UMR3348 – Intégrité du génome, ARN et cancer

Publications de l’unité

Année de publication : 2017

Anissia Ait Saada, Ana Teixeira-Silva, Ismail Iraqui, Audrey Costes, Julien Hardy, Giulia Paoletti, Karine Fréon, Sarah A E Lambert (2017 May 4)

Unprotected Replication Forks Are Converted into Mitotic Sister Chromatid Bridges.

Molecular cell : 398-410.e4 : DOI : 10.1016/j.molcel.2017.04.002 En savoir plus
Résumé

Replication stress and mitotic abnormalities are key features of cancer cells. Temporarily paused forks are stabilized by the intra-S phase checkpoint and protected by the association of Rad51, which prevents Mre11-dependent resection. However, if a fork becomes dysfunctional and cannot resume, this terminally arrested fork is rescued by a converging fork to avoid unreplicated parental DNA during mitosis. Alternatively, dysfunctional forks are restarted by homologous recombination. Using fission yeast, we report that Rad52 and the DNA binding activity of Rad51, but not its strand-exchange activity, act to protect terminally arrested forks from unrestrained Exo1-nucleolytic activity. In the absence of recombination proteins, large ssDNA gaps, up to 3 kb long, occur behind terminally arrested forks, preventing efficient fork merging and leading to mitotic sister chromatid bridging. Thus, Rad52 and Rad51 prevent temporarily and terminally arrested forks from degrading and, despite the availability of converging forks, converting to anaphase bridges causing aneuploidy and cell death.

Free acces : authors.elsevier.com/a/1U~li3vVUP2C0m

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Hamza Mameri, Ivan Bieche, Dider Meseure, Elisabetta Marangoni, Géraldine Buhagiar-Labarchède, Andre Nicolas, Sophie Vacher, Rosine Onclercq-Delic, Vinodh Rajapakse, Sudhir Varma, William C Reinhold, Yves Pommier, Mounira Amor-Guéret (2017 Apr 15)

Cytidine deaminase deficiency reveals new therapeutic opportunities against cancer.

Clinical cancer research : an official journal of the American Association for Cancer Research : DOI : 10.1158/1078-0432.CCR-16-0626 En savoir plus
Résumé

One of the main challenges in cancer therapy is the identification of molecular mechanisms mediating resistance or sensitivity to treatment. Cytidine deaminase (CDA) was reported to be downregulated in cells derived from patients with Bloom syndrome, a genetic disease associated with a strong predisposition to a wide range of cancers. The purpose of this study was to determine whether CDA deficiency could be associated with tumors from the general population and could constitute a predictive marker of susceptibility to anti-tumor drugs.

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Sudarshan Gadadhar, Satish Bodakuntla, Kathiresan Natarajan, Carsten Janke (2017 Apr 15)

The tubulin code at a glance.

Journal of cell science : 1347-1353 : DOI : 10.1242/jcs.199471 En savoir plus
Résumé

Microtubules are key cytoskeletal elements of all eukaryotic cells and are assembled of evolutionarily conserved α-tubulin-β-tubulin heterodimers. Despite their uniform structure, microtubules fulfill a large diversity of functions. A regulatory mechanism to control the specialization of the microtubule cytoskeleton is the ‘tubulin code’, which is generated by (i) expression of different α- and β-tubulin isotypes, and by (ii) post-translational modifications of tubulin. In this Cell Science at a Glance article and the accompanying poster, we provide a comprehensive overview of the molecular components of the tubulin code, and discuss the mechanisms by which these components contribute to the generation of functionally specialized microtubules.

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Christine Tran Quang, Benedetta Zaniboni, Jacques Ghysdael (2017 Mar 31)

A TCR-switchable cell death pathway in T-ALL.

Oncoscience : 17-18 : DOI : 10.18632/oncoscience.342 En savoir plus
Résumé

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Akendengue L., Trepout S., Grana M., Voegele A., Janke C., Raynal B., Chenal A., Marco S., Wehenkel A.M. (2017 Mar 30)

Bacterial kinesin light chain (Bklc) links the Btub cytoskeleton to membranes

Scientific Reports : 7 : 45668 : DOI : 10.1038/srep45668 En savoir plus
Résumé

Bacterial kinesin light chain is a TPR domain-containing protein encoded by the bklc gene, which co-localizes with the bacterial tubulin (btub) genes in a conserved operon in Prosthecobacter. Btub heterodimers show high structural homology with eukaryotic tubulin and assemble into head-to-tail protofilaments. Intriguingly, Bklc is homologous to the light chain of the microtubule motor kinesin and could thus represent an additional eukaryotic-like cytoskeletal element in bacteria. Using biochemical characterization as well as cryo-electron tomography we show here that Bklc interacts specifically with Btub protofilaments, as well as lipid vesicles and could thus play a role in anchoring the Btub filaments to the membrane protrusions in Prosthecobacter where they specifically localize in vivo. This work sheds new light into possible ways in which the microtubule cytoskeleton may have evolved linking precursors of microtubules to the membrane via the kinesin moiety that in today’s eukaryotic cytoskeleton links vesicle-packaged cargo to microtubules.

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Montserrat Bosch Grau, Christel Masson, Sudarshan Gadadhar, Cecilia Rocha, Olivia Tort, Patricia Marques Sousa, Sophie Vacher, Ivan Bieche, Carsten Janke (2017 Mar 1)

Alterations in the balance of tubulin glycylation and glutamylation in photoreceptors leads to retinal degeneration.

Journal of cell science : DOI : 10.1242/jcs.199091 En savoir plus
Résumé

Tubulin is subject to a wide variety of posttranslational modifications, which as part of the tubulin code are involved in the regulation of microtubule functions. Glycylation has so far predominantly been found in motile cilia and flagella, and absence of this modification leads to ciliary disassembly. Here we demonstrate that the connecting cilia of photoreceptors, which are non-motile sensory cilia, are also dependent on glycylation. In contrast to many other tissues, only one glycylase, TTLL3, is expressed in retina. Ttll3(-/-) mice lack glycylation in photoreceptors, which results in shortening of connecting cilia and slow retinal degeneration. Moreover, absence of glycylation results in increased levels of tubulin glutamylation in photoreceptors, and inversely, hyperglutamylation in the pcd mouse abolishes glycylation. This suggests that both posttranslational modifications compete for modification sites, and that unbalancing the glutamylation/glycylation equilibrium on axonemes of connecting cilia, notwithstanding by which enzymatic mechanism, invariably leads to retinal degeneration.

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Rocchetti F, Tran Quang C, Maragno AL, Nguyen J, Lasgi C, Ghysdael J. (2017 Jan 1)

The calcineurin protein phosphatase is dispensable for BCR-ABL-induced B-ALL maintenance, propagation and response to dasatinib.

Leukemia : DOI : 10.1038/leu.2016.269 En savoir plus
Résumé

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Helene Malka-Mahieu, Michelle Newman, Laurent Desaubry, Caroline Robert, Stephan Vagner (2017 Jan 1)

Molecular Pathways: The eIF4F Translation Initiation Complex- New Opportunities for Cancer Treatment.

Clinical cancer research : an official journal of the American Association for Cancer Research : DOI : 10.1158/1078-0432.CCR-14-2362 En savoir plus
Résumé

The eIF4F complex regulates the cap-dependent mRNA translation process. It is becoming increasingly evident that aberrant activity of this complex is observed in many cancers leading to the selective synthesis of proteins involved in tumour growth and metastasis. The selective translation of cellular mRNAs controlled by this complex also contributes to resistance to cancer treatments, and downregulation of the eIF4F complex components can restore sensitivity to various cancer therapies. Here we review the contribution of the eIF4F complex to tumourigenesis with a focus on its role in chemoresistance as well as the promising use of new small molecule inhibitors of the complex, including flavaglines/rocaglates, hippuristanol and pateamine A.

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Année de publication : 2016

Nathalie Ly, Nadia Elkhatib, Enzo Bresteau, Olivier Piétrement, Mehdi Khaled, Maria M Magiera, Carsten Janke, Eric Le Cam, Andrew D Rutenberg, Guillaume Montagnac (2016 Oct 18)

αTAT1 controls longitudinal spreading of acetylation marks from open microtubules extremities.

Scientific reports : 35624 : DOI : 10.1038/srep35624 En savoir plus
Résumé

Acetylation of the lysine 40 of α-tubulin (K40) is a post-translational modification occurring in the lumen of microtubules (MTs) and is controlled by the α-tubulin acetyl-transferase αTAT1. How αTAT1 accesses the lumen and acetylates α-tubulin there has been an open question. Here, we report that acetylation starts at open ends of MTs and progressively spreads longitudinally from there. We observed acetylation marks at the open ends of in vivo MTs re-growing after a Nocodazole block, and acetylated segments growing in length with time. Bias for MTs extremities was even more pronounced when using non-dynamic MTs extracted from HeLa cells. In contrast, K40 acetylation was mostly uniform along the length of MTs reconstituted from purified tubulin in vitro. Quantitative modelling of luminal diffusion of αTAT1 suggested that the uniform acetylation pattern observed in vitro is consistent with defects in the MT lattice providing lateral access to the lumen. Indeed, we observed that in vitro MTs are permeable to macromolecules along their shaft while cellular MTs are not. Our results demonstrate αTAT1 enters the lumen from open extremities and spreads K40 acetylation marks longitudinally along cellular MTs. This mode of tip-directed microtubule acetylation may allow for selective acetylation of subsets of microtubules.

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C. Boutros C. Mateus E. Routier S. Chouaib C. Libenciuc M. Reigneau I. Girault C. Caramella S. Hibat S. Vagner Y.G. Tao N. Chaput J. Adam J-C. Soria A. Eggermont E. Deutsch C. Robert (2016 Oct 11)

A dose escalation phase 1 study of radiotherapy (RT) in combination with anti-cytotoxic-T-lymphocyte-associated antigen 4 (CTLA-4) monoclonal antibody ipilimumab (Ipi) in patients (pts) with metastatic melanoma

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Résumé

https://academic.oup.com/annonc/article/27/suppl_6/1117P/2799932

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Soumyananda Chakraborti, Kathiresan Natarajan, Julian Curiel, Carsten Janke, Judy Liu (2016 Oct 1)

The emerging role of the tubulin code: From the tubulin molecule to neuronal function and disease.

Cytoskeleton (Hoboken, N.J.) : DOI : 10.1002/cm.21290 En savoir plus
Résumé

Across different cell types and tissues, microtubules are assembled from highly conserved dimers of α- and β-tubulin. Despite their highly similar structures, microtubules have functional heterogeneity, generated either by the expression of different tubulin genes, encoding distinct isotypes, or by post-translational modifications of tubulin. This genetically encoded and post-translationally generated heterogeneity of tubulin – the ‘tubulin code’ – has the potential to modulate microtubule structure, dynamics, and interactions with associated proteins. The tubulin code is therefore believed to regulate microtubule functions on a cellular and sub-cellular level. This review highlights the importance of the tubulin code for tubulin structure, as well as on microtubule dynamics and functions in neurons. It further summarizes recent developments in the understanding of mutations in tubulin genes, and how they are linked to neurodegenerative and neurodevelopmental disorders. The current advances in the knowledge of the tubulin code on the molecular and the functional level will certainly lead to a better understanding of how complex signaling events control microtubule functions, especially in cells of the nervous system. This article is protected by copyright. All rights reserved.

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Hélène Malka-Mahieu, Isabelle Girault, Margot Rubington, Melissa Leriche, Caroline Welsch, Nyam Kamsu-Kom, Qian Zhao, Laurent Desaubry, Stéphan Vagner, Caroline Robert (2016 Sep 16)

Synergistic effects of eIF4A and MEK inhibitors on proliferation of NRAS-mutant melanoma cell lines.

Cell cycle (Georgetown, Tex.) : 1-5 : DOI : 10.1080/15384101.2016.1208862 En savoir plus
Résumé

Activating mutations of the NRAS (neuroblastoma rat sarcoma viral oncogene) protein kinase, present in many cancers, induce a constitutive activation of both the RAS-RAF-MEK-ERK mitogen-activated protein kinase (MAPK) signal transduction pathway and the PI(3)K-AKT-mTOR, pathway. This in turn regulates the formation of the eIF4F eukaryotic translation initiation complex, comprising the eIF4E cap-binding protein, the eIF4G scaffolding protein and the eIF4A RNA helicase, which binds to the 7-methylguanylate cap (m(7)G) at the 5′ end of messenger RNAs. Small molecules targeting MEK (MEKi: MEK inhibitors) have demonstrated activity in NRAS-mutant cell lines and tumors, but resistance sets in most cases within months of treatment. Using proximity ligation assays, that allows visualization of the binding of eIF4E to the scaffold protein eIF4G, generating the active eIF4F complex, we have found that resistance to MEKi is associated with the persistent formation of the eIF4F complex in MEKi-treated NRAS-mutant cell lines. Furthermore, inhibiting the eIF4A component of the eIF4F complex, with a small molecule of the flavagline/rocaglate family, synergizes with inhibiting MEK to kill NRAS-mutant cancer cell lines.

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Catharina von Nicolai, Åsa Ehlén, Charlotte Martin, Xiaodong Zhang, Aura Carreira (2016 Sep 15)

A second DNA binding site in human BRCA2 promotes homologous recombination.

Nature communications : 12813 : DOI : 10.1038/ncomms12813 En savoir plus
Résumé

BRCA2 tumour-suppressor protein is well known for its role in DNA repair by homologous recombination (HR); assisting the loading of RAD51 recombinase at DNA double-strand breaks. This function is executed by the C-terminal DNA binding domain (CTD) which binds single-stranded (ss)DNA, and the BRC repeats, which bind RAD51 and modulate its assembly onto ssDNA. Paradoxically, analysis of cells resistant to DNA damaging agents missing the CTD restore HR proficiency, suggesting another domain may take over its function. Here, we identify a region in the N terminus of BRCA2 that exhibits DNA binding activity (NTD) and provide evidence for NTD promoting RAD51-mediated HR. A missense variant detected in breast cancer patients located in the NTD impairs HR stimulation on dsDNA/ssDNA junction containing substrates. These findings shed light on the function of the N terminus of BRCA2 and have implications for the evaluation of breast cancer variants.

CLICK HERE : Access the recommendation on F1000Prime

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Amélie Trinquand, Nuno R Dos Santos, Christine Tran Quang, Francesca Rocchetti, Benedetta Zaniboni, Mohamed Belhocine, Cindy Da Costa de Jesus, Ludovic Lhermitte, Melania Tesio, Michael Dussiot, François-Loïc Cosset, Els Verhoeyen, Françoise Pflumio, Norbert Ifrah, Hervé Dombret, Salvatore Spicuglia, Lucienne Chatenoud, David-Alexandre Gross, Olivier Hermine, Elizabeth Macintyre, Jacques Ghysdael, Vahid Asnafi (2016 Sep 6)

Triggering the TCR Developmental Checkpoint Activates a Therapeutically Targetable Tumor Suppressive Pathway in T-cell Leukemia.

Cancer discovery : 972-85 : DOI : 10.1158/2159-8290.CD-15-0675 En savoir plus
Résumé

Cancer onset and progression involves the accumulation of multiple oncogenic hits, which are thought to dominate or bypass the physiologic regulatory mechanisms in tissue development and homeostasis. We demonstrate in T-cell acute lymphoblastic leukemia (T-ALL) that, irrespective of the complex oncogenic abnormalities underlying tumor progression, experimentally induced, persistent T-cell receptor (TCR) signaling has antileukemic properties and enforces a molecular program resembling thymic negative selection, a major developmental event in normal T-cell development. Using mouse models of T-ALL, we show that induction of TCR signaling by high-affinity self-peptide/MHC or treatment with monoclonal antibodies to the CD3ε chain (anti-CD3) causes massive leukemic cell death. Importantly, anti-CD3 treatment hampered leukemogenesis in mice transplanted with either mouse- or patient-derived T-ALLs. These data provide a strong rationale for targeted therapy based on anti-CD3 treatment of patients with TCR-expressing T-ALL and demonstrate that endogenous developmental checkpoint pathways are amenable to therapeutic intervention in cancer cells.

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Simon Gemble, Géraldine Buhagiar-Labarchède, Rosine Onclercq-Delic, Denis Biard, Sarah Lambert, Mounira Amor-Guéret (2016 Aug 15)

A balanced pyrimidine pool is required for optimal Chk1 activation to prevent ultrafine anaphase bridge formation.

Journal of cell science : 3167-77 : DOI : 10.1242/jcs.187781 En savoir plus
Résumé

Cytidine deaminase (CDA) deficiency induces an excess of cellular dCTP, which reduces basal PARP-1 activity, thereby compromising complete DNA replication, leading to ultrafine anaphase bridge (UFB) formation. CDA dysfunction has pathological implications, notably in cancer and in Bloom syndrome. It remains unknown how reduced levels of PARP-1 activity and pyrimidine pool imbalance lead to the accumulation of unreplicated DNA during mitosis. We report that a decrease in PARP-1 activity in CDA-deficient cells impairs DNA-damage-induced Chk1 activation, and, thus, the downstream checkpoints. Chemical inhibition of the ATR-Chk1 pathway leads to UFB accumulation, and we found that this pathway was compromised in CDA-deficient cells. Our data demonstrate that ATR-Chk1 acts downstream from PARP-1, preventing the accumulation of unreplicated DNA in mitosis, and, thus, UFB formation. Finally, delaying entry into mitosis is sufficient to prevent UFB formation in both CDA-deficient and CDA-proficient cells, suggesting that both physiological and pathological UFBs are derived from unreplicated DNA. Our findings demonstrate an unsuspected requirement for a balanced nucleotide pool for optimal Chk1 activation both in unchallenged cells and in response to genotoxic stress.

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