P53 Laboratory A STAR

Singapore, Singapore

P53 Laboratory A STAR

Singapore, Singapore
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Coffill C.R.,Quantitative Group | Muller P.A.J.,Beatson Institute for Cancer Research | Oh H.K.,Quantitative Group | Neo S.P.,Quantitative Group | And 6 more authors.
EMBO Reports | Year: 2012

The invasiveness of tumour cells depends on changes in cell shape, polarity and migration. Mutant p53 induces enhanced tumour metastasis in mice, and human cells overexpressing p53R273H have aberrant polarity and increased invasiveness, demonstrating the 'gain of functiong' of mutant p53 in carcinogenesis. We hypothesize that p53R273H interacts with mutant p53-specific binding partners that control polarity, migration or invasion. Here we analyze the p53R273H interactome using stable isotope labelling by amino acids in cell culture and quantitative mass spectrometry, and identify at least 15 new potential mutant p53-specific binding partners. The interaction of p53R273H with one of them-nardilysin (NRD1)-promotes an invasive response to heparin binding-epidermal growth factor-like growth factor that is p53R273H-dependant but does not require Rab coupling protein or p63. Advanced proteomics has thus allowed the detection of a new mechanism of p53-driven invasion. © 2012 European Molecular Biology Organization.

ElSawy K.M.,University of York | ElSawy K.M.,Qassim University | Sim A.,Bioinformatics Institute A STAR | Lane D.P.,p53 Laboratory A STAR | And 4 more authors.
Cell Cycle | Year: 2015

The interaction of p53 and MDM2 is modulated by the phosphorylation of p53. This mechanism is key to activating p53, yet its molecular determinants are not fully understood. To study the spatiotemporal characteristics of this molecular process we carried out Brownian dynamics simulations of the interactions of the MDM2 protein with a p53 peptide in its wild type state and when phosphorylated at Thr18 (pThr18) and Ser20 (pSer20). We found that p53 phosphorylation results in concerted changes in the topology of the interaction landscape in the diffusively bound encounter complex domain. These changes hinder phosphorylated p53 peptides from binding to MDM2 well before reaching the binding site. The underlying mechanism appears to involve shift of the peptide away from the vicinity of the MDM2 protein, peptide reorientation, and reduction in peptide residence time relative to wild-type p53 peptide. pThr18 and pSr20 p53 peptides experience reduction in residence times by factors of 13.6 and 37.5 respectively relative to the wild-type p53 peptide, indicating a greater role for Ser20 phosphorylation in abrogating p53 MDM2 interactions. These detailed insights into the effect of phosphorylation on molecular interactions are not available from conventional experimental and theoretical approaches and open up new avenues that incorporate molecular interaction dynamics, for stabilizing p53 against MDM2, which is a major focus of anticancer drug lead development. © 2015 Crown copyright.

Cheok C.F.,P53 Laboratory A STAR | Kua N.,P53 Laboratory A STAR | Kaldis P.,Institute of Molecular and Cell Biology A STAR | Lane D.P.,P53 Laboratory A STAR
Cell Death and Differentiation | Year: 2010

Chemotherapeutics (e.g., aurora kinase inhibitors) designed to target proliferative cells are often nonspecific for tumor cells as normal cycling cells are also susceptible. Indeed, one of the major dose-limiting toxicities of aurora kinase inhibitors is a dangerous depletion of neutrophils in patients. In this study we proposed a strategy to selectively target p53 mutant cells while sparing normal ones. The strategy is based on the understanding that normal cells have an intact p53 pathway but not tumor cells carrying p53 mutations. Nongenotoxic activation of p53 using nutlin led to a reversible activation of G1 and G2 arrest in normal cells, which prevents them from entering mitosis, thus protecting them from the side effects of aurora kinase inhibition (VX-680), namely endoreduplication and apoptosis. Cells carrying mutant p53 are selectively killed by the nutlin/VX-680 combination, whereas p53 wild-type cells retain their proliferative capacity. The major implications drawn from these results are: (1) reversible nongenotoxic activation of p53 may be used as a strategy for the chemoprotection of normal tissues, and (2) aurora kinase inhibitors may have alleviated side effects when used in combination with nutlin-like inhibitors. We highlight the distinct roles of p53 and p73 in mediating the cellular responses to VX-680 and suggest that dual protection by p53 and p73 are needed to guard against endoreduplication and polyploidy. © 2010 Macmillan Publishers Limited. All rights reserved.

Van Leeuwen I.M.M.,Karolinska Institutet | Higgins M.,University of Dundee | Campbell J.,University of Dundee | Brown C.J.,p53 Laboratory A StAR | And 5 more authors.
Cell Cycle | Year: 2011

Recent advances in the field of pharmacological activation of the p53 tumor suppressor are beginning to be translated into the clinic. In addition, small molecules that activate p53 through established mechanisms of action are proving invaluable tools for basic research. Here we analyze and compare the effects of nutlin-3, tenovin-6 and low doses of actinomycin-D on p53 and its main negative regulator, mdm2. We reveal striking differences in the speed at which these compounds increase p53 protein levels, with nutlin-3 having a substantial impact within minutes. We also show that nutlin-3 is very effective at increasing the synthesis of mdm2 mRNA, mdm2 being not only a modulator of p53 but also a transcriptional target. In addition, we show that nutlin-3 stabilises mdm2's conformation and protects mdm2 from degradation. These strong effects of nutlin-3 on mdm2 correlate with a remarkable rate of recovery of p53 levels upon removal of the compound. We discuss the potential application of our results as molecular signatures to assess the on-target effects of small-molecule mdm2 inhibitors. To conclude, we discuss the implications of our observations for using small-molecule p53 activators to reduce the growth of tumors retaining wild-type p53 or to protect normal tissues against the undesired side effects of conventional chemotherapy. © 2011 Landes Bioscience.

Lane D.P.,p53 Laboratory A STAR | Cheok C.F.,p53 Laboratory A STAR | Brown C.,p53 Laboratory A STAR | Madhumalar A.,Matrix | And 2 more authors.
Cell Cycle | Year: 2010

The p53 protein is the most commonly mutated tumor suppressor gene in man. Understanding of its evolutionary origins have been enhanced by the recent discovery of p53 family genes in the Sea Anemone Nematostella vectensis. This amino acid sequence conservation has been reflected in biological activity since the early p53 proteins, like their human counterparts, are responsible for DNA damage-induced cellular apoptosis, albeit restricted to the germ cell compartment in model organisms such as the nematode and fruit fly. In vertebrates from zebrafish to man the function of p53 is tightly and absolutely constrained by a negative regulator Mdm2. However the Mdm2 gene has not been detected in the genome of the model nematode (C. elegans) and insect (D. melanogaster) species. We have found that the p53 gene and the Mdm2 gene are present in Placozoans, one of the simplest of all free living multi-cellular organisms, implying that both proteins arose much earlier in evolution than previously thought. Detailed sequence analysis shows the exceptional retention of key features of both proteins from man to Placazoan implying that the p53-Mdm2 interaction and its regulation have been conserved from a basal eumetazoan since the pre-cambrian era over 1 billion years ago. © 2010 Landes Bioscience.

Dey A.,P53 Laboratory a star | Lane D.P.,P53 Laboratory a star | Verma C.S.,Matrix
Seminars in Cancer Biology | Year: 2010

p53 is a transcription factor that protects cells against stress, by modulating genes that induce growth arrest, repair, apoptosis, senescence or altered metabolism. Activation of p53 can potentially be used to modulate disease states. We describe here recent developments that attempt to modulate the function of p53 and outline strategies that are being investigated for pharmacological intervention in the p53 pathway. These include interruption of the interactions between p53 and its negative regulators, restabilization of mutant/misfolded p53, activation of p53 dependant transcription and modulation of p53 function systemically to affect the therapeutic profile of existing drugs. In addition the development of new animal models to investigate the above developments, including mice and zebrafish will be highlighted. © 2010 Elsevier Ltd.

Dastidar S.G.,Bioinformatics Institute A STAR | Raghunathan D.,Bioinformatics Institute A STAR | Nicholson J.,University of Edinburgh | Hupp T.R.,University of Edinburgh | And 2 more authors.
Cell Cycle | Year: 2011

Phosphorylation of S17 in the N-terminal "lid" of MDM2 (residues 1-24) is proposed to regulate the binding of p53. The lid is composed of an intrinsically disordered peptide motif that is not resolved in the crystal structure of the MDM2 N-terminal domain. Molecular dynamics simulations of MDM2 provide novel insights into how the lid undergoes complex dynamics depending on its phosphorylation state that have not been revealed by NMR analyses. The difference in charges between the phosphate and the phosphomimetic 'Asp' and the change in shape from tetrahedral to planar are manifested in differences in strengths and durations of interactions that appear to modulate access of the binding site to ligands and peptides differentially. These findings unveil the complexities that underlie protein-protein interactions and reconcile some differences between the biochemical and NMR data suggesting that lid mutation or deletion can change the specific activity of MDM2 and provide concepts for future approaches to evaluate the effects of S17 modification on p53 binding. © 2011 Landes Bioscience.

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