Mihalas GI, Simon Z, Balea G, Popa E. Possible oscillatory behaviour in P53-MDM2 interaction computer simulation. J Biol Syst 2000;8(1):21-9] and the process described into [Kohn KW, Pommier Y. Molecular interaction map of P53 and MDM2 logic elements, which control the off-on switch of P53 in response to DNA damage. Biochem Biophys Res Commun 2005;331:816-27] we enveloped a new model of this interaction. Choosing the delay as a bifurcation parameter we study the direction and stability of the bifurcating periodic solutions. Some numerical examples are finally given for justifying the theoretical results.

  13. Benzyl Isothiocyanate potentiates p53 signaling and antitumor effects against breast cancer through activation of p53-LKB1 and p73-LKB1 axes

    Science.gov (United States)

    Xie, Bei; Nagalingam, Arumugam; Kuppusamy, Panjamurthy; Muniraj, Nethaji; Langford, Peter; Győrffy, Balázs; Saxena, Neeraj K.; Sharma, Dipali

    2017-01-01

    Functional reactivation of p53 pathway, although arduous, can potentially provide a broad-based strategy for cancer therapy owing to frequent p53 inactivation in human cancer. Using a phosphoprotein-screening array, we found that Benzyl Isothiocynate, (BITC) increases p53 phosphorylation in breast cancer cells and reveal an important role of ERK and PRAS40/MDM2 in BITC-mediated p53 activation. We show that BITC rescues and activates p53-signaling network and inhibits growth of p53-mutant cells. Mechanistically, BITC induces p73 expression in p53-mutant cells, disrupts the interaction of p73 and mutant-p53, thereby releasing p73 from sequestration and allowing it to be transcriptionally active. Furthermore, BITC-induced p53 and p73 axes converge on tumor-suppressor LKB1 which is transcriptionally upregulated by p53 and p73 in p53-wild-type and p53-mutant cells respectively; and in a feed-forward mechanism, LKB1 tethers with p53 and p73 to get recruited to p53-responsive promoters. Analyses of BITC-treated xenografts using LKB1-null cells corroborate in vitro mechanistic findings and establish LKB1 as the key node whereby BITC potentiates as well as rescues p53-pathway in p53-wild-type as well as p53-mutant cells. These data provide first in vitro and in vivo evidence of the integral role of previously unrecognized crosstalk between BITC, p53/LKB1 and p73/LKB1 axes in breast tumor growth-inhibition. PMID:28071670

  14. p53 gene in treatment of hepatic carcinoma:Status quo

    Institute of Scientific and Technical Information of China (English)

    Yong-Song Guan; Zi La; Lin Yang; Qing He; Ping Li

    2007-01-01

    Hepatocellular carcinoma(HCC)is one of the 10 most common cancers worldwide.There is no ideal treatment for HCC yet and many researchers are trying to improve the effects of treatment by changing therapeutic strategies.As the majority of human cancers seem to exhibit either abnormal p53 gene or disrupted p53 gene activation pathways,intervention to restore wild-type p53 (wt-p53)activities is an attractive anti-cancer therapy including HCC.Abnormalities of p53 are also considered a predisposition factor for hepatocarcinogenesis.p53 is frequently mutated in HCC.Most HCCs have defects in the p53-mediated apoptotic pathway although they carry wt-p53.High expression of p53 in vivo may exert therapeutic effects on HCC in two aspects:(1)High expression of exogenous p53 protein induces apoptosis of tumor cells by inhibiting proliferation of cells through several biologic pathways and(2)Exogenous p53 renders HCC more sensitive to some chemotherapeutic agents.Several approaches have been designed for the treatment of HCC via the p53 pathway by restoring the tumor suppression function from inactivation,rescuing the mutated p53 gene from instability,or delivering therapeutic exogenous p53.Products with p53 status as the target have been studied extensively in vitro and in vivo.This review elaborates some therapeutic mechanisms and advances in using recombinant human adenovirus p53 and oncolytic virus products for the treatment of HCC.

  15. ΔNp63 transcriptionally regulates ATM to control p53 Serine-15 phosphorylation

    Directory of Open Access Journals (Sweden)

    Smith Graeme

    2010-07-01

    Full Text Available Abstract Background ΔNp63α is an epithelial progenitor cell marker that maintains epidermal stem cell self-renewal capacity. Previous studies revealed that UV-damage induced p53 phosphorylation is confined to ΔNp63α-positive cells in the basal layer of human epithelium. Results We now report that phosphorylation of the p53 tumour suppressor is positively regulated by ΔNp63α in immortalised human keratinocytes. ΔNp63α depletion by RNAi reduces steady-state ATM mRNA and protein levels, and attenuates p53 Serine-15 phosphorylation. Conversely, ectopic expression of ΔNp63α in p63-null tumour cells stimulates ATM transcription and p53 Serine-15 phosphorylation. We show that ATM is a direct ΔNp63α transcriptional target and that the ΔNp63α response element localizes to the ATM promoter CCAAT sequence. Structure-function analysis revealed that the ΔNp63-specific TA2 transactivation domain mediates ATM transcription in coordination with the DNA binding and SAM domains. Conclusions Germline p63 point mutations are associated with a range of ectodermal developmental disorders, and targeted p63 deletion in the skin causes premature ageing. The ΔNp63α-ATM-p53 damage-response pathway may therefore function in epithelial development, carcinogenesis and the ageing processes.

  16. p53 acetylation enhances Taxol-induced apoptosis in human cancer cells.

    Science.gov (United States)

    Kim, Jae Hyeong; Yoon, Eun-Kyung; Chung, Hye-Jin; Park, Seong-Yeol; Hong, Kyeong-Man; Lee, Chang-Hun; Lee, Yeon-Su; Choi, Kyungho; Yang, Young; Kim, Kyungtae; Kim, In-Hoo

    2013-01-01

    Microtubule inhibitors (MTIs) such as Taxol have been used for treating various malignant tumors. Although MTIs have been known to induce cell death through mitotic arrest, other mechanisms can operate in MTI-induced cell death. Especially, the role of p53 in this process has been controversial for a long time. Here we investigated the function of p53 in Taxol-induced apoptosis using p53 wild type and p53 null cancer cell lines. p53 was upregulated upon Taxol treatment in p53 wild type cells and deletion of p53 diminished Taxol-induced apoptosis. p53 target proteins including MDM2, p21, BAX, and β-isoform of PUMA were also upregulated by Taxol in p53 wild type cells. Conversely, when the wild type p53 was re-introduced into two different p53 null cancer cell lines, Taxol-induced apoptosis was enhanced. Among post-translational modifications that affect p53 stability and function, p53 acetylation, rather than phosphorylation, increased significantly in Taxol-treated cells. When acetylation was enhanced by anti-Sirt1 siRNA or an HDAC inhibitor, Taxol-induced apoptosis was enhanced, which was not observed in p53 null cells. When an acetylation-defective mutant of p53 was re-introduced to p53 null cells, apoptosis was partially reduced compared to the re-introduction of the wild type p53. Thus, p53 plays a pro-apoptotic role in Taxol-induced apoptosis and acetylation of p53 contributes to this pro-apoptotic function in response to Taxol in several human cancer cell lines, suggesting that enhancing acetylation of p53 could have potential implication for increasing the sensitivity of cancer cells to Taxol.

  17. The oncoprotein HBXIP modulates the feedback loop of MDM2/p53 to enhance the growth of breast cancer.

    Science.gov (United States)

    Li, Hang; Liu, Qian; Wang, Zhen; Fang, Runping; Shen, Yu; Cai, Xiaoli; Gao, Yuen; Li, Yinghui; Zhang, Xiaodong; Ye, Lihong

    2015-09-11

    MDM2 and p53 form a negative feedback loop, in which p53 as a transcription factor positively regulates MDM2 and MDM2 negatively regulates tumor suppressor p53 through promoting its degradation. However, the mechanism of the feedback loop is poorly understood in cancers. We had reported previously that the oncoprotein hepatitis B X-interacting protein (HBXIP) is a key oncoprotein in the development of cancer. Thus, we supposed that HBXIP might be involved in the event. Here, we observed that the expression levels of HBXIP were positively correlated to those of MDM2 in clinical breast cancer tissues. Interestingly, HBXIP was able to up-regulate MDM2 at the levels of mRNA and protein in MCF-7 breast cancer cells. Mechanically, HBXIP increased the promoter activities of MDM2 through directly binding to p53 in the P2 promoter of MDM2. Strikingly, we identified that the acetyltransferase p300 was recruited by HBXIP to p53 in the promoter of MDM2. Moreover, we validated that HBXIP enhanced the p53 degradation mediated by MDM2. Functionally, the knockdown of HBXIP or/and p300 inhibited the proliferation of breast cancer cells in vitro, and the depletion of MDM2 or overexpression of p53 significantly blocked the HBXIP-promoted growth of breast cancer in vitro and in vivo. Thus, we concluded that highly expressed HBXIP accelerates the MDM2-mediated degradation of p53 in breast cancer through modulating the feedback loop of MDM2/p53, resulting in the fast growth of breast cancer cells. Our findings provide new insights into the mechanism of the acceleration of the MDM2/p53 feedback loop in the development of cancer.

  18. Anti-cancer efficacy of SREBP inhibitor, alone or in combination with docetaxel, in prostate cancer harboring p53 mutations.

    Science.gov (United States)

    Li, Xiangyan; Wu, Jason Boyang; Chung, Leland W K; Huang, Wen-Chin

    2015-12-01

    Mutant p53 proteins (mutant p53s) have oncogenic gain-of-function properties correlated with tumor grade, castration resistance, and prostate cancer (PCa) tumor recurrence. Docetaxel is a standard first-line treatment for metastatic castration-resistant PCa (mCRPC) after the failure of hormone therapy. However, most mCRPC patients who receive docetaxel experience only transient benefits and rapidly develop incurable drug resistance, which is closely correlated with the p53 mutation status. Mutant p53s were recently reported to regulate the metabolic pathways via sterol regulatory element-binding proteins (SREBPs). Therefore, targeting the SREBP metabolic pathways with docetaxel as a combination therapy may offer a potential strategy to improve anti-tumor efficacy and delay cellular drug resistance in mCRPC harboring mutant p53s. Our previous data showed that fatostatin, a new SREBP inhibitor, inhibited cell proliferation and induced apoptosis in androgen receptor (AR)-positive PCa cell lines and xenograft mouse models. In this study, we demonstrated that mutant p53s activate the SREBP-mediated metabolic pathways in metastatic AR-negative PCa cells carrying mutant p53s. By blocking the SREBP pathways, fatostatin inhibited cell growth and induced apoptosis in metastatic AR-negative PCa cells harboring mutant p53s. Furthermore, the combination of fatostatin and docetaxel resulted in greater proliferation inhibition and apoptosis induction compared with single agent treatment in PCa cells in vitro and in vivo, especially those with mutant p53s. These data suggest for the first time that fatostatin alone or in combination with docetaxel could be exploited as a novel and promising therapy for metastatic PCa harboring p53 mutations.

  19. Gradual reduction in rRNA transcription triggers p53 acetylation and apoptosis via MYBBP1A.

    Science.gov (United States)

    Kumazawa, Takuya; Nishimura, Kazuho; Katagiri, Naohiro; Hashimoto, Sayaka; Hayashi, Yuki; Kimura, Keiji

    2015-06-05

    The nucleolus, whose primary function is ribosome biogenesis, plays an essential role in p53 activation. Ribosome biogenesis is inhibited in response to cellular stress and several nucleolar proteins translocate from the nucleolus to the nucleoplasm, where they activate p53. In this study, we analysed precisely how impaired ribosome biogenesis regulates the activation of p53 by depleting nucleolar factors involved in rRNA transcription or rRNA processing. Nucleolar RNA content decreased when rRNA transcription was inhibited. In parallel with the reduced levels of nucleolar RNA content, the nucleolar protein Myb-binding protein 1 A (MYBBP1A) translocated to the nucleoplasm and increased p53 acetylation. The acetylated p53 enhanced p21 and BAX expression and induced apoptosis. In contrast, when rRNA processing was inhibited, MYBBP1A remained in the nucleolus and nonacetylated p53 accumulated, causing cell cycle arrest at the G1 phase by inducing p21 but not BAX. We propose that the nucleolus functions as a stress sensor to modulate p53 protein levels and its acetylation status, determining cell fate between cell cycle arrest and apoptosis by regulating MYBBP1A translocation.

  20. Regulation of autophagy by cytoplasmic p53.

    Science.gov (United States)

    Tasdemir, Ezgi; Maiuri, M Chiara; Galluzzi, Lorenzo; Vitale, Ilio; Djavaheri-Mergny, Mojgan; D'Amelio, Marcello; Criollo, Alfredo; Morselli, Eugenia; Zhu, Changlian; Harper, Francis; Nannmark, Ulf; Samara, Chrysanthi; Pinton, Paolo; Vicencio, José Miguel; Carnuccio, Rosa; Moll, Ute M; Madeo, Frank; Paterlini-Brechot, Patrizia; Rizzuto, Rosario; Szabadkai, Gyorgy; Pierron, Gérard; Blomgren, Klas; Tavernarakis, Nektarios; Codogno, Patrice; Cecconi, Francesco; Kroemer, Guido

    2008-06-01

    Multiple cellular stressors, including activation of the tumour suppressor p53, can stimulate autophagy. Here we show that deletion, depletion or inhibition of p53 can induce autophagy in human, mouse and nematode cells subjected to knockout, knockdown or pharmacological inhibition of p53. Enhanced autophagy improved the survival of p53-deficient cancer cells under conditions of hypoxia and nutrient depletion, allowing them to maintain high ATP levels. Inhibition of p53 led to autophagy in enucleated cells, and cytoplasmic, not nuclear, p53 was able to repress the enhanced autophagy of p53(-/-) cells. Many different inducers of autophagy (for example, starvation, rapamycin and toxins affecting the endoplasmic reticulum) stimulated proteasome-mediated degradation of p53 through a pathway relying on the E3 ubiquitin ligase HDM2. Inhibition of p53 degradation prevented the activation of autophagy in several cell lines, in response to several distinct stimuli. These results provide evidence of a key signalling pathway that links autophagy to the cancer-associated dysregulation of p53.

  1. The XPB and XPD DNA helicases are components of the p53-mediated apoptosis pathway.

    NARCIS (Netherlands)

    X.W. Wang (Xin Wei); W. Vermeulen (Wim); J.D. Coursen; M.K. Gibson (Michael); S.E. Lupold; K. Forrester; G. Xu; L. Elmore; H. Yeh; J.H.J. Hoeijmakers (Jan); C.C. Harris

    1996-01-01

    textabstractThe molecular pathway of p53-dependent apoptosis (programmed cell death) is poorly understood. Because p53 binds to the basal transcription-repair complex TFIIH and modulates its DNA helicase activities, we hypothesized that TFIIH DNA helicases XPB and XPD are members of the p53-mediated

  2. ATF-2 controls transcription of Maspin and GADD45 alpha genes independently from p53 to suppress mammary tumors.

    Science.gov (United States)

    Maekawa, T; Sano, Y; Shinagawa, T; Rahman, Z; Sakuma, T; Nomura, S; Licht, J D; Ishii, S

    2008-02-14

    The activating transcription factor, ATF-2, is a target of p38 and JNK that are involved in stress-induced apoptosis. Heterozygous Atf-2 mutant (Atf-2+/-) mice are highly prone to mammary tumors. The apoptosis-regulated gene GADD45alpha and the breast cancer suppressor gene Maspin, both of which are known to be p53 target genes, are downregulated in the mammary tumors arisen in Atf-2+/- mice. Here, we have analysed how ATF-2 controls the transcription of GADD45alpha and Maspin. ATF-2 and p53 independently activate the GADD45alpha transcription. ATF-2 does not directly bind to the GADD45alpha promoter; instead, it is recruited via Oct-1 and NF-I. ATF-2 simultaneously binds to Oct-1, NF-I and breast cancer suppressor BRCA1 to activate transcription. With regard to Maspin, ATF-2 and p53 directly bind to different sites in the Maspin promoter to independently activate its transcription. Consistent with the observation that ATF-2 and p53 independently activate the transcription of Maspin and GADD45alpha is that the loss of one copy of p53 shortened the period required for mammary tumor development in Atf-2+/- mice. These studies suggest the functional link between the ATF-2 and the two tumor suppressors BRCA1 and p53.

  3. Long Noncoding RNA PURPL Suppresses Basal p53 Levels and Promotes Tumorigenicity in Colorectal Cancer

    Directory of Open Access Journals (Sweden)

    Xiao Ling Li

    2017-09-01

    Full Text Available Basal p53 levels are tightly suppressed under normal conditions. Disrupting this regulation results in elevated p53 levels to induce cell cycle arrest, apoptosis, and tumor suppression. Here, we report the suppression of basal p53 levels by a nuclear, p53-regulated long noncoding RNA that we termed PURPL (p53 upregulated regulator of p53 levels. Targeted depletion of PURPL in colorectal cancer cells results in elevated basal p53 levels and induces growth defects in cell culture and in mouse xenografts. PURPL associates with MYBBP1A, a protein that binds to and stabilizes p53, and inhibits the formation of the p53-MYBBP1A complex. In the absence of PURPL, MYBBP1A interacts with and stabilizes p53. Silencing MYBBP1A significantly rescues basal p53 levels and proliferation in PURPL-deficient cells, suggesting that MYBBP1A mediates the effect of PURPL in regulating p53. These results reveal a p53-PURPL auto-regulatory feedback loop and demonstrate a role for PURPL in maintaining basal p53 levels.

  4. Biological activity and safety of adenoviral vector-expressed wild-type p53 after intratumoral injection in melanoma and breast cancer patients with p53-overexpressing tumors

    NARCIS (Netherlands)

    Dummer, R; Bergh, J; Karlsson, Y; Horovitz, JA; Mulder, NH; Huinin, DT; Burg, G; Hofbauer, G; Osanto, S

    2000-01-01

    p53 mutations are common genetic alterations in human cancer. Gene transfer of a wild-type (wt) p53 gene reverses the loss of normal p53 function in vitro and in vivo. A phase I dose escalation study of single intratumoral (i.t.) injection of a replication-defective adenoviral expression vector cont

  5. p53 inhibits the upregulation of sirtuin 1 expression induced by c-Myc.

    Science.gov (United States)

    Yuan, Fang; Liu, Lu; Lei, Yonghong; Tang, Peifu

    2017-10-01

    Sirtuin 1 (Sirt1), a conserved NAD(+) dependent deacetylase, is a mediator of life span by calorie restriction. However, Sirt1 may paradoxically increase the risk of cancer. Accordingly, the expression level of Sirt1 is selectively elevated in numerous types of cancer cell; however, the mechanisms underlying the differential regulation remain largely unknown. The present study demonstrated that oncoprotein c-Myc was a direct regulator of Sirt1, which accounts for the upregulation of Sirt1 expression only in the cells without functional p53. In p53 deficient cells, the overexpression of c-Myc increased Sirt1 mRNA and protein expression levels as well as its promoter activity, whereas the inhibitor of c-Myc, 10058-F4, induced decreased Sirt1 basal mRNA and protein expression levels. Deletion/mutation mapping analyses revealed that c-Myc bound to the conserved E-box[-189 to -183 base pair (bp)] of the Sirt1 promoter. In addition, p53 and c-Myc shared at least response element and the presence of p53 may block the binding of c-Myc to the Sirt1 promoter, thus inhibit the c-Myc mediated upregulation of Sirt1 promoter activity. The present study indicated that the expression level of Sirt1 was tightly regulated by oncoprotein c-Myc and tumor suppressor p53, which aids an improved understanding of its expression regulation and tumor promoter role in certain conditions.

  6. p53 Superfamily proteins in marine bivalve cancer and stress biology.

    Science.gov (United States)

    Walker, Charles W; Van Beneden, Rebecca J; Muttray, Annette F; Böttger, S Anne; Kelley, Melissa L; Tucker, Abraham E; Thomas, W Kelley

    2011-01-01

    The human p53 tumour suppressor protein is inactivated in many cancers and is also a major player in apoptotic responses to cellular stress. The p53 protein and the two other members of this protein family (p63, p73) are encoded by distinct genes and their functions have been extensively documented for humans and some other vertebrates. The structure and relative expression levels for members of the p53 superfamily have also been reported for most major invertebrate taxa. The functions of homologous proteins have been investigated for only a few invertebrates (specifically, p53 in flies, nematodes and recently a sea anemone). These studies of classical model organisms all suggest that the gene family originally evolved to mediate apoptosis of damaged germ cells or to protect germ cells from genotoxic stress. Here, we have correlated data from a number of molluscan and other invertebrate sequencing projects to provide a framework for understanding p53 signalling pathways in marine bivalve cancer and stress biology. These data suggest that (a) the two identified p53 and p63/73-like proteins in soft shell clam (Mya arenaria), blue mussel (Mytilus edulis) and Northern European squid (Loligo forbesi) have identical core sequences and may be splice variants of a single gene, while some molluscs and most other invertebrates have two or more distinct genes expressing different p53 family members; (b) transcriptional activation domains (TADs) in bivalve p53 and p63/73-like protein sequences are 67-69% conserved with human p53, while those in ecdysozoan, cnidarian, placozoan and choanozoan eukaryotes are ≤33% conserved; (c) the Mdm2 binding site in the transcriptional activation domain is 100% conserved in all sequenced bivalve p53 proteins (e.g. Mya, Mytilus, Crassostrea and Spisula) but is not present in other non-deuterostome invertebrates; (d) an Mdm2 homologue has been cloned for Mytilus trossulus; (e) homologues for both human p53 upstream regulatory and

  7. Inhibition of Casein kinase-2 induces p53-dependent cell cycle arrest and sensitizes glioblastoma cells to tumor necrosis factor (TNFα)-induced apoptosis through SIRT1 inhibition.

    Science.gov (United States)

    Dixit, D; Sharma, V; Ghosh, S; Mehta, V S; Sen, E

    2012-02-09

    Glioblastoma multiforme (GBM) are resistant to TNFα-induced apoptosis and blockade of TNFα-induced NF-κB activation sensitizes glioma cells to apoptosis. As Casein kinase-2 (CK2) induces aberrant NF-κB activation and as we observed elevated CK2 levels in GBM tumors, we investigated the potential of CK2 inhibitors (CK2-Is) - DRB and Apigenin in sensitizing glioma cells to TNFα-induced apoptosis. CK2-Is and CK2 small interfering RNA (siRNA) reduced glioma cell viability, inhibited TNFα-mediated NF-κB activation, and sensitized cell to TNFα-induced apoptosis. Importantly, CK2-Is activated p53 function in wild-type but not in p53 mutant cells. Activation of p53 function involved its increased transcriptional activation, DNA-binding ability, increased expression of p53 target genes associated with cell cycle progression and apoptosis. Moreover, CK2-Is decreased telomerase activity and increased senescence in a p53-dependent manner. Apoptotic gene profiling indicated that CK2-Is differentially affect p53 and TNFα targets in p53 wild-type and mutant glioma cells. CK2-I decreased MDM2-p53 association and p53 ubiquitination to enhance p53 levels. Interestingly, CK2-Is downregulated SIRT1 activity and over-expression of SIRT1 decreased p53 transcriptional activity and rescued cells from CK2-I-induced apoptosis. This ability of CK2-Is to sensitize glioma to TNFα-induced death via multiple mechanisms involving abrogation of NF-κB activation, reactivation of wild-type p53 function and SIRT1 inhibition warrants investigation.

  8. Ligand dependent restoration of human TLR3 signaling and death in p53 mutant cells.

    Science.gov (United States)

    Menendez, Daniel; Lowe, Julie M; Snipe, Joyce; Resnick, Michael A

    2016-09-20

    Diversity within the p53 transcriptional network can arise from a matrix of changes that include target response element sequences and p53 expression level variations. We previously found that wild type p53 (WT p53) can regulate expression of most innate immune-related Toll-like-receptor genes (TLRs) in human cells, thereby affecting immune responses. Since many tumor-associated p53 mutants exhibit change-of-spectrum transactivation from various p53 targets, we examined the ability of twenty-five p53 mutants to activate endogenous expression of the TLR gene family in p53 null human cancer cell lines following transfection with p53 mutant expression vectors. While many mutants retained the ability to drive TLR expression at WT levels, others exhibited null, limited, or change-of-spectrum transactivation of TLR genes. Using TLR3 signaling as a model, we show that some cancer-associated p53 mutants amplify cytokine, chemokine and apoptotic responses after stimulation by the cognate ligand poly(I:C). Furthermore, restoration of WT p53 activity for loss-of-function p53 mutants by the p53 reactivating drug RITA restored p53 regulation of TLR3 gene expression and enhanced DNA damage-induced apoptosis via TLR3 signaling. Overall, our findings have many implications for understanding the impact of WT and mutant p53 in immunological responses and cancer therapy.

  9. Aberrant splicing of the DMP1-ARF-MDM2-p53 pathway in cancer.

    Science.gov (United States)

    Inoue, Kazushi; Fry, Elizabeth A

    2016-07-01

    Alternative splicing (AS) of mRNA precursors is a ubiquitous mechanism for generating numerous transcripts with different activities from one genomic locus in mammalian cells. The gene products from a single locus can thus have similar, dominant-negative or even opposing functions. Aberrant AS has been found in cancer to express proteins that promote cell growth, local invasion and metastasis. This review will focus on the aberrant splicing of tumor suppressor/oncogenes that belong to the DMP1-ARF-MDM2-p53 pathway. Our recent study shows that the DMP1 locus generates both tumor-suppressive DMP1α (p53-dependent) and oncogenic DMP1β (p53-independent) splice variants, and the DMP1β/α ratio increases with neoplastic transformation of breast epithelial cells. This process is associated with high DMP1β protein expression and shorter survival of breast cancer (BC) patients. Accumulating pieces of evidence show that ARF is frequently inactivated by aberrant splicing in human cancers, demonstrating its involvement in human malignancies. Splice variants from the MDM2 locus promote cell growth in culture and accelerate tumorigenesis in vivo. Human cancers expressing these splice variants are associated with advanced stage/metastasis, and thus have negative clinical impacts. Although they lack most of the p53-binding domain, their activities are mostly dependent on p53 since they bind to wild-type MDM2. The p53 locus produces splice isoforms that have either favorable (β/γ at the C-terminus) or negative impact (Δ40, Δ133 at the N-terminus) on patients' survival. As the oncogenic AS products from these loci are expressed only in cancer cells, they may eventually become targets for molecular therapies.

  10. The p53 Transcriptional Network Influences Microglia Behavior and Neuroinflammation.

    Science.gov (United States)

    Aloi, Macarena S; Su, Wei; Garden, Gwenn A

    2015-01-01

    The tumor-suppressor protein p53 belongs to a family of proteins that play pivotal roles in multiple cellular functions including cell proliferation, cell death, genome stability, and regulation of inflammation. Neuroinflammation is a common feature of central nervous system (CNS) pathology, and microglia are the specialized resident population of CNS myeloid cells that initiate innate immune responses. Microglia maintain CNS homeostasis through pathogen containment, phagocytosis of debris, and initiation of tissue-repair cascades. However, an unregulated pro-inflammatory response can lead to tissue injury and dysfunction in both acute and chronic inflammatory states. Therefore, regulation of the molecular signals that control the induction, magnitude, and resolution of inflammation are necessary for optimal CNS health. We and others have described a novel mechanism by which p53 transcriptional activity modulates microglia behaviors in vitro and in vivo. Activation of p53 induces expression of microRNAs (miRNAs) that support microglia pro-inflammatory functions and suppress anti-inflammatory and tissue repair behaviors. In this review, we introduce the previously described roles of the p53 signaling network and discuss novel functions of p53 in the microglia-mediated inflammatory response in CNS health and disease. Ultimately, improved understanding of the molecular regulators modulated by p53 transcriptional activity in microglia will enhance the development of rational therapeutic strategies to harness the homeostatic and tissue repair functions of microglia.

  11. Nanoparticle-mediated p53 gene therapy for tumor inhibition

    OpenAIRE

    Sharma, Blanka; Ma, Wenxue; Adjei, Isaac Morris; Panyam, Jayanth; Dimitrijevic, Sanja; Labhasetwar, Vinod

    2011-01-01

    The p53 tumor suppressor gene is mutated in 50% of human cancers, resulting in more aggressive disease with greater resistance to chemotherapy and radiation therapy. Advances in gene therapy technologies offer a promising approach to restoring p53 function. We have developed polymeric nanoparticles (NPs), based on poly (lactic-co-glycolic acid), that provide sustained intracellular delivery of plasmid DNA, resulting in sustained gene expression without vector-associated toxicity. Our previous...

  12. Small-Molecule NSC59984 Restores p53 Pathway Signaling and Antitumor Effects against Colorectal Cancer via p73 Activation and Degradation of Mutant p53.

    Science.gov (United States)

    Zhang, Shengliang; Zhou, Lanlan; Hong, Bo; van den Heuvel, A Pieter J; Prabhu, Varun V; Warfel, Noel A; Kline, Christina Leah B; Dicker, David T; Kopelovich, Levy; El-Deiry, Wafik S

    2015-09-15

    The tumor-suppressor p53 prevents cancer development via initiating cell-cycle arrest, cell death, repair, or antiangiogenesis processes. Over 50% of human cancers harbor cancer-causing mutant p53. p53 mutations not only abrogate its tumor-suppressor function, but also endow mutant p53 with a gain of function (GOF), creating a proto-oncogene that contributes to tumorigenesis, tumor progression, and chemo- or radiotherapy resistance. Thus, targeting mutant p53 to restore a wild-type p53 signaling pathway provides an attractive strategy for cancer therapy. We demonstrate that small-molecule NSC59984 not only restores wild-type p53 signaling, but also depletes mutant p53 GOF. NSC59984 induces mutant p53 protein degradation via MDM2 and the ubiquitin-proteasome pathway. NSC59984 restores wild-type p53 signaling via p73 activation, specifically in mutant p53-expressing colorectal cancer cells. At therapeutic doses, NSC59984 induces p73-dependent cell death in cancer cells with minimal genotoxicity and without evident toxicity toward normal cells. NSC59984 synergizes with CPT11 to induce cell death in mutant p53-expressing colorectal cancer cells and inhibits mutant p53-associated colon tumor xenograft growth in a p73-dependent manner in vivo. We hypothesize that specific targeting of mutant p53 may be essential for anticancer strategies that involve the stimulation of p73 in order to efficiently restore tumor suppression. Taken together, our data identify NSC59984 as a promising lead compound for anticancer therapy that acts by targeting GOF-mutant p53 and stimulates p73 to restore the p53 pathway signaling.

  13. DIMP53-1: A novel small-molecule dual inhibitor of p53-MDM2/X interactions with multifunctional p53-dependent anticancer properties.

    Science.gov (United States)

    Soares, Joana; Espadinha, Margarida; Raimundo, Liliana; Ramos, Helena; Gomes, Ana Sara; Gomes, Sara; Loureiro, Joana B; Inga, Alberto; Reis, Flávio; Gomes, Célia; Santos, Maria M M; Saraiva, Lucília

    2017-03-10

    The transcription factor p53 plays a crucial role in cancer development and dissemination, and thus p53-targeted therapies are amongst the most encouraging anticancer strategies. In human cancers with wild-type (wt) p53, its inactivation by interaction with murine double minute (MDM)2 and MDMX is a common event. Simultaneous inhibition of the p53 interaction with both MDMs is crucial to restore the tumor suppressor activity of p53. Here we describe the synthesis of the new tryptophanol-derived oxazoloisoindolinone DIMP53-1 and identify its activity as a dual inhibitor of the p53-MDM2/X interactions using a yeast-based assay. DIMP53-1 caused growth inhibition, mediated by p53 stabilization and upregulation of p53 transcriptional targets involved in cell cycle arrest and apoptosis, in wt p53-expressing tumor cells, including MDM2- or MDMX-overexpressing cells. Importantly, DIMP53-1 abolishes the p53-MDM2/X interactions by binding to p53, in human colon adenocarcinoma HCT116 cells. DIMP53-1 also inhibited the migration and invasion of HCT116 cells, and the migration and tube formation of HMVEC-D endothelial cells. Notably, in human tumor xenograft mice models, DIMP53-1 showed a p53-dependent antitumor activity through induction of apoptosis and inhibition of proliferation and angiogenesis. Finally, no genotoxicity or undesirable toxic effects were observed with DIMP53-1. In conclusion, DIMP53-1 is a novel p53 activator, which potentially binds to p53 inhibiting its interaction with MDM2 and MDMX. Although target-directed, DIMP53-1 has a multifunctional activity, targeting major hallmarks of cancer through its anti-proliferative, pro-apoptotic, anti-angiogenic, anti-invasive and anti-migratory properties. DIMP53-1 is a promising anticancer drug candidate and an encouraging starting point to develop improved derivatives for clinical application.

  14. Rational design of cyclic peptide modulators of the transcriptional coactivator CBP: a new class of p53 inhibitors.

    Science.gov (United States)

    Gerona-Navarro, Guillermo; Yoel-Rodríguez; Mujtaba, Shiraz; Frasca, Antonio; Patel, Jigneshkumar; Zeng, Lei; Plotnikov, Alexander N; Osman, Roman; Zhou, Ming-Ming

    2011-02-23

    The CREB binding protein (CBP) is a human transcriptional coactivator consisting of several conserved functional modules, which interacts with distinct transcription factors including nuclear receptors, CREB, and STAT proteins. Despite the importance of CBP in transcriptional regulation, many questions regarding the role of its particular domains in CBP functions remain unanswered. Therefore, developing small molecules capable of selectively modulating a single domain of CBP is of invaluable aid at unraveling its prominent activities. Here we report the design, synthesis, and biological evaluation of conformationally restricted peptides as novel modulators for the acetyl-lysine binding bromodomain (BRD) of CBP. Utilizing a target structure-guided and computer-aided rational design approach, we developed a series of cyclic peptides with affinity for CBP BRD significantly greater than those of its biological ligands, including lysine-acetylated histones and tumor suppressor p53. The best cyclopeptide of the series exhibited a K(d) of 8.0 μM, representing a 24-fold improvement in affinity over that of the linear lysine 382-acetylated p53 peptide. This lead peptide is highly selective for CBP BRD over BRDs from other transcriptional proteins. Cell-based functional assays carried out in colorectal carcinoma HCT116 cells further demonstrated the efficacy of this compound to modulate p53 stability and function in response to DNA damage. Our results strongly argue that these CBP modulators can effectively inhibit p53 transcriptional activity by blocking p53K382ac binding to CBP BRD and promoting p53 instability by changes of its post-translational modification states, a different mechanism than that of the p53 inhibitors reported to date.

  15. Identification of p53 and Its Isoforms in Human Breast Carcinoma Cells

    Directory of Open Access Journals (Sweden)

    Zorka Milićević

    2014-01-01

    Full Text Available In breast carcinoma, disruption of the p53 pathway is one of the most common genetic alterations. The observation that the p53 can express multiple protein isoforms adds a novel level of complexity to the outcome of p53 mutations. p53 expression was analysed by Western immunoblotting and immunohistochemistry using monoclonal antibodies DO-7, Pab240, and polyclonal antiserum CM-1. The more frequently p53-positive nuclear staining has been found in the invasive breast tumors. One of the most intriguing findings is that mutant p53 appears as discrete dot-shaped regions within the nucleus of breast cancer cells. In many malignant cells, the nucleolar sequestration of p53 is evident. These observations support the view that the nucleolus is involved directly in the mediation of p53 function or indirectly by the control of the localization of p53 interplayers. p53 expressed in the nuclear fraction of breast cancer cells revealed a wide spectrum of isoforms. p53 isoforms ΔNp53 (47 kDa and Δ133p53β (35 kDa, known as dominant-negative repressors of p53 function, were detected as the most predominant variants in nuclei of invasive breast carcinoma cells. The isoforms expressed also varied between individual tumors, indicating potential roles of these p53 variants in human breast cancer.

  16. Identification of Semaphorin3B as a Direct Target of p53

    Directory of Open Access Journals (Sweden)

    Kensuke Ochi

    2002-01-01

    Full Text Available A cDNA microarray analysis indicated that Semaphorin3B. (20Sema3B, a gene whose product is involved in axon guidance and axonal repulsion, is inducible by p53. Introduction of exogenous p53 into a glioblastoma cell line lacking wild-type p53. (20U373MG dramatically induced expression of Sema3B mRNA. An electrophoretic mobility shift assay and a reporter assay confirmed that a potential p53 binding site present in the promoter region had p53-dependent transcriptional activity. Expression of endogenous Sema3B was induced in response to genotoxic stresses caused by adriamycin treatment or UV irradiation in a p53-dependent manner. Ectopic expression of Sema3B in p53-defective cells reduced the number of colonies in colony formation assays. These results suggest that Sema3B might play some role in regulating cell growth as a mediator of p53 tumor- suppressor activity.

  17. Mitochondrial localization of the low level p53 protein in proliferative cells

    Energy Technology Data Exchange (ETDEWEB)

    Ferecatu, Ioana; Bergeaud, Marie; Rodriguez-Enfedaque, Aida; Le Floch, Nathalie [Laboratoire de Genetique et Biologie Cellulaire - CNRS UMR 8159, Universite de Versailles Saint-Quentin-en-Yvelines, Versailles, France and Laboratoire de Genetique Moleculaire et Physiologique, Ecole Pratique des Hautes Etudes, Versailles (France); Oliver, Lisa [INSERM U601, Universite de Nantes, Faculte de Medecine, Nantes Cedex (France); Rincheval, Vincent; Renaud, Flore [Laboratoire de Genetique et Biologie Cellulaire - CNRS UMR 8159, Universite de Versailles Saint-Quentin-en-Yvelines, Versailles, France and Laboratoire de Genetique Moleculaire et Physiologique, Ecole Pratique des Hautes Etudes, Versailles (France); Vallette, Francois M. [INSERM U601, Universite de Nantes, Faculte de Medecine, Nantes Cedex (France); Mignotte, Bernard [Laboratoire de Genetique et Biologie Cellulaire - CNRS UMR 8159, Universite de Versailles Saint-Quentin-en-Yvelines, Versailles, France and Laboratoire de Genetique Moleculaire et Physiologique, Ecole Pratique des Hautes Etudes, Versailles (France); Vayssiere, Jean-Luc, E-mail: jean-luc.vayssiere@uvsq.fr [Laboratoire de Genetique et Biologie Cellulaire - CNRS UMR 8159, Universite de Versailles Saint-Quentin-en-Yvelines, Versailles, France and Laboratoire de Genetique Moleculaire et Physiologique, Ecole Pratique des Hautes Etudes, Versailles (France)

    2009-10-02

    p53 protein plays a central role in suppressing tumorigenesis by inducing cell cycle arrest or apoptosis through transcription-dependent and -independent mechanisms. Emerging publications suggest that following stress, a fraction of p53 translocates to mitochondria to induce cytochrome c release and apoptosis. However, the localization of p53 under unstressed conditions remains largely unexplored. Here we show that p53 is localized at mitochondria in absence of apoptotic stimuli, when cells are proliferating, localization observed in various cell types (rodent and human). This is also supported by acellular assays in which p53 bind strongly to mitochondria isolated from rat liver. Furthermore, the mitochondria subfractionation study and the alkaline treatment of the mitochondrial p53 revealed that the majority of mitochondrial p53 is present in the membranous compartments. Finally, we identified VDAC, a protein of the mitochondrial outer-membrane, as a putative partner of p53 in unstressed/proliferative cells.

  18. Effect of p53 genotype on gene expression profiles in murine liver

    Energy Technology Data Exchange (ETDEWEB)

    Morris, Suzanne M. [Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079 (United States)], E-mail: suzanne.morris@fda.hhs.gov; Akerman, Gregory S. [Toxicology Branch, Health Effects Division (7509P), US Environmental Protection Agency, 1200 Pennsylvania Avenue, NW, Washington, DC 20460 (United States); Desai, Varsha G. [Division of Systems Toxicology, National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079 (United States); Tsai, Chen-an [Biostatistics Center and Department of Public Health, China Medical University, Taichung, 40402, Taiwan (China); Tolleson, William H.; Melchior, William B. [Division of Biochemical Toxicology, National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079 (United States); Lin, Chien-Ju [Division of Personalized Nutrition and Medicine, National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079 (United States); Fuscoe, James C. [Division of Systems Toxicology, National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079 (United States); Casciano, Daniel A. [Dan Casciano and Associates, 47 Marcella Drive, Little Rock, AR 72233 (United States); Chen, James J. [Division of Personalized Nutrition and Medicine, National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079 (United States)

    2008-04-02

    The tumor suppressor protein p53 is a key regulatory element in the cell and is regarded as the 'guardian of the genome'. Much of the present knowledge of p53 function has come from studies of transgenic mice in which the p53 gene has undergone a targeted deletion. In order to provide additional insight into the impact on the cellular regulatory networks associated with the loss of this gene, microarray technology was utilized to assess gene expression in tissues from both the p53{sup -/-} and p53{sup +/-} mice. Six male mice from each genotype (p53{sup +/+}, p53{sup +/-}, and p53{sup -/-}) were humanely killed and the tissues processed for microarray analysis. The initial studies have been performed in the liver for which the Dunnett test revealed 1406 genes to be differentially expressed between p53{sup +/+} and p53{sup +/-} or between p53{sup +/+} and p53{sup -/-} at the level of p {<=} 0.05. Both genes with increased expression and decreased expression were identified in p53{sup +/-} and in p53{sup -/-} mice. Most notable in the gene list derived from the p53{sup +/-} mice was the significant reduction in p53 mRNA. In the p53{sup -/-} mice, not only was there reduced expression of the p53 genes on the array, but genes associated with DNA repair, apoptosis, and cell proliferation were differentially expressed, as expected. However, altered expression was noted for many genes in the Cdc42-GTPase pathways that influence cell proliferation. This may indicate that alternate pathways are brought into play in the unperturbed liver when loss or reduction in p53 levels occurs.

  19. Microbial Regulation of p53 Tumor Suppressor.

    Directory of Open Access Journals (Sweden)

    Alexander I Zaika

    2015-09-01

    Full Text Available p53 tumor suppressor has been identified as a protein interacting with the large T antigen produced by simian vacuolating virus 40 (SV40. Subsequent research on p53 inhibition by SV40 and other tumor viruses has not only helped to gain a better understanding of viral biology, but also shaped our knowledge of human tumorigenesis. Recent studies have found, however, that inhibition of p53 is not strictly in the realm of viruses. Some bacterial pathogens also actively inhibit p53 protein and induce its degradation, resulting in alteration of cellular stress responses. This phenomenon was initially characterized in gastric epithelial cells infected with Helicobacter pylori, a bacterial pathogen that commonly infects the human stomach and is strongly linked to gastric cancer. Besides H. pylori, a number of other bacterial species were recently discovered to inhibit p53. These findings provide novel insights into host-bacteria interactions and tumorigenesis associated with bacterial infections.

  20. HDM2 impairs Noxa transcription and affects apoptotic cell death in a p53/p73-dependent manner in neuroblastoma.

    Science.gov (United States)

    Shi, Yun; Takenobu, Hisanori; Kurata, Kenji; Yamaguchi, Yohko; Yanagisawa, Ryu; Ohira, Miki; Koike, Kenichi; Nakagawara, Akira; Jiang, Ling Ling; Kamijo, Takehiko

    2010-08-01

    HDM2, a human homologue of MDM2, is a major negative regulator of p53 function, and increased expression of HDM2 by its promoter polymorphism SNP309 resulted in p53 inactivation and an increased risk of several tumours, including neuroblastoma (NB). Herein, we show that increased expression of HDM2 is related to a worse prognosis in MYCN-amplified NB patients. HDM2 plays an important role in the expression of Noxa, a pro-apoptotic molecule of the Bcl-2 family, which induces NB cell apoptotic death after doxorubcin (Doxo) treatment. Knockdown of HDM2 by siRNA resulted in the upregulation of Noxa at mRNA/protein levels and improved the sensitivity of Doxo-resistant NB cells, although these were not observed in p53-mutant NB cells. Noxa-knockdown abolished the recovered Doxo-induced cell death by HDM2 reduction. Intriguingly, resistance to Doxo was up-regulated by over-expression of HDM2 in Doxo-sensitive NB cells. By HDM2 expression, p53 was inactivated but its degradation was not accelerated, suggesting that p53 was degraded in a proteasome-independent manner in NB cells; downstream effectors of p53, p21(Cip1/Waf1) and Noxa were suppressed by HDM2. Noxa transcription was considerably regulated by both p53 and p73 in NB cells. Furthermore, in vivo binding of p53 and p73 to Noxa promoter was suppressed and Noxa promoter activation was inhibited by HDM2. Taken together, our results may indicate that the HDM2-related resistance to chemotherapeutic drugs of NB is regulated by p53/p73-dependent Noxa expression in NB.

  1. Modulation of p53 activity by IκBα: Evidence suggesting a common phylogeny between NF-κB and p53 transcription factors

    Directory of Open Access Journals (Sweden)

    Gelfand Erwin W

    2005-06-01

    Full Text Available Abstract Background In this work we present evidence that the p53 tumor suppressor protein and NF-κB transcription factors could be related through common descent from a family of ancestral transcription factors regulating cellular proliferation and apoptosis. P53 is a homotetrameric transcription factor known to interact with the ankyrin protein 53BP2 (a fragment of the ASPP2 protein. NF-κB is also regulated by ankyrin proteins, the prototype of which is the IκB family. The DNA binding sequences of the two transcription factors are similar, sharing 8 out of 10 nucleotides. Interactions between the two proteins, both direct and indirect, have been noted previously and the two proteins play central roles in the control of proliferation and apoptosis. Results Using previously published structure data, we noted a significant degree of structural alignment between p53 and NF-κB p65. We also determined that IκBα and p53 bind in vitro through a specific interaction in part involving the DNA binding region of p53, or a region proximal to it, and the amino terminus of IκBα independently or cooperatively with the ankyrin 3 domain of IκBα In cotransfection experiments, κBα could significantly inhibit the transcriptional activity of p53. Inhibition of p53-mediated transcription was increased by deletion of the ankyrin 2, 4, or 5 domains of IκBα Co-precipitation experiments using the stably transfected ankyrin 5 deletion mutant of κBα and endogenous wild-type p53 further support the hypothesis that p53 and IκBα can physically interact in vivo. Conclusion The aggregate results obtained using bacterially produced IκBα and p53 as well as reticulocyte lysate produced proteins suggest a correlation between in vitro co-precipitation in at least one of the systems and in vivo p53 inhibitory activity. These observations argue for a mechanism involving direct binding of IκBα to p53 in the inhibition of p53 transcriptional activity, analogous to

  2. Transcriptional repressor NIR interacts with the p53-inhibiting ubiquitin ligase MDM2.

    Science.gov (United States)

    Heyne, Kristina; Förster, Juliane; Schüle, Roland; Roemer, Klaus

    2014-04-01

    NIR (novel INHAT repressor) can bind to p53 at promoters and inhibit p53-mediated gene transactivation by blocking histone acetylation carried out by p300/CBP. Like NIR, the E3 ubiquitin ligase MDM2 can also bind and inhibit p53 at promoters. Here, we present data indicating that NIR, which shuttles between the nucleolus and nucleoplasm, not only binds to p53 but also directly to MDM2, in part via the central acidic and zinc finger domain of MDM2 that is also contacted by several other nucleolus-based MDM2/p53-regulating proteins. Like some of these, NIR was able to inhibit the ubiquitination of MDM2 and stabilize MDM2; however, unlike these nucleolus-based MDM2 regulators, NIR did not inhibit MDM2 to activate p53. Rather, NIR cooperated with MDM2 to repress p53-induced transactivation. This cooperative repression may at least in part involve p300/CBP. We show that NIR can block the acetylation of p53 and MDM2. Non-acetylated p53 has been documented previously to more readily associate with inhibitory MDM2. NIR may thus help to sustain the inhibitory p53:MDM2 complex, and we present evidence suggesting that all three proteins can indeed form a ternary complex. In sum, our findings suggest that NIR can support MDM2 to suppress p53 as a transcriptional activator.

  3. Prediction of dual agents as an activator of mutant p53 and inhibitor of Hsp90 by docking, molecular dynamic simulation and virtual screening.

    Science.gov (United States)

    Abbasi, Maryam; Sadeghi-Aliabadi, Hojjat; Hassanzadeh, Farshid; Amanlou, Massoud

    2015-09-01

    Heat shock protein90s (Hsp90s) play a crucial role in the development of cancer, and their inhibitors are a main target for tumor suppression. P53 also is a tumor suppressor, but in cancer cells, mutations in the p53 gene lead to the inactivation and accumulation of protein. For instance, the ninth p53 cancer mutation, Y220C, destabilizes the p53 core domain. Small molecules have been assumed to bind to Y220C DNA-binding domain and reactivate cellular mutant p53 functions. In this study, one of the mutant p53 activators is suggested as an Hsp90 inhibitor according to a pyrazole scaffold. To confirm a new ligand as a dual agent, molecular docking and molecular dynamic simulations were performed on both proteins (p53 and Hsp90). Molecular dynamic simulations were also conducted to evaluate the obtained results on the other two pyrazole structures, one known as Hsp90 inhibitor and the other as the reported mutant p53 activator. The findings indicate that the new ligand was stable in the active site of both proteins. Finally, a virtual screening was performed on ZINC database, and a set of new dual agents was proposed according to the new ligand scaffold. Copyright © 2015. Published by Elsevier Inc.

  4. The PRR11-SKA2 Bidirectional Transcription Unit Is Negatively Regulated by p53 through NF-Y in Lung Cancer Cells.

    Science.gov (United States)

    Wang, Yitao; Weng, Huali; Zhang, Ying; Long, Yinjiang; Li, Yi; Niu, Yulong; Song, Fangzhou; Bu, Youquan

    2017-03-01

    We previously identified proline-rich protein 11 (PRR11) as a novel cancer-related gene that is implicated in the regulation of cell cycle and tumorigenesis. Our recent study demonstrated that PRR11 and its adjacent gene, kinetochore associated 2 (SKA2), constitute a classic head-to-head gene pair that is coordinately regulated by nuclear factor Y (NF-Y). In the present study, we further show that the PRR11-SKA2 bidirectional transcription unit is an indirect target of the tumor suppressor p53. A luciferase reporter assay revealed that overexpression of wild type p53, but not mutant p53, significantly represses the basal activity and NF-Y mediated transactivation of the PRR11-SKA2 bidirectional promoter. Deletion and mutation analysis of the PRR11-SKA2 promoter revealed that p53-mediated PRR11-SKA2 repression is dependent on the presence of functional NF-Y binding sites. Furthermore, a co-immunoprecipitation assay revealed that p53 associates with NF-Y in lung cancer cells, and a chromatin immunoprecipitation assay showed that p53 represses PRR11-SKA2 transcription by reducing the binding amount of NF-Y in the PRR11-SKA2 promoter region. Consistently, the ability of p53 to downregulate PRR11-SKA2 transcription was significantly attenuated upon siRNA-mediated depletion of nuclear factor Y subunit beta (NF-YB). Notably, lung cancer patients with lower expression of either PRR11 or SKA2 along with wild type p53 exhibited the best overall survival compared with others with p53 mutation and/or higher expression of either PRR11 or SKA2. Taken together, our results demonstrate that p53 negatively regulates the expression of the PRR11-SKA2 bidirectional transcription unit through NF-Y, suggesting that the inability to repress the PRR11-SKA2 bidirectional transcription unit after loss of p53 might contribute to tumorigenesis.

  5. Modeling the Etiology of p53-mutated Cancer Cells.

    Science.gov (United States)

    Perez, Ricardo E; Shen, Hong; Duan, Lei; Kim, Reuben H; Kim, Terresa; Park, No-Hee; Maki, Carl G

    2016-05-06

    p53 gene mutations are among the most common alterations in cancer. In most cases, missense mutations in one TP53 allele are followed by loss-of-heterozygosity (LOH), so tumors express only mutant p53. TP53 mutations and LOH have been linked, in many cases, with poor therapy response and worse outcome. Despite this, remarkably little is known about how TP53 point mutations are acquired, how LOH occurs, or the cells involved. Nutlin-3a occupies the p53-binding site in MDM2 and blocks p53-MDM2 interaction, resulting in the stabilization and activation of p53 and subsequent growth arrest or apoptosis. We leveraged the powerful growth inhibitory activity of Nutlin-3a to select p53-mutated cells and examined how TP53 mutations arise and how the remaining wild-type allele is lost or inactivated. Mismatch repair (MMR)-deficient colorectal cancer cells formed heterozygote (p53 wild-type/mutant) colonies when cultured in low doses of Nutlin-3a, whereas MMR-corrected counterparts did not. Placing these heterozygotes in higher Nutlin-3a doses selected clones in which the remaining wild-type TP53 was silenced. Our data suggest silencing occurred through a novel mechanism that does not involve DNA methylation, histone methylation, or histone deacetylation. These data indicate MMR deficiency in colorectal cancer can give rise to initiating TP53 mutations and that TP53 silencing occurs via a copy-neutral mechanism. Moreover, the data highlight the use of MDM2 antagonists as tools to study mechanisms of TP53 mutation acquisition and wild-type allele loss or silencing in cells with defined genetic backgrounds.

  6. Ling Zhi-8 mediates p53-dependent growth arrest of lung cancer cells proliferation via the ribosomal protein S7-MDM2-p53 pathway.

    Science.gov (United States)

    Wu, Chien-Ting; Lin, Tung-Yi; Hsu, Hsien-Yeh; Sheu, Fuu; Ho, Chau-Mei; Chen, Edmund I-T

    2011-12-01

    Ling Zhi-8 (LZ-8), an immunomodulatory protein, is derived from and has been cloned from the medicinal mushroom Ganoderma lucidum (Reishi or Ling Zhi); this protein exhibits immunomodulating and antitumor properties. We investigated the effects of recombinant LZ-8 protein (rLZ-8) on the proliferation of A549 human lung cancer cells. Here, we showed that rLZ-8 inhibits cell growth and that this is correlated with increased G(1) arrest. The treatment of A549 cells with rLZ-8 activated p53 and p21 expression, and both the G(1) arrest and the antigrowth effect were found to be p53 dependent. It was further demonstrated that rLZ-8 inhibited tumor growth in mice transplanted with Lewis lung carcinoma cells. Interestingly, rLZ-8 treatment was found to lead to nucleolar stress (or ribosomal stress) as evidenced by inhibition of precursor ribosomal RNA synthesis and reduced polysome formation in A549 cells. These changes resulted in an increasing binding of ribosomal protein S7 to MDM2 and a decreased interaction between MDM2 and p53. Taking these results together, we have identified a novel rLZ-8 antitumor function that positively modulates p53 via ribosomal stress and inhibits lung cancer cell growth in vitro and in vivo. Our current results suggest that rLZ-8 may have potential as a therapeutic intervention for the treatment of cancers that contain wild-type p53 and high expression of MDM2.

  7. Zinc finger protein ZPR9 functions as an activator of AMPK-related serine/threonine kinase MPK38/MELK involved in ASK1/TGF-β/p53 signaling pathways

    Science.gov (United States)

    Seong, Hyun-A; Manoharan, Ravi; Ha, Hyunjung

    2017-01-01

    Murine protein serine-threonine kinase 38 (MPK38), an AMP‐activated protein kinase (AMPK)-related kinase, has been implicated in the induction of apoptosis signal-regulating kinase 1 (ASK1)-, transforming growth factor-β (TGF‐β)-, and p53-mediated activity involved in metabolic homeostasis. Here, zinc finger protein ZPR9 was found to be an activator of MPK38. The association of MPK38 and ZPR9 was mediated by cysteine residues present in each of these two proteins, Cys269 and Cys286 of MPK38 and Cys305 and Cys308 of ZPR9. MPK38 phosphorylated ZPR9 at Thr252. Wild‐type ZPR9, but not the ZPR9 mutant T252A, enhanced ASK1, TGF‐β, and p53 function by stabilizing MPK38. The requirement of ZPR9 Thr252 phosphorylation was validated using CRISPR/Cas9-mediated ZPR9 (T252A) knockin cell lines. The knockdown of endogenous ZPR9 showed an opposite trend, resulting in the inhibition of MPK38‐dependent ASK1, TGF‐β, and p53 function. This effect was also demonstrated in mouse embryonic fibroblast (MEF) cells that were haploinsufficient (+/−) for ZPR9, NIH 3T3 cells with inducible knockdown of ZPR9, and CRISPR/Cas9-mediated ZPR9 knockout cells. Furthermore, high-fat diet (HFD)-fed mice displayed reduced MPK38 kinase activity and ZPR9 expression compared to that in mice on control chow, suggesting that ZPR9 acts as a physiological activator of MPK38 that may participate in obesity. PMID:28195154

  8. Conversion of Fibroblasts to Neural Cells by p53 Depletion

    Directory of Open Access Journals (Sweden)

    Di Zhou

    2014-12-01

    Full Text Available Conversion from fibroblasts to neurons has recently been successfully induced. However, the underlying mechanisms are poorly understood. Here, we find that depletion of p53 alone converts fibroblasts into all three major neural lineages. The induced neuronal cells express multiple neuron-specific proteins and generate action potentials and transmitter-receptor-mediated currents. Surprisingly, depletion does not affect the well-known tumorigenic p53 target, p21. Instead, knockdown of p53 upregulates neurogenic transcription factors, which in turn boosts fibroblast-neuron conversion. p53 binds the promoter of the neurogenic transcription factor Neurod2 and regulates its expression during fibroblast-neuron conversion. Furthermore, our method provides a high efficiency of conversion in late-passage fibroblasts. Genome-wide transcriptional analysis shows that the p53-deficiency-induced neurons exhibit an expression profile different from parental fibroblasts and similar to control-induced neurons. The results may help to understand and improve neural conversion mechanisms to develop robust neuron-replacement therapy strategies.

  9. TGF-β induces p53/Smads complex formation in the PAI-1 promoter to activate transcription

    Science.gov (United States)

    Kawarada, Yuki; Inoue, Yasumichi; Kawasaki, Fumihiro; Fukuura, Keishi; Sato, Koichi; Tanaka, Takahito; Itoh, Yuka; Hayashi, Hidetoshi

    2016-01-01

    Transforming growth factor β (TGF-β) signaling facilitates tumor development during the advanced stages of tumorigenesis, but induces cell-cycle arrest for tumor suppression during the early stages. However, the mechanism of functional switching of TGF-β is still unknown, and it is unclear whether inhibition of TGF-β signaling results amelioration or exacerbation of cancers. Here we show that the tumor suppressor p53 cooperates with Smad proteins, which are TGF-β signal transducers, to selectively activate plasminogen activator inhibitor type-1 (PAI-1) transcription. p53 forms a complex with Smad2/3 in the PAI-1 promoter to recruit histone acetyltransferase CREB-binding protein (CBP) and enhance histone H3 acetylation, resulting in transcriptional activation of the PAI-1 gene. Importantly, p53 is required for TGF-β-induced cytostasis and PAI-1 is involved in the cytostatic activity of TGF-β in several cell lines. Our results suggest that p53 enhances TGF-β-induced cytostatic effects by activating PAI-1 transcription, and the functional switching of TGF-β is partially caused by p53 mutation or p53 inactivation during cancer progression. It is expected that these findings will contribute to optimization of TGF-β-targeting therapies for cancer. PMID:27759037

  10. Full p53 transcriptional activation potential is dispensable for tumor suppression in diverse lineages.

    Science.gov (United States)

    Jiang, Dadi; Brady, Colleen A; Johnson, Thomas M; Lee, Eunice Y; Park, Eunice J; Scott, Matthew P; Attardi, Laura D

    2011-10-11

    Over half of all human cancers, of a wide variety of types, sustain mutations in the p53 tumor suppressor gene. Although p53 limits tumorigenesis through the induction of apoptosis or cell cycle arrest, its molecular mechanism of action in tumor suppression has been elusive. The best-characterized p53 activity in vitro is as a transcriptional activator, but the identification of numerous additional p53 biochemical activities in vitro has made it unclear which mechanism accounts for tumor suppression. Here, we assess the importance of transcriptional activation for p53 tumor suppression function in vivo in several tissues, using a knock-in mouse strain expressing a p53 mutant compromised for transcriptional activation, p53(25,26). p53(25,26) is severely impaired for the transactivation of numerous classical p53 target genes, including p21, Noxa, and Puma, but it retains the ability to activate a small subset of p53 target genes, including Bax. Surprisingly, p53(25,26) can nonetheless suppress tumor growth in cancers derived from the epithelial, mesenchymal, central nervous system, and lymphoid lineages. Therefore, full transactivation of most p53 target genes is dispensable for p53 tumor suppressor function in a range of tissue types. In contrast, a transcriptional activation mutant that is completely defective for transactivation, p53(25,26,53,54), fails to suppress tumor development. These findings demonstrate that transcriptional activation is indeed broadly critical for p53 tumor suppressor function, although this requirement reflects the limited transcriptional activity observed with p53(25,26) rather than robust transactivation of a full complement of p53 target genes.

  11. Constitutively activated ERK sensitizes cancer cells to doxorubicin: Involvement of p53-EGFR-ERK pathway

    Indian Academy of Sciences (India)

    RATNA KUMARI; SURBHI CHOUHAN; SNAHLATA SINGH; RISHI RAJ CHHIPA; AMRENDRA KUMAR AJAY; MANOJ KUMAR BHAT

    2017-03-01

    The tumour suppressor gene p53 is mutated in approximately 50% of the human cancers. p53 is involved in genotoxicstress-induced cellular responses. The role of EGFR and ERK in DNA-damage-induced apoptosis is well known. Weinvestigated the involvement of activation of ERK signalling as a consequence of non-functional p53, in sensitivity ofcells to doxorubicin. We performed cell survival assays in cancer cell lines with varying p53 status: MCF-7 (wild-typep53, WTp53), MDA MB-468 (mutant p53, MUTp53), H1299 (absence of p53, NULLp53) and an isogenic cell lineMCF-7As (WTp53 abrogated). Our results indicate that enhanced chemosensitivity of cells lacking wild-type p53function is because of elevated levels of EGFR which activates ERK. Additionally, we noted that independent of p53status, pERK contributes to doxorubicin-induced cell death.

  12. A p53-Pax2 pathway in kidney development: implications for nephrogenesis.

    Science.gov (United States)

    Saifudeen, Zubaida; Liu, Jiao; Dipp, Susana; Yao, Xiao; Li, Yuwen; McLaughlin, Nathaniel; Aboudehen, Karam; El-Dahr, Samir S

    2012-01-01

    Congenital reduction in nephron number (renal hypoplasia) is a predisposing factor for chronic kidney disease and hypertension. Despite identification of specific genes and pathways in nephrogenesis, determinants of final nephron endowment are poorly understood. Here, we report that mice with germ-line p53 deletion (p53(-/-)) manifest renal hypoplasia; the phenotype can be recapitulated by conditional deletion of p53 from renal progenitors in the cap mesenchyme (CM(p53-/-)). Mice or humans with germ-line heterozygous mutations in Pax2 exhibit renal hypoplasia. Since both transcription factors are developmentally expressed in the metanephros, we tested the hypothesis that p53 and Pax2 cooperate in nephrogenesis. In this study, we provide evidence for the presence of genetic epistasis between p53 and Pax2: a) p53(-/-) and CM(p53-/-)embryos express lower Pax2 mRNA and protein in nephron progenitors than their wild-type littermates; b) ChIP-Seq identified peaks of p53 occupancy in chromatin regions of the Pax2 promoter and gene in embryonic kidneys; c) p53 binding to Pax2 gene is significantly more enriched in Pax2 -expressing than non-expressing metanephric mesenchyme cells; d) in transient transfection assays, Pax2 promoter activity is stimulated by wild-type p53 and inhibited by a dominant negative mutant p53; e) p53 knockdown in cultured metanephric mesenchyme cells down-regulates endogenous Pax2 expression; f) reduction of p53 gene dosage worsens the renal hypoplasia in Pax2(+/-) mice. Bioinformatics identified a set of developmental renal genes likely to be co-regulated by p53 and Pax2. We propose that the cross-talk between p53 and Pax2 provides a transcriptional platform that promotes nephrogenesis, thus contributing to nephron endowment.

  13. A p53-Pax2 pathway in kidney development: implications for nephrogenesis.

    Directory of Open Access Journals (Sweden)

    Zubaida Saifudeen

    Full Text Available Congenital reduction in nephron number (renal hypoplasia is a predisposing factor for chronic kidney disease and hypertension. Despite identification of specific genes and pathways in nephrogenesis, determinants of final nephron endowment are poorly understood. Here, we report that mice with germ-line p53 deletion (p53(-/- manifest renal hypoplasia; the phenotype can be recapitulated by conditional deletion of p53 from renal progenitors in the cap mesenchyme (CM(p53-/-. Mice or humans with germ-line heterozygous mutations in Pax2 exhibit renal hypoplasia. Since both transcription factors are developmentally expressed in the metanephros, we tested the hypothesis that p53 and Pax2 cooperate in nephrogenesis. In this study, we provide evidence for the presence of genetic epistasis between p53 and Pax2: a p53(-/- and CM(p53-/-embryos express lower Pax2 mRNA and protein in nephron progenitors than their wild-type littermates; b ChIP-Seq identified peaks of p53 occupancy in chromatin regions of the Pax2 promoter and gene in embryonic kidneys; c p53 binding to Pax2 gene is significantly more enriched in Pax2 -expressing than non-expressing metanephric mesenchyme cells; d in transient transfection assays, Pax2 promoter activity is stimulated by wild-type p53 and inhibited by a dominant negative mutant p53; e p53 knockdown in cultured metanephric mesenchyme cells down-regulates endogenous Pax2 expression; f reduction of p53 gene dosage worsens the renal hypoplasia in Pax2(+/- mice. Bioinformatics identified a set of developmental renal genes likely to be co-regulated by p53 and Pax2. We propose that the cross-talk between p53 and Pax2 provides a transcriptional platform that promotes nephrogenesis, thus contributing to nephron endowment.

  14. Loss of ribosomal protein L11 affects zebrafish embryonic development through a p53-dependent apoptotic response.

    Directory of Open Access Journals (Sweden)

    Anirban Chakraborty

    Full Text Available Ribosome is responsible for protein synthesis in all organisms and ribosomal proteins (RPs play important roles in the formation of a functional ribosome. L11 was recently shown to regulate p53 activity through a direct binding with MDM2 and abrogating the MDM2-induced p53 degradation in response to ribosomal stress. However, the studies were performed in cell lines and the significance of this tumor suppressor function of L11 has yet to be explored in animal models. To investigate the effects of the deletion of L11 and its physiological relevance to p53 activity, we knocked down the rpl11 gene in zebrafish and analyzed the p53 response. Contrary to the cell line-based results, our data indicate that an L11 deficiency in a model organism activates the p53 pathway. The L11-deficient embryos (morphants displayed developmental abnormalities primarily in the brain, leading to embryonic lethality within 6-7 days post fertilization. Extensive apoptosis was observed in the head region of the morphants, thus correlating the morphological defects with apparent cell death. A decrease in total abundance of genes involved in neural patterning of the brain was observed in the morphants, suggesting a reduction in neural progenitor cells. Upregulation of the genes involved in the p53 pathway were observed in the morphants. Simultaneous knockdown of the p53 gene rescued the developmental defects and apoptosis in the morphants. These results suggest that ribosomal dysfunction due to the loss of L11 activates a p53-dependent checkpoint response to prevent improper embryonic development.

  15. Discovery of novel tumor suppressor p53 response elements using information theory

    Science.gov (United States)

    Lyakhov, Ilya G.; Krishnamachari, Annangarachari; Schneider, Thomas D.

    2008-01-01

    An accurate method for locating genes under tumor suppressor p53 control that is based on a well-established mathematical theory and built using naturally occurring, experimentally proven p53 sites is essential in understanding the complete p53 network. We used a molecular information theory approach to create a flexible model for p53 binding. By searching around transcription start sites in human chromosomes 1 and 2, we predicted 16 novel p53 binding sites and experimentally demonstrated that 15 of the 16 (94%) sites were bound by p53. Some were also bound by the related proteins p63 and p73. Thirteen of the adjacent genes were controlled by at least one of the proteins. Eleven of the 16 sites (69%) had not been identified previously. This molecular information theory approach can be extended to any genetic system to predict new sites for DNA-binding proteins. PMID:18495754

  16. The effect of adenovirus expressing wild-type p53 on 5-fiuorouracil chemosensitivity is related to p53 status in pancreatic cancer cell lines

    Institute of Scientific and Technical Information of China (English)

    Sven Eisold; Michael Linnebacher; Eduard Ryschich; Dalibor Antolovic; Ulf Hinz; Ernst Klar; Jan Schmidt

    2004-01-01

    AIM: There are conflicting data about p53 function on cellular sensitivity to the cytotoxic action of 5-fluorouracil (5-FU).Therefore the objective of this study was to determine the combined effects of adenovirus-mediated wild-type (wt) p53gene transfer and 5-FU chemotherapy on pancreatic cancer cells with different p53 gene status.METHODS: Human pancreatic cancer cell lines Capan-1p53mut,Capan-2p53wt, FAMPACp53mut, PANC1p53mut, and rat pancreatic cancer cell lines ASp53wt and DSL6Ap53null were used for in vitro studies. Following infection with different ratios of Adp53-particles (MOI) in combination with 5-FU, proliferation of tumor cells and apoptosis were quantified by cell proliferation assay (WST-1) and FACS (PI-staining). In addition, DSL6A syngeneic pancreatic tumor cells were inoculated subcutaneously in to Lewis rats for in vivo studies.Tumor size, apoptosis (TUNEL) and survival were determined.RESULTS: Ad-p53 gene transfer combined with 5-FU significantly inhibited tumor cell proliferation and substantially enhanced apoptosis in all four cell lines with an alteration in the p53 gene compared to those two cell lines containing wt-p53. In vivo experiments showed the most effective tumor regression in animals treated with Ad-p53 plus 5-FU. Both in vitro and in vivo analyses revealed that a sublethal dose of Ad-p53 augmented the apoptotic response induced by 5-FU.CONCLUSION: Our results suggest that Ad-p53 may synergistically enhance 5-FU-chemosensitivity most strikingly in pancreatic cancer cells lacking p53 function. These findings illustrate that the anticancer efficacy of this combination treatment is dependent on the p53 gene status of the target tumor cells.

  17. Discrimination of p53 immunohistochemistry-positive tumors by its staining pattern in gastric cancer

    OpenAIRE

    2014-01-01

    Immunohistochemistry staining of p53 is a cheap and simple method to detect aberrant function of p53. However, there are some discrepancies between the result of immunohistochemistry staining and mutation analysis. This study attempted to find a new definition of p53 staining by its staining pattern. Immunohistochemistry staining of p53 and TP53 gene mutation analysis were performed in 148 gastric cancer patients. Also SNP-CGH array analysis was conducted to four cases. Positive staining of p...

  18. Control of p53 multimerization by Ubc13 is JNK-regulated

    OpenAIRE

    2009-01-01

    The p53 tumor suppressor protein is a key regulator of cellular proliferation and survival whose function is tightly regulated at the levels of transcription and protein stability. Here, we unveil the fine control of p53 on translationally active polysomes. We have previously reported that Ubc13, an E2 ubiquitin-conjugating enzyme, directly regulates p53 localization and transcriptional activity. We now demonstrate that the association of p53 and Ubc13 on polysomes requires ongoing translatio...

  19. The Histone Lysine Demethylase JMJD3/KDM6B Is Recruited to p53 Bound Promoters and Enhancer Elements in a p53 Dependent Manner

    DEFF Research Database (Denmark)

    Williams, Kristine; Christensen, Jesper; Rappsilber, Juri;

    2014-01-01

    find that the interaction is dependent on the p53 tetramerization domain. Following DNA damage, JMJD3 is transcriptionally upregulated and by performing genome-wide mapping of JMJD3, we demonstrate that it binds genes involved in basic cellular processes, as well as genes regulating cell cycle......, response to stress and apoptosis. Moreover, we find that JMJD3 binding sites show significant overlap with p53 bound promoters and enhancer elements. The binding of JMJD3 to p53 target sites is increased in response to DNA damage, and we demonstrate that the recruitment of JMJD3 to these sites is dependent...

  20. CONVERGENCE OF P53 AND TGFβ SIGNALING ON ACTIVATING EXPRESSION OF THE TUMOR SUPPRESSOR GENE MASPIN IN MAMMARY EPITHELIAL CELLS

    Science.gov (United States)

    Wang, Shizhen Emily; Narasanna, Archana; Whitell, Corbin W.; Wu, Frederick Y.; Friedman, David B.; Arteaga, Carlos L.

    2014-01-01

    Using two-dimensional difference gel electrophoresis, we identified the tumor suppressor gene maspin as a TGFβ target gene in human mammary epithelial cells. TGFβ upregulates maspin expression both at the RNA and protein levels. This upregulation required Smad2/3 function and intact p53 binding elements in the maspin promoter. DNA affinity immunoblot and chromatin immunoprecipitation (ChIP) revealed the presence of both Smads and p53 at the maspin promoter in TGFβ-treated cells, suggesting that both transcription factors cooperate to induce maspin transcription. TGFβ did not activate maspin-luciferase reporter in p53-mutant MDA-MB-231 breast cancer cells, which exhibit methylation of the endogenous maspin promoter. Expression of ectopic p53, however, restored ligand-induced association of Smad2/3 with a transfected maspin promoter. Stable transfection of maspin inhibited basal and TGFβ-stimulated MDA-MB-231 cell motility. Finally, knockdown of endogenous maspin in p53 wild-type MCF10A/HER2 cells enhanced basal and TGFβ-stimulated motility. Taken together, these data support cooperation between the p53 and TGFβ tumor suppressor pathways in the induction of maspin expression, thus leading to inhibition of cell migration. PMID:17204482

  1. Significance of Ebp1 and p53 protein expression in cervical cancer.

    Science.gov (United States)

    Liu, L; Li, X D; Chen, H Y; Cui, J S; Xu, D Y

    2015-10-02

    In this study, the ErbB3-binding protein (Ebp1) and p53 protein expression in cervical cancer tissues, and its significance in the prognosis of the disease was investigated. Ebp1 and p53 protein expression was detected by immunohistochemical analysis in cervical cancer tissues (N = 60) and normal tissues adjacent to the cancer tissues (N = 60). The rates of positive Ebp1 and p53 protein expression were 35.0 and 60.0%, respectively. Ebp1 and p53 were overexpressed in cervical cancer tissues, compared to normal tissues (P p53 protein expression was not correlated with age, tumor size, or family tumor history (P > 0.05). However, high levels of expression of Ebp1 and p53 were positively correlated with the TNM stage and lymphatic metastasis in cervical cancer patients (P p53 expression levels in cervical cancer patients could support the effective prediction of metastatic potential and patient prognosis.

  2. Loss of p53 Ser18 and Atm results in embryonic lethality without cooperation in tumorigenesis.

    Directory of Open Access Journals (Sweden)

    Heather L Armata

    Full Text Available Phosphorylation at murine Serine 18 (human Serine 15 is a critical regulatory process for the tumor suppressor function of p53. p53Ser18 residue is a substrate for ataxia-telangiectasia mutated (ATM and ATM-related (ATR protein kinases. Studies of mice with a germ-line mutation that replaces Ser18 with Ala (p53(S18A mice have demonstrated that loss of phosphorylation of p53Ser18 leads to the development of tumors, including lymphomas, fibrosarcomas, leukemia and leiomyosarcomas. The predominant lymphoma is B-cell lymphoma, which is in contrast to the lymphomas observed in Atm(-/- animals. This observation and the fact that multiple kinases phosphorylate p53Ser18 suggest Atm-independent tumor suppressive functions of p53Ser18. Therefore, in order to examine p53Ser18 function in relationship to ATM, we analyzed the lifespan and tumorigenesis of mice with combined mutations in p53Ser18 and Atm. Surprisingly, we observed no cooperation in survival and tumorigenesis in compound p53(S18A and Atm(-/- animals. However, we observed embryonic lethality in the compound mutant animals. In addition, the homozygous p53Ser18 mutant allele impacted the weight of Atm(-/- animals. These studies examine the genetic interaction of p53Ser18 and Atm in vivo. Furthermore, these studies demonstrate a role of p53Ser18 in regulating embryonic survival and motor coordination.

  3. Correlation of p53 gene mutation and expression of P53 protein in cholangiocarcinoma

    Institute of Scientific and Technical Information of China (English)

    Xiao-Fang Liu; Hao Zhang; Shi-Guang Zhu; Xian-Ting Zhou; Hai-Long Su; Zheng Xu; Shao-Jun Li

    2006-01-01

    AIM: To characterize the tumor suppressor gene p53 mutations and study the correlation of p53 gene mutation and the expression of P53 protein in cholangiocarcinoma.METHODS: A total of 36 unselected, frozen samples of cholangiocarcinoma were collected. p53 gene status(exon 5-8) and P53 protein were examined by automated sequencing and immunohistochemical staining, combined with the clinical parameters of patients.RESULTS: p53 gene mutations were found in 22 of 36 (61.1%) patients. Nineteen of 36 (52.8%) patients were positive for P53 protein expression. There were significant differences in extent of differentiation and invasion between the positive and negative expression of P53 protein. However, there were no significant differences in pathologic parameters between the mutations and non-mutations.CONCLUSION: The alterations of the p53 gene evaluated by DNA sequence analysis is relatively accurate. Expression of P53 protein could not act as an independent index to estimate the prognosis of cholangiocarcinoma.

  4. Global genomic profiling reveals an extensive p53-regulated autophagy program contributing to key p53 responses

    OpenAIRE

    Kenzelmann Broz, Daniela; Spano Mello, Stephano; Bieging, Kathryn T.; Jiang, Dadi; Dusek, Rachel L.; Brady, Colleen A.; Sidow, Arend; Attardi, Laura D

    2013-01-01

    To gain new insights into p53 biology, Kenzelmann Broz et al. used high-throughput sequencing to analyze global p53 transcriptional networks in primary mouse embryo fibroblasts in response to DNA damage. This approach identified autophagy genes as direct p53 target genes. p53-induced autophagy was important for both p53-dependent apoptosis and transformation suppression by p53. These data highlight an intimate connection between p53 and autophagy and suggest that autophagy contributes to p53-...

  5. Cyclooxygenase-2 suppresses hypoxia-induced apoptosis via a combination of direct and indirect inhibition of p53 activity in a human prostate cancer cell line.

    Science.gov (United States)

    Liu, Xin-Hua; Kirschenbaum, Alexander; Yu, Kang; Yao, Shen; Levine, Alice C

    2005-02-04

    Although p53-inactivating mutations have been described in the majority of human cancers, their role in prostate cancer is controversial as mutations are uncommon, particularly in early lesions. p53 is activated by hypoxia and other stressors and is primarily regulated by the Mdm2 protein. Cyclooxygenase (COX)-2, an inducible enzyme that catalyzes the conversion of arachidonic acid to prostaglandins and other eicosanoids, is also induced by hypoxia. COX-2 and resultant prostaglandins increase tumor cell proliferation, resistance to apoptosis, and angiogenesis. Previous reports indicate a complex, reciprocal relationship between p53 and COX-2. To elucidate the effects of COX-2 on p53 in response to hypoxia, we transfected the COX-2 gene into the p53-positive, COX-2-negative MDA-PCa-2b human prostate cancer cell line. The expression of functional p53 and Mdm2 was compared in COX-2+ versus COX-2- cells under normoxic and hypoxic conditions. Our results demonstrated that hypoxia increases both COX-2 protein levels and p53 transcriptional activity in these cells. Forced expression of COX-2 increased tumor cell viability and decreased apoptosis in response to hypoxia. COX-2+ cells had increased Mdm2 phosphorylation in either normoxic or hypoxic conditions. Overexpression of COX-2 abrogated hypoxia-induced p53 phosphorylation and promoted the binding of p53 to Mdm2 protein in hypoxic cells. In addition, COX-2-expressing cells exhibited decreased hypoxia-induced nuclear accumulation of p53 protein. Finally, forced expression of COX-2 suppressed both basal and hypoxia-induced p53 transcriptional activity, and this effect was mimicked by the addition of PGE2 to wild-type cells. These results demonstrated a role for COX-2 in the suppression of hypoxia-induced p53 activity via both direct effects and indirect modulation of Mdm2 activity. These data imply that COX-2-positive prostate cancer cells can have impaired p53 function even in the presence of wild-type p53 and that p53

  6. p53 oligomerization status modulates cell fate decisions between growth, arrest and apoptosis.

    Science.gov (United States)

    Fischer, Nicholas W; Prodeus, Aaron; Malkin, David; Gariépy, Jean

    2016-12-01

    Mutations in the oligomerization domain of p53 are genetically linked to cancer susceptibility in Li-Fraumeni Syndrome. These mutations typically alter the oligomeric state of p53 and impair its transcriptional activity. Activation of p53 through tetramerization is required for its tumor suppressive function by inducing transcriptional programs that lead to cell fate decisions such as cell cycle arrest or apoptosis. How p53 chooses between these cell fate outcomes remains unclear. Here, we use 5 oligomeric variants of p53, including 2 novel p53 constructs, that yield either monomeric, dimeric or tetrameric forms of p53 and demonstrate that they induce distinct cellular activities and gene expression profiles that lead to different cell fate outcomes. We report that dimeric p53 variants are cytostatic and can arrest cell growth, but lack the ability to trigger apoptosis in p53-null cells. In contrast, p53 tetramers induce rapid apoptosis and cell growth arrest, while a monomeric variant is functionally inactive, supporting cell growth. In particular, the expression of pro-arrest CDKN1A and pro-apoptotic P53AIP1 genes are important cell fate determinants that are differentially regulated by the oligomeric state of p53. This study suggests that the most abundant oligomeric species of p53 present in resting cells, namely p53 dimers, neither promote cell growth or cell death and that shifting the oligomeric state equilibrium of p53 in cells toward monomers or tetramers is a key parameter in p53-based cell fate decisions.

  7. A Regulatory Loop Composed of RAP80-HDM2-p53 Provides RAP80-enhanced p53 Degradation by HDM2 in Response to DNA Damage*

    Science.gov (United States)

    Yan, Jun; Menendez, Daniel; Yang, Xiao-Ping; Resnick, Michael A.; Jetten, Anton M.

    2009-01-01

    The ubiquitin interaction motif-containing protein RAP80 plays a key role in DNA damage response signaling. Using genomic and functional analysis, we established that the expression of the RAP80 gene is regulated in a DNA damage-responsive manner by the master regulator p53. This regulation occurs at the transcriptional level through a noncanonical p53 response element in the RAP80 promoter. Although it is inducible by p53, RAP80 is also able to regulate p53 through an association with both p53 and the E3 ubiquitin ligase HDM2, providing HDM2-dependent enhancement of p53 polyubiquitination. Depletion of RAP80 by small interfering RNA stabilizes p53, which, following DNA damage, results in an increased transactivation of several p53 target genes as well as greater apoptosis. Consistent with these observations, exogenous expression of RAP80 selectively inhibits p53-dependent transactivation of target genes in an mdm2-dependent manner in MEF cells. Thus, we identify a new DNA damage-associated role for RAP80. It can function in an autoregulatory loop consisting of RAP80, HDM2, and the p53 master regulatory network, implying an important role for this loop in genome stability and oncogenesis. PMID:19433585

  8. KR-POK interacts with p53 and represses its ability to activate transcription of p21WAF1/CDKN1A.

    Science.gov (United States)

    Jeon, Bu-Nam; Kim, Min-Kyeong; Choi, Won-Il; Koh, Dong-In; Hong, Sung-Yi; Kim, Kyung-Sup; Kim, Minjung; Yun, Chae-Ok; Yoon, Juyong; Choi, Kang-Yell; Lee, Kyung-Ryul; Nephew, Kenneth P; Hur, Man-Wook

    2012-03-01

    Transcriptional regulation by p53 is thought to play a role in its ability to suppress tumorigenesis. However, there remain gaps in understanding about how p53 regulates transcription and how disrupting this function may promote cancer. Here we report a role in these processes for the kidney cancer-related gene KR-POK (ZBTB7C), a POZ domain and Krüppel-like zinc finger transcription factor that we found to physically interact with p53. Murine embryonic fibroblasts isolated from genetically deficient mice (Kr-pok(-/-) MEFs) exhibited a proliferative defect relative to wild-type mouse embryonic fibroblasts (MEF). The zinc finger domain of Kr-pok interacted directly with the DNA binding and oligomerization domains of p53. This interaction was essential for Kr-pok to bind the distal promoter region of the CDKN1A gene, an important p53 target gene encoding the cell-cycle regulator p21WAF1, and to inhibit p53-mediated transcriptional activation of CDKN1A. Kr-pok also interacted with the transcriptional corepressors NCoR and BCoR, acting to repress histone H3 and H4 deacetylation at the proximal promoter region of the CDKN1A gene. Importantly, Kr-pok(-/-) MEFs displayed an enhancement in CDKN1A transactivation by p53 during the DNA damage response, without any parallel changes in transcription of either the p53 or Kr-pok genes themselves. Furthermore, Kr-pok promoted cell proliferation in vitro and in vivo, and its expression was increased in more than 50% of the malignant human kidney cancer cases analyzed. Together, our findings define KR-POK as a transcriptional repressor with a pro-oncogenic role that relies upon binding to p53 and inhibition of its transactivation function.

  9. Analysis of P53 mutations and their expression in 56 colorectal cancer cell lines

    DEFF Research Database (Denmark)

    Liu, Ying; Bodmer, Walter F

    2006-01-01

    protein by assaying the induced expression of phosphorylated p53 and p21 after exposing cells to gamma-rays. In a few cases where there was no production of p53 message nor evidence of functional p53 protein, all of the p53 exons were sequenced directly. Thirteen of the 56 cell lines had functional p53...... a valuable source of TP 53 mutations for further studies and raise the question of the extent to which truncating mutations may have dominant negative effects, even when no truncated protein can be detected by standard methods....

  10. p53 gene therapy using RNA interference.

    Science.gov (United States)

    Berindan-Neagoe, I; Balacescu, O; Burz, C; Braicu, C; Balacescu, L; Tudoran, O; Cristea, V; Irimie, A

    2009-09-01

    p53 gene, discovered almost 35 years ago, keeps the main role in cell cycle control, apoptosis pathways and transcription. p53 gene is found mutated in more than 50% of all human cancers in different locations. Many structures from viral to non viral were designed to incorporate and deliver in appropriate conditions forms of p53 gene or its transcripts, systemically to target tumor cells and to eliminate them through apoptosis or to restore the normal tumor suppressor gene role. Each delivery system presents advantages and low performance in relation to immune system recognition and acceptance. One of the major discoveries in the last years, silencing of RNA, represents a powerful tool for inhibiting post transcriptional control of gene expression. According to several studies, the RNA silencing technology for p53 transcripts together with other carriers or transporters at nano level can be used for creating new therapeutic models. RNA interference for p53 uses different double-stranded (ds) molecules like short interfering (si) RNA and, despite the difficulty of introducing them into mammalian cells due to immune system response, it can be exploited in cancer therapy.

  11. Genome-wide profiling of p53-regulated enhancer RNAs uncovers a subset of enhancers controlled by a lncRNA

    NARCIS (Netherlands)

    Léveillé, Nicolas; Melo, Carlos A; Rooijers, Koos; Díaz-Lagares, Angel; Melo, Sonia A; Korkmaz, Gozde; Lopes, Rui; Akbari Moqadam, Farhad; Maia, Ana R; Wijchers, Patrick J; Geeven, Geert; den Boer, Monique L; Kalluri, Raghu; de Laat, Wouter; Esteller, Manel; Agami, Reuven

    2015-01-01

    p53 binds enhancers to regulate key target genes. Here, we globally mapped p53-regulated enhancers by looking at enhancer RNA (eRNA) production. Intriguingly, while many p53-induced enhancers contained p53-binding sites, most did not. As long non-coding RNAs (lncRNAs) are prominent regulators of chr

  12. A Comprehensive and High-Resolution Genome-wide Response of p53 to Stress

    Directory of Open Access Journals (Sweden)

    Gue Su Chang

    2014-07-01

    Full Text Available Tumor suppressor p53 regulates transcription of stress-response genes. Many p53 targets remain undiscovered because of uncertainty as to where p53 binds in the genome and the fact that few genes reside near p53-bound recognition elements (REs. Using chromatin immunoprecipitation followed by exonuclease treatment (ChIP-exo, we associated p53 with 2,183 unsplit REs. REs were positionally constrained with other REs and other regulatory elements, which may reflect structurally organized p53 interactions. Surprisingly, stress resulted in increased occupancy of transcription factor IIB (TFIIB and RNA polymerase (Pol II near REs, which was reduced when p53 was present. A subset associated with antisense RNA near stress-response genes. The combination of high-confidence locations for p53/REs, TFIIB/Pol II, and their changes in response to stress allowed us to identify 151 high-confidence p53-regulated genes, substantially increasing the number of p53 targets. These genes composed a large portion of a predefined DNA-damage stress-response network. Thus, p53 plays a comprehensive role in regulating the stress-response network, including regulating noncoding transcription.

  13. p53 suppresses tetraploid development in mice.

    Science.gov (United States)

    Horii, Takuro; Yamamoto, Masamichi; Morita, Sumiyo; Kimura, Mika; Nagao, Yasumitsu; Hatada, Izuho

    2015-03-10

    Mammalian tetraploid embryos die in early development because of defects in the epiblast. Experiments with diploid/tetraploid chimeric mice, obtained via the aggregation of embryonic stem cells, clarified that while tetraploid cells are excluded from epiblast derivatives, diploid embryos with tetraploid extraembryonic tissues can develop to term. Today, this method, known as tetraploid complementation, is usually used for rescuing extraembryonic defects or for obtaining completely embryonic stem (ES) cell-derived pups. However, it is still unknown why defects occur in the epiblast during mammalian development. Here, we demonstrated that downregulation of p53, a tumour suppressor protein, rescued tetraploid development in the mammalian epiblast. Tetraploidy in differentiating epiblast cells triggered p53-dependent cell-cycle arrest and apoptosis, suggesting the activation of a tetraploidy checkpoint during early development. Finally, we found that p53 downregulation rescued tetraploid embryos later in gestation.

  14. Reverting p53 activation after recovery of cellular stress to resume with cell cycle progression.

    Science.gov (United States)

    Lazo, Pedro A

    2017-05-01

    The activation of p53 in response to different types of cellular stress induces several protective reactions including cell cycle arrest, senescence or cell death. These protective effects are a consequence of the activation of p53 by specific phosphorylation performed by several kinases. The reversion of the cell cycle arrest, induced by p53, is a consequence of the phosphorylated and activated p53, which triggers its own downregulation and that of its positive regulators. The different down-regulatory processes have a sequential and temporal order of events. The mechanisms implicated in p53 down-regulation include phosphatases, deacetylases, and protein degradation by the proteasome or autophagy, which also affect different p53 protein targets and functions. The necessary first step is the dephosphorylation of p53 to make it available for interaction with mdm2 ubiquitin-ligase, which requires the activation of phosphatases targeting both p53 and p53-activating kinases. In addition, deacetylation of p53 is required to make lysine residues accessible to ubiquitin ligases. The combined action of these downregulatory mechanisms brings p53 protein back to its basal levels, and cell cycle progression can resume if cells have overcome the stress or damage situation. The specific targeting of these down-regulatory mechanisms can be exploited for therapeutic purposes in cancers harbouring wild-type p53.

  15. Promotion of CHIP-mediated p53 degradation protects the heart from ischemic injury.

    Science.gov (United States)

    Naito, Atsuhiko T; Okada, Sho; Minamino, Tohru; Iwanaga, Koji; Liu, Mei-Lan; Sumida, Tomokazu; Nomura, Seitaro; Sahara, Naruhiko; Mizoroki, Tatsuya; Takashima, Akihiko; Akazawa, Hiroshi; Nagai, Toshio; Shiojima, Ichiro; Komuro, Issei

    2010-06-11

    The number of patients with coronary heart disease, including myocardial infarction, is increasing and novel therapeutic strategy is awaited. Tumor suppressor protein p53 accumulates in the myocardium after myocardial infarction, causes apoptosis of cardiomyocytes, and plays an important role in the progression into heart failure. We investigated the molecular mechanisms of p53 accumulation in the heart after myocardial infarction and tested whether anti-p53 approach would be effective against myocardial infarction. Through expression screening, we found that CHIP (carboxyl terminus of Hsp70-interacting protein) is an endogenous p53 antagonist in the heart. CHIP suppressed p53 level by ubiquitinating and inducing proteasomal degradation. CHIP transcription was downregulated after hypoxic stress and restoration of CHIP protein level prevented p53 accumulation after hypoxic stress. CHIP overexpression in vivo prevented p53 accumulation and cardiomyocyte apoptosis after myocardial infarction. Promotion of CHIP function by heat shock protein (Hsp)90 inhibitor, 17-allylamino-17-demethoxy geldanamycin (17-AAG), also prevented p53 accumulation and cardiomyocyte apoptosis both in vitro and in vivo. CHIP-mediated p53 degradation was at least one of the cardioprotective effects of 17-AAG. We found that downregulation of CHIP level by hypoxia was responsible for p53 accumulation in the heart after myocardial infarction. Decreasing the amount of p53 prevented myocardial apoptosis and ameliorated ventricular remodeling after myocardial infarction. We conclude that anti-p53 approach would be effective to treat myocardial infarction.

  16. Substrate phosphorylation and feedback regulation in JFK-promoted p53 destabilization.

    Science.gov (United States)

    Sun, Luyang; Shi, Lei; Wang, Feng; Huangyang, Peiwei; Si, Wenzhe; Yang, Jie; Yao, Zhi; Shang, Yongfeng

    2011-02-11

    The p53 tumor suppressor plays a central role in integrating cellular responses to various stresses. Tight regulation of p53 is thus essential for the maintenance of genome integrity and normal cell proliferation. Previously, we reported that JFK, the only Kelch domain-containing F-box protein in human, promotes ubiquitination and degradation of p53 and that unlike the other E3 ligases for p53, all of which possess an intrinsic ubiquitin ligase activity, JFK destabilizes p53 through the assembly of a Skp1-Cul1-F-box complex. Here, we report that the substrate recognition by JFK requires phosphorylation of p53 in its central core region by CSN (COP9 signalosome)-associated kinase. Significantly, inhibition of CSN-associated kinase activity or knockdown of CSN5 impairs JFK-promoted p53 degradation, enhances p53-dependent transcription, and promotes cell growth suppression, G(1) arrest, and apoptosis. Moreover, we showed that JFK is transcriptionally regulated by p53 and forms an auto-regulatory negative feedback loop with p53. These data may shed new light on the functional connection between CSN, Skp1-Cul1-F-box ubiquitin ligase, and p53 and provide a molecular mechanism for the regulation of JFK-promoted p53 degradation.

  17. Structural Basis of Competitive Recognition of p53 and MDM2 by HAUSP/USP7: Implications for the Regulation of the p53-MDM2 Pathway.

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available Herpesvirus-associated ubiquitin-specific protease (HAUSP, also known as USP7, a deubiquitylating enzyme of the ubiquitin-specific processing protease family, specifically deubiquitylates both p53 and MDM2, hence playing an important yet enigmatic role in the p53-MDM2 pathway. Here we demonstrate that both p53 and MDM2 specifically recognize the N-terminal tumor necrosis factor-receptor associated factor (TRAF-like domain of HAUSP in a mutually exclusive manner. HAUSP preferentially forms a stable HAUSP-MDM2 complex even in the presence of excess p53. The HAUSP-binding elements were mapped to a peptide fragment in the carboxy-terminus of p53 and to a short-peptide region preceding the acidic domain of MDM2. The crystal structures of the HAUSP TRAF-like domain in complex with p53 and MDM2 peptides, determined at 2.3-A and 1.7-A resolutions, respectively, reveal that the MDM2 peptide recognizes the same surface groove in HAUSP as that recognized by p53 but mediates more extensive interactions. Structural comparison led to the identification of a consensus peptide-recognition sequence by HAUSP. These results, together with the structure of a combined substrate-binding-and-deubiquitylation domain of HAUSP, provide important insights into regulation of the p53-MDM2 pathway by HAUSP.

  18. The role of tumor suppressor p53 in the antioxidant defense and metabolism

    OpenAIRE

    2014-01-01

    Tumor suppressor p53 is inactivated in most cancers and the critical role of p53 in the suppression of carcinogenesis has been confirmed in many mouse models. The protein product of the tumor suppressor p53 gene works as a transcriptional regulator, activating expression of numerous genes involved in cell death, cell cycle arrest, senescence, DNA-repair and many other processes. In spite of the multiple efforts to characterize the functions of p53, the mechanisms of tumor suppression by p53 a...

  19. Cloning and sequencing of a DNA fragment encoding N37 apoptotic peptide derived from p53

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Objective It was reported that p53 apoptotic peptide (N37) could inhibit p73 gene through being bound with iASPP,which could induce tumor cell apoptosis. To further explore the function of N37,we constructed the cloning plasmid of DNA fragment encoding p53 (N37) apoptotic peptide by using DNA synthesis and molecular biology methods. Methods According to human p53 sequence from the GenBank database,the primer of p53(N37) gene was designed using Primer V7.0 software. The DNA fragment encoding p53 (N37) apopto...

  20. Transcriptional activation of APAF1 by KAISO (ZBTB33) and p53 is attenuated by RelA/p65.

    Science.gov (United States)

    Koh, Dong-In; An, Haemin; Kim, Min-Young; Jeon, Bu-Nam; Choi, Seo-Hyun; Hur, Sujin Susanne; Hur, Man-Wook

    2015-09-01

    KAISO, a member of the POK protein family, is induced by DNA-damaging agents to enhance apoptosis in a p53-dependent manner. Previously, we found that p53 interacts with KAISO, and acetylation of p53 lysine residues by p300 is modulated by KAISO. APAF1, the core molecule of the apoptosome, is transcriptionally activated by KAISO only in cells expressing p53, which binds to APAF1 promoter p53-response elements (p53REs). APAF1 transcriptional upregulation is further enhanced by KAISO augmentation of p53 binding to the APAF1 promoter distal p53RE#1 (bp, -765 to -739). Interestingly, a NF-κB response element, located close to the p53RE#1, mediates APAF1 transcriptional repression by affecting interaction between KAISO and p53. Ectopic RelA/p65 expression led to depletion of nuclear KAISO, with KAISO being mainly detected in the cytoplasm. RelA/p65 cytoplasmic sequestration of KAISO prevents its nuclear interaction with p53, decreasing APAF1 transcriptional activation by a p53-KAISO-p300 complex in cells exposed to genotoxic stresses. While KAISO enhances p53-dependent apoptosis by increasing APAF1 gene expression, RelA/p65 decreases apoptosis by blocking interaction between KAISO and p53. These findings have relevance to the phenomenon of cancer cells' diminished apoptotic capacity and the onset of chemotherapy resistance.

  1. Necdin regulates p53 acetylation via Sirtuin1 to modulate DNA damage response in cortical neurons.

    Science.gov (United States)

    Hasegawa, Koichi; Yoshikawa, Kazuaki

    2008-08-27

    Sirtuin1 (Sirt1), a mammalian homolog of yeast Sir2, deacetylates the tumor suppressor protein p53 and attenuates p53-mediated cell death. Necdin, a p53-interacting protein expressed predominantly in postmitotic neurons, is a melanoma antigen family protein that promotes neuronal differentiation and survival. In mammals, the necdin gene (Ndn) is maternally imprinted, and mutant mice carrying mutated paternal Ndn show abnormalities of neuronal development. Here we report that necdin regulates the acetylation status of p53 via Sirt1 to suppress p53-dependent apoptosis in postmitotic neurons. Double-immunostaining analysis demonstrated that necdin colocalizes with Sirt1 in postmitotic neurons of mouse embryonic forebrain in vivo. Coimmunoprecipitation and in vitro binding analyses revealed that necdin interacts with both p53 and Sirt1 to potentiate Sirt1-mediated p53 deacetylation by facilitating their association. Primary cortical neurons prepared from paternal Ndn-deficient mice have high p53 acetylation levels and are sensitive to the DNA-damaging compounds camptothecin and hydrogen peroxide. Moreover, DNA transfection per se increases p53 acetylation and apoptosis in paternal Ndn-deficient neurons, whereas small interfering RNA-mediated p53 knockdown completely blocks these changes. However, Sirt1 knockdown increases both acetylated p53 level and apoptosis in wild-type neurons but fails to affect them in paternal Ndn-deficient neurons. In organotypic forebrain slice cultures treated with hydrogen peroxide, p53 is accumulated and colocalized with necdin and Sirt1 in cortical neurons. These results suggest that necdin downregulates p53 acetylation levels by forming a stable complex with p53 and Sirt1 to protect neurons from DNA damage-induced apoptosis.

  2. p53 Gene and Tumorigenesis%p53基因与肿瘤形成

    Institute of Scientific and Technical Information of China (English)

    韩涛; 杨德吉

    2008-01-01

    肿瘤抑制基因的研究已经成为继癌基因之后肿瘤遗传学、分子生物学领域的前沿和热点,尤其是抑癌基因p53越来越被人们重视.研究表明正常的p53,又称野生型p53,在细胞损伤后的修复过程中发挥重要作用.正常p53的功能像"分子警察"一样监视着基因组DNA的完整性.在细胞发生DNA损伤时,p53蛋白能使细胞分裂终止在G1/S期,以使细胞有足够的时间修复损伤,恢复正常状态.若不能修复,野生型p53还能启动细胞的凋亡过程从而引发细胞的程序性死亡,阻止具有癌变倾向的突变细胞产生.而突变型p53基因会导致肿瘤的发生,大多数肿瘤与p53的突变有关.文章着重阐述了p53的表达与突变、p53的稳定调节及p53的转录调控等.

  3. Effects of p53 overexpression on neoplastic cell pro-liferation and apoptosis in thymic carcinoma

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    To investigate p53 overexpression and its correlation with neoplastic cell proliferation and apoptosis in 20 thymic carcinomas. Methods: 20 surgical samples of thymic carcinoma were collected randomly during the past 15 years in the Guangzhou area. Immunohistochemical staining was performed using LSAB method with anti-p53 monoclonal antibody (DO-7) and proliferating cell nuclear antigen (clone PC 10) as primary antibodies. The p53 index was indicated by the number of p53 positive cells among 100 carcinoma cells. More than 25 percentage of p53 positive cells found in tissue sections was recognized as p53 overexpression. Carcinoma cell proliferation activity was assayed by PCNA index (PI), and apoptosis degree was evaluated by TUNEL (TdT-mediated dUTP-X nick end labeling) index (TI) using Boehringer Mannheim In Situ Death Detection Kit. Results: P53 positive cells could be found in vast majority of thymic carcinomas (19/20) and the overexpression rate reached 35% (7/20). The median PI (40%) of 7 cases with p53 overexpression was higher than that (31%) of 13 cases without p53 overexpression, but there was no statistical significance that existed between these two data (P>0.05). The median TI (0.5/HPF) of 7 p53 overexpression cases was much lower than that (4.5/HPF) of 13 non-overexpression cases, and there was a significant difference statistically (P<0.05). Conclusion: p53 expression was a frequent finding in thymic carcinoma cells, and the p53 overexpression which might represent p53 inactivation or gene mutation was often involved in thymic carcino-genesis. The median PCNA index of p53 overexpression group was higher than that of non-overexpression group though there existed no statistical difference. This indicates that the inhibiting function of p53 on cell proliferation seemed lost in p53 overexpressed thymic carcinomas. It is worthy to be specially mentioned that the inducing function of p53 on cell apoptosis was markedly lost in p53 overexpressed thymic

  4. Mdm2 Splice isoforms regulate the p53/Mdm2/Mdm4 regulatory circuit via RING domain-mediated ubiquitination of p53 and Mdm4.

    Science.gov (United States)

    Fan, Chuandong; Wang, Xinjiang

    2017-02-06

    p53 is regulated by heterodimer E3 ligase Mdm2-Mdm4 via RING domain interaction. Mdm2 transcripts undergo alternative splicing, and Mdm2 splice isoforms are increased in cancer and induced by DNA damage. Although two major Mdm2 splice isoforms that do not bind to p53 were reported to impact the p53 pathway, the underlying biochemical mechanisms were not understood. Here, we show that these Mdm2 splice isoforms ubiquitinate Mdm2 and Mdm4 in vitro and regulate the activity of Mdm2-Mdm4 E3 complex in cells. The Mdm2 isoforms are capable of promoting p53 ubiquitination in the absence of Mdm2 or Mdm4. The two isoforms stimulate Mdm2 or Mdm4 activity for p53 ubiquitination in vitro and promote degradation of p53 and Mdm4 in cells. However, the Mdm2 isoforms have opposing effects on the steady-state p53 levels depending on the stoichiometric ratios of Mdm2, Mdm4 and the isoforms, causing either decreased or increased p53 levels in cells. Our data indicate that the Mdm2 splice isoforms can act as independent E3 ligases for p53 when Mdm2 and Mdm4 are absent, form potent heterodimer E3 ligases with either Mdm2 or Mdm4 for targeting p53 degradation, or act as inhibitory regulators of Mdm2-Mdm4 E3 ligase activity by downregulating Mdm4. These findings suggest that Mdm2 splice isoforms may play critical roles in the regulatory loop of p53/Mdm2-Mdm4 via a RING domain-mediated biochemical mechanism.

  5. A HLA-A2 restricted human CTL line recognizes a novel tumor cell expressed p53 epitope

    DEFF Research Database (Denmark)

    Würtzen, Peter A; Claesson, Mogens H

    2002-01-01

    line, indicating that this novel p53 peptide epitope is endogenously processed and presented by the HLA-A2 molecules of the tumor cells. In conclusion, CTL reactivity towards a wild-type p53 peptide was revealed through induction with DC pulsed with a pool of HLA-A2 binding p53 peptides. In addition...

  6. Alterations in tumour suppressor gene p53 in human gliomas from Indian patients

    Indian Academy of Sciences (India)

    Pornima Phatak; S Kalai Selvi; T Divya; A S Hegde; Sridevi Hegde; Kumaravel Somasundaram

    2002-12-01

    Alterations in the tumour suppressor p53 gene are among the most common defects seen in a variety of human cancers. In order to study the significance of the p53 gene in the genesis and development of human glioma from Indian patients, we checked 44 untreated primary gliomas for mutations in exons 5–9 of the p53 gene by PCR-SSCP and DNA sequencing. Sequencing analysis revealed six missense mutations. The incidence of p53 mutations was 13.6% (6 of 44). All the six mutations were found to be located in the central core domain of p53, which carries the sequence-specific DNA-binding domain. These results suggest a rather low incidence but a definite involvement of p53 mutations in the gliomas of Indian patients.

  7. DNA intercalator korkormicin A preferentially kills tumor cells expressing wild type p53.

    Science.gov (United States)

    Kitagaki, Jirouta; Yang, Yili

    2011-10-14

    Korkormicin A belongs to a family of nature-produced cyclic depsipeptides. It has potent antitumor activity against both leukemia cell P388 and carcinoma cell M109. To further explore its potential as a cancer therapeutic, the mechanism of its antitumor activity was investigated. We found that korkormicin A can bind to DNA through intercalation. It also induces p53 phosphorylation, which leads to inhibition of p53 degradation and activation of p53-dependent transcription. Furthermore, korkormicin A preferentially induces apoptosis in transformed cells retaining wild type p53. As it has been shown that p53 usually induces apoptosis in transformed cells, but only growth arrest in untransformed cells, these results indicate that korkormicin A is a potential antitumor agent for cancers with wild type p53. Published by Elsevier Inc.

  8. Aspirin acetylates wild type and mutant p53 in colon cancer cells: identification of aspirin acetylated sites on recombinant p53.

    Science.gov (United States)

    Ai, Guoqiang; Dachineni, Rakesh; Kumar, D Ramesh; Marimuthu, Srinivasan; Alfonso, Lloyd F; Bhat, G Jayarama

    2016-05-01

    Aspirin's ability to inhibit cell proliferation and induce apoptosis in cancer cell lines is considered to be an important mechanism for its anti-cancer effects. We previously demonstrated that aspirin acetylated the tumor suppressor protein p53 at lysine 382 in MDA-MB-231 human breast cancer cells. Here, we extended these observations to human colon cancer cells, HCT 116 harboring wild type p53, and HT-29 containing mutant p53. We demonstrate that aspirin induced acetylation of p53 in both cell lines in a concentration-dependent manner. Aspirin-acetylated p53 was localized to the nucleus. In both cell lines, aspirin induced p21(CIP1). Aspirin also acetylated recombinant p53 (rp53) in vitro suggesting that it occurs through a non-enzymatic chemical reaction. Mass spectrometry analysis and immunoblotting identified 10 acetylated lysines on rp53, and molecular modeling showed that all lysines targeted by aspirin are surface exposed. Five of these lysines are localized to the DNA-binding domain, four to the nuclear localization signal domain, and one to the C-terminal regulatory domain. Our results suggest that aspirin's anti-cancer effect may involve acetylation and activation of wild type and mutant p53 and induction of target gene expression. This is the first report attempting to characterize p53 acetylation sites targeted by aspirin.

  9. Ovarian tumor domain-containing protein 1 deubiquitinates and stabilizes p53.

    Science.gov (United States)

    Piao, Shudong; Pei, Han Zhong; Huang, Bin; Baek, Suk-Hwan

    2017-05-01

    Ubiquitination and deubiquitination pathways play important roles in the regulation of p53 stability and activity. p53 is ubiquitinated and destabilized by E3 ubiquitin ligases and is deubiquitinated and stabilized by deubiquitinases (DUBs). We screened ovarian tumor (OTU) subfamily proteins to identify novel DUBs that stabilized p53. OTU domain-containing protein 1 (OTUD1) is a DUB belonging to the OTU family; however, its substrates and its role in cells are unknown. Here, we used an overexpression and knockdown system to show that OTUD1 is a novel regulator of p53 stability. OTUD1 overexpression increased p53 stability, whereas OTUD1 knockdown decreased p53 stability. Moreover, we observed that OTUD1 directly interacted with p53. Our results showed that OTUD1 deubiquitinated p53 and that functional OTUD1 was required for p53 stabilization. The deubiquitination activity of OTUD1 was necessary for p53 stabilization, as confirmed using an inactive OTUD1 mutant (C320S OTUD1 mutant). We also found that wild-type OTUD1 upregulated p21 and Mdm2 expression but inactive OTUD1 mutant did not. Furthermore, OTUD1 significantly suppressed colony formation. Next, we confirmed that OTUD1 overexpression increased the cleavage of caspase-3 and PARP and subsequently increased apoptosis. Together, these results suggest that OTUD1 is a novel regulator of p53 stability and activity.

  10. Single Molecule Study of the Weak Biological Interactions Between P53 and DNA%纳米通道单分子检测P53蛋白与DNA的弱相互作用

    Institute of Scientific and Technical Information of China (English)

    应佚伦; 张星; 刘钰; 薛梦竹; 李洪林; 龙亿涛

    2013-01-01

    Many important cellular events, including protein-DNA interactions, are attributed to weak interactions. Almost all of the known biological functions of P53 depend critically upon its DNA-binding properties via numerous weak interactions. At the single-molecule level, information about the weak interactions between each residue of the P53 DNA binding domain (P53 DBD) and DNA is essential for understanding the biological function of P53 and for anti-cancer drug design. Here, we used the a-hemolysin (α-HL) pore to detect the weak interaction between a peptide of the P53 DBD (P53-P) and a 40-bp double-stranded DNA (B40) that includes the p21 wafl/cipl DNA response element. The weak interactions in the complex of p53-P and B40 (p53-P:B40) produce a unique current trace through an a-HL nanopore with diagnostic ionic current blockages. Each current trace at a particular potential is related to the characterized behavior of captured p53-P:B40. Nanopore analysis indicates that the conformation of B40 might be changed by binding to p53-P, this change is confirmed by the molecule docking simulation. In the presence of the weak interactions between p53-P and B40, the analyte exhibits an increase in the rate constant of association with the nanopore vestibule. This reveals that the analyte-pore interactions could be enhanced by the weak interactions between p53-P and B40. The distorted B40 might be prone to translocate through the narrow constriction in the nanopore at the higher potential (> +120 mV). Moreover, our findings demonstrate that the structure of distorted B40 in p53-P:B40 could be broken by the electric force. Our results support the possibility of identifying the weak interaction between two biomolecules. In addition, the analyte-pore association rate constant could be used to estimate the weak binding energy between different parts of the p53 binding domain and the target sequence. The signatures of the current trace may assist in the prediction of the

  11. Wildtype p53-specific antibody and T-cell responses in cancer patients

    DEFF Research Database (Denmark)

    Pedersen, Anders Elm; Stryhn, Anette; Justesen, Sune

    2011-01-01

    Mutation in the p53 gene based on single amino acid substitutions is a frequent event in human cancer. Accumulated mutant p53 protein is released to antigen presenting cells of the immune system and anti-p53 immune responses even against wt p53 is induced and observed in a number of human cancer...... patients. Detection of antibodies against wt p53 protein has been used as a diagnostic and prognostic marker and discovery of new T-cell epitopes has enabled design of cancer vaccination protocols with promising results. Here, we identified wt p53-specific antibodies in various cancer patients......(264-272) in breast cancer patients and against HLA-A*01:01 binding peptide wt p53(226-234) and HLA-B*07:02 binding peptide wt p53(74-82) in renal cell cancer and breast cancer patients, respectively. Finally, we analyzed antibody and T-cell responses against wt p53 15-mer peptides in patients with metastatic renal...

  12. The Toll-like receptor gene family is integrated into human DNA damage and p53 networks.

    Directory of Open Access Journals (Sweden)

    Daniel Menendez

    2011-03-01

    Full Text Available In recent years the functions that the p53 tumor suppressor plays in human biology have been greatly extended beyond "guardian of the genome." Our studies of promoter response element sequences targeted by the p53 master regulatory transcription factor suggest a general role for this DNA damage and stress-responsive regulator in the control of human Toll-like receptor (TLR gene expression. The TLR gene family mediates innate immunity to a wide variety of pathogenic threats through recognition of conserved pathogen-associated molecular motifs. Using primary human immune cells, we have examined expression of the entire TLR gene family following exposure to anti-cancer agents that induce the p53 network. Expression of all TLR genes, TLR1 to TLR10, in blood lymphocytes and alveolar macrophages from healthy volunteers can be induced by DNA metabolic stressors. However, there is considerable inter-individual variability. Most of the TLR genes respond to p53 via canonical as well as noncanonical promoter binding sites. Importantly, the integration of the TLR gene family into the p53 network is unique to primates, a recurrent theme raised for other gene families in our previous studies. Furthermore, a polymorphism in a TLR8 response element provides the first human example of a p53 target sequence specifically responsible for endogenous gene induction. These findings-demonstrating that the human innate immune system, including downstream induction of cytokines, can be modulated by DNA metabolic stress-have many implications for health and disease, as well as for understanding the evolution of damage and p53 responsive networks.

  13. The Toll-like receptor gene family is integrated into human DNA damage and p53 networks.

    Directory of Open Access Journals (Sweden)

    Daniel Menendez

    2011-03-01

    Full Text Available In recent years the functions that the p53 tumor suppressor plays in human biology have been greatly extended beyond "guardian of the genome." Our studies of promoter response element sequences targeted by the p53 master regulatory transcription factor suggest a general role for this DNA damage and stress-responsive regulator in the control of human Toll-like receptor (TLR gene expression. The TLR gene family mediates innate immunity to a wide variety of pathogenic threats through recognition of conserved pathogen-associated molecular motifs. Using primary human immune cells, we have examined expression of the entire TLR gene family following exposure to anti-cancer agents that induce the p53 network. Expression of all TLR genes, TLR1 to TLR10, in blood lymphocytes and alveolar macrophages from healthy volunteers can be induced by DNA metabolic stressors. However, there is considerable inter-individual variability. Most of the TLR genes respond to p53 via canonical as well as noncanonical promoter binding sites. Importantly, the integration of the TLR gene family into the p53 network is unique to primates, a recurrent theme raised for other gene families in our previous studies. Furthermore, a polymorphism in a TLR8 response element provides the first human example of a p53 target sequence specifically responsible for endogenous gene induction. These findings-demonstrating that the human innate immune system, including downstream induction of cytokines, can be modulated by DNA metabolic stress-have many implications for health and disease, as well as for understanding the evolution of damage and p53 responsive networks.

  14. PBK/TOPK interacts with the DBD domain of tumor suppressor p53 and modulates expression of transcriptional targets including p21.

    Science.gov (United States)

    Hu, F; Gartenhaus, R B; Eichberg, D; Liu, Z; Fang, H-B; Rapoport, A P

    2010-10-07

    PBK/TOPK (PDZ-binding kinase, T-LAK-cell-originated protein kinase) is a serine-threonine kinase that is overexpressed in a variety of tumor cells but its role in oncogenesis remains unclear. Here we show, by co-immunoprecipitation experiments and yeast two-hybrid analysis, that PBK/TOPK physically interacts with the tumor suppressor p53 through its DNA-binding (DBD) domain in HCT116 colorectal carcinoma cells that express wild-type p53. PBK also binds to p53 mutants carrying five common point mutations in the DBD domain. The PBK-p53 interaction appears to downmodulate p53 transactivation function as indicated by PBK/TOPK knockdown experiments, which show upregulated expression of the key p53 target gene and cyclin-dependent kinase inhibitor p21 in HCT116 cells, particularly after genotoxic damage from doxorubicin. Furthermore, stable PBK/TOPK knockdown cell lines (derived from HCT116 and MCF-7 cells) showed increased apoptosis, G(2)/M arrest and slower growth as compared to stable empty vector-transfected control cell lines. Gene microarray studies identified additional p53 target genes involved in apoptosis or cell cycling, which were differentially regulated by PBK knockdown. Together, these data suggest that increased levels of PBK/TOPK may contribute to tumor cell development and progression through suppression of p53 function and consequent reductions in the cell-cycle regulatory proteins such as p21. PBK/TOPK may therefore be a valid target for antineoplastic kinase inhibitors to sensitize tumor cells to chemotherapy-induced apoptosis and growth suppression.

  15. The Increased Level of Serum p53 in Hepatitis B-Associated Liver Cirrhosis

    Directory of Open Access Journals (Sweden)

    Parisa Shahnazari

    2014-09-01

    Full Text Available Background: The ability of tumour suppressor protein p53 (P53 to regulate cell cycle processes can be modulated by hepatitis B virus (HBV. While preliminary evidences indicates the involvement of protein-x of HBV (HBx in altering p53 DNA binding, no further data have been accumulated for the significance of serum p53 in chronic hepatitis B virus infected patients. Methods: 72 non-cirrhotic and 19 cirrhotic patients infected by HBV were enrolled for the analysis in this study. Enzyme linked immunosorbent assay (ELISA was performed to study the concentrations of serum p53 protein. The tertiary structures of HBx and P53 were docked by Z-dock and Hex servers for in-silico protein-protein interaction analysis. Results: There was a significant association between the serum p53 and cirrhosis (OR=1.81 95% CI: 1.017-3.2, P=0.044. Cirrhotic patients had higher level of serum p53 compare with chronic infection of HBV (1.98±1.22 vs. 1.29±0.72 U/ml, P=0.05. No evidence of correlation was seen between the different variables such as age, gender, log viral load, serum alkaline phosphatase (ALP and alanine aminotransferase (ALT with serum p53. Tertiary model shows that the amino acid residues from Arg110 to Lys132 of the N-terminal of P53 which is critical for ubiquitination, are bonded to a region in N- terminal of HBx amino acid residues from Arg19 to Ser33. Conclusion: There is an increase in serum p53 in HBV-related cirrhosis patients. In this case, HBx might be responsible for such higher concentration of p53 through HBx-p53 protein-protein interaction, as is shown by molecular modeling approach.

  16. The p53 Isoform Δ133p53β Promotes Cancer Stem Cell Potential

    Directory of Open Access Journals (Sweden)

    Nikola Arsic

    2015-04-01

    Full Text Available Cancer stem cells (CSC are responsible for cancer chemoresistance and metastasis formation. Here we report that Δ133p53β, a TP53 splice variant, enhanced cancer cell stemness in MCF-7 breast cancer cells, while its depletion reduced it. Δ133p53β stimulated the expression of the key pluripotency factors SOX2, OCT3/4, and NANOG. Similarly, in highly metastatic breast cancer cells, aggressiveness was coupled with enhanced CSC potential and Δ133p53β expression. Like in MCF-7 cells, SOX2, OCT3/4, and NANOG expression were positively regulated by Δ133p53β in these cells. Finally, treatment of MCF-7 cells with etoposide, a cytotoxic anti-cancer drug, increased CSC formation and SOX2, OCT3/4, and NANOG expression via Δ133p53, thus potentially increasing the risk of cancer recurrence. Our findings show that Δ133p53β supports CSC potential. Moreover, they indicate that the TP53 gene, which is considered a major tumor suppressor gene, also acts as an oncogene via the Δ133p53β isoform.

  17. Perturbation of Ribosome Biogenesis Drives Cells into Senescence through 5S RNP-Mediated p53 Activation

    Directory of Open Access Journals (Sweden)

    Kazuho Nishimura

    2015-03-01

    Full Text Available The 5S ribonucleoprotein particle (RNP complex, consisting of RPL11, RPL5, and 5S rRNA, is implicated in p53 regulation under ribotoxic stress. Here, we show that the 5S RNP contributes to p53 activation and promotes cellular senescence in response to oncogenic or replicative stress. Oncogenic stress accelerates rRNA transcription and replicative stress delays rRNA processing, resulting in RPL11 and RPL5 accumulation in the ribosome-free fraction, where they bind MDM2. Experimental upregulation of rRNA transcription or downregulation of rRNA processing, mimicking the nucleolus under oncogenic or replicative stress, respectively, also induces RPL11-mediated p53 activation and cellular senescence. We demonstrate that exogenous expression of certain rRNA-processing factors rescues the processing defect, attenuates p53 accumulation, and increases replicative lifespan. To summarize, the nucleolar-5S RNP-p53 pathway functions as a senescence inducer in response to oncogenic and replicative stresses.

  18. Perturbation of ribosome biogenesis drives cells into senescence through 5S RNP-mediated p53 activation.

    Science.gov (United States)

    Nishimura, Kazuho; Kumazawa, Takuya; Kuroda, Takao; Katagiri, Naohiro; Tsuchiya, Mai; Goto, Natsuka; Furumai, Ryohei; Murayama, Akiko; Yanagisawa, Junn; Kimura, Keiji

    2015-03-03

    The 5S ribonucleoprotein particle (RNP) complex, consisting of RPL11, RPL5, and 5S rRNA, is implicated in p53 regulation under ribotoxic stress. Here, we show that the 5S RNP contributes to p53 activation and promotes cellular senescence in response to oncogenic or replicative stress. Oncogenic stress accelerates rRNA transcription and replicative stress delays rRNA processing, resulting in RPL11 and RPL5 accumulation in the ribosome-free fraction, where they bind MDM2. Experimental upregulation of rRNA transcription or downregulation of rRNA processing, mimicking the nucleolus under oncogenic or replicative stress, respectively, also induces RPL11-mediated p53 activation and cellular senescence. We demonstrate that exogenous expression of certain rRNA-processing factors rescues the processing defect, attenuates p53 accumulation, and increases replicative lifespan. To summarize, the nucleolar-5S RNP-p53 pathway functions as a senescence inducer in response to oncogenic and replicative stresses. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  19. p53 Aggregates penetrate cells and induce the co-aggregation of intracellular p53.

    Directory of Open Access Journals (Sweden)

    Karolyn J Forget

    Full Text Available Prion diseases are unique pathologies in which the infectious particles are prions, a protein aggregate. The prion protein has many particular features, such as spontaneous aggregation, conformation transmission to other native PrP proteins and transmission from an individual to another. Protein aggregation is now frequently associated to many human diseases, for example Alzheimer's disease, Parkinson's disease or type 2 diabetes. A few proteins associated to these conformational diseases are part of a new category of proteins, called prionoids: proteins that share some, but not all, of the characteristics associated with prions. The p53 protein, a transcription factor that plays a major role in cancer, has recently been suggested to be a possible prionoid. The protein has been shown to accumulate in multiple cancer cell types, and its aggregation has also been reproduced in vitro by many independent groups. These observations suggest a role for p53 aggregates in cancer development. This study aims to test the «prion-like» features of p53. Our results show in vitro aggregation of the full length and N-terminally truncated protein (p53C, and penetration of these aggregates into cells. According to our findings, the aggregates enter cells using macropinocytosis, a non-specific pathway of entry. Lastly, we also show that once internalized by the cell, p53C aggregates can co-aggregate with endogenous p53 protein. Together, these findings suggest prion-like characteristics for p53 protein, based on the fact that p53 can spontaneously aggregate, these aggregates can penetrate cells and co-aggregate with cellular p53.

  20. Immunohistochemical detection of P53 and Mdm2 in vitiligo

    Science.gov (United States)

    Bakry, Ola A.; Hammam, Mostafa A.; Wahed, Moshira M. Abdel

    2012-01-01

    Background: Vitiligo is a common depigmented skin disorder that is caused by selective destruction of melanocytes. It is generally accepted that the main function of melanin resides in the protection of skin cells against the deleterious effect of ultraviolet rays (UVRs). Association of vitiligo and skin cancer has been a subject of controversy. Occurrence of skin cancer in long-lasting vitiligo is rare despite multiple evidences of DNA damage in vitiliginous skin. Aim: To detect the expression of P53 and Mdm2 proteins in both depigmented and normally pigmented skin of vitiligo patients and to compare it to control subjects suffering from nonmelanoma skin cancer (NMSC). Materials and Methods: Thirty-four patients with vitiligo and 30 age and sex-matched patients with nodulo-ulcerative basal cell carcinoma (BCC) as a control group were selected. Both patients and control subjects had outdoor occupations. Skin biopsies were taken from each case and control subjects. Histopathological examination of Hematoxylin and eosin-stained sections was done. Expression of P53 and Mdm2 proteins were examined immunohistochemically. Results: Both P53 and Mdm2 were strongly expressed in depigmented as well as normally pigmented skin of vitiligo patients. This expression involved the epidermis, skin adnexa and blood vessels with significant differences between cases and controls. Conclusions: The overexpression of P53 and Mdm2 proteins in both normally pigmented and depigmented skin of patients with vitiligo could contribute to the decreased occurrence of actinic damage and NMSC in these patients. PMID:23189248

  1. The p53 tumor suppressor-like protein nvp63 mediates selective germ cell death in the sea anemone Nematostella vectensis.

    Directory of Open Access Journals (Sweden)

    Sandra Pankow

    Full Text Available Here we report the identification and molecular function of the p53 tumor suppressor-like protein nvp63 in a non-bilaterian animal, the starlet sea anemone Nematostella vectensis. So far, p53-like proteins had been found in bilaterians only. The evolutionary origin of p53-like proteins is highly disputed and primordial p53-like proteins are variably thought to protect somatic cells from genotoxic stress. Here we show that ultraviolet (UV irradiation at low levels selectively induces programmed cell death in early gametes but not somatic cells of adult N. vectensis polyps. We demonstrate with RNA interference that nvp63 mediates this cell death in vivo. Nvp63 is the most archaic member of three p53-like proteins found in N. vectensis and in congruence with all known p53-like proteins, nvp63 binds to the vertebrate p53 DNA recognition sequence and activates target gene transcription in vitro. A transactivation inhibitory domain at its C-terminus with high homology to the vertebrate p63 may regulate nvp63 on a molecular level. The genotoxic stress induced and nvp63 mediated apoptosis in N. vectensis gametes reveals an evolutionary ancient germ cell protective pathway which relies on p63-like proteins and is conserved from cnidarians to vertebrates.

  2. 5-Aza-2'-deoxycytidine Activates the p53/p21waf1/Cip1 Pathway to Inhibit Cell Proliferation

    Institute of Scientific and Technical Information of China (English)

    Wei-GuoZhu; TheresaHileman; YangKe; PeichangWang; ShaoliLu; WenruiDuan; ZunyanDai;