UMR3244 – Dynamique de l’information génétique

Publications de l’équipe

Année de publication : 2021

Samar Ali, Emilia Puig Lombardi, Deepanjan Ghosh, Tao Jia, Géraldine Vitry, Lina Saker, Joël Poupon, Marie-Paule Teulade-Fichou, Alain Nicolas, Arturo Londono-Vallejo, Sophie Bombard (2021 May 22)

Pt-ttpy, a G-quadruplex binding platinum complex, induces telomere dysfunction and G-rich regions DNA damage.

Metallomics : integrated biometal science : 13 : mfab029 : DOI : 10.1093/mtomcs/mfab029 En savoir plus
Résumé

PMID-34021581

Pt-ttpy (tolyl terpyridin-Pt complex) covalently binds to G-quadruplex (G4) structures in vitro and to telomeres in cellulo via its Pt moiety. Here, we identified its targets in the human genome, in comparison to Pt-tpy, its derivative without G4 affinity, and cisplatin. Pt-ttpy, but not Pt-tpy, induces the release of the shelterin protein TRF2 from telomeres concomitantly to the formation of DNA damage foci at telomeres but also at other chromosomal locations. γ-H2AX chromatin immunoprecipitation (ChIP-seq) after treatment with Pt-ttpy or cisplatin revealed accumulation in G- and A-rich tandemly repeated sequences, but not particularly in potential G4 forming sequences. Collectively, Pt-ttpy presents dual targeting efficiency on DNA, by inducing telomere dysfunction and genomic DNA damage at specific loci.

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Marsolier, Justine Prompsy, Pacôme Durand, Adeline Lyne, Anne-Marie Landragin, Camille Trouchet, Amandine Bento, Sabrina Tenreira Eisele, Almut Foulon, Sophie Baudre, Léa Grosselin, Kevin Bohec, Mylène Baulande, Sylvain Dahmani, Ahmed Sourd, Laura Letouzé, Eric Marangoni, Elisabetta Perié, Leïla Vallot, Céline (2021 Jan 4)

H3K27me3 is a determinant of chemotolerance in triple-negative breast cancer

bioRxivbioRxiv : DOI : 10.1101/2021.01.04.423386 En savoir plus
Résumé

Triple-negative breast cancer is associated with the worst prognosis and the highest risk of recurrence among all breast cancer subtypes[1][1]. Residual disease, formed by cancer cells persistent to chemotherapy, remains one of the major clinical challenges towards full cure[2][2],[3][3]. There is now consensus that non-genetic processes contribute to chemoresistance in various tumor types, notably through the initial emergence of a reversible chemotolerant state[4][4]–[6][5]. Understanding non-genetic tumor evolution stands now as a prerequisite for the design of relevant combinatorial approaches to delay recurrence. Here we show that the repressive histone mark H3K27me3 is a determinant of cell fate under chemotherapy exposure, monitoring epigenomes, transcriptomes and lineage with single-cell resolution. We identify a reservoir of persister basal cells with EMT markers and activated TGF-β pathway leading to multiple chemoresistance phenotypes. We demonstrate that, in unchallenged cells, H3K27 methylation is a lock to the expression program of persister cells. Promoters are primed with both H3K4me3 and H3K27me3, and removing H3K27me3 is sufficient for their transcriptional activation. Leveraging lineage barcoding, we show that depleting H3K27me3 alters tumor cell fate under chemotherapy insult – a wider variety of tumor cells tolerate chemotherapy. Our results highlight how chromatin landscapes shape the potential of unchallenged cancer cells to respond to therapeutic stress.

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Année de publication : 2020

Arijita Chakraborty, Piroon Jenjaroenpun, Jing Li, Sami El Hilali, Andrew McCulley, Brian Haarer, Elizabeth A Hoffman, Aimee Belak, Audrey Thorland, Heidi Hehnly, Carl Schildkraut, Chun-Long Chen, Vladimir A Kuznetsov, Wenyi Feng (2020 Sep 23)

Replication Stress Induces Global Chromosome Breakage in the Fragile X Genome.

Cell reports : 108179 : DOI : S2211-1247(20)31168-2 En savoir plus
Résumé

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by mutations in the FMR1 gene and deficiency of a functional FMRP protein. FMRP is known as a translation repressor whose nuclear function is not understood. We investigated the global impact on genome stability due to FMRP loss. Using Break-seq, we map spontaneous and replication stress-induced DNA double-strand breaks (DSBs) in an FXS patient-derived cell line. We report that the genomes of FXS cells are inherently unstable and accumulate twice as many DSBs as those from an unaffected control. We demonstrate that replication stress-induced DSBs in FXS cells colocalize with R-loop forming sequences. Exogenously expressed FMRP in FXS fibroblasts ameliorates DSB formation. FMRP, not the I304N mutant, abates R-loop-induced DSBs during programmed replication-transcription conflict. These results suggest that FMRP is a genome maintenance protein that prevents R-loop accumulation. Our study provides insights into the etiological basis for FXS.

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Zhiming Li, Xu Hua, Albert Serra-Cardona, Xiaowei Xu, Songlin Gan, Hui Zhou, Wen-Si Yang, Chun-Long Chen, Rui-Ming Xu, Zhiguo Zhang (2020 Sep 14)

DNA polymerase α interacts with H3-H4 and facilitates the transfer of parental histones to lagging strands.

Science advances : eabb5820 : DOI : 10.1126/sciadv.abb5820 En savoir plus
Résumé

How parental histones, the carriers of epigenetic modifications, are deposited onto replicating DNA remains poorly understood. Here, we describe the eSPAN method (enrichment and sequencing of protein-associated nascent DNA) in mouse embryonic stem (ES) cells and use it to detect histone deposition onto replicating DNA strands with a relatively small number of cells. We show that DNA polymerase α (Pol α), which synthesizes short primers for DNA synthesis, binds histone H3-H4 preferentially. A Pol α mutant defective in histone binding in vitro impairs the transfer of parental H3-H4 to lagging strands in both yeast and mouse ES cells. Last, dysregulation of both coding genes and noncoding endogenous retroviruses is detected in mutant ES cells defective in parental histone transfer. Together, we report an efficient eSPAN method for analysis of DNA replication-linked processes in mouse ES cells and reveal the mechanism of Pol α in parental histone transfer.

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Sanchez Aurore, Borde Valérie (2020 Sep 1)

Methods to Map Meiotic Recombination Proteins in Saccharomyces cerevisiae

Methods in Molecular BiologyHomologous Recombination : 2153 : 295-306 : DOI : 10.1007/978-1-0716-0644-5_21 En savoir plus
Résumé

Meiotic recombination is triggered by programmed DNA double-strand breaks (DSBs), catalyzed by the type II topoisomerase-like Spo11 protein. Meiotic DSBs are repaired by homologous recombination, which produces either crossovers or noncrossovers, this decision being linked to the binding of proteins specific of each pathway. Mapping the binding of these proteins along chromosomes in wild type or mutant yeast background is extremely useful to understand how and at which step the decision to repair a DSB with a crossover is taken. It is now possible to obtain highly synchronous yeast meiotic populations, which, combined with appropriate negative controls, enable to detect by chromatin immunoprecipitation followed by sequencing (ChIP-Seq) the transient binding of diverse recombination proteins with high sensitivity and resolution.

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Gnan Stefano, Liu Yaqun, Spagnuolo Manuela, Chen Chun-Long (2020 Aug 31)

The impact of transcription-mediated replication stress on genome instability and human disease

Genome Instability & Disease : 1 : 207-234 : DOI : 10.1007/s42764-020-00021-y En savoir plus
Résumé

DNA replication is a vital process in all living organisms. At each cell division, > 30,000 replication origins are activated in a coordinated manner to ensure the duplication of > 6 billion base pairs of the human genome. During differentiation and development, this program must adapt to changes in chromatin organization and gene transcription: its deregulation can challenge genome stability, which is a leading cause of many diseases including cancers and neurological disorders. Over the past decade, great progress has been made to better understand the mechanisms of DNA replication regulation and how its deregulation challenges genome integrity and leads to human disease. Growing evidence shows that gene transcription has an essential role in shaping the landscape of genome replication, while it is also a major source of endogenous replication stress inducing genome instability. In this review, we discuss the current knowledge on the various mechanisms by which gene transcription can impact on DNA replication, leading to genome instability and human disease.

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Elda Cannavo, Aurore Sanchez, Roopesh Anand, Lepakshi Ranjha, Jannik Hugener, Céline Adam, Ananya Acharya, Nicolas Weyland, Xavier Aran-Guiu, Jean-Baptiste Charbonnier, Eva R Hoffmann, Valérie Borde, Joao Matos, Petr Cejka (2020 Aug 21)

Regulation of the MLH1-MLH3 endonuclease in meiosis.

Nature : DOI : 10.1038/s41586-020-2592-2 En savoir plus
Résumé

During prophase of the first meiotic division, cells deliberately break their DNA. These DNA breaks are repaired by homologous recombination, which facilitates proper chromosome segregation and enables the reciprocal exchange of DNA segments between homologous chromosomes. A pathway that depends on the MLH1-MLH3 (MutLγ) nuclease has been implicated in the biased processing of meiotic recombination intermediates into crossovers by an unknown mechanism. Here we have biochemically reconstituted key elements of this pro-crossover pathway. We show that human MSH4-MSH5 (MutSγ), which supports crossing over, binds branched recombination intermediates and associates with MutLγ, stabilizing the ensemble at joint molecule structures and adjacent double-stranded DNA. MutSγ directly stimulates DNA cleavage by the MutLγ endonuclease. MutLγ activity is further stimulated by EXO1, but only when MutSγ is present. Replication factor C (RFC) and the proliferating cell nuclear antigen (PCNA) are additional components of the nuclease ensemble, thereby triggering crossing-over. Saccharomyces cerevisiae strains in which MutLγ cannot interact with PCNA present defects in forming crossovers. Finally, the MutLγ-MutSγ-EXO1-RFC-PCNA nuclease ensemble preferentially cleaves DNA with Holliday junctions, but shows no canonical resolvase activity. Instead, it probably processes meiotic recombination intermediates by nicking double-stranded DNA adjacent to the junction points. As DNA nicking by MutLγ depends on its co-factors, the asymmetric distribution of MutSγ and RFC-PCNA on meiotic recombination intermediates may drive biased DNA cleavage. This mode of MutLγ nuclease activation might explain crossover-specific processing of Holliday junctions or their precursors in meiotic chromosomes.

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Alexy Promonet, Ismaël Padioleau, Yaqun Liu, Lionel Sanz, Anna Biernacka, Anne-Lyne Schmitz, Magdalena Skrzypczak, Amélie Sarrazin, Clément Mettling, Maga Rowicka, Krzysztof Ginalski, Frédéric Chedin, Chun-Long Chen, Yea-Lih Lin, Philippe Pasero (2020 Aug 10)

Topoisomerase 1 prevents replication stress at R-loop-enriched transcription termination sites.

Nature communications : 3940 : DOI : 10.1038/s41467-020-17858-2 En savoir plus
Résumé

R-loops have both positive and negative impacts on chromosome functions. To identify toxic R-loops in the human genome, here, we map RNA:DNA hybrids, replication stress markers and DNA double-strand breaks (DSBs) in cells depleted for Topoisomerase I (Top1), an enzyme that relaxes DNA supercoiling and prevents R-loop formation. RNA:DNA hybrids are found at both promoters (TSS) and terminators (TTS) of highly expressed genes. In contrast, the phosphorylation of RPA by ATR is only detected at TTS, which are preferentially replicated in a head-on orientation relative to the direction of transcription. In Top1-depleted cells, DSBs also accumulate at TTS, leading to persistent checkpoint activation, spreading of γ-H2AX on chromatin and global replication fork slowdown. These data indicate that fork pausing at the TTS of highly expressed genes containing R-loops prevents head-on conflicts between replication and transcription and maintains genome integrity in a Top1-dependent manner.

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Wang W., Klein K., Proesmans K., Yang H., Marchal C., Zhu X., Borrman T., Hastie A., Weng Z., Bechhoefer J., Chen C.L., Gilbert D.M., Rhind N. (2020 Aug 1)

Genome-Wide Mapping of Human DNA Replication by Optical Replication Mapping Supports a Stochastic Model of Eukaryotic Replication Timing

bioRxiv : 2020.08.24.263459 : DOI : 10.1101/2020.08.24.263459 En savoir plus
Résumé

DNA replication is regulated by the location and timing of replication initiation. Therefore, much effort has been invested in identifying and analyzing the sites of human replication initiation. However, the heterogeneous nature of eukaryotic replication kinetics and the low efficiency of individual initiation site utilization in metazoans has made mapping the location and timing of replication initiation in human cells difficult. A potential solution to the problem of human replication mapping is single-molecule analysis. However, current approaches do not provide the throughput required for genome-wide experiments. To address this challenge, we have developed Optical Replication Mapping (ORM), a high-throughput single-molecule approach to map newly replicated DNA, and used it to map early initiation events in human cells. The single-molecule nature of our data, and a total of more than 2000-fold coverage of the human genome on 27 million fibers averaging ~300 kb in length, allow us to identify initiation sites and their firing probability with high confidence. In particular, for the first time, we are able to measure genome-wide the absolute efficiency of human replication initiation. We find that the distribution of human replication initiation is consistent with inefficient, stochastic initiation of heterogeneously distributed potential initiation complexes enriched in accessible chromatin. In particular, we find sites of human replication initiation are not confined to well-defined replication origins but are instead distributed across broad initiation zones consisting of many initiation sites. Furthermore, we find no correlation of initiation events between neighboring initiation zones. Although most early initiation events occur in early-replicating regions of the genome, a significant number occur in late replicating regions. The fact that initiation sites in typically late-replicating regions have some probability of firing in early S phase suggests that the major difference between initiation events in early and late replicating regions is their intrinsic probability of firing, as opposed to a qualitative difference in their firing-time distributions. Moreover, modeling of replication kinetics demonstrates that measuring the efficiency of initiation-zone firing in early S phase suffices to predict the average firing time of such initiation zones throughout S phase, further suggesting that the differences between the firing times of early and late initiation zones are quantitative, rather than qualitative. These observations are consistent with stochastic models of initiation-timing regulation and suggest that stochastic regulation of replication kinetics is a fundamental feature of eukaryotic replication, conserved from yeast to humans. ### Competing Interest Statement Alex Hastie is an employee of Bionano Genomics.

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Eléonore Toufektchan, Vincent Lejour, Romane Durand, Neelam Giri, Irena Draskovic, Boris Bardot, Pierre Laplante, Sara Jaber, Blanche P Alter, José-Arturo Londono-Vallejo, Sharon A Savage, Franck Toledo (2020 Apr 18)

Germline mutation of MDM4, a major p53 regulator, in a familial syndrome of defective telomere maintenance.

Science advances : eaay3511 : DOI : 10.1126/sciadv.aay3511 En savoir plus
Résumé

Dyskeratosis congenita is a cancer-prone inherited bone marrow failure syndrome caused by telomere dysfunction. A mouse model recently suggested that p53 regulates telomere metabolism, but the clinical relevance of this finding remained uncertain. Here, a germline missense mutation of , a negative regulator of p53, was found in a family with features suggestive of dyskeratosis congenita, e.g., bone marrow hypocellularity, short telomeres, tongue squamous cell carcinoma, and acute myeloid leukemia. Using a mouse model, we show that this mutation (p.T454M) leads to increased p53 activity, decreased telomere length, and bone marrow failure. Variations in p53 activity markedly altered the phenotype of mutant mice, suggesting an explanation for the variable expressivity of disease symptoms in the family. Our data indicate that a germline activation of the p53 pathway may cause telomere dysfunction and point to polymorphisms affecting this pathway as potential genetic modifiers of telomere biology and bone marrow function.

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Franck Toledo and Michelle Debatisse (2020 Apr 17)

Mechanisms generating cancer genome complexity : a look back at the interphase breakage model

Science : Vol. 368, Issue 6488 : eaba0712 : DOI : 10.1126/science.aba0712 En savoir plus
Résumé

Understanding the mechanims responsible for cancer genome complexity has been an important goal for many decades. Umbreit et al. recently combined live cell imaging and single cell genome sequencing to analyze the cascade of genome rearrangements following the formation of a chromosome bridge in human cells (1). Their results suggest that this bridge leads to an initial breakage-fusion-bridge (BFB) cycle, followed by additional BFB cycles interwoven with episodes of micronucleation and chromothripsis, to generate complex genome rearrangements (1).
This conclusion is strikingly consistent with the previously proposed “interphase breakage model” (2). In the 1990s, fluorescent in situ hybridization (FISH) provided unprecedented insights into the mechanisms underlying gene amplification in mammalian cells. FISH made it possible to analyze the distribution of amplified genes at the level of a single cell, just a few cell divisions after initiation of the amplification process, in model systems of cultured cells selected for resist

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Année de publication : 2019

Maïté Courel, Yves Clément, Clémentine Bossevain, Dominika Foretek, Olivia Vidal Cruchez, Zhou Yi, Marianne Bénard, Marie-Noëlle Benassy, Michel Kress, Caroline Vindry, Michèle Ernoult-Lange, Christophe Antoniewski, Antonin Morillon, Patrick Brest, Arnaud Hubstenberger, Hugues Roest Crollius, Nancy Standart, Dominique Weil (2019 Dec 20)

GC content shapes mRNA storage and decay in human cells.

eLife : DOI : 10.7554/eLife.49708 En savoir plus
Résumé

mRNA translation and decay appear often intimately linked although the rules of this interplay are poorly understood. In this study, we combined our recent P-body transcriptome with transcriptomes obtained following silencing of broadly acting mRNA decay and repression factors, and with available CLIP and related data. This revealed the central role of GC content in mRNA fate, in terms of P-body localization, mRNA translation and mRNA stability: P-bodies contain mostly AU-rich mRNAs, which have a particular codon usage associated with a low protein yield; AU-rich and GC-rich transcripts tend to follow distinct decay pathways; and the targets of sequence-specific RBPs and miRNAs are also biased in terms of GC content. Altogether, these results suggest an integrated view of post-transcriptional control in human cells where most translation regulation is dedicated to inefficiently translated AU-rich mRNAs, whereas control at the level of 5′ decay applies to optimally translated GC-rich mRNAs.

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Olivier Brison, Sami El-Hilali, Dana Azar, Stéphane Koundrioukoff, Mélanie Schmidt, Viola Nähse, Yan Jaszczyszyn, Anne-Marie Lachages, Bernard Dutrillaux, Claude Thermes, Michelle Debatisse, Chun-Long Chen (2019 Dec 15)

Transcription-mediated organization of the replication initiation program across large genes sets common fragile sites genome-wide.

Nature communications : 5693 : DOI : 10.1038/s41467-019-13674-5 En savoir plus
Résumé

Common fragile sites (CFSs) are chromosome regions prone to breakage upon replication stress known to drive chromosome rearrangements during oncogenesis. Most CFSs nest in large expressed genes, suggesting that transcription could elicit their instability; however, the underlying mechanisms remain elusive. Genome-wide replication timing analyses here show that stress-induced delayed/under-replication is the hallmark of CFSs. Extensive genome-wide analyses of nascent transcripts, replication origin positioning and fork directionality reveal that 80% of CFSs nest in large transcribed domains poor in initiation events, replicated by long-travelling forks. Forks that travel long in late S phase explains CFS replication features, whereas formation of sequence-dependent fork barriers or head-on transcription-replication conflicts do not. We further show that transcription inhibition during S phase, which suppresses transcription-replication encounters and prevents origin resetting, could not rescue CFS stability. Altogether, our results show that transcription-dependent suppression of initiation events delays replication of large gene bodies, committing them to instability.

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Mireille Bétermier, Valérie Borde, Jean-Pierre de Villartay (2019 Dec 11)

Coupling DNA Damage and Repair: an Essential Safeguard during Programmed DNA Double-Strand Breaks?

Trends in cell biology : DOI : S0962-8924(19)30201-6 En savoir plus
Résumé

DNA double-strand breaks (DSBs) are the most toxic DNA lesions given their oncogenic potential. Nevertheless, programmed DSBs (prDSBs) contribute to several biological processes. Formation of prDSBs is the ‘price to pay’ to achieve these essential biological functions. Generated by domesticated PiggyBac transposases, prDSBs have been integrated in the life cycle of ciliates. Created by Spo11 during meiotic recombination, they constitute a driving force of evolution and ensure balanced chromosome content for successful reproduction. Produced by the RAG1/2 recombinase, they are required for the development of the adaptive immune system in many species. The coevolution of processes that couple introduction of prDSBs to their accurate repair may constitute an effective safeguard against genomic instability.

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(2019 Nov 15)

Reference-free transcriptome exploration reveals novel RNAs for prostate cancer diagnosis.

Life Sci Alliance : DOI : 10.26508/lsa.201900449 En savoir plus
Résumé

The use of RNA-sequencing technologies held a promise of improved diagnostic tools based on comprehensive transcript sets. However, mining human transcriptome data for disease biomarkers in clinical specimens are restricted by the limited power of conventional reference-based protocols relying on unique and annotated transcripts. Here, we implemented a blind reference-free computational protocol, DE-kupl, to infer yet unreferenced RNA variations from total stranded RNA-sequencing datasets of tissue origin. As a bench test, this protocol was powered for detection of RNA subsequences embedded into putative long noncoding (lnc)RNAs expressed in prostate cancer. Through filtering of 1,179 candidates, we defined 21 lncRNAs that were further validated by NanoString for robust tumor-specific expression in 144 tissue specimens. Predictive modeling yielded a restricted probe panel enabling more than 90% of true-positive detections of cancer in an independent The Cancer Genome Atlas cohort. Remarkably, this clinical signature made of only nine unannotated lncRNAs largely outperformed PCA3, the only used prostate cancer lncRNA biomarker, in detection of high-risk tumors. This modular workflow is highly sensitive and can be applied to any pathology or clinical application.

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