Hélène Tourrière

Publications (11)79.53 Total impact

• Source

  Available from: Philippe Pasero

  Article: Analysis of DNA replication profiles in budding yeast and mammalian cells using DNA combing.

  Julien N Bianco, Jérôme Poli, Julie Saksouk, Julien Bacal, Maria Joao Silva, Kazumasa Yoshida, Yea-Lih Lin, Hélène Tourrière, Armelle Lengronne, Philippe Pasero
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  ABSTRACT: DNA combing is a powerful method developed by Bensimon and colleagues to stretch DNA molecules on silanized glass coverslips. This technique provides a unique way to monitor the activation of replication origins and the progression of replication forks at the level of single DNA molecules, after incorporation of thymidine analogs, such as 5-bromo-2'-deoxyuridine (BrdU), 5-iodo-2'-deoxyuridine (IdU) and 5-chloro-2'-deoxyuridine (CldU) in newly-synthesized DNA. Unlike microarray-based approaches, this assay gives access to the variability of replication profiles in individual cells. It can also be used to monitor the effect of DNA lesions on fork progression, arrest and restart. In this review, we propose standard DNA combing methods to analyze DNA replication in budding yeast and in human cells. We also show that 5-ethynyl-2'-deoxyuridine (EdU) can be used as a good alternative to BrdU for DNA combing analysis, as unlike halogenated nucleotides, it can be detected without prior denaturation of DNA.
  Methods 05/2012; 57(2):149-57. · 4.01 Impact Factor
• Article: Topoisomerase I suppresses genomic instability by preventing interference between replication and transcription.

  Sandie Tuduri, Laure Crabbé, Chiara Conti, Hélène Tourrière, Heidi Holtgreve-Grez, Anna Jauch, Véronique Pantesco, John De Vos, Aubin Thomas, Charles Theillet, Yves Pommier, Jamal Tazi, Arnaud Coquelle, Philippe Pasero
  Nature Cell Biology 11/2010; 12(11):1122. · 19.49 Impact Factor
• Article: Exo1 competes with repair synthesis, converts NER intermediates to long ssDNA gaps, and promotes checkpoint activation.

  Michele Giannattasio, Cindy Follonier, Hélène Tourrière, Fabio Puddu, Federico Lazzaro, Philippe Pasero, Massimo Lopes, Paolo Plevani, Marco Muzi-Falconi
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  ABSTRACT: Ultraviolet (UV) light induces DNA-damage checkpoints and mutagenesis, which are involved in cancer protection and tumorigenesis, respectively. How cells identify DNA lesions and convert them to checkpoint-activating structures is a major question. We show that during repair of UV lesions in noncycling cells, Exo1-mediated processing of nucleotide excision repair (NER) intermediates competes with repair DNA synthesis. Impediments of the refilling reaction allow Exo1 to generate extended ssDNA gaps, detectable by electron microscopy, which drive Mec1 kinase activation and will be refilled by long-patch repair synthesis, as shown by DNA combing. We provide evidence that this mechanism may be stimulated by closely opposing UV lesions, represents a strategy to redirect problematic repair intermediates to alternative repair pathways, and may also be extended to physically different DNA damages. Our work has significant implications for understanding the coordination between repair of DNA lesions and checkpoint pathways to preserve genome stability.
  Molecular cell 10/2010; 40(1):50-62. · 14.61 Impact Factor
• Source

  Available from: Philippe Pasero

  Article: Does interference between replication and transcription contribute to genomic instability in cancer cells?

  Sandie Tuduri, Laure Crabbe, Hélène Tourrière, Arnaud Coquelle, Philippe Pasero
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  ABSTRACT: We have recently reported that topoisomerase 1 (Top1) cooperates with ASF/SF2, a splicing factor of the SR family, to prevent unscheduled replication fork arrest and genomic instability in human cells. Our results suggest that Top1 execute this function by suppressing the formation of DNA-RNA hybrids during transcription, these so-called R-loops interfering with the progression of replication forks. Using ChIP-chip, we have shown that γ-H2AX, a marker of DNA damage, accumulates at gene-rich regions of the genome in Top1-deficient cells. This is best illustrated at histone genes, which are highly expressed during S phase and display discrete γ-H2AX peaks on ChIP-chip profiles. Here, we show that these γ-H2AX domains are different from those induced by camptothecin, a Top1 inhibitor inducing double-strand DNA breaks throughout the genome. These data support the view that R-loops promote genomic instability at specific sites by blocking fork progression and inducing chromosome breaks. Whether this type of transcription-dependent fork arrest contributes to the replication stress observed in precancerous lesions is an important question that deserves further attention.
  Cell cycle (Georgetown, Tex.) 05/2010; 9(10):1886-92. · 5.36 Impact Factor
• Article: Defining replication origin efficiency using DNA fiber assays.

  Sandie Tuduri, Hélène Tourrière, Philippe Pasero
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  ABSTRACT: The timely duplication of eukaryotic genomes depends on the coordinated activation of thousands of replication origins distributed along the chromosomes. Origin activation follows a temporal program that is imposed by the chromosomal context and is under the control of S-phase checkpoints. Although the general mechanisms regulating DNA replication are now well-understood at the level of individual origins, little is known on the coordination of thousands of initiation events at a genome-wide level. Recent studies using DNA combing and other single-molecule assays have shown that eukaryotic genomes contain a large excess of replication origins. Most of these origins remain "dormant" in normal growth conditions but are activated when fork progression is impeded. In this review, we discuss how DNA fiber technologies have changed our view of eukaryotic replication programs and how origin redundancy contributes to the maintenance of genome integrity in eukaryotic cells.
  Chromosome Research 01/2010; 18(1):91-102. · 3.09 Impact Factor
• Source

  Available from: Philippe Pasero

  Article: Maintenance of fork integrity at damaged DNA and natural pause sites.

  Hélène Tourrière, Philippe Pasero
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  ABSTRACT: S phase is a period of great vulnerability for the genome of eukaryotic cells. Many complicated processes are undertaken during this critical phase of the cell cycle, including the complete unwinding and the duplication of enormously complex DNA molecules. During this process, replication forks frequently encounter obstacles that impede their progression. Arrested forks are unstable structures that have to be stabilized and restarted in order to prevent the formation of double-strand breaks and/or unscheduled homologous recombination. To this aim, cells have evolved complex surveillance mechanisms sensing DNA damage and replication stress. The past decade has seen a dramatic advance in our understanding of how these regulatory pathways act in response to exogenous replication stress. However, the mechanism by which fork integrity is maintained at natural replication-impeding sequences remains obscure. Here, we discuss recent findings about how checkpoint-dependent and -independent mechanisms cooperate to prevent genomic instability at stalled forks, both in normal S phase and in the presence of exogenous genotoxic stress.
  DNA Repair 08/2007; 6(7):900-13. · 4.14 Impact Factor
• Article: Control of fetal growth and neonatal survival by the RasGAP-associated endoribonuclease G3BP.

  Latifa Zekri, Karim Chebli, Hélène Tourrière, Finn C Nielsen, Thomas V O Hansen, Abdelhaq Rami, Jamal Tazi
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  ABSTRACT: The regulation of mRNA stability plays a major role in the control of gene expression during cell proliferation, differentiation, and development. Here, we show that inactivation of the RasGAP-associated endoribonuclease (G3BP)-encoding gene leads to embryonic lethality and growth retardation. G3BP-/- mice that survived to term exhibited increased apoptotic cell death in the central nervous system and neonatal lethality. Both in mouse embryonic fibroblasts and during development, the absence of G3BP altered the expression of essential growth factors, among which imprinted gene products and growth arrest-specific mRNAs were outstanding. The results demonstrate that G3BP is essential for proper embryonic growth and development by mediating the coordinate expression of multiple imprinted growth-regulatory transcripts.
  Molecular and Cellular Biology 11/2005; 25(19):8703-16. · 5.53 Impact Factor
• Article: Mrc1 and Tof1 promote replication fork progression and recovery independently of Rad53.

  Hélène Tourrière, Gwennaëlle Versini, Violeta Cordón-Preciado, Constance Alabert, Philippe Pasero
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  ABSTRACT: The yeast checkpoint factors Mrc1p and Tof1p travel with the replication fork and mediate the activation of the Rad53p kinase in response to a replication stress. We show here that both proteins are required for normal fork progression but play different roles at stalled forks. Tof1p is critical for the activity of the rDNA replication fork barrier (RFB) but plays a minor role in the replication checkpoint. In contrast, Mrc1p is not necessary for RFB activity but is essential to mediate the replication stress response. Interestingly, stalled forks did not collapse in mrc1Delta cells exposed to hydroxyurea (HU) as they do in rad53 mutants. However, forks failed to restart when mrc1Delta cells were released from the block. The critical role of Mrc1p in HU is therefore to promote fork recovery in a Rad53p-independent manner, presumably through the formation of a stable fork-pausing complex.
  Molecular Cell 10/2005; 19(5):699-706. · 14.18 Impact Factor
• Article: Regulation of cytoplasmic stress granules by apoptosis-inducing factor.

  Céline Candé, Nicola Vahsen, Didier Métivier, Hélène Tourrière, Karim Chebli, Carmen Garrido, Jamal Tazi, Guido Kroemer
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  ABSTRACT: Stress granules (SG) are dynamic cytoplasmic foci in which stalled translation initiation complexes accumulate. In conditions of acute cellular redox, stress cells manipulated to lose the expression of apoptosis-inducing factor (AIF) nucleate SG signature proteins (e.g. TIA-1, PABP1) more efficiently than AIF-positive controls. AIF also inhibited SG formation induced by the RasGAP-associated endoribonuclease G3BP. Retransfection of mouse AIF into cells subjected to human AIF-specific siRNA revealed that only AIF imported into mitochondria could repress SGs and that redox-active domains of AIF, which are dispensable for its apoptogenic action, were required for SG inhibition. In response to oxidative stress, AIF-negative cells were found to deplete non-oxidized glutathione more rapidly than AIF-expressing cells. Exogenous supplementation of glutathione inhibited SG formation elicited by arsenate or G3BP. Together, these data suggest that the oxidoreductase function of AIF is required for the maintenance of glutathione levels in stress conditions and that glutathione is a major regulator of SG.
  Journal of Cell Science 10/2004; 117(Pt 19):4461-8. · 6.11 Impact Factor
• Article: mRNA degradation machines in eukaryotic cells.

  Hélène Tourrière, Karim Chebli, Jamal Tazi
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  ABSTRACT: The steady-state levels of mRNAs depend upon their combined rates of synthesis and processing, transport from the nucleus to cytoplasm, and decay in the cytoplasm. In eukaryotic cells, the degradation of mRNA is an essential determinant in the regulation of gene expression, and it can be modulated in response to developmental, environmental, and metabolic signals. This level of regulation is particularly important for proteins that are active for a brief period, such as growth factors, transcription factors, and proteins that control cell cycle progression. The mechanisms by which mRNAs are degraded and the sequence elements within the mRNAs that affect their stability are the subject of this review. We will summarize the current state of knowledge regarding cis-acting elements in mRNA and trans-acting factors that contribute to mRNA regulation decay. We will then consider the mechanisms by which specific signaling proteins seem to contribute to a dynamic organization of the mRNA degradation machinery in response to physiological stimuli.
  Biochimie 09/2002; 84(8):821-37. · 3.02 Impact Factor
• Source

  Available from: Veronique Pantesco

  Article: Topoisomerase 1 suppresses replication stress and genomic instability by preventing interference between replication and transcription.

  Sandie Tuduri, Laure Crabbé, Chiara Conti, Hélène Tourrière, Heidi Holtgreve-Grez, Anna Jauch, Véronique Pantesco, John De Vos, Aubin Thomas, Charles Theillet, Yves Pommier, Jamal Tazi, Arnaud Coquelle, Philippe Pasero
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  ABSTRACT: Topoisomerase I (Top1) is a key enzyme acting at the interface between DNA replication, transcription and mRNA maturation. Here, we show that Top1 suppresses genomic instability in mammalian cells by preventing conflicts between transcription and DNA replication. Using DNA combing and ChIP-on-chip, we found that Top1-deficient cells accumulate stalled replication forks and chromosome breaks in S phase and that breaks occur preferentially at gene-rich regions of the genome. Strikingly, these phenotypes were suppressed by preventing the formation of RNA-DNA hybrids (R-loops) during transcription. Moreover, these defects could be mimicked by depletion of the splicing factor ASF/SF2, which interacts functionally with Top1. Taken together, these data indicate that Top1 prevents replication fork collapse by suppressing the formation of R-loops in an ASF/SF2-dependent manner. We propose that interference between replication and transcription represents a major source of spontaneous replication stress, which could drive genomic instability during early stages of tumorigenesis.
  Nature Cell Biology.