Добірка наукової літератури з теми "Origine de réplication – Dissertation universitaire"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся зі списками актуальних статей, книг, дисертацій, тез та інших наукових джерел на тему "Origine de réplication – Dissertation universitaire".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Дисертації з теми "Origine de réplication – Dissertation universitaire":
Laroussi, Haifa. "Étude des mécanismes moléculaires d'initiation du transfert conjugatif d'ICESt3, médiée par une relaxase MOBT chez la bactérie Gram+ Streptococcus thermophilus." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0176.
Bacterial genomes evolve mainly through horizontal gene transfer. Bacterial conjugation is one of the major mechanisms for these transfers. Conjugation is mediated by integrative and conjugative elements (ICE). In addition to their transfer function, ICEs encode other functions that may provide an adaptive advantage to their host, such as resistance to antibiotics whose dissemination is a major public health issue. It is therefore necessary to understand how ICEs are transferred in order to limit their dissemination.The transfer of an ICE from a donor cell to a recipient cell requires its excision from the chromosome, its transfer from one cell to the other and then its integration into the genomes of the two partner cells. According to the literature, the initiation of ICE transfer is mediated by a nucleoprotein complex called relaxosome, whose key protein is the relaxase, a transesterase encoded by the element. The role of the relaxase is to perform a single-stranded cleavage on the DNA of the ICE at a conserved site, called nic. This cleavage releases a free 3'OH end, used as a primer to initiate rolling circle replication. The DNA-relaxase complex is then driven to the conjugation pore.During my PhD thesis, I studied ICESt3 from Streptococcus thermophilus which belongs to the ICESt3/Tn916/ICEBs1 superfamily, widespread among Firmicutes. These ICEs encode a non-canonical relaxase belonging to the MOBT family, which is related to the rolling circle replication initiators of the Rep_trans family. The general objective of my thesis was to elucidate the function of the RelSt3 relaxase in order to decipher the molecular mechanisms of initiation of conjugative transfer mediated by a MOBT relaxase.My work led to the identification of the RelSt3 binding site on ICESt3 origin of transfer (oriT). This site, called bind, is peculiar in that it is distant from the nic site, which is not the case for other relaxase families. RelSt3 possesses an HTH domain at its N-terminus. I have shown that this domain is required for the binding of RelSt3 to its bind site, and that it is important for its catalytic activity. Conjugation assays demonstrated that this HTH domain is crucial for the conjugative transfer of ICESt3. Structural predictions of the HTH domain in complex with DNA led to the identification of the interaction interface with the bind site, confirmed by mutagenesis. I also demonstrated that RelSt3 exhibits a nicking-closing activity and that it covalently binds to the 5' end of the cleaved strand, demonstrating that this enzyme participates in both initial and final steps of conjugation.In the literature, it has been shown that relaxases interact frequently with other accessory proteins, encoded by the ICE or by the host bacteria, participating in relaxosome formation. The second objective of my thesis was to identify RelSt3 partners. Comparisons with available data on ICEBs1 from Bacillus subtilis allowed to identify two candidate proteins, OrfL and OrfM, that may belong to the relaxosome of ICESt3, as well as a cellular helicase, PcrA , probably involved in the rolling circle replication. A characterization of these proteins was performed using biochemical and biophysical approaches. The interaction network between all of these proteins was established using in vitro approaches, as well as with the in vivo two-hybrid approach. These data provide a first insight into the components of the ICESt3 relaxasome. I also showed that OrfL and OrfM stimulate the catalytic activity of RelSt3 in vitro, and that they are both essential for ICESt3 conjugation.This work lead to a better understanding of the molecular mechanisms required during the conjugation of an ICE driven by a MOBT family relaxase
Thomas, Mélissa. "Origins of Cellular Lethality Resulting From a Defect in Homologous Recombination in Human Cells." Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASL027.
Homologous recombination (HR) is involved in repairing DNA double strand breaks, and in protecting and restarting stalled or collapsed replication forks. Rad51 and BRCA2 are two key proteins of HR. I have showed that inhibiting HR, as well as over expressing Rad51, is lethal in human cells, although a very few cells still survive the inhibition. Moreover, many cancers carry mutations in an HR gene (BRCA1/2 in breast and ovary cancers) or over express an HR gene. My project aims to identify the mechanisms and the causes behind the lethality triggered by a dysregulation of HR, and to understand how a few cells manage to survive it. I have determined, through FACS and phosphorylated histone H3 labeling (IF), that HR deficient human cells, or those over expressing Rad51, accumulate at the G2/M checkpoint.At the same time, time-lapse microscopy experiments seemed to indicate that the cells died from apoptosis, which was confirmed by data from experiments using Annexin-V as an apoptosis marker and from Western-Blots. Western-Blots showed that the G2/M checkpoint is activated, through analysis of CyclinB1 and of cdk1, and that apoptosis is triggered, through analysis of PARP cleavage. My main working hypothesis was that overexpressing a dominant negative form of Rad51, and possibly also overexpressing Rad51 WT, would lead to replication defects, whose accumulation would in turn lead to an activation of the checkpoint. BrdU incorporation experients and use of the molecular combing technique confirmed this hypothesis : in HR-dysregulated cells, replication speed is slowed down and there are more stalled forks. In-silico analyses have showed that HR-mutated cancers often carry a second mutation in another gene, involved in either the G2/M checkpoint or in restarting stalled replication forks. Based on these analyses and on results from RNAseq experiments performed on FANCD1 patients' fibroblasts, candidate genes have already been listed, confirming the in-silico analysis
Labit, Hélène. "Régulation de l'initiation de la réplication chez les vertèbrés : analyse du programme temporel d'activation des origines de réplication dans les extraits d'oeufs de xénope." Paris 7, 2007. http://www.theses.fr/2007PA077176.
In Vertebrates, replication origins are activated according to a spatial and temporal program. In early Xenopus embryos, origins are located at apparently random sequences and are activated in clusters that fire at different times throughout S phase. The main object of the present work is to characterize the temporal regulation of replication in Xenopus egg extracts through analysis of origin activation on single DNA fibers and replication foci distribution in sperm nuclei. Using molecular combing of DNA, we compared the distributions of replication origins fired at the beginning of two following S phases. Absence of significative coincidence between origins shows that the temporal order of replication does not depend on genomic position. Furthermore, no epigenetic central regulates the moment of origin firing. However the detection of coincidence between replication foci labeled at the beginning of two following S phases suggests that the chromosomal organization may influence the replication timing. Using FISH, we showed that the replication of the ribosomic DNA is delayed compared to the replication of whole genomic DNA. An altered chromatin structure may be responsible for this delay. Mapping of origins revealed that initiation frequency is two fold lower in the G+C rich intergenic spacer than in the coding rDNA sequence. At the rDNA, local parameters such as nucleotide composition may influence the localization of replication origins
Ferlin, Juliette. "Etude de la voie de signalisation GBF1-ARF au cours de la réplication virale." Thesis, Lille 2, 2018. http://www.theses.fr/2018LIL2S047.
GBF1 has recently emerged as a cellular factor essential for the replication of single-stranded positive-sense RNA ((+)RNA) viruses from different families. GBF1 is a guanine-nucleotide exchange factor of small G proteins of the Arf family, known to regulate the early secretory pathway. By studying the hepatitis C virus (HCV) as a model, we have shown that the role of GBF1 in viral replication is distinct from its regulatoryfunction of the sercretory pathway. Indeed, GBF1 function in HCV replication is mediated by Arf4 and Arf5,whereas another pair, Arf1 and Arf4, mediates the regulation of the secretion. To determine if this mechanism ofaction is conserved among (+)RNA viruses, we showed that GBF1 is involved in yellow fever virus (YFV),sindbis virus (SINV), human coronavirus 229E (HCoV-229E) and coxsackievirus B4 (CVB4) infection. Our results indicate that YFV, SINV and HCoV-229E infections are Arf4 and Arf5 dependent, as we previouslyshowed for HCV. However, YFV and SINV would also use another Arf pair, Arf1 and Arf4, during their lifecycle. In addition, CVB4 infection depends on GBF1, but doesn’t seem to depend on any Arf. Although GBF1 is required for (+)RNA viruses replication, its mechanism of action appears not to be conserved.The Arf4-Arf5 pair appears to be involved in the replication of several (+)RNA viruses. However, these twoproteins have been poorly studied so far, contrary to Arf1. Our hypothesis is that the Arf4-Arf5 pair regulatesspecific effectors involved in viral replication. Our results indicate that Arf4 and Arf5 simultaneous depletionalters the morphology of the Golgi apparatus, which becomes condense, and of lipid droplets (LD), whichaccumulate and grow bigger at the cell periphery. However, a lipidomic analysis of Arf4 and Arf5 depleted cellsdisplayed an unaltered lipid composition, which suggests a morphologic impact on LD, rather than a disruptionof the lipid metabolism. A transcriptomic analysis identified proteins up- or down-regulated after Arf4 and Arf5 depletion. We assessed the function of some of these proteins in HCV replication, but none of them proved implicated.In conclusion, our results hightlighed new GBF1 functions, mediated by the pair Arf4-Arf5. Arf4 and Arf5 are involved in regulating the morphology of Golgi complex and of LDs, as well as the replication of (+) RNA viruses. It remains to assess if these functions are independent or related to each other, and which specific effectors they use
Farhat, Rayan. "Etude des mécanismes dépendants de GBF1 et impliqués dans la réplication du virus de l'hépatite C." Thesis, Lille 2, 2014. http://www.theses.fr/2014LIL2S040/document.
The hepatitis C virus (HCV) infection progresses in most of the cases into a chronic hepatitis and can lead to cirrhosis or hepatocellular carcinoma. Despite the recent improvement of hepatitis C treatments, which inhibit or even block the progress of this infection into a chronic stage, a vaccine still not available and the worldwide distribution of the disease makes the hepatitis C a major public health problem. Most of the available treatments target viral proteins. However many mechanisms of the HCV life cycle remain unclear.As for many positive RNA viruses, HCV replication occurs in reorganized cellular membranes. These membrane rearrangements are closely linked to the early secretory pathway of the cell. It has been shown that GBF1, an exchange factor of small G proteins of the Arf family that regulates the membrane dynamics in the secretory pathway, is required for HCV replication. GBF1 inhibition by brefeldin A (BFA) inhibits the secretion of newly synthesized proteins and also inhibits HCV replication. To investigate the role of GBF1 in HCV infection, we isolated cell lines resistant to BFA. Two of these cell lines were 100 times more resistant than the parental cells to BFA-induced apoptosis, inhibition of proteins secretion and inhibition of HCV infection. This resistance was due to a point mutation in the catalytic sec7 domain of GBF1 of these cells. Another group of resistant cells was showing a partial resistance to the inhibition of proteins secretion while maintaining their sensitivity to the inhibition of HCV infection in the same conditions. These results suggest that GBF1 might fulfill another function, in addition to the regulation of the secretory pathway, during HCV replication. Using GBF1 deletion mutants we showed that the catalytic activity of the sec7 domain of GBF1 is required for HCV infection. This suggests that the function of GBF1 during HCV replication is mediated by Arf activation. The involvement of Arf was confirmed with the overexpression of restricted mutants of Arf1 and by the inhibition of ArfGAP1, another regulator of Arf function. We then tested the possible involvement of different Arfs (Arf1, 3, 4 and 5) in HCV infection. It has been reported that Arfs have redundant functions. The results confirm the involvement of Arf1 and indicate that all the other BFA-sensitive Arfs (Arf3, Arf4 and Arf5) are also involved in HCV infection. The combined knockdown of Arfs strongly inhibited HCV replication, showing that the Arf proteins are working together in HCV replication probably by activating several host factors required for the virus life cycle.The study of cellular factors required for HCV infection is crucial to better understand the interaction of the virus with the host cell and thus the whole HCV life cycle. This could help to develop new therapies targeting the host cell, regardless of viral genotypes and reducing the risk of emergence of new resistant forms
Ben, Yamin Rosen Barbara. "Fonction et régulation de l'ADN polymérase zêta au cours de la réplication de l'ADN : conséquences sur la stabilité du génome. DNA Polymerase Zeta Contributes to Heterochromatin Replication to Prevent Genome Instability." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS031.
DNA replication is a fundamental process that ensures accurate duplication of the genetic information. Various perturbations can impede replication fork progression, and thus threatening genome integrity. To prevent fork collapse, replicative DNA polymerases can be replaced by error-prone DNA polymerases called translesion (TLS) polymerases, able to bypass DNA damage at the cost of increased mutations. Among TLS polymerases, Polζ is unique because inactivation of its catalytic subunit, REV3L, leads to embryonic lethality in mice underscoring its biological importance. However, little is known about its function and regulation in mammalian cells. We showed that loss of REV3L impairs S phase progression with a disruption of replication timing at specific genomic loci that replicate in mid-late S-phase, and this is associated with increased mutagenic events and aberrant epigenetic landscape. We also revealed that REV3L interacts with heterochromatin components and localizes in pericentromeric regions, suggesting that Polζ contributes to replicate heterochromatin regions to limit genome instability. In a second part, we discovered that REV3L protein is proteolytically processed by the endopeptidase TASP1 to generate two polypeptides that heterodimerize to form a stable complex that associates with REV7, likely representing the active complex of Polζ. We also found that REV3L is finely regulated in physiological conditions and after genotoxic stress at multiple levels: (1) transcriptionally, (2) proteolytically by TASP1 and (3) post-translationally by phosphorylation. Altogether these findings highlight a unique mechanism to control the function of an error-prone polymerase in mammalian cells. These data are particularly important given that Polζ is an important factor for tumor resistance to chemotherapeutic agents
Said, Maha. "Interplay Between Senataxin and FANCD2 in Genome Maintenance DNA Replication Stress and Chromosomal Instability: Dangerous Liaisons." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL050.
Genomic instability is an enabling characteristic of cancer and a common feature of neurodegenerative diseases. In the scientific community, there is a general consensus that DNA replication stress (RS), which arises following the cell’s exposure to various exogenous and endogenous genotoxic agents, is a key driver of genomic instability.Interestingly, the genome organization and dynamics per se can also favor RS under some circumstances. Examples of genomic regions where completion of replication is particularly challenging are common fragile sites (CFS), genomic loci that tend to form breaks, gaps, or constrictions on mitotic chromosomes under RS conditions. Recently, a plethora of proteins that guard the genome from RS, which if mutated can induce genome instability have been identified. In more recent years, scientists have discovered that a key source of RS, and subsequently genomic instability, is transcription, especially if not spatially and temporally separated from replication. Fanconi Anemia (FA) is a rare inherited bone marrow failure disease characterized by congenital abnormalities and cancer predisposition, caused by mutations in any of the 22 identified FANC genes. FA is characterized by chromosome fragility and hypersensitivity to DNA interstrand-crosslinking (ICL) agents. Furthermore, the FA proteins play roles in resolving DNA damage arising during replication and transcription, and in coordinating both processes. Interestingly, breakpoints occurring in FA cells frequently overlap CFS. At CFS, FANCD2 is recruited with structure-specific endonucleases SLX4, XPF–ERCC1 and MUS81–EME1 to process replication intermediates that can lead to chromosome segregation defects. In addition, FANCD2 at CFSs limits the formation of R-loops. R-loops play key regulatory roles, but may also pose a threat to the genome when they occur in an unscheduled manner. R-loops are monitored by resolving factors such as senataxin (SETX), a RNA:DNA helicase mutated in neurodegenerative diseases. SETX is implicated in several genome maintenance pathways analogous to those regulated by FANC proteins. Prominent functions shared by SETX and FANC proteins include the coordination of replication with transcription and the repair of ICLs. In addition, SETX functions in concert with BRCA1 (FANCS) to allow faithful transcription termination, and forms nuclear foci in response to replication stress, both critical for the maintenance of the genome. Loss-of-function of SETX also causes infertility in mice (a phenotype common to FA mice and patients). Taking into account the common cellular processes that the FANC pathway and SETX participate in, we asked whether there is a functional relationship between them in the maintenance of the genome stability. I show that the absence of SETX induces spontaneous breaks on mitotic chromosomes. The regions involved in these breaks are targeted by FANCD2, which participates in resolution of under-replicated DNA during mitosis, preventing chromosome mis-segregation and allowing cells to continue proliferating. I also show that FANCD2 promotes mitotic DNA synthesis that is dependent on MUS81 and XPF. Co-depleting FANCD2 and SETX impairs cell proliferation, an effect that appears specific to transformed cells. Therefore, I uncovered a synthetic lethal interaction between SETX and FANCD2 that may be exploited in cancer therapy