Добірка наукової літератури з теми "Ribose méthylation"
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Статті в журналах з теми "Ribose méthylation":
Cavaillé, J., and JP Bachellerie. "Les méthylations sur le ribose des ARN ribosomiques : une modification post transcriptionnelle guidée par les petits ARN nucléolaires antisens." médecine/sciences 13, no. 5 (1997): 742. http://dx.doi.org/10.4267/10608/454.
Дисертації з теми "Ribose méthylation":
Ghabreau, Lina. "Poly(ADP-ribose)polymérase-1 (PARP-1) et méthylation de l'ADN, nouveaux partenaires des récepteurs hormonaux dans la carcinogenèse de l'endomètre." Lyon 1, 2005. http://www.theses.fr/2005LYO10067.
Darzacq, Xavier. "Etude des petits ARN guides de méthylation en 2 -O-ribose et guides de pseudouridylation : Biogénèse, fonction et organisation nucléaire des petits ARN guides." Toulouse 3, 2002. http://www.theses.fr/2002TOU30042.
Nguyen, Van Long Flora. "Altérations de composition des ribosomes dans les cancers du sein : analyses de cohortes humaines et modèles cellulaires." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1095/document.
Ribosomes are responsible of translating mRNAs to proteins. Alterations of ribosome composition modify its translation activity and favour tumourigenesis. Identification of ribosomes composition alterations in breast cancers might correspond to a new mechanism responsible of mammary tumourigenesis and might open up novel therapeutic approaches. Indeed breast cancers represent the first cause of women mortality due to cancers and their heterogeneity induces an important therapeutic problem.In this context, alterations of ribosomes composition were determined in human cohorts and in EMT (Epithelial to Mesenchymal Transition) cellular models, the EMT being a process involved in mammary tumourigenesis. This studies identify : (i) two factors involved in ribosome biogenesis, FBL (fibrillarin) and NCL (nucleolin) whose expression variations are associated with poor prognosis in patients and (ii) variations of ribosome composition and its translational activity in EMT. Altogether, this data support the presence of ribosomes composition alterations in breast cancers
Hebras, Jade. "Caractérisation moléculaire du petit ARN nucléolaire SNORD115 : un rôle dans la régulation de l'expression et de la fonction du récepteur à la sérotonine 5-HT2C ?" Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30209.
The nucleolus of mammalian cells contains hundreds of box C/D small nucleolar RNAs (SNORDs). Majority of them, guide sequence-specific 2'-O ribose methylations into ribosomal RNA (rRNA). Some of them facilitate RNA folding and cleavages of ribosomal RNA precursors or guide ribose methylations into spliceosomal small nuclear RNA U6. Recent studies propose that some SNORD could target other transcripts, possibly messenger RNA as suggested by the brain-specific SNORD115. SNORD115 is processed from tandemly repeated genes embedded in the imprinted SNURF-SNRPN domain. Defects in gene expression at this domain are causally linked to rare disease: the Prader-Willi Syndrome (PWS). Excitingly, SNORD115 displays an extensive region of complementary to a brain-specific mRNA encoding the serotonin receptor 5-HT2C. SNORD115 could influence 5-HT2C signaling by fine-tuning alternative splicing or A to I RNA editing of 5-HT2C pre-mRNA. Reduced 5-HT2C receptor activity could contribute to impaired emotional response and/or compulsive overeating that characterized the syndrome. My work was to test this hypothesis using a CRISPR/Cas9-mediated SNORD115 knockout mouse model. My results show that loss of SNORD115 expression, in vivo, does not alter the post-transcriptional regulation of 5-HT2C pre-mRNA processing. Others results from the team do not reveal any defects in anxio-depressive phenotypes and eating behaviour. Our study questions the regulatory roles of SNORD115 in brain functions and behavioural disturbance associated with PWS. On other hand, I have studied ribose methylation sites in rRNA from mouse tissues. This work was included in emerging field of the specialized ribosome hypothesis which suggests heterogeneity in ribosomes may impact activity of ribosomes. Our results show significant changes at few discrete set of sites, especially in rRNA from developing tissues. Also, rRNA from developing tissues is globally less methylated than rRNA from adult tissues. We focus on LSU-Gm4593 site because this position is specifically methylated only during development and hardly ever detected in adult tissues. Methylation at LSU-G4593 is guided by SNORD78. We propose that the expression levels of SNORD78 during development appeared to be regulated by alternative splicing of the host-gene and to correlate with the methylation level of its target site at LSU-G4593. We've used a human cell line (HEK293T) inactivated for the SNORD78 gene in order to understand the functionally role of the corresponding ribose methylation. Our work did not demonstrate any overt cellular phenotypes, even though translation fidelity and the precise function of LSU-Gm4593 remains unknown
Figaro, Sabine. "Rôle de la méthylation des facteurs de terminaison de la traduction." Paris 6, 2009. http://www.theses.fr/2009PA066260.
Sournia, Pierre. "La méthylation flavine-dépendante d’acides nucléiques : aspects évolutifs, métaboliques, biochimiques et spectroscopiques." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX108/document.
Enzymes catalyzing the methylation of uridine at its carbon 5 position have appeared independently in different forms across evolution. Thymidylate synthases ThyA and the flavoprotein ThyX catalyze the de novo synthesis of dTMP, an essential DNA precursor in the three domains of life. They are encoded by heterologous genes and have drastically different structures and reaction mechanisms. On the other hand, this uridine methylation is also performed by tRNA and rRNA post-transcriptional modification enzymes.This thesis assesses the question of the evolutionary constraints that have led independently to four kinds of uridine methylation. The first part describes the identification of a metabolic pathway allowing the complementation of thymidine auxotrophy by non-natural nucleotide analogs in Escherichia coli. A synthetic biology approach, aiming to establish an alternative pathway for thymidylate biosynthesis, was also implemented and a selection strategy for thymidine auxotrophy-complementing genes, could be developed.In a second part, biochemical and spectral studies where realised on the flavin-dependent methyltransferase TrmFO, responsible for the post-transcriptional methylation of uridine at the invariant position 54 of tRNA in several microorganisms. The involvement of specific amino acid residues in substrate fixation and in stabilization of potential reaction intermediates was demonstrated. Their spectral characterization supports previously proposed reaction schemes for flavin-dependent thymidylate forming enzymes. These observations are currently being pursued by parallel approaches combining time-resolved spectroscopy and molecular dynamics simulations, aiming to further our understanding of how flavin mediates the transfer of carbon molecules from folate to uracil rings
Gillot-Chafia, Sandra. "Impact de la composition du ribosome sur la fidélité de la traduction." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS168.
Ribosomes are composed of proteins and RNAs. During these last years, the concept of « specialized ribosome » has been revived. This concept is based on the principle that ribosomes are heterogeneous in protein composition and rRNA chemical modifications. These different ribosomes populations would present different translational specificities. During my thesis, I was interested in a particular rRNA chemical modification, ribose 2’-O-methylation, its variability and its role in translational fidelity and regulation.To make this study, a HeLa cell-line in which fibrillarin (the methyltransferase responsible for 2’-O-methylations) synthesis is inhibited by a shRNA (small hairpin RNA) stably integrated in the genome. The study of impact of fibrillarin decrease on 2’-O-methylations enabled us to show that rRNA methylation decrease is global but varies with the position. So, some positions are more sensitive than others positions to fibrillarin decrease.First I studied rRNA methylation decrease effects on global translation, by ribosome profiling. This method is based on high-throughput sequencing of ribosome-protected mRNA fragments. By this way I revealed 43 candidate genes that are differentially translated in rRNA hypomethylated condition. From this list I searched functional and/or molecular elements common to several candidate genes. Then I showed that readthrough and frameshifting rates increase when rRNA is hypomethylated. So rRNA methylation decrease leads to translational fidelity decrease.Previous studies have shown that IRES-dependant initiation is impacted by rRNA methylation decrease. Then I performed a global study of translation initiation by adapting ribosome profiling method to identify initiating ribosomes specifically. Therefore I revealed that 66 initiation sites are impacted by rRNA methylation decrease.We localized the most impacted methylated positions on the 3D ribosome structure. It enabled us to group modifications by region. We focused our interest on one group of methylations conserved between yeast and human and localized around the peptide exit tunnel. I deleted snoRNAs responsible for these methylations in S. cerevisiae. Then I analysed if the loss of these methylations impacts the cell growth and the antibiotics sensitivity. I also make measures of readthrough and frameshifting. My results show that the targeted deletion of three out of four snoRNAs involved in the methylations around the peptide exit tunnel has no effect on translational fidelity.During this study in yeast, I revealed an unprecedented effect of ASC1 gene deletion on stop codons readthrough. Asc1p is a scaffold protein associated with the ribosome, whose absence causes a decrease of codon stop readthrough. Currently molecular mechanisms implicated remain unknown.During my thesis, I showed with global and specific approaches that rRNA methylation decrease leads to specific variations of protein expression together with specific decrease of translational fidelity. Molecular mechanisms are still actively investigated
Cavaillé, Jérôme. "Biosynthèse et fonction dans la méthylation de l'ARNr du petit ARN nucléolaire d'origine intronique U20 : [thèse en partie soutenue sur un ensemble de travaux]." Toulouse 3, 1997. http://www.theses.fr/1997TOU30082.
Belin, Stéphane. "Implication de la biogenèse des ribosomes dans la tumorigenèse." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10309.
Ribosome biogenesis is a fundamental and extremely complex cell process. In mammals, ribosome synthesis coordinates the assembly of 80 proteins and 4 rRNA to form the two ribosomal sub-units. The maturation of the ribosome is a multi-step post-transcriptional process essential to obtain functional ribosomes. It is now well demonstrated that ribosome biogenesis and its regulation is altered during transformation process. However, if the increase of ribosome synthesis in cancer cell is well documented, there are numerous recent data suggesting that post-transcriptional steps could also be altered. In this biological context, the objectives of my Ph.D were to determine if: i) the maturation of rRNA is altered during the increase of ribosome synthesis; ii) these alterations could modify the ribosomes and alter their function and iii) these modifications directly participate to the deregulation of translation observed in cancer cells. We have explored the major steps of ribosome biogenesis as well as the structure of the cytoplasmic ribosomes and their functional capacity in different cellular models of tumor progression and/or aggressively. The results obtained show that in addition of the increase of the level of ribosome synthesis, post-transcriptional modifications are altered, particularly the level of rRNA methylation. These modifications are associated with strong defect of translation (stop codon bypass, misincorporation of amino-acid) and an increase of the IRES-dependant translation of important factors playing a crucial role in tumorigenesis. These results suggest that modifications of ribosome biogenesis could be a key step of cancer cell transformation
Thomet, Manon. "Stress and translation : implication of 16S rRNA methylations in Escherichia coli and characterization of a toxin-antitoxin system of Sinorhizobium meliloti." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1B045/document.
Bacteria are able to live in a large variety of environments and they face constantly changing conditions. Therefore they have to adapt quickly to their metabolism using different regulations at the transcriptional and translational levels. Those types of regulation are extensively studied and well characterized. However, the implications of the ribosome in modulation of translation during stress response remains poorly understood. In this context of ribosomal regulation, the heterogeneity of the machinery could play a relevant role. Indeed, the ribosome is not an invariable particle and its components (rRNAs, r-proteins) and their modifications may vary. Modifications of ribosomal RNAs are clustered in the functional sites of the ribosome and are particularly conserved, underlying their potential importance. However their physiological role is still unclear. We focused on methylations of the 16S rRNA and investigated their role in translation under favourable and stressful conditions. We successfully demonstrated that lack of some methylations increases translation under stressful and non stressful conditions. So, lack of methylation may give an advantage to ribosomes during stress response. Another way to act on translation under stressful conditions resides in targeting mRNAs. This is particularly the case for endoribonuclease toxins that are specifically produced during detrimental conditions. Thus, we characterized S. meliloti toxin-antitoxin system HicAB. We plan to use it in order to study the response to HicA toxin of mutants lacking some ribosomal modifications