Thèses sur le sujet « Interactions protéine-RNA »
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Corsi, Flavia. « Towards the in silico reconstruction of protein interaction networks : identification of DNA- and RNA-protein interfaces, and construction of a database of multiple interactions of proteins ». Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS452.pdf.
Texte intégralThis thesis focuses on the characterization and prediction of DNA- and RNA-binding sites on protein structures, with some comparisons with protein-protein ones. We compiled and manually curated a non-redundant and representative set of 187 high resolution protein-DNA complexes, with the available 82 protein unbound conformations, that could be used as a reference benchmark. We conducted a comprehensive analysis of sequence- and structure-based properties of protein-DNA/RNA interfaces and compared them with respect to protein-protein interfaces and to non-interacting protein regions. We developed JET2DNA and JET2RNA, new methods for predicting DNA- and RNA-binding sites on protein surfaces. Combining four biologically meaningful descriptors, they outperform other machine-learning methods, in terms of predictive power and robustness to conformational changes. Our tools demonstrated to be instrumental in discovering alternative DNA/RNA-binding sites and in deciphering their properties. This could be very helpful for drug design and repurposing. To give a comprehensive view of plasticity of DNA-binding proteins and structural information on their multiple interactions, we constructed the Protein-(Protein)-DNA database (P(P)DNAdb). It comprises the 187 protein-DNA complexes in our benchmark, protein unbound forms and structures of other complexes where the proteins, or closed homologs, were in contact with other proteins. The user can access properties of the interfaces, visualize conformational changes associated to the binding of different partners and the location of the DNA-binding residues on the unbound structures and on the complexes with the other protein partners
Ribeiro, Diogo. « Discovery of the role of protein-RNA interactions in protein multifunctionality and cellular complexity ». Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0449/document.
Texte intégralOver time, life has evolved to produce remarkably complex organisms. To cope with this complexity, organisms have evolved a plethora of regulatory mechanisms. For instance, thousands of long non-coding RNAs (lncRNAs) are transcribed by mammalian genomes, presumably expanding their regulatory capacity. An emerging concept is that lncRNAs can serve as protein scaffolds, bringing proteins in proximity, but the prevalence of this mechanism is yet to be demonstrated. In addition, for every messenger RNA encoding a protein, regulatory 3’ untranslated regions (3’UTRs) are also present. Recently, 3’UTRs were shown to form protein complexes during translation, affecting the function of the protein under synthesis. However, the extent and importance of these 3’UTR-protein complexes in cells remains to be assessed.This thesis aims to systematically discover and provide insights into two ill-known regulatory mechanisms involving the non-coding portion of the human transcriptome. Concretely, the assembly of protein complexes promoted by lncRNAs and 3’UTRs is investigated using large-scale datasets of protein-protein and protein-RNA interactions. This enabled to (i) predict hundreds of lncRNAs as possible scaffolding molecules for more than half of the known protein complexes, as well as (ii) infer more than a thousand distinct 3’UTR-protein complexes, including cases likely to post-translationally regulate moonlighting proteins, proteins that perform multiple unrelated functions. These results indicate that a high proportion of lncRNAs and 3’UTRs may be employed in regulating protein function, potentially playing a role both as regulators and as components of complexity
Mahmoudi, Ikram. « Structural and evolutionary analysis of protein-RNA interfaces and prediction perspectives ». Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASQ024.
Texte intégralProtein-RNA interactions are crucial in numerous cellular pathways and pathologies. Knowledge of their 3D structures is critical for understanding their functions, yet their experimental determination remains challenging. The scarcity of structural data and the inherent flexibility of these complexes have hindered the advancement of protein-RNA interface structural prediction. At the same time, tremendous progress has been made recently for protein-protein interaction prediction thanks to methods leveraging evolutionary information and deep learning.My thesis focused on a detailed evolutionary analysis of protein-RNA interface structures. I first identified 2,022 pairs of structurally homologous interfaces. I explored the conservation of interface contacts among these pairs, discovering a high conservation rate for distance-based and apolar contacts, even in distant homologs. Hydrogen bonds, salt bridges, and π-stacking interactions displayed higher versatility. I investigated mechanisms compensating for non-conserved interactions. I contributed to developing a web interface allowing the community to explore evolutionary structural insights in our datasets. I also participated in a collaborative project with biologists to study a specific protein-RNA interface.Then, I investigated how to incorporate evolutionary signals into protein-RNA structural modeling methods using machine learning models, including logistic regression and CatBoost classifiers. I assessed these models' ability to learn how to transfer contacts from remote interologs and generalize across datasets while mitigating overfitting. Lastly, I explored developing functions based on contact propensities to score protein-RNA docking poses. These efforts constitute a step towards improving protein-RNA structure prediction
Michaux, Charlotte. « Identification et caractérisation fonctionnelle de petits ARN non codants chez Enterococcus faecalis et analyse d'une protéine "RNA-binding" ». Caen, 2013. http://www.theses.fr/2013CAEN2094.
Texte intégralChevrollier, Nicolas. « Développement et application d’une approche de docking par fragments pour modéliser les interactions entre protéines et ARN simple-brin ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS106/document.
Texte intégralRNA-protein interactions mediate numerous fundamental cellular processes. Atomic scale details of these interactions shed light on their functions but can also allow the rational design of ligands that could modulate them. NMR and X-ray crystallography are the 2 main techniques used to resolve 3D highresolution structures between two interacting molecules. Docking approaches can also be utilized to give models as an alternative. However, the application of these approaches to RNA-protein complexes is hampered by an issue. RNA-protein interactions often relies on the specific recognition of a short singlestranded RNA (ssRNA) sequence by the protein. The inherent flexibility of the ssRNA segment would impose, in a classical docking approach, to explore their resulting large conformation space which is not computationally reliable. The goal of this project is to overcome this barrier by using a fragment-based docking approach. This approach developed from some of the most represented RNA-binding domains showed excellent results in the prediction of the ssRNA-protein binding mode from the RNA sequence and also a great potential to predict preferential RNA binding sequences
Angius, Federica. « Molecular basis of membrane protein production and intracellular membranes proliferation in E. coli ». Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC217/document.
Texte intégralThe most successful expression system used to produce membrane proteins for structural studies is the one based on the T7 RNA polymerase (T7 RNAP) (Hattab et al., 2015). However, the major drawback of this system is the overtranscription of the target gene due to the T7 RNAP transcription activity that is over ten times faster than the E. coli enzyme. Since the isolation of spontaneous mutants, namely C41(DE3) and C43(DE3) (Miroux and Walker, 1996) and the identification of their mutation in the genome, it becomes clear that reducing the amount of the T7 RNAP level removes the toxicity associated with the expression of some membrane proteins (Wagner et al., 2008; Kwon et al., 2015). Also, some membrane proteins require a very low rate of transcription to be correctly folded at the E. coli membrane. The first objective of my PhD was to extend the promoter strength coverage of the T7 based expression system. We used genetic and genomic approaches to isolate and characterize new bacterial strains (Angius et al., 2016) in which the level of T7 RNAP is differently regulated than in existing hosts. A second objective was to understand intracellular membrane proliferation in E. coli. Indeed it has been shown that over-expression of membrane proteins, like overexpression of AtpF of E. coli F1Fo ATP synthase is accompanied by the proliferation of intracellular membranes enriched in cardiolipids (Arechaga et al., 2000). To understand metabolic pathways involved in membrane biogenesis, proliferation and organization, we used a RNA sequencing approach at several time point upon over-expression of the F-ATPase b subunit in C43(DE3) host. On the other hand, in collaboration with Gerardo Carranza and Ignacio Arechaga (University of Cantabria, Spain) we studied C43(DE3) cls mutants, in which the cardiolipids genes A, B and C are deleted, to test how they participate to intracellular membranes structuration
Capozi, Serena. « Dynamique d'interaction entre la protéine SRSF1 et l'ARN et cinétique de formation du spliceosome ». Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT067.
Texte intégralSRSF1, formerly known as ASF/SF2, belongs to the SR protein family, which is a conserved family of RNA-binding protein that plays essential roles as regulators of both constitutive and alternative splicing. Hundreds of RNA targets have been described for SRSF1 but how SRSF1 selects its targets from the entire pool of cellular pre-mRNAs remains an open question. In vitro and in vivo studies have shown that SR proteins recognize short degenerated motifs often present in multiple copies at ESEs. Similar cryptic motifs are however frequently present in pre-mRNAs, and this low specificity of binding contrasts with the great fidelity of exon definition. To better understand the mechanism of action of SRSF1, I performed a kinetic study of SRSF1-RNA interactions in live cells using advanced microscopic techniques. Taking advantage by the CRISPR system, I tagged endogenous SRSF1 with Halo protein, and I combined photobleaching (FRAP) and single particle tracking (SPT) techniques to estimate diffusion and binding rates of SRSF1. I measured the duration of individual binding events, both on the cellular pool of pre-mRNAs and on specific targets. Our results indicate that binding of SRSF1 does not exceed few seconds, even on high-affinity targets. This rapid kinetics allows SRSF1 to rapidly sample the entire pool of nascent RNAs continuously produced in cells. Moreover, we provided a kinetic analysis of snRNP dynamics at a single-molecule resolution in the nucleoplasm of living cells. Our results enabled us to determine diffusion coefficients of snRNPs and their RNA binding duration in vivo
Robert-Paganin, Julien. « Étude structurale et fonctionnelle de la régulation de l’hélicase Prp43 ». Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05P633/document.
Texte intégralRNA helicases from the DEAH/RHA family are involved in most of essential processes of life such as pre-mRNA splicing, ribosome biogenesis, replication, transcription or viral RNA sensing. These enzymes are able to catalyze RNA unwinding, secondary structures reorganization or RNA-protein complexes remodeling. The DEAH/RHA helicase Prp43 is remarkable because it is bifunctional, as it is involved both in pre-mRNA splicing, where it is responsible of spliceosome and lariat recycling and in the biogenesis of the two ribosomal subunits. Prp43 is activated by five protein partners: Ntr1, Gno1, Pfa1, RBM5 and GPATCH2. These protein partners all possess a G-patch domain and are able to stimulate helicase and ATPase activity of Prp43. The structure of Prp43 in complex with ADP has been solved by X-ray crystallography. The structure reveals that the nucleotide is bound to the enzyme in a novel mode that has never been observed in other known helicase structures. The specific feature of this binding mode is the base, stacked between phenylalanine (F357) from RecA2 domain and an arginine (R159) from RecA1 domain. Features of the activation of Prp43 by G-patch proteins are unclear. In this work, we investigated the role of base stacking in the activation of Prp43. We present several structures of Prp43 bound to all the nucleotide diphosphates (NDP) and deoxynucleotide diphosphates (dNTP). These results indicate that there are differences in stacking according to the (d)NDP bound to the enzyme. NTPase activity assays revealed that when stacking is weakened, Prp43 activity cannot be properly regulated by its protein partner Pfa1. Moreover, point mutations F357A and R159A show that stacking of F357 permits to modulate Prp43 activity. All these results allow us to propose a model of NTPase activity activation of Prp43 by G-patch proteins and to highlight the importance of base stacking in this regulation
Paternina, Osorio J. Antonio. « Biocomputational tools for transcriptome-wide analyses of RNA-binding proteins ». Electronic Thesis or Diss., Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLE058.
Texte intégralPost-transcriptional Gene Expression Regulation is a complex network that involves RNA-binding proteins and non-coding RNAs to orchestrate the complex life of mRNAs. In metazoans, the Exon Junction Complex (EJC) is a multi-protein complex deposited onto mRNAs exon junctions during splicing. The EJC interacts with numerous factors and is important for coupling pre-mRNA splicing with mRNA nuclear export, localization, translation, and decay. Despite its central role in gene expression and in organism development, the comprehensive map of EJC binding sites is lacking. Crosslinking and immunoprecipitation coupled with high-throughput sequencing (CLIP-seq) aims to identify transcriptome-wide RNAprotein interactions in vivo. Yet, current trends in CLIP-seq data analysis gravitate towards painting a global landscape rather than characterizing individual binding sites. However, we observed that current peak callers applied to EJC CLIP data yield results with limited reproducibility and sensibility. During my PhD, we developed a dedicated strategy to detect EJC signal enrichment at the exon level. By aggregating data from several replicates, we built a list of robust genes with reproducible EJC loading rate. Within robust genes, we assigned a robustness score to each exon according to frequency of detection across replicates. We found that the exon robustness score was correlated to the thymidine (T) content of EJC binding sites. Assuming this was due to cross-linking chemistry, we corrected the score for the T content and found exons with either high or low detection rates. The last suggests that EJC loading is not homogeneous along a transcript, but rather differential. Thus, we established an unprecedented binding site map of the EJC in living cells validated by statistical tools. Crossing this map with other information showed that EJC loading is independent of transcript expression levels or known gene functional annotations. Although the scope of this work does not include possible explanations for this differential loading, it presents a first reproducible and specific data analysis pipeline to detect EJC-loaded exons. Altogether, our contribution is twofold. First, we proposed a robust way to detect EJC signal enrichment at the exon level and demonstrated quantitatively that our approach is more reproducible and more sensitive compared to conventional tools. Second, we proved that the EJC can be present on some, and absent on other exons of the same transcript suggesting that EJC loading is a regulated process following a code that remains to be discovered
Ben, ouirane Kaouther. « Apport des approches in silico aux études structure-fonction de la polymérase du virus de l'hépatite C ». Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS323.
Texte intégralThe hepatitis C virus is an RNA virus that synthesises its new genomes in the infected host cells thanks to an RNA-dependent RNA polymerase (RdRp) termed NS5B. This polymerase has been a prime target for antiviral therapy. Numerous direct antiviral drugs are now approved in the HCV treatment and allow very high rates of treatment success. These drugs target among others the HCV NS5B RdRp with the sofosbuvir being one of the most successful drugs.Tremendous efforts have been made in the past decades to characterize NS5B, in particular structurally and biochemically. However, there is little information about the molecular mechanisms of NS5B ribonucleotides entry and selection and in general on the atomistic details of the RNA replication mechanism, although the involvement of two magnesium dications in catalysis is well established in this family of polymerases. Since 2015, structures of ternary complexes of NS5B have been resolved by crystallography offering very valuable details about the binding of nucleotides at the NS5B active site.In this work, we took advantage of these structural data to address the ribonucleotides entry and to further explore the nucleotide addition cycle in NS5B using molecular modelling and molecular dynamics simulations. We used both conventional molecular dynamics techniques and biased simulations that enhance sampling such as Steered Molecular Dynamics (SMD), Targeted Molecular Dynamics (TMD) or accelerated Molecular dynamics (aMD).Based on our modelling results, we found that the access to the active site through the nucleotides tunnel is checked by successive NS5B elements. First, the entering ribonucleotide together with an associated magnesium Mg(B) binds next to a loop that overhangs the nucleotide tunnel and interactions with its triphosphate moiety orient it base-first towards the active site. Second, the ribonucleotide encounters a checkpoint constituted by the residues of motif F3(R158) and motif F1(E143) where it is blocked until the arrival of a second magnesium ion, the Mg(A). This allowed the motif F3 to undergo small structural rearrangements leading to the advancement of the nucleotide towards the active site to interrogate the RNA template base prior to the complete nucleotide insertion into the active site.Our simulations pointed out that these dynamics are finely regulated by the second magnesium dication, thus coordinating the entry of the correct magnesium-bound nucleotide with shuttling of the second magnesium necessary for the two-metal ion catalysis. This entry mechanism is specific to viral RdRps and may explain why modified ribonucleotides can be so successful as drugs against RNA viruses
Bulfoni, Manuel. « Exploring new paradigms of translational control in eukaryotes ». Thesis, Sorbonne Paris Cité, 2018. https://theses.md.univ-paris-diderot.fr/Bulfoni_Manuel_2_complete_20181129.pdf.
Texte intégralRegulation of protein synthesis is a key regulatory step of gene expression of many cellular processes allowing the cell to quickly adapt to the changing environment including external stimuli and stresses. Most of the translational regulation occurs at the the initiation step when ribosomes are recruited to the mRNAs, by disrupting eIF4F, the complex bound to the 5’ mRNA extremity through eIF4E, or by reducing the availability of the eIF2 ternary complex (eIF2-GTP-Met-tRNAMet). During my thesis I showed how these universal steps are regulated to specifically modulate the translation rates of different mRNAs.We showed that Angel1, an eIF4E interacting protein, is specifically localized to the perinuclear compartment where it regulates mRNA translation of specific mRNAs.We also described a novel RNA operon characterized by the specific binding of Hek2, a yeast hnRNP K-like protein, to a subset of nuclear-pore-encoding mRNAs regulating their translation. Moreover, we showed that Hek2 binding to the mRNA is impeded by the SUMOylation, a post-translational modification which is counteracted by Ulp1, a SUMO-protease. Finally, we reported that perturbation of the nuclear pore integrity by either mutations or stress, induced the accumulation of the SUMOylated form of Hek2. Hek2-SUMO is unable to bind to the mRNAs whose translation is thereby enhanced in a feedback process.In the last part of my thesis, we performed the first ever translatome study of a human pancreatic β cell line in response to glucose stimulation. We report that glucose stimulates translation of a defined set of mRNAs and identified their specific features providing important advances to better understand regulation of gene expression by glucose. Taken together our results allowed us to establish new paradigms of translational regulation
Kravchenko, Anna. « Fragment-based modelling of protein-RNA complexes for protein design ». Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0370.
Texte intégralProtein-RNA complexes play crucial roles in cell regulation. Predicting their 3D structure has applications in protein design and drug development. The ITN project RNAct aimed to combine experimental and computational methods to design new "RNA recognition motifs" (RRM) - protein domains interacting with single-stranded RNA (ssRNA) - for applications in synthetic biology and bioanalysis. Modelling protein-ssRNA complexes (docking) is an arduous task due to the flexibility of ssRNA, which lacks a proper structure in its free form. Traditional docking methods sample the relative positions (poses) of 2 molecular structures and score them to select the correct (near-native) ones. It is not directly applicable here due to the absence of free ssRNA structures, nor is deep learning due to the too low number of known structures for training. Fragment-based docking (FBD), the state-of-the-art approach for ssRNA, docks all possible conformations of RNA fragments onto a protein and assembles their best-scored poses combinatorially. ssRNA'TTRACT, our FBD method, uses the well-known ATTRACT docking software, with its coarse-grained representation that replaces atom groups by one bead. Yet the RNA-protein parameters of ATTRACT scoring function (ASF) are not ssRNA-specific and require optimisation. Additionally, RRM-specific features can be learned and used to guide the docking. With my colleague H. Dhondge, we have developed a data-driven FBD pipeline for RRM-ssRNA complexes, as an updated version of an existing strategy. RRMs have two aromatic amino acids (aa) in conserved positions, each stacking with a nucleotide of the bound ssRNA. H. Dhondge collected all known RRM-ssRNA structures with such stacking and clustered them to obtain a set of prototypes for the 3D coordinates of such interactions in RRM. I then set up a docking pipeline with as input the RRM and RNA sequences and the identification of the stacked nucleotides. The pipeline retrieves the RRM structure from AlphaFoldDB, identifies possible 3D positions of the stacked nucleotides and runs ssRNA'TTRACT with maximal distance restraints toward each position. In parallel, we addressed the weakness of ASF for ssRNA by deriving HIPPO (HIstogram-based Pseudo-POtential), a new scoring potential for ATTRACT poses of ssRNA on RRM, based on the frequency of bead-bead distances in near-native versus wrong poses. It combines 4 distinct parameter sets (four Η) into a consensus scoring, to better account for the diverse RRM-ssRNA binding modes. Tested in a leave-one-out approach, HIPPO reaches a 3-fold enrichment of near-natives in 20% top-scored poses for ½ of the ssRNA fragments, versus ¼ with ASF. It even reaches a 4-fold enrichment for ⅓ of the fragments, versus 7% of the fragments with ASF. Surprisingly, HIPPO performed better than ASF also on a benchmark of non-RRM proteins, while trained only on RRMs. Most FBD approaches encounter inherent scoring issues, probably due to some fragments binding more specifically/strongly than others. To address this point, we examined the best-scored fragment per complex and found that HIPPO consistently selects more near-natives than ASF for this fragment. This inspired an incremental docking approach: the top-ranked poses of one fragment are used as a starting point to build a full RNA chain incrementally. This strategy eliminates the need for known conserved contacts, which have been required so far to obtain accurate models, making it generalizable to non-RRM proteins. Future research aims to identify the best-performing Η for each fragment, potentially using (deep) machine learning. Our workflow to derive scoring parameters is in principle applicable to any protein/ligand type and we plan to expand it to other RNA-binding protein domains, as well as ssDNA and long peptides
Hipper, Clémence. « Nature du complexe viral impliqué dans le mouvement à longue distance du virus de la jaunisse du navet ». Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAJ063/document.
Texte intégralIn the project, Turnip yellows virus (TuYV) transport in the phloem was analysed. The first objective was to identify the nature of the viral complex involved in vascular movement: virions and/or ribonucleoprotein complexes. Mutant viruses were modified in the capsid protein gene to inhibit formation of virions. By analyzing their movement in different host plants, in the absence or in the presence of the wild-type capsid proteins brought in trans, we demonstrated a strong relation between virion formation and virus long-distance movement. The second objective was to identify cellular partners of the TuYV-P4 protein, a putative movement protein which is host-specific. Two proteins were identified by screening a cDNA library of A. thaliana using the yeast two hybrid technique, and their function in the virus cycle was assessed by performing sub-cellular localizations and infection of A. thaliana KO mutants
Collet, Axelle. « Caractérisation des enzymes de formation de la coiffe du virus du Nil Occidental et du métapneumovirus humain ». Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4087.
Texte intégralMy PhD project is focus on the study of the enzymatic activities involved in the RNA capping pathway of two RNA viruses: the West Nile Virus (WNV) and the human metapneumovirus (hMPV). These viruses encode for enzymes allowing the addition of a cap-1 structure (m7GpppN2’Om) to their mRNA 5’ ends. The NS5 N-terminal domain (NS5MTase) of WNV harbours the N7- and 2’O-methyltransferase activities (N7- and 2’O-MTase); and it has been proposed that NS5MTase also bears a guanylyltransferase activity (GTase). I have identified residues involved in the NS5MTase interaction sites with their RNAs substrate. My assays demonstrate the importance of the cap-binding site for the 2’O-methylation but not for the N7-methylation. In parallel, I have tried to identify putative catalytic residues of the GTase activity by reverse genetics. Preliminary results suggest that NS5MTase K29 could be a catalytic residue.Concerning hMPV, I performed a functional analysis of CR-VI+ domain of the protein L. I demonstrated that the CR-VI+ domain harbours the N7- and 2’O-MTase activities and identified the residues involved in the mRNA recruitment. I showed that the methylation order is not canonical with the 2’O-methylation preceding the N7-methylation. Finally, I showed that the domain harbours an additional GTP hydrolysis activity, representing the first step of RNA cap formation for Mononegavirales.This work demonstrates that this MTase domains harbour 2 or 3 of the enzymatic activities required for viral RNA cap synthesis and represent attractive targets for the development of antivirals
Jarrige, Domitille. « Déchiffrer le "code OPR" pour une meilleure compréhension du rôle physiologique des protéines OPR ». Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS632.
Texte intégralFollowing endosymbiosis, the chloroplast genome shrunk and became reliant on the host genome for its expression. In Chlamydomonas reinhardtii, Octotricopeptide repeat proteins (OPR), encoded in the nucleus, control the expression of a specific organellar mRNA. The OPR repeat is a degenerate motif of 38 amino-acids, folding into a tandem of antiparallel α-helices which can bind to RNA. An individual OPR repeat is predicted to interact with one given nucleotide thanks to specificity-conferring residues at defined positions within the repeat. OPR proteins contain tracks of successive OPR motifs, thus they can bind to a specific RNA “target” sequence and act on it. I aimed to study this specificity, called the “OPR code”, starting with a draft code based on known OPR protein/mRNA couples. I mutated in vivo the chloroplast targets of some OPR factors to disrupt the OPR/RNA interaction, and then tried to restore it by mutating the specificity-conferring residues in the corresponding repeats. Surprisingly, OPR/RNA interactions seem very resilient, challenging our view of how the specificity is established in vivo. Complementary functional studies that I performed on the OPR factors MDB1 and MTHI1 revealed that chloroplast gene expression might rely on complex networks of nuclear factors. By cooperating those putative systems would be both more specific and more resilient
D'Ascenzo, Luigi. « Etude des réseaux de reconnaissance biomoléculaire à l'échelle atomique pour les systèmes ARN et ARN/protéines ». Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAJ108/document.
Texte intégralTogether with hydrogen bonds, uncommon non-covalent interactions are fundamental for recognition networks in RNA and RNA-protein systems. Among them, I focused on oxygen-pi stacking. This interaction takes the form of phosphate-pi within U-turns and of ribose O4’-pi within “Z-RNA” motifs. In that respect, a novel classification of tetraloops is proposed, defining U-turns and Z-turns based on their oxygen-pi stacking properties. Further, “Z-like” motifs are found to pervade small and large RNAs, being also a recognition pattern for immunology-related proteins. To better understand biomolecular recognition networks, we reviewed the binding of metal ions and anions within RNA, finding many examples of ions misattribution in PDB structures. We propose rules to avoid attribution errors. The results of this thesis will improve our knowledge and understanding of biomolecular recognition networks, as well as assist structural determination and structural modelling techniques of RNA systems
El, Meshri Salah Edin. « Etude du trafic intracellulaire de la protéine Gag du VIH et rôle de son domaine NCp7 ». Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAJ025/document.
Texte intégralThe Gag structural polyprotein of HIV-1 orchestrates viral particle assembly in producer cells, in a process that requires two platforms, the genomic RNA on the one hand and a membrane with a lipid bilayer, on the other. During its transportation from translating ribosomes to plasma membrane, Gag hijacks cellular proteins of the cytoskeleton and the ESCRT proteins like TSG101, Alix, etc., to egress viral particles. However, a number of questions remain to be answered before they are clearly apprehended. In this thesis, , we studied the role of the NC domain alone or as part of Gag (GagNC) in Gag-Gag and Gag-TSG101 interactions, which are essential for the assembly and budding of HIV-1 particles using quantitative fluorescent microscopy and biochemical approach. Results, showed that the absence of NC domain lead to (1) an accumulation of Gag as large aggregates that are dispersed in the cytoplasm, (2) a decrease of Gag-Gag condensation and (3) a delay for Gag-Gag complexes in reaching the PM, (4) improved interaction between Gag and TSG101, and (5) by its virtue in Gag trafficking docks TSG101 to the PM. This regulatory effect of NCp7 domain in either TSG101 or Gag or both protein- regulated pathways during virus budding can be exploited to develop inhibitors targeting HIV-1
Schelcher, Cédric. « Détermination du mode d'action et des substrats de RNases P protéiques chez Arabidopsis thaliana ». Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAJ044/document.
Texte intégralRNase P is the essential activity that removes 5'-leader sequences from transfer RNA precursors. “PRORP” (PROteinaceous RNase P) defines a novel category of protein only RNase P. Before the characterization of PRORP, RNase P enzymes were thought to occur universally as ribonucleoproteins (RNP). The characterization of PRORP revealed an enzyme with two main domains, an N-terminal domain containing multiple PPR motifs and a C-terminal NYN domain holding catalytic activity. We used a combination of biochemical and biophysical approaches to characterize the PRORP / tRNA complex. The structure of the complex in solution was determined by small angle X-ray scattering and Kd values of the PRORP / tRNA interaction were determined by analytical ultracentrifugation. We also analyzed direct interaction of a collection of PPR mutants with tRNA in order to determine the relative importance of individual PPR motifs for RNA binding. This reveals to what extent PRORP target recognition process conforms to the mode of action of PPR proteins interacting with linear RNA. Altogether, our analysis reveals an interesting case of convergent evolution. It suggests that PRORP has evolved an RNA recognition process similar to that of RNP RNase P. Moreover, we also implemented a PRORP-RNA co-immunoprecipitation approach to determine the full extent of PRORP substrates
Malabirade, Antoine Baptiste. « Auto-assemblage de la protéine bactérienne Hfq, actrice du métabolisme de l’ARN : rôle structural du domaine C-terminal ». Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS234/document.
Texte intégralRNA-based regulations of gene expression allow quick and versatile responses from cells to changing environmental conditions. However, these regulations are often protein-mediated. The bacterial protein Hfq is one of the most studied RNA-based regulation partner. Found in various prokaryotes, it is an important virulence factor involved in many cellular processes. Hfq’s structure resembles a torus, formed by multiple β-sheets. Apart from this N-terminal region (NTR), a supplemental C-terminal region (CTR) with variable lengths and sequences may exist in some species. In E. coli, this specific region measures around 30 residues and is predicted as intrinsically disordered. Few studies focused on Hfq-CTR until recently.This work highlights new potential roles for Hfq-CTR. First, this region is able to self-interact and forms amyloid fibers which explains the self-assembled Hfq superstructures observed in vivo. Second, the protein can bind and efficiently condense DNA in vitro, strengthening the suggested role of Hfq in shaping the bacterial chromosome. This compaction is fully dependent on the CTR which is responsible for DNA bridging. Third, the CTR also gives to Hfq the ability to self-assemble on a lipid bilayer, explaining its membrane-localized fraction observed in vivo. The subsequent membrane reorganization might facilitate the release of RNAs in the extracellular medium, with potential implications on bacterial communication and interaction with surrounding cells and environment
Rekad, Zeinab. « Rôle de la protéine de liaison aux ARNs SAM68 dans l'adhésion des cellules endothéliales et la genèse de leur matrice extracellulaire ». Electronic Thesis or Diss., Université Côte d'Azur, 2023. http://www.theses.fr/2023COAZ6006.
Texte intégralAngiogenesis is the process underlying the formation of new blood vessels from pre-existing ones. This process relies on the modification of the adhesive properties of vascular endothelial cells as well as the production and assembly of their specialized extracellular matrix (ECM) known as the basement membrane. Endothelial cell adhesion is mediated by interactions between extracellular matrix (ECM) components and transmembrane receptors (integrins) that, upon engagement, drive the formation of dynamic multimolecular adhesion complexes that regulate cytoskeletal organization and force transmission (mechanotransduction) for cell migration and function. Recent studies suggest that local protein production at adhesion sites contributes to their consolidation and maturation.Proteomics screens performed on adhesion sites have identified the presence of RNA-binding proteins (RBP) with gene expression regulatory functions. SAM68 (Src associated in mitosis, of 68 kDa), a member of the STAR (signal transduction and activation of RNA metabolism) family of RBPs, is one such protein known to regulate both RNA biogenesis and signal transduction by playing a scaffolding role following receptor activation at the cell surface. Indeed, SAM68 has been shown to associate with Src kinase following receptor activation and to participate in alternative splicing of genes encoding ECM and ECM-associated proteins, such tenascin-C and the cell surface glycoprotein CD44 involved in adhesion/migration. In the context of angiogenesis and endothelial cell adhesion, we hypothesized that the RBP SAM68 may constitute a molecular relay during integrin-mediated mechanotransduction at adhesion sites by participating in the formation of focal adhesions and downstream transcriptional/post-transcriptional responses that regulates the angiogenic phenotype.Using 2- and 3-D cultures of primary endothelial cells, we showed that the RBP SAM68 participates in the establishment of focal adhesions through its contribution to the localized supply of mRNAs (including the β-actin transcript) required for adhesion site maturation. Further, we demonstrated that SAM68 regulates the expression of genes encoding basement membrane proteins, in particular via regulation of the promoter of the FN1 gene, thus conditioning the sub-endothelial matrix and angiogenic phenotype of cells. Indeed, in a 3-D context, SAM68-depletion was found to hamper endothelial cell sprouting activity and capillary-like tube formation.This work paves the way to explore the role of other RNA-binding proteins as regulators of adhesion signaling and assessment of their function in physiological and pathological angiogenesis processes
Chabrolles, Hélène. « Interaction de la protéine Core du virus de l’Hépatite B avec les protéines de liaison aux ARN : effets sur la réplication virale et perspectives thérapeutiques ». Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1321.
Texte intégralConverging evidences suggest that the Hepatitis B virus (HBV) core protein, beside its well-known structural role to form nucleocapsids in the cytoplasm, could have important regulatory functions in the nucleus of infected hepatocytes. Indeed, nuclear Core was shown to associate with the cccDNA and to the promoters of some cellular genes, suggesting that Core may control viral and/or cellular gene expression. In addition, Core has the capacity to bind RNA, and may thus regulate HBV RNA metabolism. To elucidate these functions, we performed a proteomic analysis of the cellular factors interacting with nuclear Core in human hepatocytes. This interactome revealed a majority of highly interconnected RNA-binding proteins (RBPs), which participate in several steps of mRNA metabolism, including transcription, splicing and nuclear egress. We focused on two major Core-interacting factors, SRSF10 and RBMX that were previously involved in splicing and DNA repair. Functional analyses performed by a siRNA approach indicated that RBMX and SRSF10 were able to differentially regulate the levels of all viral RNAs most likely by acting at different steps of the viral life-cycle. Similarly, a small compound, affecting the activity of selected RBPs, severely impaired HBV replication by strongly reducing viral RNA accumulation. Altogether, these results strongly suggest that Core interacts with some selected RBPs to control the fate of viral and/or cellular RNAs and provide new critical information for the development of novel host-targeting antiviral agents (HTA)
Raoelijaona, Raivoniaina. « Compréhension des rôles des complexes Nob1/Pno1 et RPS14/Cinap dans la maturation cytoplasmique de la petite sous-unité ribosomique (pré-40S) chez les eucaryotes ». Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0221/document.
Texte intégralRibosomes are translational machineries universally responsible of protein synthesis. In eukaryote, ribosome assembly is a complex and highly regulated process that requires coordinated action of more than 200 biogenesis factors. Ribosome assembly is initiated in the nucleolus, continues in the nucleoplasm and terminates in the cytoplasm. The cytoplasmic maturation events of the small ribosomal subunit are associated with sequential release of the late assembly factors and concomitant maturation of the pre-rRNA. During final maturation of the small subunit, the pre-18S rRNA is cleaved off by the endonuclease Nob1, which activity is coordinated by its binding partner Pno1. Detailed information on pre-ribosomal particle architectures have been provided by structural snapshots of maturation events. However, key functional aspects such as the architecture required for pre-rRNA cleavage have remained elusive. In order to better understand these late steps of cytoplasmic pre-40S maturation, we first redefine the domain organization of Nob1, then study its binding mode with Pno1 using different tools such as sequence analysis, structure prediction and biochemical experiments and, we then performed functional assay to elucidate the role played by Pno1 during the pre-18S rRNA maturation.Our results have shown that eukaryotic Nob1 adopts an atypical PIN domain conformation: two fragments (res 1-104 and 230-255) separated by an internal loop, which is essential for Pno1 recognition. We also found out that Pno1 inhibits Nob1 activity likely by masking the cleavage site. Our findings further support the recently published cryo-EM structure of the pre-40S, where Nob1 displays an inactive conformation. Moreover, 18S rRNA 3’-end cleavage has to happen and this implies structural rearrangement or requirement of some accessory proteins such as Cinap, an atypical kinase involved in pre-18S processing. Studying the interplay between proteins localized in the pre-40S platform (RPS14, RPS26, Nob1/Pno1 complex) has shown that Cinap is able to form a trimeric complex with Nob1 and its binding partner Pno1. Furthermore, Cinap can recognize RPS26 in a RPS14-dependent manner, which had already been studied with its yeast counterpart. It is important to note that RPS26 is the ribosomal protein replacing Pno1 in the mature ribosome. Our finding clearly suggests a mechanism where RPS26 recruitment to the ribosome requires Pno1 dissociation. This exchange would be carried out by Cinap. Therefore, we can suggest a simplified model as follow: upon binding with Pno1, the newly formed complex (Cinap/Pno1) will trigger a conformational change, which will allow the endonuclease Nob1 to reach its substrate (D-site) and perform its cleavage resulting in mature 18 rRNA generation
Genovese, Sara. « Emergence and regulation of cell hierarchy in a Drosophila model of neuro-developmental tumor ». Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0482.
Texte intégralIn hierarchical tumors, cancer stem cells (CSCs), at the top of the tumor hierarchy, can self-renew and differentiate in transient-amplifying progenitors (TAPs), with a limited self-renewal potential. Understanding the molecular mechanisms that drive tumor hierarchy and heterogeneity is crucial to develop effective therapies to eliminate CSCs. During development, Drosophila asymmetrically-dividing neural stem cells, called neuroblasts (NBs), sequentially express two antagonistic RNA-binding proteins, Imp and Syncrip (Syp), that respectively promote and repress NB self-renewal. Genetic perturbation of NB asymmetric division cause NB amplification and malignant tumors. By using lineage tracing, clonal analysis and stochastic mathematical modeling of tumor growth, we demonstrated that Imp+ progenitors act as CSCs. They are able to self-renew endlessly and differentiate in Syp+ progenitors, that have a limited self-renewal potential and the high tendency to undergo quiescence. NB tumors follow a rigid hierarchical organization, where the Imp-to-Syp transition is irreversible. Hence, Syp+ progenitors cannot revert to an Imp+ malignant state. Transcriptomic analysis revealed that the Imp-to-Syp transition in tumors induces a downregulation of glycolytic and respiratory genes that exhausts the growth and self-renewing potential of Syp+ progenitors. The striking conservation of these RNA-binding proteins opens the exciting possibility that analogous Imp-Syp hierarchies may exist in human cancers
Takeuchi, Akiko. « RNA-protein interaction in the selenoprotein synthesis machinery ». Strasbourg, 2009. http://www.theses.fr/2009STRA6054.
Texte intégralThe 21st amino acid selenocysteine is encoded by a UGA codon that usually signifies translational termination. Selenoprotein synthesis therefore requires specialized factors. Among these is SBP2 that binds the SECIS, a stem-loop structure in the 3’UTR of selenoprotein mRNAs. In structural analyses of SBP2, we isolated and functionally characterized Drosophila melanogaster SBP2. By comparing it with human SBP2, we identified an additional RNA binding domain that is essential for SECIS and 60S ribosomal subunit binding, and also enables SECIS structure selectivity. In addition, computational and biophysical analyses established that SBP2 is globally unfolded, supporting our hypothesis that SBP2 is an Intrinsically Disordered Protein and becomes folded in the presence of partners yet to be identified. Finally, we searched for potential partners of SBP2 and our results showed that the molecular assembly of selenoprotein mRNPs has many similarities with that of sn/snoRNPs
Munoz-Ruiz, Raphaël. « Novel aspects of TDP-43's interaction with ALS-related autophagy genes ». Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS268.
Texte intégralAmyotrophic Lateral Sclerosis (ALS) is a degenerative disease of motoneurons. Its histological hallmark is the presence of ubiquitin-positive cytoplasmic inclusions in motor neurons of patients which indicates defective proteostasis. In the majority of cases, these inclusions are positive for TDP-43, an RNA-binding protein. Alterations of autophagy and RNA metabolism are widely investigated in ALS. This thesis explores the role of TDP-43 on autophagy regulation with a focus on autophagy receptors p62 and OPTN and their upstream activator TBK1. In the zebrafish embryo, knockdown of tardbp leads to an altered motor phenotype and correlates with a downregulation of tbk1. Human TBK1 RNA ameliorates this phenotype in a significant manner. In SH-SY5Y cells, knockdown of TARDBP leads to a profile of expression of key autophagy genes that is in opposition with the one obtained in the zebrafish. However, activating basal autophagy through Torin 1 treatment unveils conditional effect of TDP-43 on p62/SQSTM1 and TBK1. Moreover, Torin 1 treatment inhibits binding of TDP-43 to RAPTOR and OPTN mRNAs but promotes novel binding to p62/SQSTM1 and TBK1 mRNAs. In these cell lines, increasing overexpression of TARDBP also seems to affect p62/SQSTM1 in different manners. Overall, modulating TARDBP expression is accompanied by the appearance of characteristic traits of TDP-43 pathology in ALS. In parallel, techniques to visualize target RNAs in vivo and in vitro are being developed. This work highlights TDP-43 ability to adapt to cellular context and affect autophagy in different manners
Ferhadian, Damien. « Structure de l'ARN au sein des ribonucléoprotéines des Influenzavirus A ». Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAJ066.
Texte intégralThe Influenzavirus genome comprises eight segments of single-stranded RNA of negative polarity packaged in viral ribonucleoproteins (vRNP). Genome segmentation complicates packaging as a full set of vRNPs is required needed for virus infectivity. It is now accepted that packaging is selective and involves interactions between the RNA components of vRNPs that likely depend on the RNA structure. Our goal was to characterize the binding of the viral protein NP, the major component of the vRNP, on in vitro transcribed RNA. We also developed an experimental strategy to determine the RNA structure inside the viral particles. Both parts of the project were addressed with chemical mapping experiments, that interrogates the flexibility of each nucleotide in the RNA structure. Our results show that NP possess an RNA chaperone activity and binds preferential sites. Our in viro approach demonstrate that using two chemical probes allow us to discriminate between RNA-RNA and RNA-NP interactions
Tabet, Ricardos. « Bases moléculaires de la physiopathologie du syndrome de l'X fragile ». Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAJ090.
Texte intégralFragile X syndrome is the leading cause of inherited intellectual disability and is due to the absence of the RNA binding protein FMRP (Fragile X Mental Retardation Protein). FMRP is proposed to bind and regulate synaptic expression of mRNA targets upon mGluR-I activation. Thousands of mRNA targets have already been proposed in the literature, but only a few have been validated leaving unsolved the question of the genes mostly affected by the absence of FMRP in the brain of fragile Xpatients. The main project of the thesis was to identify the mRNAs associated with FMRP in cortical neurons by performing cross-linking immunoprecipitation approach (CLIP). We found that FMRP principally targets one unique mRNA which encodes an important synaptic kinase. This enzyme controls the level of two second lipid messengers important for remodeling of dendritic spines. Consequently, the mGluR-I-dependant activation of the enzyme is lost in absence of FMRP, leading to several lipid species alterations in the neuron. These defects may explain the morphological and functional alterations of dendritic spines, the hallmark of fragile X syndrome
Gilbert, Agathe. « Impact of protein-protein interactions and phosphorylation on RNA decapping for nonsense mediated mRNA decay (NMD) ». Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS386.
Texte intégralIn yeast, mRNA degradation is mainly initiated through the cleavage of the pyrophosphate bond between the mRNA and the cap structure at its 5’-end. While this step is important for the decay of most mRNAs, it is particularly critical to initiate the degradation of unstable RNA, targets of the NMD machinery. This pathway allows degradation of transcripts that contain a premature termination codon and thus is entirely dependent on translation. First considered as conserved throughout eucaryotes due to high sequence similarity of its core factors – the Upf proteins -, the discovery of the Smg proteins in C. elegans (Page et al., 1999) and the description of the SURF/DECID mechanism depending on phosphorylation of Upf1 (Kashima et al., 2006) indicated a divergence of NMD mechanisms between organisms. However, recently our laboratory described two NMD complexes revolving around Upf1 – named Detector and Effector - and identified the protein kinase Hrr25 as a member of a Upf1-decapping complex (Dehecq et al., 2018). The conserved protein kinase Hrr25 is the yeast equivalent of mammalian casein kinase 1 (CK1delta and CK1epsilon) and is involved in major cellular processes, including tRNA modification, ribosome biogenesis, transcription elongation and meiosis (Abdel-Fattah et al., 2015; Ghalei et al., 2015; Ye et al., 2016; Nemec et al., 2019). I demonstrated that the Hrr25 kinase activity has a role in NMD that is independent of its function in mRNA translation and DNA transcription. The association of Hrr25 to Upf1 was dependent on the kinase activity of the protein and on the presence of the decapping enzyme Dcp2. We identified conserved serine residues located in the C-terminal region of yeast Upf1 whose phosphorylation was dependent on Hrr25 and was modulated, like the phosphorylation of Upf1 in other organisms, by the presence of other NMD factors, such as Upf2 and Ebs1 (SMG5/7 equivalent). These results indicate that protein kinases can modulate NMD by direct interactions with the enzymes involved in RNA degradation and suggest that, contrary to previous beliefs, protein kinases are universally required for NMD
Boudoukha, Selim. « Étude de la régulation post-transcriptionnelle de l’expression des gènes par la protéine de liaison à l’ARN IMP-2 au cours de la myogenèse ». Thesis, Paris 11, 2011. http://www.theses.fr/2011PA11T095/document.
Texte intégralThe RNA-binding proteins IMPs (IGF-II mRNA binding protein) first discovered in rhabdomyosarcoma cells (RMS) are expressed during embryonic development but their expression is decreased in adult tissues.We showed that IMPs and particularly IMP-2 are strongly expressed in mouse myoblatsts, during early regeneration of skeletal muscle in vivo and in and RMS. IMP-2 loss of function experiments using siRNA have shown that IMP-2 is necessary for microtubules stability(MTs), cell motility and invasion of myoblasts and RMS.Expression of IMP-2 specifically increases MTs stability by an enrichment of detyrosinated tubulin Glu-tubulin. Detyrosination is indispensable for myogenic differentiation and plays substantial role in tumor growth. Additionaly, MTs stabilization play an important role in focal adhesion remodeling, in cytoskeleton integrity, cell adhesion and cell motility.To get new insight into molecular mechanism underlying the function of IMP-2 in MTs stability and cell motility, full ranscriptome analysis was performed between IMP-2 knockdown (KD) myoblasts and control myoblatsts. We have further shown that IMP-2 controls the mRNA levels of many important mediators of cell adhesion such as PINCH-2, as well as multiple cytoskeleton remodeling, such as MuRF-3.We have identified a number of functionally relevant protein partners of IMP-2.Moreover subsequent RNAi screens have revealed the importance of IMP-2 regulated transcripts involved in cell motility and cell adhesion In conclusion, we show that IMP-2 dependent regulation of mRNA such as MuRF3 and PINCH2 largely contributes to the motility –deficient in IMP-2 KD cells. Moreover these results indicate clearly, that further analysis of IMP2 protein partners and RNA targets regulated by IMP-2 will help to characterized the function of IMP-2 and to propose a model of IMP-2 transcriptional regulation of gene expression in myoblasts and RMS cells
Martin, Sophie. « Le composant des granules de stress G3BP : caractérisation phénotypique de souris KO, et identification de son interactome ribonucléoprotéique dans le cerveau de souris ». Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20247.
Texte intégralRNA binding proteins (RBPs) are essential in the different steps of processing of the messenger RNAs (mRNAs), directing their localization and fate within the cell, and forming with them the ribonucleoprotein particles (mRNPs). mRNPs can assemble into dynamic cellular structures in which they are routed towards specific functions. RNA granules such as stress granules (SGs) contain translationally silenced mRNPs storing transiently repressed mRNAs.My thesis work consisted in the functional characterization of G3BP (RasGAP SH3 binding protein), an RBP that is expressed ubiquitously in both humans and mice and is involved in the assembly of SGs. Using classical homozygous recombination, viable G3BP1 knock out mice were generated that demonstrated short lifespan.and behavioral defects linked to the Central Nervous System (CNS), notably an ataxia phenotype. Electrophysiology experiments showed an alteration of synaptic plasticity in the hippocampus of KO mice. Therefore, I used Cross-Linking and Immunoprecipitation (CLIP) to purify from mouse brain a stable complex containing G3BP, and performed High-Throughput Sequencing (HITS-CLIP) to identify associated RNAs. Strikingly, most of the G3BP targets correspond to intron sequence-retaining transcripts and non-coding RNAs. My results also showed that G3BP1 depletion influences the stability of these premature transcripts in the cerebellum, which can be correlated to the ataxia phenotype of the G3BP1 KO mice. This comprehensive analysis suggests a new mechanism of gene regulation based on stabilization of silenced premature transcripts which might be converted to mature transcripts under stress condition and sequestration of G3BP in SGs
Bernard, Laure. « Regulation of heterochromatin by a pluripotency-associated long non coding RNA in mouse embryonic stem cells and in oocytes : implications for early embryogenesis ». Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS179.
Texte intégralHistone H3 Lysine 9 (H3K9) methylation, a mark of heterochromatin, is progressively implemented during development to contribute to cell fate restriction as differentiation proceeds. For instance, in mouse Embryonic Stem cells (mESCs) the global levels of H3K9 methylation are rather low and increase only upon differentiation. Conversely, H3K9 methylation represents an epigenetic barrier for reprogramming somatic cells back to pluripotency. How global H3K9 methylation levels are coupled with the acquisition and loss of pluripotency remains unknown. Here, we identify SUV39H1, a major H3K9 di- and tri-methylase, as an indirect target of pluripotency Transcription Factors (pTFs). We find that the pTFs OCT4 activates the expression of an antisense long non-coding RNA to Suv39h1, named Suv39h1as. In turn, Suv39h1as downregulates Suv39h1 expression via the modulation of the chromatin status of the locus and a possible alteration of Suv39h1 isoforms. The loss of Suv39h1as expression triggers increased SUV39H1 expression and H3K9me2/3 levels, leading to accelerated commitment into differentiation. We report, therefore, a simple genetic circuitry coupling the global levels of H3K9 methylation to pluripotency in mESCs. We also created a mouse line deleted for Suv39h1as expression and demonstrated that this regulation is also present during mouse oocyte maturation
Werner, Andreas. « Structural and biophysical studies of RNase P and RNA aptamers ». Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/restreint/theses_doctorat/2005/WERNER_Andreas_2005.pdf.
Texte intégralThe research in this Ph. D. Thesis is part of an ongoing effort to improve our understanding of RNA structure and stability: In the first part, an RNA aptamer is studied in complex with its target, the Sec7 domain of intracellular protein cytohesin-1. Aptamers are in vitro selected RNA molecules that have an affinity rivaling that of monoclonal antibodies, possess interesting pharmacological properties and are a powerful tool for functional analysis in vivo. We also present a systematic structural investigation of how aptamers and their natural counterparts bind their ligands in order to delineate common principles. In the second part, we study the counterion-induced collapse of prokaryotic RNase P RNAs by UV melting, with the goal of optimizing secondary and tertiary structure for crystallization. We demonstrate the utility of this method in two test cases: First, thermodynamic parameters are extracted from the kissing complex, a typical tertiary interaction found in many RNAs. This leads to the discovery that the ionic strength dependence may give clues about the structural transitions observed. Second, we study the effect of mutations on a more complex RNA, the IRES site of hepatitis C virus, and correlate UV melting data to a dynamic equilibrium between alternative structures. The lessons learned from these experiments are then applied to RNase P to disrupt specific tertiary interactions to facilitate crystallization. The effect of these mutations is investigated using both UV melting and a novel, fluorescence-based approach. Finally, crystallization screens are constructed using methods of experimental design, and a new approach for crystallization in gels is developed
Blond, Aurélie. « Synthèse orientée vers la diversité de cis-1,3-diamines pipéridiniques et cyclohexaniques : ligands potentiels d’ARN ». Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05P617.
Texte intégralMoissiard, Guillaume. « Induction, suppression, amplification of RNA silencing during viral infection ». Université Louis Pasteur (Strasbourg) (1971-2008), 2007. http://www.theses.fr/2007STR13023.
Texte intégralRNA silencing is a mechanism involved in the suppression of gene expression through nucleotide sequence-specific interactions mediated by RNA. A double-stranded RNA is processed by Dicer into 21- to 24-nt RNAs, called short-interfering (si)RNA that incorporate into a RNA-Induced Silencing Complex, to guide cleavage target mRNA in a sequence-specific manner. RNA silencing plays important antiviral role in plants. In parallel, most of phytoviruses produce suppressor proteins to counteract RNA silencing. RNA silencing can be amplified through the activity of the cellular RNA-dependent RNA polymerase (RDR). We studied RNA silencing during Cauliflower mosaic virus (CaMV) infection. We found that the four Arabidopsis Dicer-like (DCLs) proteins are involved to produce two classes of viral siRNAs. Then, we analysed the interactions between five silencing suppressors and RDR6 and identified the DCLs associated to RDR6. We also showed that, at least in some cases, RDR6 uses small RNAs as primers
Mamigonian, Bessa Luíza. « Investigation of the hepatitis C virus RNA polymerase NS5B in solution by nuclear magnetic resonance and its interaction with intrinsically disordered domain 2 of the NS5A protein ». Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10117/document.
Texte intégralNS5B is the hepatitis C virus (HCV) RNA-dependent RNA polymerase. This protein has been extensively studied by X-ray crystallography and shows an organization in three subdomains called fingers, palm and thumb. Whereas static crystallographic data are abundant, structural studies of this protein in solution are limited. Nuclear magnetic resonance (NMR) spectroscopy was used to study the 65 kDa NS5B in solution as well as its interaction with binding partners. It was characterized using selective isotopic labeling of isoleucine side-chain methyl groups, which gives rise to a simplified NMR spectrum with an improved signal-to-noise ratio. This characterization confirmed the presence of particular dynamics in the subdomains, especially in the thumb, as well as long-range effects that are transmitted through to other subdomains. Furthermore, this system was used to investigate the binding of the domain 2 of NS5A (NS5A-D2), a disordered domain of another HCV protein that has been shown to directly interact with NS5B in vitro. With paramagnetic relaxation enhancement experiments we showed that NS5A-D2 binds to NS5B via, at least, two binding sites on the thumb subdomain. As one of these sites was the binding site of allosteric inhibitor filibuvir, we characterized the binding of this small molecule to NS5B by NMR and found long-range effects of its binding throughout the polymerase. Finally, we studied the binding of a small RNA template strand to NS5B and found that both NS5A-D2 and filibuvir reduce but do not abolish the interaction between the polymerase and RNA. In sum, NMR spectroscopy was used to study dynamic properties of NS5B and its interactions with binding partners
Cattelin, Céline. « Exploration de la diversité des protéines à solénoïdes alpha, régulatrices de l'expression des gènes des organites dans les lignées eucaryotes photosynthétiques et étude de la dynamique conformationnelle des protéines à "PentatricoPeptide Repeats" ». Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS158.
Texte intégralIn Archaeplastida (photosynthetic eukaryotes that acquired a chloroplast following endosymbiosis with an ancestral cyanobacterium) the chloroplast and mitochondrial genomes of green algae and land plants are regulated post-transcriptionally, mainly by alpha-solenoid proteins encoded in the nucleus. These nuclear factors are composed of degenerate repeat motifs (PPR and OPR proteins, respectively pentatricopeptide repeat and octatricopeptide repeats) that interact specifically with part of their target RNA sequence and form large families of paralogs. PPR proteins are very abundant in terrestrial plants while OPRs are abundant in green algae. These differential expansions, in parallel with the evolution of RNA metabolism in organelles, may reflect genetic adaptations that preserve phototrophy under different conditions and ecological niches. In other Archaeplastids (red algae and Glaucophytes) and in eukaryotes that originate from endosymbiosis with an ancestral microalga such as the Diatoms, the regulation of organelle genomes remains poorly explored. A first objective of my thesis was to describe the diversity and evolutionary dynamics of known or candidate alpha-solenoid proteins for the regulation of organelle genome expression in all photosynthetic eukaryotes. To identify them, I developed an approach that combines distant sequence homology detection and sequence similarity independent classification. I validated this approach by finding and completing the known OPR and PPR families in the model species Chlamydomonas reinhardtii and Arabidopsis thaliana. I showed that OPR expansions were restricted within Chlorophytes and that outside of green algae and land plants, PPR and OPR proteins were few in number, suggesting that other players in the regulation of organelle genome expression remain to be discovered. I also identified several dozen other families of organelle-addressed alpha-solenoid proteins in all the proteomes studied, some of which have as yet unknown functions and whose experimental characterisation in model organisms would be relevant. In a second step, I used molecular dynamics approaches to better understand the affinity and specificity of binding between PPRs and their target RNAs. In particular, I studied the dynamics of the repeat motifs and the geometry of the nucleotide binding sites as a function of their position in the PPR motif sequence, including the effects of the number of repeats and the presence or absence of N- and C-terminal domains, in addition to the evolution of the overall conformation of the protein. Our results suggest the role of PPR protein flexibility, both at the protein and motif level, in binding to its RNA target and its relevance to the affinity and specificity of nucleotide recognition
Parmentier, Delphine. « Fonction de la protéine Tex chez Staphylococcus aureus : un lien potentiel avec les ARN régulateurs ? » Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAJ090/document.
Texte intégralS. aureus RNAIII is considered as a master regulator of virulence gene expression. The RNA regulates gene expression at the post-transcriptional level allowing repression of surface proteins and activation of exotoxins. In vitro pulled-down experiments led to the identification of two proteins interacting with RNAIII, the endoribonuclease III (RNase III), known to degrade RNAIII‐mRNA duplexes and Tex. Tex (Toxin Expression) is an ortholog of the eukaryotic protein Spt6, known to be involved in transcriptional and post‐transcriptional regulation. It is composed of two DNA binding domains (HtH and HhH) and two RNA binding domains (S1 and YqgF). To decipher the RNA binding capacity of Tex, we have constructed a variant of the protein lacking the putative RNA‐binding domain S1 (TexΔS1), and analyzed the binding properties of both the wild type and the Tex‐ΔS1 protein by different in vitro techniques. Indeed Tex recognizes preferentially unpaired A/U rich sequences of several regulatory RNAs, and that the S1 domain is per se, the RNA‐binding domain. However, other domains of Tex seem to be also involved in RNA binding. To better define the function of Tex in vivo, we inserted an intron into the coding region of tex. Wild type and mutant strains grew at the same rate in rich and minimal media, meaning that Tex is not essential. On the other hand, mutated strains produced more biofilm than the wild type strains, suggesting a role of Tex in virulence. Finally, a combination of immunoprecipitation and proteomics experiments highlighted a possible role of Tex in the regulation of virulence factors expression at the transcriptional and/or posttranscriptional level during the transition from colonisation to invasion of the host
Floriot, Océane. « Virus de l’Hépatite B et transcription cellulaire : impact de la protéine HBx et de ses interactions avec les ARNs non-codants ». Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1319/document.
Texte intégralHepatitis B virus (HBV) remains a major health problem worldwide despite the availability of the vaccine. No cure is available for the 240 million peoples chronically infected with HBV that are at risk to develop liver cirrhosis and hepatocellular carcinoma (HCC). Viral suppression, achieved by long term treatment with nucleotides analogues (NUCs), impacts on liver fibrosis and prevents liver decompensation but HCC risk is not reduced in the first 5 years of treatment. HBV is a small hepatotropic virus with a partially double strand DNA (rcDNA) genome. After hepatocyte infection the rcDNA is converted into the cccDNA episome that is then organized into a viral minichromosome that is the template for all viral transcripts and initiates replication. The hepatitis B x protein (HBx) is recruited on the cccDNA and is required to launch and maintain cccDNA transcription. HBx has also been shown to directly target cellular genes and this has been related to HCC development.We used a ChIP-Seq approach to determine the full repertoire of HBx genomic targets in HBV replicating cells. HBx targets include both protein coding genes and ncRNA (75 miRNAs and 34 lncRNAs). We showed that HBx represses a subset of miRNAs that would negatively regulate viral replication (i.e. miR-24) and miRNAs involved in HCC development (i.e. miR-21). Among the HBx targeted lncRNAs we focused DLEU2, which is strongly upregulated in HBV infection and HCC. We further showed that DLEU2 binds both HBx the Ezh2 histone methyltransferase, the catalytic subunit of the repressive PRC2 complex. The interaction with DLEU2 and HBx re-wires Ezh2/PRC2 functions leading to the constitutive activation of a subset of Ezh2 target genes that are normally kept in a repressed state. We also showed that HBx interaction with DLEU2 occurs on the cccDNA minichromosome where it boosts HBV transcription/replication. Finally, we characterized by ATAC-Seq HBV imposed changes of chromatin accessibility in primary human hepatocytes
Uchikawa, Emiko. « A structural approach of RNA-protein recognition and kinetics of binding in two examples : tRNA aminoacylation by arginyl-tRNA synthetase and 7SK stabilization by LaRP7 ». Strasbourg, 2011. http://www.theses.fr/2011STRA6052.
Texte intégralIn the cell, RNA-protein interactions are fundamental to many processes involved in the regulation of gene expression, including pre-mRNA splicing, polyadenylation, editing, transport, cytoplasmic targeting, mRNA turnove and translation. In addition to these post-transcriptional processes, RNA-prote in interactions may also play a key rôle in transcription. Indeed, in addition to its coding capacity, which makes both DNA and RNA recipients of the genetic message, the high variability and conformationnal flexibility of RNA structure creates a number of unique binding sites and the potential for complex regulation by RNA binding proteins. These use a large Iibrary of structural modules in order to recognize RNAs in a combination of sequence- or structure-dependent ways, leading to a wide range of transient to more stable interactions. This manuscript describes our endeavour to reveal the details of RNAprotein interactions at the molecular level in several examples taken in two different fields of cell biology, transcription and translation. Our targets were chosen to better understand the molecular foundation of interactions critical for the cell survival, and represent different binding modes ofproteins to RNA. Aiming to use X-ray crystallography, a well-accepted and reliable mean to analyze recognition details at atomic resolution, we developed for each target a purification protocolleading to homogeneous preparations that were used for crystallization and subjected to various anai}'ses, including functional assays and biophysical characterization
Nguyen, Chi Mai. « Post-transcriptional regulation during spermatogenesis : Role of the RNA-binding protein hu ». Toulouse 3, 2008. http://thesesups.ups-tlse.fr/365/.
Texte intégralSpermatogenesis, the elaborate process by which sperm are produced, is marked by dramatic proliferation and differentiation. During the late steps of spermatogenesis, transcription suddenly ceases prior the end of differentiation, because of drastic epigenetic modifications that result in chromatin compaction. Thus, haploid germ cells make use of extensive temporal mRNA storage and translation regulation to ensure stage-specific protein synthesis. Factors and cellular compartments involved in these post-transcriptional controls are still poorly understood. During my PhD, I hypothesized that the two RNA binding proteins HuR/ELAVL1 and AUF1/hnRNP D, might play a role in these controls. They bind AU-rich element-containing mRNAs (ARE-mRNAs) in somatic cells and regulate their stability and translation: HuR protects ARE-mRNAs from degradation and favours their translation, whereas AUF1 usually induces their degradation. First, to investigate the contribution of HuR and AUF1 to the post-transcriptional mechanisms occurring in germ cells, I used transgenic mice derived in our laboratory overexpressing HuR (HuRtg) and AUF1 (AUF1tg) in their testes. Strikingly, whereas spermatogenesis proceeded normally in AUF1tg mice, HuR overexpression impaired spermatogenesis, revealing the importance of a regulated expression of HuR to fulfill male germ cell differentiation. The comparative analysis of AU-transcriptome of pre-pubertal wild type testes with that of HuRtg and AUF1tg testes, combined with computational analyses and RNA/Protein immunoprecipitation experiments, revealed that these two proteins regulate different targets mRNAs and thus exhibit different activities. .
Frenal, Karine. « Caractérisation structurale et fonctionnelle de TgDRE : une enzyme de réparation de l' ADN du parasite Toxoplasma gondii ». Paris 6, 2006. http://www.theses.fr/2006PA066031.
Texte intégralSgro, Jean-Yves. « Etude structurale du RNA et de la protéine du virus de la mosai͏̈que du brome et de leur interaction par pontage covalent ». Grenoble 1, 1986. http://www.theses.fr/1986GRE10047.
Texte intégralSubissi, Lorenzo. « Biochemical insights into SARS-CoV replication ». Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5002.
Texte intégralThis work focused on the enzymatic machinery involved in Severe Acute Respiratory Syndrome-Coronavirus (SARS-CoV) RNA replication and transcription. Firstly, I established a robust in vitro polymerase assay with the canonical SARS-CoV RNA-dependent RNA polymerase (RdRp) nsp12. I showed that nsp12, in order to engage processive RNA synthesis, needs two viral proteins, i.e. nsp7 and nsp8. This nsp7/nsp8 complex not only activates nsp12-RdRp, but also acts as a processivity factor. Thus, using this processive polymerase complex, I could investigate SARS-CoV proofreading for which only indirect evidences were reported. Indeed, coronaviruses encode for a 3'-5' exonuclease (nsp14-ExoN), putatively involved in a mechanism that proofreads coronavirus RNA during viral replication. We first showed in vitro that nsp14-ExoN, which is stimulated by nsp10, is able to excise specifically dsRNA as well as all primer/templates bearing a 3' mismatch on the primer. Moreover, we could confirm by sequencing that a RNA 3' mismatch was indeed corrected in vitro by the nsp7/nsp8/nsp12/nsp14 complex. We provide for the first time direct evidence that nsp14-ExoN, in coordination with the polymerase complex, is able to proofread RNA. Interestingly, using this in vitro system we found an element that could possibly explain the inefficacy of ribavirin therapeutic treatment on SARS-patients: ribavirin, which is incorporated by the SARS-CoV polymerase complex, would also be excised by nsp14. In conclusion, this system will drive future development of antivirals, particularly of the nucleoside analogue type, against coronaviruses
Richard, Charles-Adrien. « La protéine M2-1 du virus respiratoire syncytial : structure et interactions avec des partenaires viraux et cellulaires ». Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLV029.
Texte intégralRespiratory syncytial virus (RSV) is the leading cause of lower respiratory tract illness in infants and calves. The RSV genome consists of a single strand, negative-sense RNA, which is replicated and transcribed by the viral RNA-dependent RNA polymerase complex (RdRp). This complex is composed of the nucleoprotein N, the large protein L, the phosphoprotein P and the transcription anti-terminator M2-1. The aim of this work was to better characterize the structure and function of P and M2-1.M2-1 is a tetramer with 4 domains: a zinc-finger, a helical oligomerization domain, a flexible region, a RNA and P binding core domain and a C-terminal disordered region. Based on the crystal structure of the full-length M2-1 protein, I identified residues in the zinc-finger and the flexible loop critical for M2-1 antitermination activity.Then I identified a region of P critical for P – M2-1 interaction and show that it is required for the recruitment of M2-1 to cytoplasmic inclusion bodies. I also show that M2-1 dephosphorylation, which is critical for viral transcription, is modulated by a complex formed by P and the cellular phosphatase protein-1 (PP1).Finally cyclopamine, a natural chemical compound, inhibits the RSV replication. I show that a single R151K mutation in M2-1 is sufficient to confer virus resistance to cyclopamine. These data open a new avenue for the development of future therapies against RSV infection
Meznad, Koceila. « Interaction entre l’oncoprotéine E6 d’HPV16 et le métabolisme des ARN messagers ». Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCE012.
Texte intégralHuman papillomaviruses (HPV) are double strand DNA viruses that infect skin and mucosa. HPV infections, although mostly asymptomatic, cause cell proliferation defects that can sometimes give rise to cancer. According to their carcinogenic potential, we distinguish low-risk HPVs (lr-HPV) causing benign lesions, and high-risk HPV (hr-HPV) responsible for the appearance of numerous anogenital and some head and neck squamous-cell cancers. Among the hr-HPV, HPV16 is the most prevalent. Hr-HPV-induced carcinogenesis is correlated with the expression of the viral oncoproteins, E6 and E7, which deregulate many cellular processes. Viral gene expression, performed by the host cell machine, is finely regulated particularly at the post-transcriptional level. Besides, alternative splicing generates about twenty viral transcripts, leading to the expression of viral proteins. The splicing within the E6 open reading frame that generates an E6*I mRNA only in hr-HPV, but not in the lr-HPV, suggests its involvement in hr-HPV-induced carcinogenesis. However, the biological role of E6*I protein produced by HPV-HR is still controversial.In order to better understand the mechanisms of hr-HPV-induced carcinogenesis, we have interested in: (i) the study of the biological functions of the E6*I isoform, and (ii) the mechanisms involved in the regulation of E6 and E7 expression.To get insight the biological role of HPV16 E6*I, we used RNA sequencing to identify targets deregulated by its ectopic expression. Expression of HPV16 E6 and E6*I isoforms in negative HPV cells deregulate several transcripts involved in biological processes related to viral gene expression, viral carcinogenesis, signal transduction and translation. The expression of E6*I alone, deregulates transcripts involved in the organization of the extracellular matrix, signaling pathways and cell adhesion. Interestingly, it was shown that the genes deregulated by E6*I expression are commonly affected by the intracellular level of ROS (reactive oxygen species). These results support the role of E6*I in increasing ROS production. The ROS-associated oxidative stress could favor viral genome integration with that of the host cell, a characteristic of hr-induced carcinogenesis. In sum, E6*I may have an oncogenic role independent of E6, and intervene in the carcinogenesis associated with hr-HPV.We also studied the role of the exon junction complex (EJC) in the posttranscriptional regulation of E6 and E7 expression. EJC is a multiprotein complex deposited on mRNAs via splicing, thus influencing their fate. We have shown that a factor of EJC, eukaryotic initiation factor 4A3 (eIF4A3), binds to viral mRNAs. Moreover, we have observed that the components of the EJC affected, in different ways, the expression of E6 and E7. Finally, we also studied the effect of nonsense-mediated mRNA decay (NMD), a mechanism linked to the EJC, on the expression of E6 and E7. Our results suggest that not only NMD inhibits the expression of E6 and E7, but we have also observed that HPV16 E6 protein reduces NMD activity. This inhibition would allow HPV16 to have control over its transcripts but also to affect NMD cellular targets. Given the involvement of NMD-regulated genes in the maintenance of cellular homeostasis and adaptation, it would be interesting to understand the role of this new E6 activity in carcinogenesis associated with HPV-HR
Sourimant, Julien. « Caractérisation structurale et fonctionnelle de la polymérase du virus respiratoire syncytial ». Thesis, Versailles-St Quentin en Yvelines, 2015. http://www.theses.fr/2015VERS019V.
Texte intégralRespiratory syncytial virus (RSV) is the leading cause of calves bronchopneumonia andinfants bronchiolitis. Neither vaccine nor antiviral treatments are currently available for use inhumans. Viral genome is replicated and transcribed by a set of viral proteins constituting theviral RNA-dependent RNA polymerase (RdRp) complex: the nucleoprotein (N), thephosphoprotein (P), the transcription factor (M2-1) and the large subunit (L). This workaimed to unveil new structural and functional data regarding the viral RdRp, especially the PLcouple. With this aim in view, I have first conceived a protocol to produce and purifyrecombinant L and P proteins expressed in insect cells. This tool enabled the fine mappingand characterization of the L binding domain of the RSV phosphoprotein. This highlightedthe interaction between the L protein and the C-terminal region of the P protein, especiallyresidues 216 to 239. Further data suggests that this area constitutes an alpha helix formingmolecular recognition element (« MoRE ») during P-L interaction. Furthermore, this studyunveiled a new region of the P protein encompassing residues 164 to 205, involved in therecruitment of L protein to viral inclusion bodies. These new results open the way toupcoming structural studies of RSV RdRp and allow us to define a new target for thedevelopment of antiviral drugs against RSV
Bruzzone, Lucía. « A crosstalk between the RNA binding protein Smaug and the Hedgehog pathway links cell signaling to mRNA regulation in drosophila ». Thesis, Sorbonne Paris Cité, 2018. https://theses.md.univ-paris-diderot.fr/BRUZZONE_Lucia_1_va_20180319.pdf.
Texte intégralPost-transcriptional regulation of gene expression plays a critical role in a variety of cellular processes during development. RNA binding proteins are fundamental mediators of post-transcriptional regulations that control mRNA expression by recognizing specific cis acting elements within the target transcripts. Smaug is a highly conserved sequence specific RNA-binding protein that is essential during Drosophila early embryogenesis. Smaug binds Smaug Recognition Elements (SRE) in the target mRNA and recruits additional factors, via protein-protein interactions, that regulate the bound mRNA. An emergent concept that signaling pathways can modulate RBP activity by post-translation modifications adds a new layer in the control of gene expression. During my thesis work, I sought to understand how the Hedgehog pathway regulates Smaug by promoting its phosphorylation. My work shows that HH signaling downregulates Smaug protein levels affecting its ability to repress mRNA translation. This negative effect seems to be dependent on the interaction between Smaug and the HH signal transducer Smoothened. Moreover, Smaug is constitutively phosphorylated in its RNA binding domain, which appears to be necessary for cytoplasmic Smaug foci formation
Seissler, Tanja. « Inhibition traductionnelle du facteur de restriction APOBEC3G par la protéine Vif du VIH-1 : rôle d'une uORF dans la 5'-UTR de l'ARNm d'A3G et identification de facteurs cellulaires ». Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAJ028.
Texte intégralThe HIV-1 Vif protein counteracts the restriction factor APOBEC3G (A3G) by downregulating its expression level in infected cells. This is achieved in different ways, one of which is translational inhibition, a mechanism that is still poorly understood. The first part of my thesis contributes to the characterization of a small upstream ORF (uORF), that is found in the 5'-UTR of A3G and A3F mRNAs. This uORF has been found to be crucial for regulation of A3G translation and is necessary to allow Vif-mediated translational inhibition. In the second part of this thesis, different protocols have been set up in order to identify A3G mRNA-associated cellular proteins which might play a role in the mechanism of Vif-mediated translational inhibition. Several proteins, whose presence on A3G mRNA seems to be modulated by Vif have been identified
Delbianco, Alice. « Molecular mechanisms involved in the pathogenesis of beet soil-borne viruses ». Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01017177.
Texte intégralGuerrero, Santiago. « Role of HIV-1 Vif in viral replication : translational regulation of APOBEC3G and RNA chaperone activity ». Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAJ060/document.
Texte intégralThe HIV-1 viral infectivity factor (Vif) is a small basic protein essential for viral fitness and pathogenicity. Vif allows productive infection of non-permissive cells (including most natural HIV-1 targets) by counteracting cellular cytosine deaminases APOBEC3G (A3G) and A3F by different mechanisms and thus preventing its incorporation into viral particles. The Vif-induced degradation of A3G through the proteasome pathway has been extensively studied, but little is known about the translational repression of A3G mRNA by Vif. After cellular co-transfection of A3G mRNA constructs mutated in their untranslated regions (UTRs) in presence or absence of Vif, and in conditions where the proteasome-induced degradation of A3G was inhibited, we show that the 5’-UTR of A3G mRNA is crucial for the translational inhibition by Vif. The core binding factor, CBF-, required to stabilize the Vif/A3G complex is dispensable for this specific repression. According to our previous secondary structural model of the 5’-UTR, the two distal stem-loop structures are sufficient for a complete translational inhibition of A3G. We show that residue K26 of Vif is critical for A3G neutralization, both for its proteasome-induced degradation and translation inhibition of itsmRNA. Interestingly, we observe a strict correlation between the cellular reduction of A3G through translation inhibition and the quantity of A3G incorporated into viral particles. Both mechanisms account for about 50% decrease of A3G in cell. Thus, we showed for the first time that A3G mRNA translational inhibition by Vif is a 5’-UTR mRNA-dependent mechanism, and that any of these two mechanisms, degradation or translation, is sufficient to restore viral infectivity. Regulating the translation of A3G could thus be considered as a new target to restore a functional expression of A3G and viral restriction