Publications by authors named "Evelyne Lima-Fernandes"

21 Publications

  • Page 1 of 1

The RanBP2/RanGAP1-SUMO complex gates β-arrestin2 nuclear entry to regulate the Mdm2-p53 signaling axis.

Oncogene 2021 Mar 1;40(12):2243-2257. Epub 2021 Mar 1.

Inserm, U1016, Institut Cochin, Paris, France.

Mdm2 antagonizes the tumor suppressor p53. Targeting the Mdm2-p53 interaction represents an attractive approach for the treatment of cancers with functional p53. Investigating mechanisms underlying Mdm2-p53 regulation is therefore important. The scaffold protein β-arrestin2 (β-arr2) regulates tumor suppressor p53 by counteracting Mdm2. β-arr2 nucleocytoplasmic shuttling displaces Mdm2 from the nucleus to the cytoplasm resulting in enhanced p53 signaling. β-arr2 is constitutively exported from the nucleus, via a nuclear export signal, but mechanisms regulating its nuclear entry are not completely elucidated. β-arr2 can be SUMOylated, but no information is available on how SUMO may regulate β-arr2 nucleocytoplasmic shuttling. While we found β-arr2 SUMOylation to be dispensable for nuclear import, we identified a non-covalent interaction between SUMO and β-arr2, via a SUMO interaction motif (SIM), that is required for β-arr2 cytonuclear trafficking. This SIM promotes association of β-arr2 with the multimolecular RanBP2/RanGAP1-SUMO nucleocytoplasmic transport hub that resides on the cytoplasmic filaments of the nuclear pore complex. Depletion of RanBP2/RanGAP1-SUMO levels result in defective β-arr2 nuclear entry. Mutation of the SIM inhibits β-arr2 nuclear import, its ability to delocalize Mdm2 from the nucleus to the cytoplasm and enhanced p53 signaling in lung and breast tumor cell lines. Thus, a β-arr2 SIM nuclear entry checkpoint, coupled with active β-arr2 nuclear export, regulates its cytonuclear trafficking function to control the Mdm2-p53 signaling axis.
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http://dx.doi.org/10.1038/s41388-021-01704-wDOI Listing
March 2021

Colorectal Cancer Cells Enter a Diapause-like DTP State to Survive Chemotherapy.

Cell 2021 Jan;184(1):226-242.e21

Princess Margaret Cancer Center, University Health Network, Toronto, ON M5G 1L7, Canada; Ontario Institute for Cancer Research, Toronto, ON M5G 0A3, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Surgery, University Health Network, Toronto, ON M5G 1L7, Canada. Electronic address:

Cancer cells enter a reversible drug-tolerant persister (DTP) state to evade death from chemotherapy and targeted agents. It is increasingly appreciated that DTPs are important drivers of therapy failure and tumor relapse. We combined cellular barcoding and mathematical modeling in patient-derived colorectal cancer models to identify and characterize DTPs in response to chemotherapy. Barcode analysis revealed no loss of clonal complexity of tumors that entered the DTP state and recurred following treatment cessation. Our data fit a mathematical model where all cancer cells, and not a small subpopulation, possess an equipotent capacity to become DTPs. Mechanistically, we determined that DTPs display remarkable transcriptional and functional similarities to diapause, a reversible state of suspended embryonic development triggered by unfavorable environmental conditions. Our study provides insight into how cancer cells use a developmentally conserved mechanism to drive the DTP state, pointing to novel therapeutic opportunities to target DTPs.
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http://dx.doi.org/10.1016/j.cell.2020.11.018DOI Listing
January 2021

GLUT1 inhibition blocks growth of RB1-positive triple negative breast cancer.

Nat Commun 2020 08 21;11(1):4205. Epub 2020 Aug 21.

Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada.

Triple negative breast cancer (TNBC) is a deadly form of breast cancer due to the development of resistance to chemotherapy affecting over 30% of patients. New therapeutics and companion biomarkers are urgently needed. Recognizing the elevated expression of glucose transporter 1 (GLUT1, encoded by SLC2A1) and associated metabolic dependencies in TNBC, we investigated the vulnerability of TNBC cell lines and patient-derived samples to GLUT1 inhibition. We report that genetic or pharmacological inhibition of GLUT1 with BAY-876 impairs the growth of a subset of TNBC cells displaying high glycolytic and lower oxidative phosphorylation (OXPHOS) rates. Pathway enrichment analysis of gene expression data suggests that the functionality of the E2F pathway may reflect to some extent OXPHOS activity. Furthermore, the protein levels of retinoblastoma tumor suppressor (RB1) strongly correlate with the degree of sensitivity to GLUT1 inhibition in TNBC, where RB1-negative cells are insensitive to GLUT1 inhibition. Collectively, our results highlight a strong and targetable RB1-GLUT1 metabolic axis in TNBC and warrant clinical evaluation of GLUT1 inhibition in TNBC patients stratified according to RB1 protein expression levels.
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http://dx.doi.org/10.1038/s41467-020-18020-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7442809PMC
August 2020

Epigenetic Switch-Induced Viral Mimicry Evasion in Chemotherapy-Resistant Breast Cancer.

Cancer Discov 2020 Sep 16;10(9):1312-1329. Epub 2020 Jun 16.

Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.

Tumor progression upon treatment arises from preexisting resistant cancer cells and/or adaptation of persister cancer cells committing to an expansion phase. Here, we show that evasion from viral mimicry response allows the growth of taxane-resistant triple-negative breast cancer (TNBC). This is enabled by an epigenetic state adapted to taxane-induced metabolic stress, where DNA hypomethylation over loci enriched in transposable elements (TE) is compensated by large chromatin domains of H3K27me3 to warrant TE repression. This epigenetic state creates a vulnerability to epigenetic therapy against EZH2, the H3K27me3 methyltransferase, which alleviates TE repression in taxane-resistant TNBC, leading to double-stranded RNA production and growth inhibition through viral mimicry response. Collectively, our results illustrate how epigenetic states over TEs promote cancer progression under treatment and can inform about vulnerabilities to epigenetic therapy. SIGNIFICANCE: Drug-resistant cancer cells represent a major barrier to remission for patients with cancer. Here we show that drug-induced metabolic perturbation and epigenetic states enable evasion from the viral mimicry response induced by chemotherapy in TNBC. These epigenetic states define a vulnerability to epigenetic therapy using EZH2 inhibitors in taxane-resistant TNBC...
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http://dx.doi.org/10.1158/2159-8290.CD-19-1493DOI Listing
September 2020

Discovery of a chemical probe for PRDM9.

Nat Commun 2019 12 17;10(1):5759. Epub 2019 Dec 17.

Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada.

PRDM9 is a PR domain containing protein which trimethylates histone 3 on lysine 4 and 36. Its normal expression is restricted to germ cells and attenuation of its activity results in altered meiotic gene transcription, impairment of double-stranded breaks and pairing between homologous chromosomes. There is growing evidence for a role of aberrant expression of PRDM9 in oncogenesis and genome instability. Here we report the discovery of MRK-740, a potent (IC: 80 ± 16 nM), selective and cell-active PRDM9 inhibitor (Chemical Probe). MRK-740 binds in the substrate-binding pocket, with unusually extensive interactions with the cofactor S-adenosylmethionine (SAM), conferring SAM-dependent substrate-competitive inhibition. In cells, MRK-740 specifically and directly inhibits H3K4 methylation at endogenous PRDM9 target loci, whereas the closely related inactive control compound, MRK-740-NC, does not. The discovery of MRK-740 as a chemical probe for the PRDM subfamily of methyltransferases highlights the potential for exploiting SAM in targeting SAM-dependent methyltransferases.
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http://dx.doi.org/10.1038/s41467-019-13652-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6917776PMC
December 2019

A chemical toolbox for the study of bromodomains and epigenetic signaling.

Nat Commun 2019 04 23;10(1):1915. Epub 2019 Apr 23.

Structural Genomics Consortium, Buchmann Institute for Life Sciences, Goethe-University Frankfurt, 60438, Frankfurt, Germany.

Bromodomains (BRDs) are conserved protein interaction modules which recognize (read) acetyl-lysine modifications, however their role(s) in regulating cellular states and their potential as targets for the development of targeted treatment strategies is poorly understood. Here we present a set of 25 chemical probes, selective small molecule inhibitors, covering 29 human bromodomain targets. We comprehensively evaluate the selectivity of this probe-set using BROMOscan and demonstrate the utility of the set identifying roles of BRDs in cellular processes and potential translational applications. For instance, we discovered crosstalk between histone acetylation and the glycolytic pathway resulting in a vulnerability of breast cancer cell lines under conditions of glucose deprivation or GLUT1 inhibition to inhibition of BRPF2/3 BRDs. This chemical probe-set will serve as a resource for future applications in the discovery of new physiological roles of bromodomain proteins in normal and disease states, and as a toolset for bromodomain target validation.
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http://dx.doi.org/10.1038/s41467-019-09672-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6478789PMC
April 2019

Targeting bivalency de-represses Indian Hedgehog and inhibits self-renewal of colorectal cancer-initiating cells.

Nat Commun 2019 03 29;10(1):1436. Epub 2019 Mar 29.

Princess Margaret Cancer Centre, University Health Network, Toronto, ON, M5G1L7, Canada.

In embryonic stem cells, promoters of key lineage-specific differentiation genes are found in a bivalent state, having both activating H3K4me3 and repressive H3K27me3 histone marks, making them poised for transcription upon loss of H3K27me3. Whether cancer-initiating cells (C-ICs) have similar epigenetic mechanisms that prevent lineage commitment is unknown. Here we show that colorectal C-ICs (CC-ICs) are maintained in a stem-like state through a bivalent epigenetic mechanism. Disruption of the bivalent state through inhibition of the H3K27 methyltransferase EZH2, resulted in decreased self-renewal of patient-derived C-ICs. Epigenomic analyses revealed that the promoter of Indian Hedgehog (IHH), a canonical driver of normal colonocyte differentiation, exists in a bivalent chromatin state. Inhibition of EZH2 resulted in de-repression of IHH, decreased self-renewal, and increased sensitivity to chemotherapy in vivo. Our results reveal an epigenetic block to differentiation in CC-ICs and demonstrate the potential for epigenetic differentiation therapy of a solid tumour through EZH2 inhibition.
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http://dx.doi.org/10.1038/s41467-019-09309-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6441108PMC
March 2019

Direct interaction between the PRDM3 and PRDM16 tumor suppressors and the NuRD chromatin remodeling complex.

Nucleic Acids Res 2019 02;47(3):1225-1238

Department of Medical Biophysics, University of Toronto, Toronto, ON, M5G 1L7, Canada.

Aberrant isoform expression of chromatin-associated proteins can induce epigenetic programs related to disease. The MDS1 and EVI1 complex locus (MECOM) encodes PRDM3, a protein with an N-terminal PR-SET domain, as well as a shorter isoform, EVI1, lacking the N-terminus containing the PR-SET domain (ΔPR). Imbalanced expression of MECOM isoforms is observed in multiple malignancies, implicating EVI1 as an oncogene, while PRDM3 has been suggested to function as a tumor suppressor through an unknown mechanism. To elucidate functional characteristics of these N-terminal residues, we compared the protein interactomes of the full-length and ΔPR isoforms of PRDM3 and its closely related paralog, PRDM16. Unlike the ΔPR isoforms, both full-length isoforms exhibited a significantly enriched association with components of the NuRD chromatin remodeling complex, especially RBBP4. Typically, RBBP4 facilitates chromatin association of the NuRD complex by binding to histone H3 tails. We show that RBBP4 binds to the N-terminal amino acid residues of PRDM3 and PRDM16, with a dissociation constant of 3.0 μM, as measured by isothermal titration calorimetry. Furthermore, high-resolution X-ray crystal structures of PRDM3 and PRDM16 N-terminal peptides in complex with RBBP4 revealed binding to RBBP4 within the conserved histone H3-binding groove. These data support a mechanism of isoform-specific interaction of PRDM3 and PRDM16 with the NuRD chromatin remodeling complex.
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http://dx.doi.org/10.1093/nar/gky1192DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6379669PMC
February 2019

Administration of Hypoxia-Activated Prodrug Evofosfamide after Conventional Adjuvant Therapy Enhances Therapeutic Outcome and Targets Cancer-Initiating Cells in Preclinical Models of Colorectal Cancer.

Clin Cancer Res 2018 05 23;24(9):2116-2127. Epub 2018 Feb 23.

Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.

Cancer-initiating cells (C-IC) have been described in multiple cancer types, including colorectal cancer. C-ICs are defined by their capacity to self-renew, thereby driving tumor growth. C-ICs were initially thought to be static entities; however, recent studies have determined these cells to be dynamic and influenced by microenvironmental cues such as hypoxia. If hypoxia drives the formation of C-ICs, then therapeutic targeting of hypoxia could represent a novel means to target C-ICs. Patient-derived colorectal cancer xenografts were treated with evofosfamide, a hypoxia-activated prodrug (HAP), in combination with 5-fluorouracil (5-FU) or chemoradiotherapy (5-FU and radiation; CRT). Treatment groups included both concurrent and sequential dosing regimens. Effects on the colorectal cancer-initiating cell (CC-IC) fraction were assessed by serial passage limiting dilution assays. FAZA-PET imaging was utilized as a noninvasive method to assess intratumoral hypoxia. Hypoxia was sufficient to drive the formation of CC-ICs and colorectal cancer cells surviving conventional therapy were more hypoxic and C-IC-like. Using a novel approach to combination therapy, we show that sequential treatment with 5-FU or CRT followed by evofosfamide not only inhibits tumor growth of xenografts compared with 5-FU or CRT alone, but also significantly decreases the CC-IC fraction. Furthermore, noninvasive FAZA-PET hypoxia imaging was predictive of a tumor's response to evofosfamide. Our data demonstrate a novel means to target the CC-IC fraction by adding a HAP sequentially after conventional adjuvant therapy, as well as the use of FAZA-PET as a biomarker for hypoxia to identify tumors that will benefit most from this approach. .
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http://dx.doi.org/10.1158/1078-0432.CCR-17-1715DOI Listing
May 2018

The EED protein-protein interaction inhibitor A-395 inactivates the PRC2 complex.

Nat Chem Biol 2017 04 30;13(4):389-395. Epub 2017 Jan 30.

AbbVie Inc., North Chicago, Illinois, USA.

Polycomb repressive complex 2 (PRC2) is a regulator of epigenetic states required for development and homeostasis. PRC2 trimethylates histone H3 at lysine 27 (H3K27me3), which leads to gene silencing, and is dysregulated in many cancers. The embryonic ectoderm development (EED) protein is an essential subunit of PRC2 that has both a scaffolding function and an H3K27me3-binding function. Here we report the identification of A-395, a potent antagonist of the H3K27me3 binding functions of EED. Structural studies demonstrate that A-395 binds to EED in the H3K27me3-binding pocket, thereby preventing allosteric activation of the catalytic activity of PRC2. Phenotypic effects observed in vitro and in vivo are similar to those of known PRC2 enzymatic inhibitors; however, A-395 retains potent activity against cell lines resistant to the catalytic inhibitors. A-395 represents a first-in-class antagonist of PRC2 protein-protein interactions (PPI) for use as a chemical probe to investigate the roles of EED-containing protein complexes.
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http://dx.doi.org/10.1038/nchembio.2306DOI Listing
April 2017

PR Domain-containing Protein 7 (PRDM7) Is a Histone 3 Lysine 4 Trimethyltransferase.

J Biol Chem 2016 Jun 29;291(26):13509-19. Epub 2016 Apr 29.

From the Structural Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7, the Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8, Canada

PR domain-containing protein 7 (PRDM7) is a primate-specific histone methyltransferase that is the result of a recent gene duplication of PRDM9. The two proteins are highly homologous, especially in the catalytic PR/SET domain, where they differ by only three amino acid residues. Here we report that PRDM7 is an efficient methyltransferase that selectively catalyzes the trimethylation of H3 lysine 4 (H3K4) both in vitro and in cells. Through selective mutagenesis we have dissected the functional roles of each of the three divergent residues between the PR domains of PRDM7 and PRDM9. These studies indicate that after a single serine to tyrosine mutation at residue 357 (S357Y), PRDM7 regains the substrate specificities and catalytic activities similar to its evolutionary predecessor, including the ability to efficiently methylate H3K36.
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http://dx.doi.org/10.1074/jbc.M116.721472DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4919437PMC
June 2016

Rapid Detection of Dynamic PTEN Regulation in Living Cells Using Intramolecular BRET.

Methods Mol Biol 2016 ;1388:95-110

Inserm, U1016, Institut Cochin, 27, Rue du Faubourg Saint Jacques, 75014, Paris, France.

Tumor suppressor PTEN phosphatase acts to inhibit the PI3K/AKT pathway and thus regulates cell proliferation, survival, and migration. Dysregulation of PTEN function is observed in a wide range of cancers. In addition to alterations of the PTEN gene, repression of PTEN function can also occur at the protein level through changes in PTEN conformation, localization, activity, and stability. The ability to follow switches in PTEN conformation in live cells provides a rapid approach to study changes in PTEN function and may provide a basis to screen pharmacological agents aimed at enhancing or reestablishing PTEN-dependent signaling pathways that have gone awry in cancer. Here, we describe methods to use an intramolecular bioluminescent resonance energy transfer (BRET)-based biosensor that reports dynamic signal-dependent changes in PTEN conformational rearrangement and function.
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http://dx.doi.org/10.1007/978-1-4939-3299-3_8DOI Listing
December 2016

Kinetic characterization of human histone H3 lysine 36 methyltransferases, ASH1L and SETD2.

Biochim Biophys Acta 2015 Sep 19;1850(9):1842-8. Epub 2015 May 19.

Structural Genomics Consortium, University of Toronto, Toronto, ON M5G 1L7, Canada; Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada. Electronic address:

Background: Dysregulation of methylation of lysine 36 on histone H3 (H3K36) have been implicated in a variety of diseases including cancers. ASH1L and SETD2 are two enzymes among others that catalyze H3K36 methylation. H3K4 methylation has also been reported for ASH1L.

Methods: Radioactivity-based enzyme assays, Western and immunoblotting using specific antibodies and molecular modeling were used to characterize substrate specificity of ASH1L and SETD2.

Results: Here we report on the assay development and kinetic characterization of ASH1L and SETD2 and their substrate specificities in vitro. Both enzymes were active with recombinant nucleosome as substrate. However, SETD2 but not ASH1L methylated histone peptides as well indicating that the interaction of the basic post-SET extension with substrate may not be critical for SETD2 activity. Both enzymes were not active with nucleosome containing a H3K36A mutation indicating their specificity for H3K36. Analyzing the methylation state of the products of ASH1L and SETD2 reactions also confirmed that both enzymes mono- and dimethylate H3K36 and are inactive with H3K4 as substrate, and that only SETD2 is able to trimethylate H3K36 in vitro.

Conclusions: We determined the kinetic parameters for ASH1L and SETD2 activity enabling screening for inhibitors that can be used to further investigate the roles of these two proteins in health and disease. Both ASH1L and SETD2 are H3K36 specific methyltransferases but only SETD2 can trimethylate this mark. The basic post-SET extension is critical for ASH1L but not SETD2 activity.

General Significance: We provide full kinetic characterization of ASH1L and SETD2 activity.
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http://dx.doi.org/10.1016/j.bbagen.2015.05.013DOI Listing
September 2015

A biosensor to monitor dynamic regulation and function of tumour suppressor PTEN in living cells.

Nat Commun 2014 Jul 16;5:4431. Epub 2014 Jul 16.

1] Department of Endocrinology, Metabolism and Diabetes, Inserm, U1016, Institut Cochin, 27 rue du Faubourg St Jaques, Paris 75014, France [2] CNRS, UMR8104, Paris 75014, France [3] University Paris Descartes, Sorbonne Paris Cité, Paris 75014, France.

Tumour suppressor PTEN is a phosphatase that negatively regulates the PI3K/AKT pathway. The ability to directly monitor PTEN conformation and function in a rapid, sensitive manner is a key step towards developing anti-cancer drugs aimed at enhancing or restoring PTEN-dependent pathways. Here we developed an intramolecular bioluminescence resonance energy transfer (BRET)-based biosensor, capable of detecting signal-dependent PTEN conformational changes in live cells. The biosensor retains intrinsic properties of PTEN, enabling structure-function and kinetic analyses. BRET shifts, indicating conformational change, were detected following mutations that disrupt intramolecular PTEN interactions, promoting plasma membrane targeting and also following physiological PTEN activation. Using the biosensor as a reporter, we uncovered PTEN activation by several G protein-coupled receptors, previously unknown as PTEN regulators. Trastuzumab, used to treat ERBB2-overexpressing breast cancers also elicited activation-associated PTEN conformational rearrangement. We propose the biosensor can be used to identify pathways regulating PTEN or molecules that enhance its anti-tumour activity.
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http://dx.doi.org/10.1038/ncomms5431DOI Listing
July 2014

Targeting spare CC chemokine receptor 5 (CCR5) as a principle to inhibit HIV-1 entry.

J Biol Chem 2014 Jul 22;289(27):19042-52. Epub 2014 May 22.

From the INSERM U1108, Viral Pathogenesis Unit, Department of Virology, Institut Pasteur, 75015 Paris, France,

CCR5 binds the chemokines CCL3, CCL4, and CCL5 and is the major coreceptor for HIV-1 entry into target cells. Chemokines are supposed to form a natural barrier against human immunodeficiency virus, type 1 (HIV-1) infection. However, we showed that their antiviral activity is limited by CCR5 adopting low-chemokine affinity conformations at the cell surface. Here, we investigated whether a pool of CCR5 that is not stabilized by chemokines could represent a target for inhibiting HIV infection. We exploited the characteristics of the chemokine analog PSC-RANTES (N-α-(n-nonanoyl)-des-Ser(1)-[l-thioprolyl(2), l-cyclohexylglycyl(3)]-RANTES(4-68)), which displays potent anti-HIV-1 activity. We show that native chemokines fail to prevent high-affinity binding of PSC-RANTES, analog-mediated calcium release (in desensitization assays), and analog-mediated CCR5 internalization. These results indicate that a pool of spare CCR5 may bind PSC-RANTES but not native chemokines. Improved recognition of CCR5 by PSC-RANTES may explain why the analog promotes higher amounts of β-arrestin 2·CCR5 complexes, thereby increasing CCR5 down-regulation and HIV-1 inhibition. Together, these results highlight that spare CCR5, which might permit HIV-1 to escape from chemokines, should be targeted for efficient viral blockade.
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http://dx.doi.org/10.1074/jbc.M114.559831DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4081942PMC
July 2014

Trimethylation of histone H3 lysine 36 by human methyltransferase PRDM9 protein.

J Biol Chem 2014 Apr 14;289(17):12177-12188. Epub 2014 Mar 14.

Structural Genomics Consortium, University of Toronto, Toronto, Ontario M5G 1L7; Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8. Electronic address:

PRDM9 (PR domain-containing protein 9) is a meiosis-specific protein that trimethylates H3K4 and controls the activation of recombination hot spots. It is an essential enzyme in the progression of early meiotic prophase. Disruption of the PRDM9 gene results in sterility in mice. In human, several PRDM9 SNPs have been implicated in sterility as well. Here we report on kinetic studies of H3K4 methylation by PRDM9 in vitro indicating that PRDM9 is a highly active histone methyltransferase catalyzing mono-, di-, and trimethylation of the H3K4 mark. Screening for other potential histone marks, we identified H3K36 as a second histone residue that could also be mono-, di-, and trimethylated by PRDM9 as efficiently as H3K4. Overexpression of PRDM9 in HEK293 cells also resulted in a significant increase in trimethylated H3K36 and H3K4 further confirming our in vitro observations. Our findings indicate that PRDM9 may play critical roles through H3K36 trimethylation in cells.
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http://dx.doi.org/10.1074/jbc.M113.523183DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4002121PMC
April 2014

Arrestins as regulatory hubs in cancer signalling pathways.

Handb Exp Pharmacol 2014 ;219:405-25

Inserm, U1016, Institut Cochin, 27, Rue du Faubourg Saint Jacques, 75014, Paris, France,

Non-visual arrestins were initially appreciated for the roles they play in the negative regulation of G protein-coupled receptors through the processes of desensitisation and endocytosis. The arrestins are also now known as protein scaffolding platforms that act downstream of multiple types of receptors, ensuring relevant transmission of information for an appropriate cellular response. They function as regulatory hubs in several important signalling pathways that are often dysregulated in human cancers. Interestingly, several recent studies have documented changes in expression and localisation of arrestins that occur during cancer progression and that correlate with clinical outcome. Here, we discuss these advances and how changes in expression/localisation may affect functional outputs of arrestins in cancer biology.
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http://dx.doi.org/10.1007/978-3-642-41199-1_21DOI Listing
April 2014

Self-renewal as a therapeutic target in human colorectal cancer.

Nat Med 2014 Jan 1;20(1):29-36. Epub 2013 Dec 1.

1] Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada. [2] Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada. [3] Department of Surgery, Toronto General Hospital, Toronto, Ontario, Canada. [4].

Tumor recurrence following treatment remains a major clinical challenge. Evidence from xenograft models and human trials indicates selective enrichment of cancer-initiating cells (CICs) in tumors that survive therapy. Together with recent reports showing that CIC gene signatures influence patient survival, these studies predict that targeting self-renewal, the key 'stemness' property unique to CICs, may represent a new paradigm in cancer therapy. Here we demonstrate that tumor formation and, more specifically, human colorectal CIC function are dependent on the canonical self-renewal regulator BMI-1. Downregulation of BMI-1 inhibits the ability of colorectal CICs to self-renew, resulting in the abrogation of their tumorigenic potential. Treatment of primary colorectal cancer xenografts with a small-molecule BMI-1 inhibitor resulted in colorectal CIC loss with long-term and irreversible impairment of tumor growth. Targeting the BMI-1-related self-renewal machinery provides the basis for a new therapeutic approach in the treatment of colorectal cancer.
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http://dx.doi.org/10.1038/nm.3418DOI Listing
January 2014

Distinct functional outputs of PTEN signalling are controlled by dynamic association with β-arrestins.

EMBO J 2011 Jun 3;30(13):2557-68. Epub 2011 Jun 3.

INSERM, U1016, Institut Cochin, Paris, France.

The tumour suppressor PTEN (phosphatase and tensin deleted on chromosome 10) regulates major cellular functions via lipid phosphatase-dependent and -independent mechanisms. Despite its fundamental pathophysiological importance, how PTEN's cellular activity is regulated has only been partially elucidated. We report that the scaffolding proteins β-arrestins (β-arrs) are important regulators of PTEN. Downstream of receptor-activated RhoA/ROCK signalling, β-arrs activate the lipid phosphatase activity of PTEN to negatively regulate Akt and cell proliferation. In contrast, following wound-induced RhoA activation, β-arrs inhibit the lipid phosphatase-independent anti-migratory effects of PTEN. β-arrs can thus differentially control distinct functional outputs of PTEN important for cell proliferation and migration.
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http://dx.doi.org/10.1038/emboj.2011.178DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155309PMC
June 2011

Secreted factors from brain endothelial cells maintain glioblastoma stem-like cell expansion through the mTOR pathway.

EMBO Rep 2011 May 1;12(5):470-6. Epub 2011 Apr 1.

INSERM U1016, Institut Cochin, 22 rue Mechain, 75014 Paris.

Glioma stem-cells are associated with the brain vasculature. However, the way in which this vascular niche regulates stem-cell renewal and fate remains unclear. Here, we show that factors emanating from brain endothelial cells positively control the expansion of long-term glioblastoma stem-like cells. We find that both pharmacological inhibition of and RNA interference with the mammalian target of rapamycin (mTOR) pathway reduce their spheroid growth. Conversely, the endothelial secretome is sufficient to promote this mTOR-dependent survival. Thus, interfering with endothelial signals might present opportunities to identify treatments that selectively target malignant stem-cell niches.
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http://dx.doi.org/10.1038/embor.2011.39DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3090013PMC
May 2011