Teses / dissertações sobre o tema "Maturation ribosomique"
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Soudet, Julien. "Étude de la maturation cytoplasmique de la petite sous-unité ribosomique chez Saccharomyces cerevisiae". Toulouse 3, 2009. http://thesesups.ups-tlse.fr/2286/.
Texto completo da fonteRibosomes constitute one of the major actors of the mechanism of translation in any living cell. The synthesis of ribosomes is a complex process beginning with the transcription of a pre-ribosomal RNA (rRNA) containing future mature rRNAs as well as sequences that are eliminated during ribosome biogenesis. In Saccharomyces cerevisiae, no less than 200 factors are implicated in this process. We were more precisely interested in the cytoplasmic step of the small ribosomal subunit maturation consisting of an endonucleolytic cleavage of the 20S pre-rRNA contained in a pre-40S particle and leading to the mature 18S rRNA contained in the 40S ribosomal subunit. The initial model was that 40S ribosomal subunit maturation might be a pre-requisite for translation initiation. Our experiments have led to the observation that a fraction of 20S pre-rRNA co-sediments with 80S complexes and polysomes. This 20S pre-rRNA fraction can be increased in mutants impaired in the cytoplasmic step of 40S ribosomal subunit maturation. By biochemical approaches, we confirmed the occurrence of ribosomes containing pre-40S particles and mRNAs. Thus, our data suggest that pre-40S particles can initiate translation. These aberrant ribosomes are then degraded via the No Go decay pathway involved in the quality control of some cytoplasmic RNAs. No-Go Decay would function as an ultimate quality control mechanism of the 40S ribosomal subunit
Pintard, Lionel. "Spb1p est une méthylase de levure impliquée dans la maturation des ARNr". Montpellier 1, 2000. http://www.theses.fr/2000MON1T019.
Texto completo da fonteLouvet, Emilie. "Dynamique et compartimentation de la machinerie de maturation des ARN ribosomiques en cellules vivantes". Paris 5, 2005. http://www.theses.fr/2005PA05S025.
Texto completo da fonteThe functional organisation of the nucleus depends on machineries that are distributed in domains named nuclear bodies. To understand how this distribution is regulated we have chosen the nucleolus as example. We have focused our attention on traffic and compartmentation of the rRNA processing machinery during interphase and mitosis. To follow proteins in living cells we have used microscopy technologies such as: FRAP, videomicroscopy and tdFLIM-FRET. A reversible system capable of disconnecting the processing from the transcription machineries during interphase permitted us to show that the processing machinery can be disconnected from the transcription sites and accumulates in nuclear masses originating from the nucleolar granular component. We named these granular masses. This reversible process permitted us to study reformation of the nucleolus. In control cells and in an assay using permeabilized cells set up in the laboratory, we have shown that nucleolar reformation depends on ATP hydrolysis and that CK2 is involved in nucleolar compartmentation. At the exit of mitosis, we have shown that early and late processing machineries pass through the same PNB. The convergence of the machineries in a single site could be at the origin of PNB formation. Furthermore, we have demonstrated that Nop52 and B23 interact in the same PNB. For this reason, we propose that PNB are preassembly platforms for rRNA processing complexes
Bousquet-Antonelli, Cécile. "Caracterisation de partenaires fonctionnels de la proteine garlp de saccharomyces cerevisiae requise pour la maturation du pre-arn ribosomique". Toulouse 3, 1998. http://www.theses.fr/1998TOU30058.
Texto completo da fonteBaudin-Baillieu, Agnès. "Contribution a l'etude systematique du genome de la levure saccharomyces cerevisiae et analyse fonctionnelle d'un nouveau gene implique dans la maturation de l'arn ribosomique". Paris 11, 1997. http://www.theses.fr/1997PA112085.
Texto completo da fonteRaoelijaona, 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.
Texto completo da fonteRibosomes 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
Halladjian, Maral. "Etude de la fonction de l'hélicase Prp43 dans la synthèse des ribosomes et des connexions entre synthèse et maturation du pré-ARN ribosomique chez la levure". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30156.
Texto completo da fonteIn eukaryotic cells, ribosome synthesis begins with the transcription of ribosomal DNA (rDNA) by RNA polymerase I (Pol I). This process generates a primary transcript (pre-rRNA), containing the sequences corresponding to the mature 18S, 5.8S and 25S rRNAs. The fourth rRNA (5S) is transcribed independently by RNA Pol III. The pre-rRNA associates co-transcriptionally with some ribosomal proteins and many maturation factors to generate a large initial pre-ribosomal particle called the 90S particle. This particle undergoes a complex maturation process generating the pre-40S and pre-60S particles that will generate the mature ribosomal subunits. The first part of my thesis work consisted in the study of the Rpf2-Rrs1 heterodimer in yeast. This heterodimer is known to be essential for the maturation of pre-60S particles through the recruitment of the 5S RNP, a module containing the 5S rRNA associated to ribosomal proteins RpL5 and RpL11. We showed that Rpf2 and Rrs1 interact with rDNA chromatin using chromatin immunoprecipitation (ChIP) experiments and that this interaction does not depend on the integrity of the pre-ribosomal particles. Moreover, both Rpf2 and Rrs1 interact with Pol I subunits and with several rDNA chromatin-associated factors in vivo. These data suggest a function of the Rpf2-Rrs1 heterodimer in the regulation of Pol I transcription in addition to its role in the maturation of pre-60S particles. Interestingly, we observed using Miller spread experiments that loss of expression of Rpf2 or Rrs1 is correlated with strong perturbations in the organization of rDNA units. Using the "run-on" experiment, a technique allowing to determine the occupancy of active polymerases on the rDNA units, I further showed that loss of expression of Rpf2 or Rrs1 strongly affects Pol I transcription in yeast cells. Additional experiments suggest that the Rpf2-Rrs1 complex is present on rDNA units in absence of Pol I transcription in vivo and interacts with purified Pol I in vitro. These data strongly suggest that the Rpf2-Rrs1 heterodimer is a prime candidate to plays a crucial role in the functional coupling between rDNA transcription and pre-ribosome assembly in yeast cells. The second part of my thesis work focused on the study of the Prp43 helicase in yeast. Prp43 is a helicase from the DEAH/RHA family required for both the synthesis of ribosomes and the splicing of pre-mRNAs. Prp43 interacts with G-patch domain-containing proteins which activate its enzymatic activity in vitro by an unknown mechanism. During my thesis, we showed that the activation of Prp43 by G-patch proteins seems to be linked to the unique nucleotide binding mode of this helicase family. Previous structural data showed that the base of the ATP molecule is stacked between two residues, R159 of the RecA1 domain and F357 of the RecA2 domain in the active site of Prp43. The in vitro study of a Prp43 mutant bearing a substitution of F357 to an alanine (F357A) showed that the lack of stacking of the nucleotide base to the F357 residue uncouples the NTPase and helicase activities of Prp43 in vitro. In contrast the substitution of R159 to an alanine (R159A) reduced both the ATPase and helicase activities of the enzyme. We observed in addition that the Prp43 R159A mutation induces the same phenotype as the one resulting from the absence of Gno1, one of the G-patch domain-containing partners of Prp43. This result strongly suggests that the processing defects observed in the absence of Gno1 result from a failure to activate the Prp43 helicase. Overall we propose that the stacking of the ATP base between residues R159 and F357 is important for the activity and regulation of this helicase family
Al, Kadri Yasmine. "Étude de la fonction du complexe Bms1p/Rcl1p dans les étapes précoces de la synthèse des ribosomes et des connexions entre synthèse et maturation du pré-ARN ribosomique chez Saccharomyces cerevisiae". Toulouse 3, 2014. http://www.theses.fr/2014TOU30099.
Texto completo da fonteIn eukaryotic cells, ribosome synthesis begins with the transcription of ribosomal DNA (rDNA) by RNA polymerase I (Pol. I) in the nucleolus. This transcription generates a primary transcript precursor to the mature 18S, 5. 8S and 25S. This transcript is co-transcriptionally associated with some ribosomal proteins, many assembly and maturation factors and a set of small ribonucleoprotein particles to generate a giant initial pre-ribosomal particle. This particle undergoes a complex maturation process which begins in the nucleolus and ends in the cytoplasm where the formation of mature ribosomal subunits occurs. Ribosome synthesis is one of the most energy-consuming cellular processes; it must be highly regulated and tightly coordinated with other fundamental cellular processes. As previously mentioned, ribosome synthesis involves around 200 dedicated to the assembly and maturation of pre-ribosomal particles. However, the function of the vast majority of them is still unknown and current challenges in the field are to understand their precise molecular role. Part of my thesis work consisted in the study of the structure / function of the Bms1p/Rcl1p complex involved in ribosome synthesis in yeast. Rcl1p and Bms1p are two essential nucleolar proteins that form a complex required for the maturation of the small ribosomal subunit (40S). Bms1p is a GTPase and Rcl1p is an endoribonuclease which catalyzes the cleavage of the pre-rRNA at site A2; the step which separates the two maturation pathways leading to the formation of ribosomal subunits 40S and 60S. The team of our collaborator Sébastien Fribourg (IECB, Bordeaux) has solved the crystal structure of Rcl1p in complex with a fragment of Bms1p and identified residues at the interface between the two proteins. The substitution of some of these amino acids affects the interaction between Rcl1p and Bms1p in vitro and induces defects in the maturation of pre-rRNA in vivo. We have shown that these defects are probably due to a problem in Rcl1p incorporation into pre-ribosomal particles. Indeed, Bms1p and Rcl1p are imported into the nucleus as a complex via the nuclear localization sequence (NLS) of Bms1p. Both proteins are then recruited simultaneously into pre-ribosomes after incorporation of UTP-A and UTP-B modules but independently of Rrp5p incorporation. Our results also suggest that the GTP-binding to Bms1p is not required for the recruitment of the complex. Following A2 cleavage, the two proteins are both released from pre-40S particles before Rio2p incorporation. Therefore, our data indicate that the direct interaction between Bms1p and Rcl1p is crucial for the incorporation of the complex into pre-ribosomes in yeast. Another part of my thesis work focused on the study of Rpf2p protein, a component of the pre-60S ribosomal particles required for the synthesis of the large ribosomal subunit. Various data from the literature suggest that Rpf2p interacts with rDNA chromatin associated factors. We have confirmed some of these interactions and our results suggest that Rpf2p is associated in vivo with rDNA chromatin and more particularly to transcriptionally active copies. These data suggest that Rpf2p could be involved in mechanisms of chromatin modification required for transcription by RNA Pol. I and indeed, nuclear "run-on" experiments indicate that the loss of Rpf2p expression affects transcription by RNA pol. I. These preliminary results suggest that Rpf2p could be involved in the functional coupling between rDNA transcription and maturation of pre-ribosomal particles
Bertrand, Alexis. "Caractérisation fonctionnelle de mutations somatiques compensatrices d'elF6 dans le contexte du syndrome de Shwachman- Diamond". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASL089.
Texto completo da fonteShwachman Diamond syndrome (SDS) is a rare genetic ribosomopathy leading to impaired protein synthesis, which causes numerous symptoms including bone marrow failure and neutropenia that can evolve to myelodysplasia syndrome or acute myeloid leukaemia. Biallelic mutations in the SBDS gene are responsible of above 90% of the SDS cases and we recently identified biallelic EFL1 mutations as a novel cause of SDS. SBDS together with EFL1 remove the anti-association factor elF6 from the pre60S ribosomal subunit, allowing its interaction with the 40S subunit to form the mature ribosome 80S. Natural acquisition of somatic genetic events over time participâtes to age-related diseases and cancer development. However, in Mendelian diseases these events can, in rare case, counteract the deleterious effect of the germline mutation and provide a sélective advantage to the somatically modified cells, a phenomenon dubbed Somatic Genetic Rescue (SGR). We recently showed that several somatic genetic events affecting the expression or function of elF6 are frequently detected in blood clones from SDS patients but not in healthy individuals, suggesting a mechanism of SGR. While most of these somatic mutations induce elF6 destabilization or EIF6 haploinsufficiency, one récurrent mutation (N106S) did not affect the expression of elF6 but rather impact its ability to interact with the 60S subunit. In order to further investigate the functional conséquences of ElF6 haploinsufficiency and N106S mutation in a context of SDS, I introduced via CRISPR/Cas9 these mutations in immortalized fibroblastic cell line from SDS patients and control. These original cellular models hâve made it possible to détermine the impact of the N106S mutation on the localisation and function of elF6 and also to clarify the effects of these mutations on several aspects of cellular fitness, in particular ribosome biogenesis, translation rate and cell prolifération. Overall, the development of these cellular models has helped to characterise how the somatic N106S mutation and elF6 haploinsufficiency confer a sélective advantage in cells déficient in SBDS or EFL1
Rouquette, Jacques. "Export nucléaire des pré-ribosomes". Toulouse 3, 2005. http://www.theses.fr/2005TOU30250.
Texto completo da fonteThe ribosome is composed of the 40S subunit (18S rRNA associated with about thirty proteins), and the 60S subunit (5. 8S, 25S/28S and 5S rRNAs and approximatively forty proteins). Different maturation steps take place as pre-ribosomal particles are transported through the nucleus, from the nucleolus to the nucleoplasm, until nucleocytoplasmic translocation. On a first stage, we studied nucleoporins function in pre-40S particle transport using budding yeast mutant strains. This project has given rise to a complete inventory of nucleoporins required in both pre-40S particle and mRNP nucleocytoplasmic trafficking. Translocation of pre-ribosomal particles and mRNPs through the NPC needs distinct nucleoporins complexes, partially overlapping, indicating different export pathways. On a second stage, we extended the study of pre-ribosome transport to mammalian cells. For the first time, we show the existence of a new 18S rRNA precursor, exported to the cytoplasm, like in yeast
Bordonné, Rémy. "Structure et expression de genes mitochondriaux de la levure saccharomyces cerevisiae : etude de la maturation des produits de transcription du dna mitochondrial". Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13187.
Texto completo da fonteGINISTY, HERVE. "Fonction de la nucleoline dans le premier evenement de maturation du precurseur des arn ribosomiques". Toulouse 3, 2000. http://www.theses.fr/2000TOU30088.
Texto completo da fonteBarneche, Fredy. "Caractérisation de gènes de fibrillarine et de petits ARN nucléolaires impliqués dans la maturation des ARN ribosomiques chez Arabidopsis thaliana". Toulouse 3, 2001. http://www.theses.fr/2001TOU30146.
Texto completo da fonteTrinquier, Aude. "Coupling between transfer RNA maturation and ribosomal RNA processing in Bacillus subtilis". Thesis, Université de Paris (2019-....), 2019. http://www.theses.fr/2019UNIP7066.
Texto completo da fonteCellular protein synthesis both requires functional ribosomes and mature transfer RNAs (tRNAs) as adapter molecules. The ribosomes are large essential ribonucleoprotein complexes whose biogenesis accounts for most of cellular transcription and consumes a major portion of the cell’s energy. Ribosome biogenesis is therefore tightly adjusted to the cellular needs and actively surveilled to rapidly degrade defective particles that could interfere with translation. Interestingly, tRNAs and ribosomal RNAs (rRNAs) are both transcribed from longer primary transcripts and universally require processing to become functional for translation. In this thesis, I have characterized a coupling mechanism between tRNA processing and ribosome biogenesis in the Gram-positive model organism Bacillus subtilis. Accumulation of immature tRNAs during tRNA maturase depletion, specifically abolishes 16S rRNA 3’ processing by the endonuclease YqfG/YbeY, the last step in small ribosomal subunit formation. We showed that this maturation deficiency resulted from a late small subunit (30S) assembly defect coinciding with changes in expression of several key 30S assembly cofactors, mediated by both transcriptional and post-transcriptional effects. Interestingly, our results indicate that accumulation of immature tRNAs is sensed by the stringent factor RelA and triggers (p)ppGpp production. We showed that (p)ppGpp synthesis and the accompanying decrease in GTP levels inhibits 16S rRNA 3’ processing, most likely by affecting GTPases involved in ribosome assembly. The inhibition of 16S rRNA 3’ processing is thought to further lead to degradation of partially assembled particles by RNase R. Thus, we propose a model where RelA senses temporary slow-downs in tRNA maturation and this leads to an appropriate readjustment of ribosome biogenesis. This coupling mechanism would maintain the physiological balance between tRNAs and rRNAs, the two major components of the translation machinery
Calderari, Andrea. "Caractérisation structurale et fonctionnelle d’enzymes impliquées dans la maturation d’alcaloïdes pyrrolizidiniques issus de voies NRPS chez des γ-protéobactéries pathogènes". Electronic Thesis or Diss., Université de Lorraine, 2024. http://www.theses.fr/2024LORR0086.
Texto completo da fonteBacterial pyrrolizidine alkaloids (PAs) are secondary metabolites of wide chemical diversity at the origin of their promising pharmacological properties (antibiotics, anticancer, etc.). Although it has been determined that the heterocyclic core is assembled by modular non-ribosomal peptide synthetases (NRPS), the molecular mechanisms which govern the structural variety of the products and underlie their biological activities remain unknown. Given the major interest of these biosynthetic systems, this project aims to establish the structure-function relationships of the XhpG hydrolase and the AzeD dehydratase involved in the post-NRPS maturation of intermediate PAs in the pathogenic γ-proteobacteria Xenorhabdus hominickii and Pseudomonas aeruginosa. In pursuit of this objective, the recombinant enzymes have been subjected to an integrative experimental strategy, from their heterologous expression within the host E. coli BL21 (DE3), in either a native or mutant form, up to their purification by liquid chromatography and subsequent analysis via dynamic light scattering. These steps have allowed to confirm the homogeneity and monodispersity of the obtained samples, conditions necessary for the in-depth structural characterization of the apo-proteins by X-ray crystallography. Therefore, the efforts undertaken in screening and refining crystallization conditions, as well as in acquiring diffraction data at atomic resolution (1.2-1.6 Å), have permitted to elucidate the three-dimensional structure of the target biosynthetic enzymes. In light of complementary analyses, these results have provided a general overview of plausible oligomeric and conformational states in solution, and also insights into the catalytic mechanism with a focus on substrate specificity. In due course, the obtained knowledge will contribute to biosynthetic engineering endeavors to generate azacyclic analogues with interesting therapeutic potential, specifically in fighting the opportunistic pathogen P. aeruginosa responsible for nosocomial infections on a global scale
Sikorska, Natalia. "The phosphorolytic activity of the exosome core complex contributes to rRNA maturation in Arabidopsis thaliana". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAJ070/document.
Texto completo da fonteThe eukaryotic RNA exosome complex is the main 3’-5’ degradation machinery that plays an essential role in RNA decay, quality control and maturation. The exosome core complex (EXO9) is catalytically inert in yeast and humans, and therefore relies on the catalytic activity of associated RNases, Rrp6 and Rrp44. In this study I demonstrated that EXO9 is catalytically active in Arabidopsis. EXO9’s activity is phosphate-dependent, releases nucleoside diphosphates and is reversible, meeting all criteria of a phosphorolytic activity. Importantly, EXO9’s in vivo substrates include the archetypical exosome substrates, rRNA maturation by-products and 5.8S rRNA precursors. My data show that AtRRP44, EXO9 and AtRRP6L2 sequentially cooperate for the processing of 5.8S rRNA. This work sets a basis for studies aiming at further understanding the biological functions of EXO9’s phosphorolytic activity in a eukaryotic organism
Das, Sadhan Chandra. "Molecular mechanism of nucleolin-mediated Pol I transcription and characterization of nucleolin acetylation". Thesis, Lyon, École normale supérieure, 2012. http://www.theses.fr/2012ENSL0767.
Texto completo da fonteHere we have shown that, in nucleolin depleted cells, lower accumulation of pre-rRNA is associated with the increase in heterochromatin marks (H3K9me2) and decrease of the euchromatin histone marks (H4K12Ac and H3K4me3) in rDNA chromatin. ChIP-seq experiments show that nucleolin is enriched in the coding and promoter region of the rDNA and is preferentially associated with the unmethylated rRNA genes. Nucleolin knockdown results in the accumulation of RNAPI at the beginning of the rDNA and a decrease of UBF in the coding and promoter regions. Nucleolin is able to interfere with the binding of TTF-1 on the promoter-proximal terminator T0 thus inhibiting the recruitment of the NoRC subunit TIP5 and HDAC1 and establishing a repressive heterochromatin state. These results reveal the importance of nucleolin in the maintenance of the euchromatin state of rDNA and transcription elongation.In this thesis we have also shown that acetylation is a novel post-translational modification of nucleolin. Immuno-fluorescence studies using anti-acetylated nucleolin antibody illustrated that acetylated nucleolin is excluded from nucleoli and interestingly, neither could we detect any significant binding of ac-nucleolin on rDNA chromatin by doing ChIP-Seq, nor did we detect any activation of Pol II transcription with ac-nucleolin from DNA and chromatin templates. Moreover, we found acetylated nucleolin had a predominant nucleoplasmic distribution where it associates with the splicing factor SC35 and partially with the structures labeled with Y12 antibody, but not with coilin containing structures
Clerget, Guillaume. "Caractérisation des propriétés d’un mutant de la protéine Rrp9p de la snoRNP U3 de levure Saccharomyces cerevisiae et mise en évidence d’un réseau de protéines au sein du complexe de maturation précoce des ARNr". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0315/document.
Texto completo da fonteRibosome biogenesis is a complex and dynamic process requiring several assembly and maturation factors needed for processing of the pre-rRNA and assembly of the ribosomal protein. In eukarya, biogenesis of the 40S small subunit starts in the nucleolus with the transcription of a long pre-rRNA, containing 3 out of the 4 future rRNAs. The 18S pre-rRNA is modified by several C/D or H/ACA box snoRNPs and processed by endonucleolytic cleavages at sites A0, A1 and A2 sites. These early cleavages occur within a huge complex termed the SSU-processome. The processome assembles at the 5’ extremity of the pre-rRNA, and contains multiple factors, including the U3 snoRNP, a C/D box snoRNP chaperoning the pre-rRNA. Indeed, the U3 snoRNA is involved in formation of 5 intermolecular helix with the pre-rRNA, which defines the A0, A1 and A2 cleavage sites. In addition to the four C/D box snoRNP core proteins, the U3 snoRNP contains additional protein, Rrp9p, required for cell viability. The Rrp9p C-terminal extremity folds into a beta propeller structure. To try to decipher the Rrp9p role, we mutated several surface residues of the beta propeller protein and the effects of the mutations on cell growth were tested. Through this approach, we found that the R289 residue is important for the maturation events at A1 and A2 sites. Moreover, we identified new protein partners of Rrp9p within the processome and showed that R289 residue is involved in a direct interaction with Rrp36p. We identified a network of protein-protein interactions including Rrp9p, Rrp36p, Sgd1p and Rrp5p : Rrp9p interacts with Rrp36p and Sgd1p, Rrp36p and Sgd1p interact together and with Rrp5p. Some of the protein domains involved in the interactions were identified. In addition, the R289A mutation in Rrp9p has a strong negative effect on growth with mutations in U3 snoRNA that destabilize the U3 snoRNA/pre-rRNA interaction