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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Mécanismes moléculaires contrôlant l’ubiquitination et l’endocytose du transporteur de fer IRON-REGULATED TRANSPORTER 1 d’Arabidopsis thaliana / Molecular mechanisms driving the ubiquitination and endocytosis of the Arabidopsis iron transporter IRON-REGULATED TRANSPORTER 1

Dubeaux, Guillaume 08 December 2016 (has links)
L’ubiquitination est une modification post-traductionnelle qui joue un rôle majeur chez les organismes vivants. Chez Arabidopsis thaliana, le transporteur de fer racinaire IRT1 est endocyté à la suite de la monoubiquitination de deux résidus lysine situés au niveau de sa grande boucle cytosolique. Cependant, les mécanismes régissant l’endocytose médiée par l’ubiquitine ainsi que son rôle biologique restent flous. Au cours de ma Thèse, j’ai mis en évidence que la dynamique d’IRT1 était contrôlée par les métaux substrats secondaires du transporteur (à savoir le zinc, le manganèse et le cobalt). En l’absence de ces métaux, IRT1 est localisé à la membrane plasmique avec une polarité latérale le positionnant sur la face externe des cellules de l’épiderme racinaire. La présence de ces mêmes métaux à un niveau physiologique entraîne la monoubiquitination d’IRT1 et son internalisation vers les endosomes précoces. J’ai démontré que lorsque les métaux substrats secondaires d’IRT1 sont présents en excès, les modifications monoubiquitine sont alors allongées en chaînes de polyubiquitines liées par le résidu lysine-63, entrainant ainsi son adressage vers la vacuole et sa dégradation. Mes travaux ont par ailleurs permis d’élucider les mécanismes moléculaires impliquées dans la réponse des plantes à l’excès de métaux substrats d’IRT1. J’ai notamment montré que l’endocytose d’IRT1 était dépendante i) d’un motif riche en résidus histidine dans la séquence d’IRT1 qui est capable de fixer ces métaux autres que le fer, ii) de la phosphorylation d’IRT1 au niveau d’un résidu thréonine par une protéine kinase en cours d’investigation, et iii) de l’E3 ligase à domaine RING IDF1. D’un point de vue physiologique, l’endocytose d’IRT1 médiée par l’ubiquitine et dépendante des métaux protège la plante d’une suraccumulation de ces métaux autres que le fer qui sont hautement réactifs. / Ubiquitination is a post-translational modification playing a major role in living organisms. In Arabidopsis thaliana, the root iron transporter IRT1 is endocytosed following the monoubiquitination of two lysine residues located in its large cytosolic loop. However, the mechanisms driving IRT1 ubiquitin-mediated endocytosis and its biological relevance remains unclear. During my PhD, I uncovered that IRT1 dynamics is controlled by its secondary metal substrates (i.e. zinc, manganese and cobalt). In the absence of these non-iron metals, IRT1 is found at the cell-surface of root epidermal cells with an outer lateral polarity, while their presence at physiological levels triggers IRT1 monoubiquitination, internalization and accumulation in early endosomes. However, upon non-iron metal excess, monoubiquitin modifications are extended into K63 polyubiquitin chains to promote the vacuolar targeting of IRT1 and its degradation. I investigated further the molecular mechanisms driving plant responses to non-iron metal excess. I notably showed that this regulation by non-iron metals is dependent on i) a histidine-rich stretch in IRT1 that is able to directly bind to non-iron metals, ii) the subsequent recruitment of a kinase currently under investigation which phosphorylates IRT1 at a threonine residue, and iii) the RING E3 ligase IDF1. Altogether, the metal-dependent ubiquitin-mediated endocytosis of IRT1 protects the plant from overaccumulation of highly reactive non-iron metals.
42

Biochemical and biophysical studies of MDM2-ligand interactions

Wang, Shao-Fang January 2012 (has links)
MDM2, murine double minute 2, is a RING type-E3 ligase protein and also an oncogene. MDM2 plays a critical role in determining the steady levels and activity of p53 in cells using two mechanisms. The N-terminal domain of MDM2 binds to the transactivation domain of p53 and inhibits its transcriptional activity. The RING domain of MDM2 plays a role in the ubiquitination (and degradation) of p53. Several proteins are responsible for the ubiquitination mechanism including the ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2) and ubiquitin ligase (E3). Since the E2-E3 interaction is essential for ubiquitination, the protein-protein recognition site is a potential drug target. Two different MDM2 RING constructs were expressed and purified: MDM2RING (residues 386-491) and MDM2RING△C (residues 386-478). Both constructs were characterised using dynamic light scattering, size exclusion chromatography, mass spectrometry, NMR and electron microscopy. E3 ligase activity in vitro was also studied. Taken together these results showed that the MDM2RING construct formed a concentration-dependent oligomeric structure. In contrast, the MDM2RING△C construct formed a dimer at all concentrations. Both MDM2RING and MDM2RING △ C retain E3 ligase activity. However, the MDM2RING△C construct is less active. Full length E2 enzyme UbcH5a was also purified. Various biophysical techniques were used to study its interaction with MDM2 as well as with potential small molecule inhibitors as in principle, small molecules which disrupt the interaction between MDM2 and UbcH5a, could prevent/promote ubiquitination of p53. The dimerisation of MDM2 is important for its E3 activity and the C8-binding site potentially provides a second druggable site. In this work, peptide 9, which has the same sequence as the C-terminus of MDMX (an MDM2 homologue) was found to inhibit MDM2 E3 activity. Various biological techniques including NMR, fluorescence anisotropy, and electrospray mass spectrometry were used to investigate the interaction between two inhibitory peptides and MDM2. A major part of project involved virtual screening (VS) to search for small molecules which can affect MDM2-dependent ubiquitination. Three potential targets were considered: (1) the C8-binding site of MDM2; (2) the UbcH5a-binding site of MDM2; and (3) the MDM2-binding site of UbcH5a. Several small molecules were identified using our virtual screening database-mining and docking programs that were shown to affect MDM2-dependent ubiquitination of p53. In terms of understanding the complex biochemical mechanism of MDM2 this work provides two interesting and functionally relevant observations: (i) the MDM2 RING△C construct is a dimer as this would not be expected form the existing studies, and has less E3 ligase activity than MDM2RING; (ii) small molecules that bind MDM2 on the E2 binding site enhanced E3 ligase activity. One model to explain these observations is that binding of small molecule activators family to the RING induces a change in the conformation of the Cterminal tail residues which may enhance E2 binding.
43

NMR Studies of SH3 Domain Structure and Function

Bezsonova, Irina 19 January 2009 (has links)
SH3 domains are excellent models for probing folding and protein interactions. This thesis describes NMR studies of several SH3 domains, including the N-terminal SH3 domain of the Drosophila adaptor protein Drk (drkN SH3 domain), the SH3 domain of the proto-oncogene tyrosine-kinase Fyn, and the SH3 domains of the human adaptor protein CIN85, involved in Cbl-mediated downregulation of epidermal growth factor receptor (EGFR) and other receptor tyrosine kinases (RTKs). The drkN SH3 domain is an ideal system for studying disordered states. The unique quality of this isolated domain is that it exists in an approximately 50/50 equilibrium between its folded and unfolded states under non-denaturating buffer conditions. Interestingly, the single T22G mutation dramatically stabilizes the domain. Here the NMR structures of the drkN SH3 domain and its T22G mutant are determined and compared in order to illuminate the causes of the marginal stability of the domain. Solvent exposure of the folded and the unfolded drkN SH3 domains are probed and compared with a novel NMR technique using molecular oxygen dissolved in solution as a paramagnetic probe. The changes in partial molar volume along the folding trajectories of the drkN SH3 and Fyn SH3 domains are also studied and analyzed here in terms of changes in protein hydration and packing accompanying folding. Finally, the interactions between the SH3 domains of CIN85 and ubiquitin are discussed. All three are shown to bind ubiquitin. The structure of the SH3-C domain in complex with ubiquitin is presented and the effect of disruption of ubiquitin binding on ubiquitination of CIN85 and EGFR in vivo is discussed. SH3 domains are easily amendable to a wide range of NMR approaches and provide a good system for development and testing of novel methods. Through the use of these approaches significant insights into details of SH3 domain structure, stability, mechanisms of folding and cellular function have been gained.
44

Non-canonical TGFb signaling pathways in prostate cancer

Song, Jie January 2016 (has links)
Prostate cancer is the second leading cause of cancer-related death in men in the Western world. Deregulation of transforming growth factor β (TGFβ) signaling pathway is frequently detected in prostate cancer and contributes to tumor growth, migration, and invasion. In normal tissue and the early stages of cancer, TGFβ acts as a tumor suppressor by regulating proliferation, differentiation, and apoptosis. In later stages of cancer, TGFβ acts as a tumor promoter by inducing angiogenesis, tumor invasion, and migration. Thus, it is important to investigate the molecular mechanisms behind the tumor-promoting effects of TGFβ, which is the topic of this thesis.   The tumor necrosis factor receptor–associated factor 6 (TRAF6) controls non-canonical TGFβ signals due to its enzymatic activity, causing polyubiquitination of the cell membrane–bound, serine/threonine kinase TGFβ type I receptor (TβRI) and its subsequent cleavage in the extracellular domain by tumor necrosis factor a–converting enzyme (TACE) in a protein kinase C ζ (PKCζ)-dependent manner. TRAF6 also recruits the active g-secretase complex to the TβRI, resulting in a second cleavage in the transmembrane region and the liberation of the TβRI intracellular domain (TβRI-ICD), which enters the nucleus, where it associates with the transcriptional co-regulator p300. In Paper I, the aim was to elucidate by which mechanisms TβRI-ICD enters the nucleus. We found that the endocytic adaptor protein APPL1 interacts with TβRI and PKCζ. APPL proteins are required for TβRI translocation from endosomes to the nucleus via microtubules in a TRAF6-dependent manner. Moreover, APPL proteins are important for TGFβ-induced cell invasion, and high levels of APPL1 are detected by immunohistochemistry in prostate cancer. Finally, we demonstrated that the APPL1–TβRI complex visualized with the in situ proximity ligation assay (PLA) correlates with Gleason score, indicating that it might be a novel prognostic marker for aggressive prostate cancer. In Paper II, the aim was to explore by which mechanisms TGFβ causes activation of the AKT pathway, which regulates migration and therapy resistance of cancer cells. We found that the E3 ligase activity of TRAF6 induces Lys63-linked polyubiquitination of p85α upon TGFβ stimulation, resulting in plasma membrane recruitment, Lys63-linked polyubiquitination, and subsequent activation of AKT. Moreover, the TRAF6 and PI3K/AKT pathway were found to be crucial for the TGFβ-induced migration. Importantly, we demonstrated, by PLA, a correlation between Lys63-linked polyubiquitination of p85α and aggressive prostate cancer in tissue sections from patients with prostate cancer. In Paper III, the aim was to investigate the mechanisms for TGFβ-induced activation of PKCζ and the role of PKCζ in tumor regression. We found that TRAF6 caused Lys63-linked polyubiquitination of PKCζ. By using two novel chemical compounds that inhibit PKCζ, we demonstrated that PKCζ is crucial for prostate cancer cell survival and invasion. In Paper IV, the aim was to investigate further the target genes for the nuclear TβRI-ICD-APPL1 complex identified in Paper I. We provide evidence that APPL proteins and the TGFβ signaling pathway are important for cell proliferation. In summary, the results reported in this thesis suggest the potential usefulness of the identified signaling components of the tumor-promoting effects of TGFβ as drug targets and biomarkers for aggressive prostate cancer.
45

Ubiquitination et ciblage des molécules du complexe majeur d'histocompatibilité de classe-II aux exosomes

Gauvreau, Marie-Élaine January 2006 (has links)
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.
46

Caracterização bioquímica e celular da proteína TRIM49 / Biochemical and cellular characterization of the TRIM49 protein

Guimarães, Dimitrius Santiago Passos Simões Fróes 10 August 2017 (has links)
A autofagia é o processo de degradação de estruturas celulares através do seu direcionamento ao lisossomo. As proteínas TRIMs reconhecem as -cargas? autofágicas e reúnem o complexo de nucleação do fagóforo, contudo se desconhece a função de cada domínio e a importância da atividade de E3 ligase para a sua atividade. A proteína TRIM49 clonada e expressa em E. coli ou em células humanas HEK293T não apresentou atividade de E3 ubiquitina ligase in vitro e reduziu os níveis totais de ubiquitinação in vivo, indicando que não é um E3 ubiquitina ligase. Células desafiadas com Htt74Q apresentaram menores níveis de citotoxicidade quando co-transfectadas com TRIM49 selvagem, mas não com os mutantes do domínio RING ou SPRY, indicando os dois domínios são necessários para sua atividade celular. A proteína selvagem se colocaliza com o marcador autofágico LC3, após o bloqueio da autofagia com bafilomicina A1. Os resultados indicam que a TRIM49 pode atuar na degradação intracelular de proteínas, por um mecanismo não dependente de atividade de E3 ligase. / Autophagy is the process of degradation of intracellular proteins through their directioning to the lysosome. TRIM proteins can directely recognize autophagic cargo and also act as a hub for the phagophore nucleation complex, however the function of each domain and the role of the E3 ligase activity in this process is unknown. The TRIM49 protein cloned and expressed in E. coli or in human cells HEK23T showed no ubiquitin E3 ligase activity in vitro and cells transfected with the wild type protein showed lower levels of polyubiquitinated proteins, indicating that TRIM49 is not a bona fide E3 ubiquitin ligase. Cells challenged with Htt74Q presented lower cytotoxicity levels when cotransfected with wild type TRIM49, when compared with the RING domain mutant or with the truncated protein lacking the SPRY domain, indicating that both domains are required for its cellular activity. The wild type protein colocalizes with the autophagic marker LC3 after treatment with the autophagy inhibitor bafilomycin A1. Taken together, these results indicate that the TRIM49 protein plays a role in protein degradation independently of a E3 ligase activity.
47

The role of NEDD8 pathway in cell invasion and strategies for the use of NEDD8 inhibitors in the clinic / Le rôle de la voie de NEDD8 dans l'invasion cellulaire et le developpement de stratégies pour l'utilisation des inhibiteurs de NEDD8 en clinique

Bou Malhab, Lara 21 October 2016 (has links)
Les modifications post-transrationnelles avec les molécules ubiquitine et ubiquitine-like sont des mécanismes essentiels pour la régulation des fonctions protéiques et des voies de signalisations. Les ubiquitine-like molécules comme par exemple NEDD8 jouent un rôle majeur dans la fonction des protéines et sont impliqués dans des maladies humaines comme par exemple les maladies neuro dégénératives. NEDD8 est essentiel pour la survie, la croissance et le développement. C’est pour ceci, l’élucidation de leurs mécanismes d’action est très importante.Dans notre laboratoire, nous nous intéressons à l’ubiquitine-like molécule NEDD8. Le mécanisme de modification avec cette protéine est dit NEDDylation et il nécessite une intervention enzymatique médiées par E1, E2 et E3. Le rôle majeur de NEDD8 est la régulation de l’activité des Cullins, des E3 ubiquitine ligases. Les Cullins sont des scaffolds dont le rôle est de faciliter la dégradation des substrats en assemblant tout le complex enzymatique. La dérégulation de l’activité des Cullins a été montrée de contribuer à l’oncogenèse suite à l’accumulation des oncoprotéines ou suite à la dégradation excessive des suppresseurs de tumeurs. Récemment, la voie de NEDDylation a été ciblée pour des interventions thérapeutiques ; MLN4924 (Provenodistat) (Millenium Pharmaceuticals) bloque la voie de NEDDylation en formant une liaison covalente avec l’enzyme E1 de la voie de NEDDylation. L’identification des mécanismes de régulation des fonctions protéiques par NEDD8 fournira plus d’informations sur le mécanisme d’action de NEDD8 d’un point de vu moléculaire, ce qui permettra l’identification de nouvelles cibles pour de nouvelles interventions thérapeutiques. Dans 50% des tumeurs, le gène p53 est muté. Dans les 50% qui restent, le gène p53 est intact mais la protéine est non fonctionnelles dû à des dérégulations des voies de signalisations. Nous avons trouvé que l’inhibition de la NEDDylation via MLN4924 bloque l’invasion des cellules de mélanomes métastatiques. D’un point de vu moléculaire, MLN4924 provoque la dégradation de Mdmx, l’homologue de Mdm2, tous les deux sont des majeurs régulateurs négatifs de p53. Ceci est dû à la formation d’un complexe entre Mdmx, Mdm2 et Cullin4A inactif. On a démontré que la dégradation de Mdmx est essentielle pour l’activation de la voie RhoA/ROCK capable de bloquer l’invasion tout en modulant le cytosquelette d’actine.De plus, Mdmx a été identifié en tant que régulateur de l’activité de RhoA. Mdmx se lie à la forme inactive de RhoA (GDP-RhoA) et contrôle son activation. Durant les travaux de recherche, nous avons aussi essayé de développer une méthode nous permettant d’utiliser MLN4924 d’une façon spécifique dans le but de minimiser les effets secondaires normalement accompagnant les traitements de chimiothérapies. MLN4924 comme tout agent chimio-thérapeutique, est toxique envers les cellules normales. Dans le but d’utiliser MLN4924 d’une manière spécifique nous permettant de cibler uniquement les cellules cancéreuses sans affecter les cellules normales, nous avons testé cette molécule dans une approche basée sur le statut de p53 appelé « cyclotherapie ».Nos résultats montrent que l’activation de p53 avec des concentrations minimes d’Actinomycine D, induit un arrêt du cycle cellulaire dans la phase G1, protégeant ainsi les cellules de l’effet toxique de MLN4924. Ceci n’est pas le cas pour les cellules cancéreuses dont p53 est déficient ou sans p53. Celles-ci progressent en phase S où elles seront éliminées par apoptose. Cette combinaison a été aussi testée in vivo, plus spécifiquement en utilisant les zebrafish comme model, ce qui nous a permis de confirmer l’effet protecteur de l’Actinomycine D contre l’effet toxique de MLN4924. Nos résultats constituent une nouvelle possibilité de combinaison de MLN4924 basé sur le statut de p53. / Post-translational modifications with ubiquitin and ubiquitin-like molecules (ubls) are essential regulatory mechanisms of protein function and signalling networks. Ubiquitin-like molecules, such as NEDD8 have emerged as major mechanisms of protein function regulation and implicated in human diseases including cancer and neurodegeneration. It is essential for viability, growth and development. Therefore, the elucidation of their mechanism of action is critical. In our lab, research is focused on NEDD8. The process called NEDDylation, involves the three enzymatic activities (E1, E2 and E3). The well-known role of NEDD8 is the regulation of the activity of E3 ubiquitin ligases called Cullin Ring Ligases through modification of Cullins. Cullins are scaffolds to facilitate E3 ligase complex assembly and mediated substrate degradation. Deregulation of Cullins activity has been shown to contribute to oncogenesis through the accumulation of oncoproteins or excessive degradation of tumour suppressors. Recently, the NEDDylation pathway has been targeted for therapeutic intervention; MLN4924 (Pevonedistat) (Millenium Parmaceuticals) forms a covalent adduct with the NEDD8 E1 enzyme and blocks the NEDDylation cascade. Identification of mechanisms of protein function regulation by NEDDylation will provide the molecular basis for the action of the NEDD8 inhibitors in clinic and potentially identify novel targets for therapeutic intervention. In 50% of tumours the TP53 is mutant. In cancer cells where TP53 is WT, upstream or downstream signalling pathways are deregulated. We found that inhibition of NEDDylation by MLN4924 dramatically blocks invasion of metastatic melanoma cells. At the molecular level, MLN4924 induces proteasomal degradation of the Mdmx oncogene product, a key negative regulator of the p53 tumor suppressor. Mechanistically, MLN4924 induces the complex formation of Mdmx with Mdm2 and inactive Cullin4A that promote Mdmx degradation. We found that the degradation of Mdmx is required for the activation of the RhoA/ROCK pathway which blocks cell invasion through changes in the cell cytoskeleton. Interestingly, Mdmx was identified as regulator of RhoA activity through binding with inactive RhoA (GDP- bound RhoA). Another question was addressed which is how to use MLN4924 in a specific manner, thus reducing side effects usually resulting from chemo treatments. MLN4924 as all chemo-agents, is toxic towards healthy cells. In order to use MLN4924 in a specific manner targeting cancer cells specifically leaving healthy cells unharmed, a p53 based cyclotherapy was tested. Our results show that low activation of wild type p53 by low doses of Actinomycin D, causes a G1 cell cycle arrest and protects normal cells from MLN4924 treatment leaving cancerous cells with mutant p53 or no p53 to progress to S-phase and selectively commit apoptosis upon MLN4924 treatment. Our protocol was tested in vivo, in zebrafish model system confirming the protective effect of LDACTD against the cytotoxic effect of MLN4924. Our results provide a possible combination therapy for MLN4924 based on the p53 status.
48

Etude structurale de protéines virales impliquées dans la réplication et régulation du cycle de multiplication d'un virus de plante

Robin, Charlotte 05 December 2011 (has links) (PDF)
Le virus de la mosaïque jaune du navet (TYMV) est un excellent modèle pour la réplication des virus à ARN simple brin de polarité positive. Ce petit virus de plante code l'ensemble desprotéines nécessaires à sa réplication sous forme d'un précurseur polyprotéine (206K). Du NauC-terminus, celui-ci porte une activité méthyltransférase, protéase à cystéine (PRO),hélicase et ARN-polymérase ARN dépendante (POL). Comme tous les virus à ARN(+)connus, son complexe de réplication est étroitement lié à des membranes cellulaires. Dans lecas du TYMV, c'est l'enveloppe des chloroplastes qui est impliquée. Un des acteurs clés de laréplication est la polymérase qui permet la synthèse de nouveaux génomes. La régulation de son activité implique dans un premier temps son clivage de la 206K par PRO. Ainsi libérée,elle est recrutée aux chloroplastes par une interaction directe avec le domaine PRO du produit de clivage 140K, afin de former le complexe de réplication. Un second clivage par PRO contenu dans 140K, à la jonction PRO-hélicase, permet de poursuivre le cycle de réplication.Récemment, il a également été montré que l'activité POL était régulée par la voie ubiquitine-protéasome durant le cycle viral. Ubiquitinilée par la cellule hôte, elle est adressée au protéasome où elle sera dégradée. Cependant, PRO, grâce à sa seconde fonction ubiquitine hydrolase, est capable de la protéger de cette dégradation. Afin de caractériser d'un point de vue structural ce mécanisme de régulation de la réplication, nous avons cristallisé, à l'aide d'un contaminant, PRO et avons résolu sa structure. L'empilement cristallin est tel que le Cterminus d'un domaine PRO est inséré dans la crevasse catalytique du domaine PRO suivant,nous fournissant ainsi des informations structurales sur son activité endopeptidase. Dans un second temps, afin d'avoir des informations sur sa seconde activité, nous avons réalisé un complexe stable entre PRO et une molécule d'ubiquitine afin de le cristalliser et résoudre sa structure. Enfin, nous avons initié l'étude cristallographique de la polymérase.
49

Role of E6-Associated Protein (E6-AP) in Mammary Gland Development and Tumorigenesis

Ramamoorthy, Sivapriya -. 09 July 2009 (has links)
E6-associated protein (E6-AP), which was originally identified as an ubiquitin-protein ligase, also functions as a co-activator that enhances the hormone-dependent transactivation of estrogen (ER) and progesterone (PR) receptors. To investigate the in vivo role of E6-AP in mammary gland development, we generated transgenic mouse lines that specifically overexpress either wild-type human E6-AP (E6-APWT) or the ubiquitin-protein ligase defective mutant E6-AP (E6-APC833S) in the mammary gland. Here we show that overexpression of E6-APWT results in impaired mammary gland development. In contrast, overexpression of E6-APC833S or loss of E6-AP (E6-APKO) increases lateral branching and alveolus-like protuberances in the mammary gland. We also show that the mammary phenotypes observed in the E6-AP transgenic and knockout mice are in large part due to the alteration of PR-B protein levels. RNAi-mediated knockdown of E6-AP in T47D breast cancer cells increased PR-B protein levels and stability. In vitro ubiquitination assay using purified E6-AP and PR-B reinforce these conclusions and demonstrate that E6-AP promotes PR-B turnover in an ubiquitin-dependent manner. Furthermore, we also show that E6-AP regulates progesterone-induced Wnt-4 expression by modulating the steady state level of PR-B in both mice and in human breast cancer cells. This novel mechanism appears to regulate normal physiology of the mammary gland and its dysregulation may prove to contribute importantly to mammary cancer development and progression. To test this hypothesis, we examined the E6-AP transgenic mice for tumor formation over a period of 6, 9, 12, 18 and 24 months. Our data shows that, unlike the E6-APWT mice that show normal phenotype, the E6-APC833S mice develop mammary hyperplasia at high penetrance (80%); with a median latency of 18 months. Our findings indicate that the inactivation of the E3-ligase function of E6-AP is sufficient to initiate the process of mammary tumor development. These findings strongly suggest that E6-AP may act as a tumor suppressor by down regulating the ER-alpha, PR-B and thereby their signaling pathways.
50

Role of IκB kinase (IKK) complex post-translational modifications in NF-κB signaling and therapeutic applications for the treatment of HIV-1 infection./Role des modifications post-traductionnelles du complexe IκB kinase (IKK)dans la cascade de signalisation NF-κB et applications thérapeutiques pour le traitement de l’infection par le HIV-1.

Calao, Miriam 23 April 2009 (has links)
Les facteurs de transcription de la famille Rel/NF-κB régulent l’expression d’un grand nombre de gènes impliqués dans les réponses immunitaires et inflammatoires ainsi que dans la régulation de la prolifération et de la survie cellulaire. Le caractère transitoire de l’activation de NF-κB est donc crucial pour poterger les cellules de l’autoxicité due à une trop forte expression des gènes cibles de ce facteur de transcription. Dans le cadre de notre thèse de doctorat, nous avons étudié les mécanismes moléculaires régulant la cinétique d’activation de NF-κB, en accordant une attention toute particulière au complexe kinase IKK, qui semble être le regulateur clef de l’activation de NF-κB. Nos résultats suggèrent que p300 pourrait réguler la durée d’activation des IKKs d’une part par acétylation directe, et d’autre part, indépendamment de son activité HAT, en stabilisant les IKKs et donc en prolongeant leur demie-vie et par conséquent leur activation. Certains virus utilisent la voie de signalisation NF-κB afin de promouvoir leur propre réplication. C’est le cas du virus HIV-1 (Human Immunodeficiency Virus type 1), qui contient dans son promoteur deux sites de liaison pour NF-κB. Notre laboratoire a précédemment montré que l’utilisation du TNFα en combinaison avec la TSA, active l’expression virale de manière synergique. L’administration combinée d’un activateur du facteur NF-κB et d’un inhibiteur de désacétylases pourrait, en présence d’une thérapie anti-HIV-1 efficace, être envisagée dans le but d’éliminer les cellules réservoirs infectées de manière latente. L’utilisation thérapeutique du TNFα ou de la TSA étant inenvisageable en raison de leur toxicité, nous avons étudié l’effet d’autres substances ayant un plus grand potentiel thérapeutique et nous avons apporté une preuve de principe du potentiel thérapeutique de la coadministration de plusieurs activateurs viraux (inhibiteurs de HDACs[HDACIs]+inducteurs de la voie NF-κB) pour réduire le pool des réservoirs cellulaires infectés de manière latente.

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