BACKGROUND: APOBEC3H (A3H) is a member the Apolipoprotein B mRNA-editing catalytic (APOBEC) polypeptide seven cytidine deaminases family. These APOBEC3 enzymes have the innate ability to deaminate a cytidine base converting it to a uridine base. Previous research has suggested that human A3H haplotypes have similar properties like those of A3G and A3DE, in which these APOBEC3 enzymes are known to entail anti-viral activity toward viruses such as human immunodeficiency virus. METHODOLOGY: Human A3H gene was amplified by polymerase chain reaction and inserted into E.Coli plasmids. Expression tests were conducted to verify that the clones were able to express protein. Ten liters of the cloned cells were grown, and A3H protein was purified using an established protocol in Dr. Chen's lab for deamination to test the enzyme activity. An inactive mutant of A3H was also cloned to use as a negative control for the wild type A3H. PRINCIPAL FINDINGS: The isolated A3H haplotype 1 (referred to as A3H hereafter) is indeed active, but the activity is very weak in comparison to other APOBEC3 proteins, in which A3F and A3A were used as controls. A3H deamination is most optimal with an acidic environment of pH 5.5 or 6.0, and concentrated protein will produce more deamination product (darker bands). The inactive A3H produced some unexpected visible smaller DNA bands, which may be the result of contaminated protein activities. In conclusion, the wild type A3H protein may have weak activity, but additional studies are required to confirm that the inactivated A3H mutant has no activity on the DNA substrates.

The AID/APOBEC protein family comprises a group of cytosine deaminases found in vertebrates that are capable of modifying cytosine to uracil in the context of RNA or singlestranded DNA. They exert diverse valuable physiological functions including antibody diversification and restriction of viral infection. However, off-target mutations have also been shown to contribute to cancer development, making it crucial to better understand the interactions and mechanisms that regulate AID/APOBEC activity and editing site fidelity. In this regard, a new focus on RNA as a putative regulator of AID/APOBECs has recently emerged. Regardless of whether it is used or not as a substrate for deamination, most members of the family have been shown to retain the ability to bind RNA, emphasizing a potential regulatory role for this interaction. However, little is known about AID/APOBECs RNA binding specificity. A promiscuous binding has been suggested in some cases while in vitro evidence for other members of the family indicate a certain level of specificity. Therefore, to thoroughly unravel the AID/APOBECs RNA binding specificity, in my doctoral research I applied cross-linking and immunoprecipitation (iCLIP), an unbiased technique that allows identification of protein-bound RNAs with nucleotide resolution in living cells. As a first approach, I adapted the technique for its use in yeast and probed the RNA binding of AID and APOBEC3G, revealing different degrees of preference for small structured RNAs and recognition of particular sites within them. I then expanded the analysis to mammalian cells (HEK293T) and evaluated an extended set of APOBECs finding that, even in the presence of a broader and more complex pool of RNAs, small RNAs were still significantly bound by some members of the family. Furthermore, the comparative analysis of AID, APOBEC1, APOBEC3G, APOBEC3A and APOBEC3B iCLIP data obtained in my research, revealed shared and individual preferences for certain RNAs, suggesting a degree of binding specificity among APOBECs. In summary, my thesis outlines for the first time a comprehensive analysis of the RNA binding specificity of different AID/APOBECs in vivo, including the description of novel interactions with nucleotide resolution. The results obtained are of great value and open the field for further investigation of the specific meaning and validation of each preferential binding, providing new insights into understanding the role of AID/APOBEC interaction with RNA.

Die Möglichkeit, durch Beeinflussung der Interaktion der Gegenspieler Apobec3G und Vif, ein neuartiges Medikament gegen HIV zu entwickeln, ist in der Literatur bereits vielfach beschrieben (Argyris und Pomerantz 2004, Cullen 2006, Sheehy et al. 2003). Als Teil des angeborenen Immunsystems bietet die Aufrechterhaltung der antiviralen Eigenschaften von Apobec3G einen viel versprechenden Ansatzpunkt, die Infektiosität des HI-Virus einzudämmen. RN18 ist als ein Vif-Antagonist in der Literatur beschrieben (Nathans et al. 2008). Um Substanzen ausfindig zu machen, die den Abbau von Apobec3G durch Vif verhindern können, wurden in dieser Arbeit niedermolekulare Substanzen auf deren Tauglichkeit diesbezüglich getestet. In einem ersten Schritt (Screening) wurde die Wirksamkeit der Testsubstanzen bei einer Konzentration von 30 μM ermittelt. Bei Substanzen, die eine ähnliche Hemmung des Abbaus des Reporterproteins EYFP-A3G im Vergleich zu RN18 bewirkten, wurde eine quantitative Analyse zur genaueren Bestimmung der halbmaximalen Hemm-konzentration durchgeführt (Titration). Einerseits wurden Derivate des bekannten Vif-Antagonisten RN18 getestet. Durch schrittweise Verbesserung der Wirksamkeit der RN18-Derivate gelang es schließlich Substanzen zu finden, für die ein besserer Effekt als für RN18 ermittelt werden konnte, den Abbau von Apobec3G durch Vif zu verhindern. Zur Beurteilung der Ergebnisse wurde der EC50-Wert berechnet, um die Wirksamkeit der Substanzen miteinander vergleichen zu können. Es wurde nach Substanzen gesucht, die bei möglichst geringen Konzentrationen wirken. Das RN18-Derivat mit dem besten Ergebnis war FM86 (EC50-Wert: 4.5 μM). Andererseits wurden niedermolekulare Substanzen aus verschiedenen Arbeitsgruppen untersucht, um weitere Substanzen zu finden, die ebenso wie RN18 in der Lage sind, die Vif/Apobec3G-Interaktion zu hemmen. Auch hier wurden mehrere Substanzen ermittelt, die eine bessere Wirksamkeit als RN18 erkennen ließen. Derivate der Substanz CBA77a konnten am effektivsten den Abbau von Apobec3G durch Vif verhindern. Das beste Ergebnis wurde für die Testsubstanz CBA82 ermittelt (EC50-Wert: 2.8 μM). Ob die Ergebnisse der Testsubstanzen ausschließlich auf die Hemmung der Vif/A3G Interaktion zurückzuführen sind, kann letztendlich nicht abschließend beurteilt werden. Eine Erweiterung des Testsystems durch unsere Arbeitsgruppe sieht daher vor, falsch positive Ergebnisse zu erkennen. / As a part of the innate immune system the maintenance of the antiviral qualities of Apobec3G offers a promising starting point to curtail the infectivity of HIV. RN18 is described as a Vif antagonist in the literature (Nathans et al. 2008). To find out substances, they are able to inhibit the reduction of Apobec3G by Vif, following tests were made in this dissertation: In a first step the effectiveness of the test substances in a concentration of 30 μM was determined (Screening). Substances, which caused a similar inhibition of the reduction of Apobec3G in comparison to RN18, a quantitative analysis was made to get the half-maximum inhibition concentration (Titration). On the one hand derivatives of the known Vif antagonist RN18 were tested. The RN18 derivative with the best result was FM86 (EC50 value: 4.5 μM). On the other hand low-molecular substances were tested, if they are able to inhibit the interaction of Apobec3G and Vif as RN18 do. Derivatives of the substance CBA77a inhibit most actually the reduction of Apobec3G by Vif. The best result was determined for the test substance CBA82 (EC50 value: 2.8 μM). It is not able to judge, if the results of the test substances are reduce exclusively to the inhibition of the Vif/Apobec3G interaction. Therefore our working group plans to extend the test system to prevent false positive results.

Die Möglichkeit, durch Beeinflussung der Interaktion der Gegenspieler Apobec3G und Vif, ein neuartiges Medikament gegen HIV zu entwickeln, ist in der Literatur bereits vielfach beschrieben (Argyris und Pomerantz 2004, Cullen 2006, Sheehy et al. 2003). Als Teil des angeborenen Immunsystems bietet die Aufrechterhaltung der antiviralen Eigenschaften von Apobec3G einen viel versprechenden Ansatzpunkt, die Infektiosität des HI-Virus einzudämmen. RN18 ist als ein Vif-Antagonist in der Literatur beschrieben (Nathans et al. 2008). Um Substanzen ausfindig zu machen, die den Abbau von Apobec3G durch Vif verhindern können, wurden in dieser Arbeit niedermolekulare Substanzen auf deren Tauglichkeit diesbezüglich getestet. In einem ersten Schritt (Screening) wurde die Wirksamkeit der Testsubstanzen bei einer Konzentration von 30 μM ermittelt. Bei Substanzen, die eine ähnliche Hemmung des Abbaus des Reporterproteins EYFP-A3G im Vergleich zu RN18 bewirkten, wurde eine quantitative Analyse zur genaueren Bestimmung der halbmaximalen Hemm-konzentration durchgeführt (Titration). Einerseits wurden Derivate des bekannten Vif-Antagonisten RN18 getestet. Durch schrittweise Verbesserung der Wirksamkeit der RN18-Derivate gelang es schließlich Substanzen zu finden, für die ein besserer Effekt als für RN18 ermittelt werden konnte, den Abbau von Apobec3G durch Vif zu verhindern. Zur Beurteilung der Ergebnisse wurde der EC50-Wert berechnet, um die Wirksamkeit der Substanzen miteinander vergleichen zu können. Es wurde nach Substanzen gesucht, die bei möglichst geringen Konzentrationen wirken. Das RN18-Derivat mit dem besten Ergebnis war FM86 (EC50-Wert: 4.5 μM). Andererseits wurden niedermolekulare Substanzen aus verschiedenen Arbeitsgruppen untersucht, um weitere Substanzen zu finden, die ebenso wie RN18 in der Lage sind, die Vif/Apobec3G-Interaktion zu hemmen. Auch hier wurden mehrere Substanzen ermittelt, die eine bessere Wirksamkeit als RN18 erkennen ließen. Derivate der Substanz CBA77a konnten am effektivsten den Abbau von Apobec3G durch Vif verhindern. Das beste Ergebnis wurde für die Testsubstanz CBA82 ermittelt (EC50-Wert: 2.8 μM). Ob die Ergebnisse der Testsubstanzen ausschließlich auf die Hemmung der Vif/A3G Interaktion zurückzuführen sind, kann letztendlich nicht abschließend beurteilt werden. Eine Erweiterung des Testsystems durch unsere Arbeitsgruppe sieht daher vor, falsch positive Ergebnisse zu erkennen. / As a part of the innate immune system the maintenance of the antiviral qualities of Apobec3G offers a promising starting point to curtail the infectivity of HIV. RN18 is described as a Vif antagonist in the literature (Nathans et al. 2008). To find out substances, they are able to inhibit the reduction of Apobec3G by Vif, following tests were made in this dissertation: In a first step the effectiveness of the test substances in a concentration of 30 μM was determined (Screening). Substances, which caused a similar inhibition of the reduction of Apobec3G in comparison to RN18, a quantitative analysis was made to get the half-maximum inhibition concentration (Titration). On the one hand derivatives of the known Vif antagonist RN18 were tested. The RN18 derivative with the best result was FM86 (EC50 value: 4.5 μM). On the other hand low-molecular substances were tested, if they are able to inhibit the interaction of Apobec3G and Vif as RN18 do. Derivatives of the substance CBA77a inhibit most actually the reduction of Apobec3G by Vif. The best result was determined for the test substance CBA82 (EC50 value: 2.8 μM). It is not able to judge, if the results of the test substances are reduce exclusively to the inhibition of the Vif/Apobec3G interaction. Therefore our working group plans to extend the test system to prevent false positive results.

Le cancer colorectal est une affection multifactorielle qui conjugue des anomalies épigénétiques et des altérations moléculaires à une déstabilisation du génome. En dehors de deux processus bien établis, l’instabilité des microsatellites et l’instabilité des chromosomes, la déstabilisation du génome peut être consécutive à la réexpression d’éléments génétiques mobiles, HERV et LINEs-­‐1. Les HERVs ont un potentiel de modulation de l’immunité qui pourrait contrôler les réactions de l’hôte dans le processus de la carcinogenèse. Compte tenu du rôle que pourrait jouer les HERV, nous avons voulu déterminer la relation entre l’infiltrat lymphocytaire intratumoral et les différentes caractéristiques moléculaires des tumeurs. L’infiltrat lymphocytaire intratumoral a été évalué pour trois marqueurs (CD3, CD8 et CD45RO). Les marqueurs moléculaires analysés ont été : les mutations des gènes B-­‐raf, k-­‐ras et Pi3K, le statut des microsatellites, la méthylation de MLH1 et des LINEs-­‐1, un polymorphisme de C-­‐met et de HLA-­‐G. Ces marqueurs ont été comparés à la prévalence de la délétion du locus Apobec 3 pour une cohorte de 135 patients porteurs de cancer colorectal. / Colorectal cancer is a multifactorial disease associated to epigenetic abnormalities and molecular alterations inducing a destabilization of the cellular genome. Besides two well-­established processes, microsatellite instability and chromosome instability, the destabilization of the genome may follow mobilisation of endongenised mobile genetic elements, such as HERV or LINEs-­‐1. HERV have a potential to modulate immune response, which suggests that they could contribute to the process of carcinogenesis. We thus wanted to determine the relationship between intratumoral lymphocytic infiltration and the different molecular characteristics of tumours, taking into account factors that could influence the expression of HERV, such as the frequently observed deletion of a locus on 22q13 containing the Apobec 3 gene family. The intratumoral lymphocytic infiltration was assessed for three markers (CD3, CD8 and CD45RO). The molecular markers analysed were: the mutations of B-­‐raf, K-­‐ras and Pi3K genes, the instability status of microsatellites, the methylation of MLH1 and LINEs-­‐1, a polymorphism in C-­‐met and in HLA-­‐G. These markers were linked to the deletion of the locus containing Apobec 3 genes, in a cohort of 135 colorectal cancer patients.

La protéine Vif (Viral infectivity factor) joue un rôle essentiel dans la réplication virale et dans le pouvoir infectieux du VIH-1. Elle est aussi qualifiée de « protéine de contre-défense » car elle neutralise un facteur cellulaire à action antivirale, APOBEC3 en recrutant le complexe de la E3 ubiquitine ligase formé de CBFβ/EloB/EloC/Cul5/Rbx2, qui va entrainer sa polyubiquitinilation et sa dégradation. APOBEC3 comprend une famille de protéines présentes dans les mammifères et capable d'induire des mutations dans l'ADN viral.La structure tridimensionnelle des molécules et complexes macromoléculaires étant intimement liée à la fonction, il est primordial de connaître la place d’A3G/F dans le complexe Vif-CBFβ-EloB-EloC ainsi que les détails des interactions entre Vif et A3G/F, ceci dans une perspective thérapeutique.La co-expression des différentes protéines de ce complexe a été réalisée dans deux systèmes d’expression : bactérien (E. coli) et eucaryote (BHK21) dû au manque de solubilité d’APOBEC et de la difficulté de sa cristallisation. Une fois les protéines exprimées et le complexe Vif-CBFβ-EloB-EloC-A3G/F formé dans les deux systèmes, des tests de cristallisation et des études structurales seront réalisés pour caractériser la structure et la fonction des protéines.Dans E. coli, j’ai réussi à obtenir le complexe Vif/CBFβ/EloB/EloC/Cul5 in vivo et in vitro de manière soluble, pure, monodisperse ainsi qu’en quantité adéquate avec les études biophysiques envisagées. Par contre, je n’ai pas réussi à surexprimer A3G. En passant dans les cellules de hamster BHK21 et en appliquant la technique du virus de la vaccine, nous avons réussi à obtenir le complexe Vif-CBFβ-EloB-EloC-A3G/F mais en quantité insuffisante pour la cristallisation.Les perspectives de ce projet seront d’améliorer : (1) les rendements du complexe pour des tests de cristallisation et (2) la pureté du complexe pour réaliser la cryo-microscopie électronique. / APOBEC3 are human antiviral cytidine deaminase and RNA/DNA-editing enzymes that belong to the innate immune defense system, targeting retroviruses or retrotransposons. Among all APOBEC3 proteins, hA3B, hA3C, hA3DE, hA3F and hA3G are able to interfere negatively with HIV-1 infectivity: they induce a deamination of dC to dU in the minus strand DNA, resulting in G to A hypermutation in the plus strand DNA. This hypermutation results either into a degradation of U-rich DNA strands by the uracyl-DNA glycosylase or into the production of aberrant viral protein. In addition, a deaminase-independent mechanism is able to inhibit the HIV-1 reverse transcription through a yet unknown mechanism.To evade the host defense system, HIV expresses the virion infectivity factor, Vif, which causes the degradation of APOBEC3G by the proteasome by recruiting the E3 ubiquitin ligase complex composed of the CBFβ, EloB, EloC, Cullin5, Rbx2 proteins. The goal of this study will be the determination of the X-ray structure of the Vif/APOBEC-3 complex. Understanding this molecular recognition might be useful to direct structure-based design of anti-HIV drugs that act by inhibiting the action of Vif and lead to new anti-HIV drugs.To overcome the solubility problems of Vif and APOBEC3G/F, a co-expression strategy had been applied with the different E3 ubiquitin ligase proteins both in prokaryotic (E. coli) and eukaryotic (BHK21) systems. Once the complex obtained, we will perform several structural and biophysical studies as well as crystallization trials.In E. coli, I managed to obtain the Vif/CBFβ/EloB/EloC/Cul5 complex in vivo and in vitro, soluble, monodisperse and in good quantities for structural studies. The protein A3G was not obtained in E. coli even by co-expression with the complex.On the other side, I succeeded in obtaining the polyprotein Vif-CBFβ-EloB-EloC-A3G/F complex in the hamster cells (BHK21) by applying the vaccinia virus strategy. Optimizing the yield and the purity is necessary for crystallization and more structural studies.

Made available in DSpace on 2015-07-22T20:49:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-10-29. Added 1 bitstream(s) on 2015-08-11T03:25:40Z : No. of bitstreams: 1 Publico-065a.pdf: 467665 bytes, checksum: 5c21c191852c281d4e2eebf6fd7a8d72 (MD5). Added 1 bitstream(s) on 2015-08-11T03:25:40Z : No. of bitstreams: 2 Publico-065a.pdf: 467665 bytes, checksum: 5c21c191852c281d4e2eebf6fd7a8d72 (MD5) Publico-065b.pdf: 1808818 bytes, checksum: ea880bd6471f0602f5add685ca9800fe (MD5) / INTRODUÇÃO: A substituição monótona de bases G → A no genoma do HIV-1 é observada desde a década de 1990, entretanto, apenas recentemente esse efeito foi atribuído às APOBECs (apolipoprotein B editing catalytic polypeptide) da imunidade inata. As APOBECs celulares atuam na deaminação de citidina a uridina na fita de DNA viral de polaridade negativa e esse efeito é verificado como excesso de adeninas na fita complementar de DNA viral resultante do processo de transcrição reversa. A presença de hipermutações ocasiona perda da capacidade replicativa da partícula do HIV-1 e pode levar populações virais à extinção. Estudos in vitro demonstraram o efeito antiretroviral das APOBECs3 baseados, principalmente, na verificação de hipermutação. Por outro lado, estudos sistemáticos in vivo são escassos e os dados da literatura são controversos com relação ao efeito da hipermutação no genoma das subpopulações de HIV-1 e na dinâmica da infecção. OBJETIVOS: Este estudo objetivou avaliar os efeitos da hipermutação em pacientes HIVpositivos não tratados correlacionando a freqüência de hipermutação com a carga viral. A carga viral é um importante indicador biológico de replicação do HIV-1 e clínico de progressão para a aids. Assim sendo, foi testado se a presença de hipermutação tem efeito protetor no controle da infecção natural pelo HIV utilizando como parâmetro de apoio a carga viral plasmática do HIV-1 nas 157 amostras de pacientes não tratados testadas para detecção de hipermutação. A integrase constitui um hot spot de hipermutação no genoma viral. MÉTODOS: Foi realizada PCR (Polymerase Chain Reaction) para amplificar um fragmento de 582 pares de bases do gene da integrase e o produto de PCR foi visualizado em gel de agarose com HA-Yellow. O corante HA-Yellow retarda a migração eletroforética de um produto de PCR proporcionalmente ao conteúdo de bases A da sequência. Nosso método de análise foi validado com base em sequências de clones e calibrado em acordo com os resultados gerados pelo programa Hypermut (disponível em http://www.hiv.lanl.gov/content/sequence/HYPERMUT/ hypermut.html). A análise dos dados realizou-se com base na estatística de K-means que permitiu agrupar as amostras clínicas de acordo com sua distância de migração no gel de agarose com HA-Yellow. RESULTADOS: Foi observada hipermutação em 31,2% (n=49/157) destas amostras e houve associação entre presença de hipermutação e maiores níveis de viremia (P=0,02, teste de Mann-Whitney). Adicionalmente, a presença de hipermutação não apresentou associação com menores níveis de linfócitos T CD4 positivos (P=0,06, Teste de Mann-Whitney), nem ao gênero ou à etnia. CONCLUSÕES: Os valores de carga viral detectados em cada indivíduo refletem a quantidade de partículas virais filtradas pelo processo de hipermutação e o substrato da hipermutação é a replicação viral. Assim sendo, nós constatamos que amostras clínicas com altos níveis de replicação viral exibiram o fenômeno de hipermutação mais frequentemente. Em resumo, a detecção de variantes provirais de HIV-1 portando hipermutação correlacionou-se com maiores níveis de carga viral nos pacientes avaliados. Assim sendo, concluímos que a hipermutação, fenômeno bioquímico de substituições G para A no HIV-1, é um processo pervasivo e está associada com níveis mais elevados de replicação viral. Palavras- Chave: HIV-1, APOBEC, imunidade inata, carga viral, hipermutação / TEDE / BV UNIFESP: Teses e dissertações

Non-small cell lung cancer (NSCLC) makes up the majority of lung cancers, which remains the leading cause of cancer mortality worldwide. NSCLC with mutant epidermal growth factor receptor (EGFR) is currently treated with tyrosine kinase inhibitors (TKIs). TKIs have proven effective in improving survival until resistance is conferred, mostly by way of the exon 20, threonine 790 to methionine (T790M) point mutation in EGFR. The mechanism by which this point mutation arises is poorly understood. Herein we report a possible pathway by which the C to T transition that leads to T790M comes about. We show that activation-induced cytidine deaminase (AID) mRNA expression is induced upon treatment with EGFR TKIs in mutant-EGFR human lung cancer cell lines but not in control cell lines. We also show that stable expression of AID is sufficient to produce resistance to one such TKI, erlotinib, and is sufficient to produce T790M itself. We also report that B-cell lymphoma 6 (BCL6) may precede AID in this pathway. Our results show that BCL6 is upregulated in these cell lines treated with EGFR TKIs but not in normal bronchial cells. We then treated human lung cancer cell lines with EGFR TKIs in combination with BCL6 inhibitors. Our results show that AID is dependent upon BCL6 expression. Finally, we report on results from a transient BCL6 overexpression which lead us to believe that AID mRNA receives input from at least one alternate pathway in addition to BCL6. We also performed these experiments on a family of apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC) cytidine deaminases, that show they may be involved in this pathway downstream of AID. Taken together, our results suggest a potential pathway involving BCL6, AID, and APOBEC cytidine deaminases that lead to the C to T transition that produces T790M, thereby conferring resistance to EGFR TKIs in mutant-EGFR NSCLC. They also provide potential new targets for treatment should further study confirm our results. / 2021-10-07T00:00:00Z

Le cancer de la vessie (BCa), est une tumeur maligne de l’urothélium, fréquente dans le monde entier, dont le traitement particulièrement coûteux ne permet cependant pas d’éviter les récidives et les progressions. FGFR3 est l'un des gènes les plus fréquemment mutés dans le BCa et les cellules tumorales sont dépendantes de son expression pour leur prolifération. La mutation FGFR3 S249C est fortement surreprésentée (62% des mutations récurrentes de FGFR3). Dans la première partie de ma thèse, en réalisant une étude de la signature de mutation, nous avons montré que cette surreprésentation de la mutation FGFR3 était liée à une pression sélective induite par la mutagenèse APOBEC et non due à un gain de fonction plus important induit par cette mutation. En plus de FGFR3 S249C, 44 mutations fréquentes (représentant près de la moitié des mutations fréquentes du BCa) ont été identifiées comme étant associées à la signature mutationnelle APOBEC et la plupart d'entre elles étaient surreprésentées par rapport à d'autres mutations au sein du même gène. Il est intéressant de noter que ces mutations associées à APOBEC incluaient à la fois de nouveaux ‘conducteurs’ et des ‘passagers’ fréquents potentiels et qu’elles pouvaient potentiellement prédire la réponse à l’immunothérapie et à un traitement anti-ATR (pas anti-ATM). Dans la deuxième partie de cette thèse, nous nous sommes intéressés aux effets fonctionnels du gène FGFR3 dans le BCa. En utilisant un modèle de souris transgénique, nous avons apporté la première preuve in vivo selon laquelle cette mutation FGFR3 S249C conférait un pouvoir de transformation maligne. Ce processus était associé à une instabilité accrue du génome, activation de MYC et à une angiogenèse accrue, probablement induites par le facteur induisant l'hypoxie (HIF1A). En outre, nous avons caractérisé le réseau de régulation contrôlé par FGFR3 en analysant des données protéomiques obtenues par spectrométrie de masse à partir d'une lignée de cellules cancéreuses du cancer de la vessie portant la mutation FGFR3 S249C - UMUC14. Plusieurs voies de signalisation bien connues comme étant régulées par FGFR3 ont été identifiées. Nous avons également mis en évidence de nouvelles cascades de signalisation suite à l'activation de FGFR3 pouvant être jouer un rôle dans la progression tumorale, notamment un axe FGFR3 / HIF1A / angiogenèse qui a été validé dans certains modèles de BCa in vitro et in vivo. / Bladder cancer (BCa) is a worldwide frequent and costly urothelial malignancy. FGFR3 is one of the most frequently mutated genes in BCa and a driver of an oncogenic dependency. Here, we systematically catalogued the FGFR3 point mutation spectrum in BCa and identified 14 recurrent residues (frequency ≥ 2). One hotspot mutation - FGFR3 S249C - was strongly over-represented compared to other recurrent FGFR3 mutations (62% of all recurrent mutations). Based on in-depth investigation of mutational signature, we revealed that this over-representation of FGFR3 S249C mutation was merely favoured by APOBEC mutagenesis rather than a stronger functional selection compared to other oncodriver mutations on FGFR3. Similarly, together with FGFR3 S249C, 44 frequent mutations (accounts for nearly half of all frequent mutations in BCa) were pinpointed to be associated with APOBEC mutational signature and most of them were over-represented compared to other mutations within the same gene. Interestingly, these APOBEC-associated mutations included both novel potential ‘drivers’ as well as ‘frequent passengers’, and had a potential to predict responders for immunotherapy and anti-ATR but not anti-ATM treatment. On the other hand, we were interested in functional effects of FGFR3 activation in BCa. We provided the first in vivo evidence that FGFR3 S249C mutation conferred potency to BCa transformation using a transgenic mice model. This process was associated with increased genome instability, MYC activation and enhanced angiogenesis probably mediated by hypoxia-inducing factor (HIF1A). Further, we tried to characterize FGFR3-driven regulatory network through mass spectrometry based proteomic data generated in a BCa cell line bearing FGFR3 S249C mutation – UMUC14. As expected, several well-known FGFR3 regulated signaling pathways could be identified. Of note, we also highlighted some novel signaling cascades that may be relevant to FGFR3 activation, including a FGFR3/HIF1A/angiogenesis signaling axis that we validated in several in vitro and in vivo BCa models.

Le Virus de l'Hépatite B (VHB) infecte 350 millions d'individus à l'échelle mondiale. Il est responsable d'hépatites aigües pouvant évoluer vers la chronicité puis le carcinome hépatocellulaire. Le génome du VHB est constitué d'un ADN partiellement bicaténaire. De par sa nature, il pourrait être sensible à l'action de certaines nucléases cellulaires qui hydrolysent l'ADN double brin. Nous avons ainsi mis en évidence la capacité de la Désoxyribonuclase I (DNase I) à être incorporée dans les virions du VHB, ce qui permet la dégradation du génome viral et la diminution de son infectivité. La DNAse I est particulièrement surexprimée en hypoxie et pourrait contribuer à l'élimination du virus chez les individus cirrhotiques. Par ailleurs, nous avons montré que la cytidine désaminase APOBEC3DE appartenant à une famille de facteurs de restriction viraux possède un rôle proviral. En effet, son association avec APOBEC3F et APOBEC3G mène à une diminution de l'activité de ces dernières et ceci favorise la réplication du VHB. La formation d'hétérodimères APOBEC3DE/APOBEC3F et APOBEC3DE/APOBEC3G semble génèrer un encombrement stérique ne permettant pas l'encaspidation d'APOBEC3F et APOBEC3G, raison pour laquelle le génome du VHB est moins muté lorsqu'APOBEC3DE est exprimée. / Hepatitis B Virus (HBV) infects 350 millions people worldwilde. It triggers accute hepatitis that can turn into cirrhosis then hepatocellular carcinoma. HBV genome is composed of a partially double-stranded DNA.Thus, it could be targeted by some cellular nucleases that hydrolyze double-stranded DNA. We have highlighted that Deoxyribunuclease I (DNase I) can be incorporated into HBV virions and degrade its genome, leading to a loss of viral infectivity. Moreover, DNase I is upregulated under hypoxia which is a caracteristic of liver cirrhosis. DNase I could be involved in HBV elimination in cirrhotic patients. In an other study, we found that APOBECDE, a cytidine deaminase of the same family than some restriction factors, has a proviral activity. Indeed, association of APOBEC3DE with APOBEC3F or APOBEC3G leads to a loss of cytidine deaminase activity and a better viral replication. When APOBEC3DE is associated with those two proteins, APOBEC3F and APOBEC3G cannot be incorporated into HBV virions. This is the reason why HBV is more infectious when APOBEC3DE is expressed.