17β-Estradiol induces E2F-1 gene expression in ZR-75 and MCF-7 human breast cancer cells. Analysis of the E2F-1 gene promoter in MCF-7 cells previously showed that hormone-induced transactivation required interactions between estrogen receptor α (ERα)/Sp1 bound to upstream GC-rich sites and NFYA bound to downstream CCAAT sites within the -169 to -54 promoter region. This promoter region was also E2-responsive in ERα-positive ZR-75 cells; however, further analysis of the promoter showed that cooperative ERα/Sp1/NFY interactions were not necessary for hormone-induced transactivation in ZR-75 cells. The upstream GC-rich motifs are activated independently by ERα/Sp1 in ZR-75 but not MCF-7 cells, and the downstream CCAAT sites were also E2-responsive. E2 also induced reporter gene activity in ZR-75 cells transfected with an expression plasmid containing the yeast GAL4 DNA binding domain fused to pM-NFYA and a construct containing five tandem GAL4 response elements. Subsequent studies showed that hormonal activation of pE2F-1jm1 and pM-NFYA are dependent on non-genomic pathways in which E2 activates cAMP/protein kinase A. Hormone-dependent regulation of E2F-1 gene expression in ZR-75 and MCF-7 involves different mechanisms, demonstrating the importance of cell context on transactivation pathways, even among ER-positive breast cancer cell lines. TCDD inhibited ERα-mediated responses in MCF-7 and ZR-75 cells. E2- induced E2F-1protein and mRNA levels in MCF-7 and ZR-75 cells and this response was inhibited by TCDD. Constructs containing GC-rich sites alone or in combination with the downstream NFY sites were used in transactivation studies to investigate the mechanism of inhibitory AhR-ERα crosstalk. Although TCDD inhibited E2-induced mRNA, protein and reporter gene actitivity, it was not possible to determine if the inhibitory response was due to limiting ERα protein levels due to proteasome degradation since proteaome inhibitors alone blocke hormone-dependent responses. TCDD also inhibited the cAMP/PKA pathway by inhibiting adenyl cyclase activity. In Drosophila SL-2 cells cotransfected with the GC-rich -169 to -54 region, ERα and Sp1 plasmids E2 induced transactivation in cells cotransfected with AhR/Arnt expression plasmids suggesting that the AhR complex suppressed ERα/Sp1 action. These results demonstrate that TCDD inhibits E2-dependent activation of both non-genomic and genomic pathways of ER-mediated E2F-1 gene expression. 17β-Estradiol induces E2F-1 gene expression in ZR-75 and MCF-7 human breast cancer cells. Analysis of the E2F-1 gene promoter in MCF-7 cells previously showed that hormone-induced transactivation required interactions between estrogen receptor α (ERα)/Sp1 bound to upstream GC-rich sites and NFYA bound to downstream CCAAT sites within the -169 to -54 promoter region. This promoter region was also E2-responsive in ERα-positive ZR-75 cells; however, further analysis of the promoter showed that cooperative ERα/Sp1/NFY interactions were not necessary for hormone-induced transactivation in ZR-75 cells. The upstream GC-rich motifs are activated independently by ERα/Sp1 in ZR-75 but not MCF-7 cells, and the downstream CCAAT sites were also E2-responsive. E2 also induced reporter gene activity in ZR-75 cells transfected with an expression plasmid containing the yeast GAL4 DNA binding domain fused to pM-NFYA and a construct containing five tandem GAL4 response elements. Subsequent studies showed that hormonal activation of pE2F-1jm1 and pM-NFYA are dependent on non-genomic pathways in which E2 activates cAMP/protein kinase A. Hormone-dependent regulation of E2F-1 gene expression in ZR-75 and MCF-7 involves different mechanisms, demonstrating the importance of cell context on transactivation pathways, even among ER-positive breast cancer cell lines. TCDD inhibited ERα-mediated responses in MCF-7 and ZR-75 cells. E2- induced E2F-1protein and mRNA levels in MCF-7 and ZR-75 cells and this response was inhibited by TCDD. Constructs containing GC-rich sites alone or in combination with the downstream NFY sites were used in transactivation studies to investigate the mechanism of inhibitory AhR-ERα crosstalk. Although TCDD inhibited E2-induced mRNA, protein and reporter gene actitivity, it was not possible to determine if the inhibitory response was due to limiting ERα protein levels due to proteasome degradation since proteaome inhibitors alone blocke hormone-dependent responses. TCDD also inhibited the cAMP/PKA pathway by inhibiting adenyl cyclase activity. In Drosophila SL-2 cells cotransfected with the GC-rich -169 to -54 region, ERα and Sp1 plasmids E2 induced transactivation in cells cotransfected with AhR/Arnt expression plasmids suggesting that the AhR complex suppressed ERα/Sp1 action. These results demonstrate that TCDD inhibits E2-dependent activation of both non-genomic and genomic pathways of ER-mediated E2F-1 gene expression.

Rationale/Background: The adult mammalian heart has a very limited potential for regeneration due to cardiomyocyte cell cycle withdrawal which occurs shortly after birth. One potential avenue to repair the heart following stress/injury is to reprogram pre-existing cardiomyocytes to re-enter the cell cycle. The E2F family is a group of transcription factors which ubiquitously regulate the cell cycle, but it has previously been difficult to fully appreciate their role in the post-natal myocardium due to either redundancy or embryonic lethality of genetic models. Thus we generated a dominant negative model of the E2F/Rb pathway via expression of the unique transcriptional repressor E2F6 in postnatal myocardium. E2F6 transgenic (Tg) mice developed dose dependent Dilated Cardiomyopathy (DCM) and sudden death without hypertrophy or apoptosis. This was accompanied by the partial loss of E2F3 (critical for cardiac development) and connexin-43 important for metabolic and electrical coupling. Methods/Results: In this thesis E2F6-Tg mice were examined for markers of cardiac differentiation/ function and exposed to stressors to evaluate the capacity for the E2F pathway to regulate cardiomyocyte growth (isoproterenol) and death (doxorubicin and cobalt chloride). E2F6-Tg mice were twice as sensitive to isoproterenol as their Wt counterparts due to the observed activation of a β2-adrenergic survival pathway. Cardiac hypertrophy in E2F6-Tg mice was accompanied by the rescue of E2F3 expression. Treatment of neonatal cardiomyocytes isolated from Wt and E2F6-Tg pups with cobalt chloride revealed a protective effect for E2F6 against apoptosis. Doxorubicin exposure led to the loss of E2F6 protein and abolished its protective effect. Examination of neonatal hearts and cardiomyocytes isolated from them demonstrated a shift in the cell cycle and metabolic profiles of E2F6-Tg myocardium. Tg cardiomyocytes show decreased glycolysis and a dramatic increase in the regulator of ketolysis, β-hydroxybutyrate dehydrogenase (BDH1), prior to DCM. The substrate of BDH1 (β-hydroxybutyrate) was demonstrated to influence the levels of CX-43 in cardiomyocytes. E2F6 also deregulated expression of T-cap which has been linked to human DCM. Conclusions: I provide evidence that the E2F pathway can regulate growth, death, and differentiation through a variety of mechanisms which link the cell cycle and metabolism to growth and survival to critically govern post-natal cardiac function. Furthermore, I reveal a new biomarker (BDH1) for early DCM which may be useful in diagnosis/ treatment of idiopathic cases of disease.

Devido ao constante ataque à camada de ozônio, as plantas, nos próximos anos, terão que lidar cada vez mais com uma maior quantidade de luz UV atingindo a atmosfera terrestre. O arroz é considerado uma planta modelo para as monocotiledôneas por possuir um genoma relativamente pequeno (aproximadamente 390 Mb) e devido a sua grande sintenia com outros cereais. Recentemente, as proteínas E2F foram descritas, especialmente em vertebrados, como fatores transcricionais que podem estar envolvidos com a resposta ao dano de DNA. Tendo como objetivo principal estudar como a família de fatores transcricionais E2F responde ao dano genotóxico em arroz, experimentos com luz UV-B foram conduzidos para avaliar o envolvimento destes com as respostas ao dano de DNA. Além disso, foram realizadas análises filogenéticas dessa família gênica com representantes de plantas. Em arroz, estudos prévios de nosso grupo identificaram seis genes pertencentes à família E2F, sendo quatro E2F típicos e dois E2F atípicos. Em resposta à luz UV, dois dos quatro genes que codificam E2F típicos e os dois genes de E2F atípicos, tiveram a expressão relativa aumentada após o estresse em relação a plantas mantidas em condição controle. Nesse experimento, além dos genes E2F e dos genes de reparo, também foram avaliados os níveis de transcritos de genes sabidamente envolvidos com ciclo celular e apoptose, permitindo-se verificar se o aumento de expressão dos genes E2F em resposta ao estresse está efetivamente relacionado com a resposta a danos no DNA e não a estes dois outros processos celulares. As análises filogenéticas revelaram que um desses dois E2F típicos, que apresentou sua expressão diferencial nas condições testadas, provavelmente atue como um repressor de transcrição. Esta afirmação está baseada em estudos comparativos com sequências da planta modelo para as dicotiledôneas, Arabidopsis thaliana. O conjunto de resultados obtidos sugere que alguns membros da família E2F de arroz estão envolvidos especificamente com as repostas ao dano ao DNA, além de permitir a proposição de um possível mecanismo de ação. / Due to the constant attack to the ozone layer, the plants, in the coming years, will have to deal with an increasing amount of UV light reaching the earth's atmosphere. Rice is considered a model plant for monocots due to its relatively small genome (approximately 390 Mb) and because its high synteny with other cereals. E2F proteins have recently been reported, especially in vertebrates, as transcriptional factors involved in the response to DNA damage. To study how the family of transcription factors E2F responds to genotoxic damage in rice, experiments with UV-B were conducted to evaluate their involvement with the responses to DNA damage. In addition, phylogenetic analyzes of this gene family in plants were performed. In rice, previous studies of our group identified six genes belonging to the E2F family, four typical and two atypical E2F. In response to UV light, two of four genes encoding typical E2F and the two atypical E2F genes increased their relative expression after stress compared to the plants grown in the control condition. In this experiment, in addition to the E2F gene and repair genes, we have also analyzed the transcriptional level of genes known to be involved with cell cycle and apoptosis, in order to verify if the increases in E2F gene expression, in response to stress, are actually related to the response to DNA damage, rather than to other two cellular processes. Phylogenetic analysis revealed that one of these two typical E2F, which showed differential expression under the conditions tested, probably acts as a transcriptional repressor. This analysis is based on comparisons with sequences from the model plant for dicots, Arabidopsis thaliana. These set of results suggest that some members of the E2F family of rice are involved specifically with responses to DNA damage and allowed the proposition of a possible mechanism of action.

Devido ao constante ataque à camada de ozônio, as plantas, nos próximos anos, terão que lidar cada vez mais com uma maior quantidade de luz UV atingindo a atmosfera terrestre. O arroz é considerado uma planta modelo para as monocotiledôneas por possuir um genoma relativamente pequeno (aproximadamente 390 Mb) e devido a sua grande sintenia com outros cereais. Recentemente, as proteínas E2F foram descritas, especialmente em vertebrados, como fatores transcricionais que podem estar envolvidos com a resposta ao dano de DNA. Tendo como objetivo principal estudar como a família de fatores transcricionais E2F responde ao dano genotóxico em arroz, experimentos com luz UV-B foram conduzidos para avaliar o envolvimento destes com as respostas ao dano de DNA. Além disso, foram realizadas análises filogenéticas dessa família gênica com representantes de plantas. Em arroz, estudos prévios de nosso grupo identificaram seis genes pertencentes à família E2F, sendo quatro E2F típicos e dois E2F atípicos. Em resposta à luz UV, dois dos quatro genes que codificam E2F típicos e os dois genes de E2F atípicos, tiveram a expressão relativa aumentada após o estresse em relação a plantas mantidas em condição controle. Nesse experimento, além dos genes E2F e dos genes de reparo, também foram avaliados os níveis de transcritos de genes sabidamente envolvidos com ciclo celular e apoptose, permitindo-se verificar se o aumento de expressão dos genes E2F em resposta ao estresse está efetivamente relacionado com a resposta a danos no DNA e não a estes dois outros processos celulares. As análises filogenéticas revelaram que um desses dois E2F típicos, que apresentou sua expressão diferencial nas condições testadas, provavelmente atue como um repressor de transcrição. Esta afirmação está baseada em estudos comparativos com sequências da planta modelo para as dicotiledôneas, Arabidopsis thaliana. O conjunto de resultados obtidos sugere que alguns membros da família E2F de arroz estão envolvidos especificamente com as repostas ao dano ao DNA, além de permitir a proposição de um possível mecanismo de ação. / Due to the constant attack to the ozone layer, the plants, in the coming years, will have to deal with an increasing amount of UV light reaching the earth's atmosphere. Rice is considered a model plant for monocots due to its relatively small genome (approximately 390 Mb) and because its high synteny with other cereals. E2F proteins have recently been reported, especially in vertebrates, as transcriptional factors involved in the response to DNA damage. To study how the family of transcription factors E2F responds to genotoxic damage in rice, experiments with UV-B were conducted to evaluate their involvement with the responses to DNA damage. In addition, phylogenetic analyzes of this gene family in plants were performed. In rice, previous studies of our group identified six genes belonging to the E2F family, four typical and two atypical E2F. In response to UV light, two of four genes encoding typical E2F and the two atypical E2F genes increased their relative expression after stress compared to the plants grown in the control condition. In this experiment, in addition to the E2F gene and repair genes, we have also analyzed the transcriptional level of genes known to be involved with cell cycle and apoptosis, in order to verify if the increases in E2F gene expression, in response to stress, are actually related to the response to DNA damage, rather than to other two cellular processes. Phylogenetic analysis revealed that one of these two typical E2F, which showed differential expression under the conditions tested, probably acts as a transcriptional repressor. This analysis is based on comparisons with sequences from the model plant for dicots, Arabidopsis thaliana. These set of results suggest that some members of the E2F family of rice are involved specifically with responses to DNA damage and allowed the proposition of a possible mechanism of action.

Devido ao constante ataque à camada de ozônio, as plantas, nos próximos anos, terão que lidar cada vez mais com uma maior quantidade de luz UV atingindo a atmosfera terrestre. O arroz é considerado uma planta modelo para as monocotiledôneas por possuir um genoma relativamente pequeno (aproximadamente 390 Mb) e devido a sua grande sintenia com outros cereais. Recentemente, as proteínas E2F foram descritas, especialmente em vertebrados, como fatores transcricionais que podem estar envolvidos com a resposta ao dano de DNA. Tendo como objetivo principal estudar como a família de fatores transcricionais E2F responde ao dano genotóxico em arroz, experimentos com luz UV-B foram conduzidos para avaliar o envolvimento destes com as respostas ao dano de DNA. Além disso, foram realizadas análises filogenéticas dessa família gênica com representantes de plantas. Em arroz, estudos prévios de nosso grupo identificaram seis genes pertencentes à família E2F, sendo quatro E2F típicos e dois E2F atípicos. Em resposta à luz UV, dois dos quatro genes que codificam E2F típicos e os dois genes de E2F atípicos, tiveram a expressão relativa aumentada após o estresse em relação a plantas mantidas em condição controle. Nesse experimento, além dos genes E2F e dos genes de reparo, também foram avaliados os níveis de transcritos de genes sabidamente envolvidos com ciclo celular e apoptose, permitindo-se verificar se o aumento de expressão dos genes E2F em resposta ao estresse está efetivamente relacionado com a resposta a danos no DNA e não a estes dois outros processos celulares. As análises filogenéticas revelaram que um desses dois E2F típicos, que apresentou sua expressão diferencial nas condições testadas, provavelmente atue como um repressor de transcrição. Esta afirmação está baseada em estudos comparativos com sequências da planta modelo para as dicotiledôneas, Arabidopsis thaliana. O conjunto de resultados obtidos sugere que alguns membros da família E2F de arroz estão envolvidos especificamente com as repostas ao dano ao DNA, além de permitir a proposição de um possível mecanismo de ação. / Due to the constant attack to the ozone layer, the plants, in the coming years, will have to deal with an increasing amount of UV light reaching the earth's atmosphere. Rice is considered a model plant for monocots due to its relatively small genome (approximately 390 Mb) and because its high synteny with other cereals. E2F proteins have recently been reported, especially in vertebrates, as transcriptional factors involved in the response to DNA damage. To study how the family of transcription factors E2F responds to genotoxic damage in rice, experiments with UV-B were conducted to evaluate their involvement with the responses to DNA damage. In addition, phylogenetic analyzes of this gene family in plants were performed. In rice, previous studies of our group identified six genes belonging to the E2F family, four typical and two atypical E2F. In response to UV light, two of four genes encoding typical E2F and the two atypical E2F genes increased their relative expression after stress compared to the plants grown in the control condition. In this experiment, in addition to the E2F gene and repair genes, we have also analyzed the transcriptional level of genes known to be involved with cell cycle and apoptosis, in order to verify if the increases in E2F gene expression, in response to stress, are actually related to the response to DNA damage, rather than to other two cellular processes. Phylogenetic analysis revealed that one of these two typical E2F, which showed differential expression under the conditions tested, probably acts as a transcriptional repressor. This analysis is based on comparisons with sequences from the model plant for dicots, Arabidopsis thaliana. These set of results suggest that some members of the E2F family of rice are involved specifically with responses to DNA damage and allowed the proposition of a possible mechanism of action.

Les facteurs de transcription E2F sont impliqués dans différents processus physiologiques comme l'apoptose, la sénescence et la progression dans le cycle cellulaire par exemple. Des travaux antérieurs dans le laboratoire ont démontré que la localisation de E2F4 est dépendante du cycle cellulaire. Dans les cellules prolifératives de la crypte intestinale, E2F4 se localise au noyau alors que dans les cellules quiescentes ou différenciées, E2F4 est cytoplasmique. La localisation cellulaire de E2F4 est un élément important pour le contrôle de son activité transcriptionnelle. Nous avons analysé l'effet de l'expression nucléaire et constitutive de E2F4 dans un modèle de cellules épithéliales intestinales humaines normales (HIEC) pour en mesurer l'impact sur la prolifération et la survie cellulaire. Nous démontrons pour la première fois que E2F4 module l'expression de gènes associés à la régulation de la voie intrinsèque et extrinsèque de l'apoptose, un rôle qui lui était inconnu jusqu'à présent. Par interférence d'ARN, nous avons diminué les niveaux d'expression de p53, un gène au coeur de la régulation de l'apoptose. Nous avons observé que la mort cellulaire est significativement retardée. De plus, nous avons démontré que l'inhibition de l'activité des caspases ne prévient pas non plus la mort cellulaire. L'implication de mécanismes de mort cellulaire alternatifs p53 indépendants a été investiguée. Nos résultats démontrent que l'inhibition de l'activité des calpaïnes/cathepsines, de RIP, de la voie JNK, même en combinaison avec une réduction des niveaux de p53, ne font que retarder la mort cellulaire mais ne l'empêche jamais. Nos résultats indiquent que plusieurs mécanismes de mort cellulaire classiques (voies intrinsèque et extrinsèque) et alternatifs (ROS, autophagie, AIF) sont probablement activés par la surexpression nucléaire de E2F4 dans les cellules épithéliales intestinales. Nous avons aussi évalué l'importance de E2F4 dans le contrôle de la prolifération des cellules épithéliales intestinales humaines normales et cancéreuses. Nous avons observé un ralentissement important de la prolifération et une cinétique d'entrée en phase S ralentie pour les populations HIEC qui expriment des niveaux réduits de E2F4. Ce ralentissement est probablement attribuable à la modulation des niveaux d'expression autant en ARNm et en protéines de nombreux gènes régulateurs de la transition G1/S tels que c-myc, cdk2, les cyclines A et D ainsi que p21 et p27 notamment. L'impact majeur de E2F4 sur le contrôle de la transition Gl/S n'avait jamais encore été décrit dans la littérature. De plus, dans les lignées cellulaires cancéreuses colorectales, E2F4 est surexprimé et se localise préférentiellement dans le noyau. Cette observation est confirmée par l'utilisation d'une banque de tissus où nous avons constaté que dans 24 spécimens sur 30, E2F4 est surexprimé dans la tumeur par rapport au tissu normal et que E2F4 est surtout nucléaire Finalement, nous avons aussi diminué les niveaux d'expression de E2F4 par interférence à l'ARN dans les lignées cellulaires Caco-2/15 et HCT-116 pour en analyser l'impact sur la prolifération et la survie cellulaire. Dans les deux lignées, la réduction de l'expression de E2F4 induit un ralentissement de la prolifération significatif et elle réduit leur capacité à former des colonies en agar mou. Par ailleurs, la réduction des niveaux d'expression de E2F4 entraîne une entrée accélérée en sénescence cellulaire dans les cellules HIEC et induit l'apparition de caractéristiques liées à la sénescence dans la lignée cellulaire Caco-2/15 révélant ainsi un rôle insoupçonné de E2F4 dans le contrôle de la sénescence cellulaire. Pris ensemble, mes résultats démontrent que E2F4 est un acteur majeur du contrôle du cycle cellulaire, de la survie et de la sénescence cellulaire dans les cellules épithéliales intestinales humaines normales et cancéreuses.

Recently developed potent and selective CDK4/6 inhibitors fall into two classes based on structure and toxicity profiles in clinical studies. One class, exemplified by palbociclib and ribociclib, exhibits neutropenia as a dose-limiting toxicity and requires discontinuous dosing. In contrast, the structurally distinct CDK4/6 inhibitor abemaciclib is dosed continuously, and has diarrhea and fatigue as dose-limiting toxicities. In preclinical models, palbociclib has been extensively studied and induces cell cycle inhibition in an RB-dependent manner. Thus far, abemaciclib has been less extensively evaluated. We found that abemaciclib cell cycle inhibitory activity is RB-dependent at clinically achievable concentrations. Abemaciclib elicited potent suppression of RB/E2F regulated genes associated with prognosis in ER-positive breast cancer. However, unlike palbociclib, at 250nM-1 mu M doses abemaciclib induced cell death in RB-deficient cell lines. This response was associated with a rapidlyinduced multi-vacuolar phenotype indicative of lysosomal membrane permeabilization that could be ameliorated with chloroquine. This event was not a reflection of inhibition of other CDK family members, but could be recapitulated with CBX4945 that inhibits casein and DYRK/HIPK kinases. To determine if these "off-target" features of abemaciclib were observed in vivo, mice harboring matched RB-positive and negative xenografts were treated with palbociclib and abemaciclib. In vivo, all of the apparent activity of abemaciclib was RB-dependent and strongly elicited suppression of cell cycle regulatory genes in a fashion markedly similar to palbociclib. Using gene expression data from cell lines and tumors treated with abemaciclib and palbociclib a composite signature of response to CDK4/6 inhibition was developed that included many genes that are individually required for tumor cell proliferation or viability. These data indicate that while abemaciclib and palbociclib can exert distinct biological and molecular effects, there are common gene expression features that could be broadly utilized in measuring the response to CDK4/6 inhibition.

No description available.

No description available.

L'ADN des cellules eucaryotes est enroulé autour de protéines appelées histones pour former la chromatine. Le niveau de compaction de la chromatine est dynamique. Ceci permet de réguler via l'accessibilité de l'ADN, les processus comme la transcription. Les histones peuvent subir des modifications post traductionnelles comme la méthylation, qui influencent le niveau de compaction de la chromatine. Par exemple, au niveau des promoteurs des gènes, la méthylation sur la lysine 9 de l'histone H3 (H3K9) est associée à la répression transcriptionnelle, tandis que la méthylation sur la lysine 4 (H3K4) est associée a l'activation transcriptionnelle. Ces marques sont mises en place par des histones méthyltransférases et enlevées par des histones déméthylases qui sont spécifiques des résidus méthylés. Ma thèse a porté sur l'étude d'histone déméthylases dans la régulation transcriptionnelle de gènes clé de la prolifération cellulaire, les gènes cibles de E2F et l'ADN ribosomique. Les facteurs E2Fs régulent des gènes comme CCNE et CDC6 impliques dans l'entrée et la progression en phase S. Ces gènes sont activés au début de la phase S. Le contrôle de la transcription de ces gènes est crucial pour un cycle cellulaire normal et leur dérégulation est associée à l'apparition de cancers. La répression et l'activation des gènes cibles de E2F au cours du cycle cellulaire fait intervenir le contrôle de la méthylation des résidus H3K4 et H3K9. Cependant, les histone déméthylases impliquées sont mal connues. Nous avons montré que les histones déméthylases JARID1A et JARID1B, spécifiques de H3K4, régulent la transcription de CCNE et CDC6 en phase S. JARID1A et JARID1B sont recrutées au promoteur de ces gènes. Elles sont importantes pour limiter leur activation lors de la progression en phase S. Cette étude montre pour la première fois l'implication de ces histones déméthylases dans la régulation fine des gènes cibles de E2F au cours du cycle cellulaire. La transcription des gènes ribosomiques ou ADNr par l'ARN Polymérase I (Pol-I) est la première étape de la biogénèse des ribosomes. Elle a lieu dans les nucléoles. Ce processus est étroitement lié à la croissance et la prolifération cellulaire. Une transcription Pol-I accrue et des nucléoles hypertrophiés sont des caractéristiques communes à un grand nombre de cellules cancéreuses. La transcription Pol-I est adaptée à la disponibilité en facteurs de croissance. Ainsi, elle est réprimée lorsque les cellules sont privées en facteurs de croissance et activée en leur présence. Cette réponse est sous le contrôle de cascades de signalisation cellulaire comme la voie Phosphatidyl-Inositol-3-Phosphate (PI3K). Il est connu que des événements dynamiques de méthylation d'histones participent à cette régulation. Cependant, on sait peu de choses sur comment les voies de signalisation régulent ces événements. En collaboration avec l'équipe du Dr. Konstantin Panov, nous avons observé que l'histone déméthylase JMJD2A, spécifique de H3K9, est présente dans les nucléoles de cellules humaines. JMJD2A, via sa capacité à déméthyler H3K9, est requise pour activer la transcription Pol-I en réponse aux facteurs de croissance. Nous montrons également que PI3K régule cette réponse chromatinienne en déclenchant l'accumulation de JMJD2A dans les nucléoles en réponse aux facteurs de croissance. Cette étude indique que la régulation de la localisation subnucléraire de JMJD2A en réponse à la voie PI3K est un des mécanismes par lesquels les cellules adaptent leur capacité de synthèse protéique à la disponibilité de facteurs de croissance. Mes travaux de thèse renforcent notre compréhension des mécanismes impliquant des histones déméthylases dans la régulation de la prolifération cellulaire. Comprendre ces mécanismes est crucial et permettra de cibler ces enzymes dans le traitement des pathologies de la prolifération cellulaire comme le cancer. / In eukaryote nuclei, DNA is wrapped around histone proteins. This structure is called the chromatin. The compaction level of chromatin is highly dynamic. This allows the regulation of gene transcription which requires free access to the DNA. Histone proteins undergo several post translational modifications including methylation that impact chromatin compaction. For example, at genes promoters, methylation on the lysine 9 of histone H3 (H3K9) is associated with chromatin compaction and thereby transcription repression, whereas methylation on histone H3 lysine 4 (H3K4) is associated with transcriptional activation. Histone methylation is set by enzymes called histone methyltransferases and removed by histone demethylases which are specific for methylated residues. During my PhD, I studied the role of histone demethylases in the transcriptional regulation of cell proliferation master genes, E2F-regulated genes and rDNA transcription. E2F transcription factors regulate genes like CCNE or CDC6 involved in entry and progression through S phase. Those genes must be activated at the onset of S phase. The transcriptional control of those genes is crucial for a normal cell cycle, and their deregulation is associated with cancer development. Histone methylation events are involved in the repression and activation of E2F target genes during cell cycle progression. However the histone demethylases involved are still unclear. We have shown that the H3K4-specific histone demethylases JARID1A and JARID1B are involved in the fine-tuning of CCNE and CDC6 transcription during S phase. JARID1A and JARID1B are recruited on the promoter of those genes and help limiting their activation at the beginning of S phase. This study shows for the first time the role of those histone demethylases in the fine tuned regulation of E2F targets genes during S phase. Ribosomal DNA (rDNA) transcription is the first step of ribosome biogenesis. rDNA is transcribed in the nucleolus by RNA polymerase I (Pol-I). Pol-I transcription is tightly linked to cell growth and proliferation. High levels of Pol-I transcription along with hypertrophied nucleoli is a hallmark of several cancers cells. Pol-I transcription must be regulated according to the availability of growth factors. It is repressed when the cells are deprived of growth factors and activated when growth factors are available. This regulation is under the control of cellular signaling pathways including the Phosphatidyl-Inositol-3-Kinase (PI3K) pathway. Histone methylation events are known to play a role in this regulation. However little is known about how the cell signaling pathways modulate the chromatin response in this process. In collaboration with the team of Dr. Konstantin Panov, we observed that the H3K9-specific histone demethylase JMJD2A is present in the nucleoli of human cells. We showed that JMJD2A, through its ability to demethylate H3K9, is required for the activation of Pol-I transcription in response to growth factors. We further show that PI3K regulate this chromatin response by triggering accumulation of JMJD2A in the nucleoli in response to growth factors. This study demonstrates a yet unknown role for JMJD2A in Pol-I transcription and suggests that the control of JMJD2A localization by the PI3K pathway is a crucial mechanism by which cells adapt protein synthesis to the availability of growth factors. My PhD work helps strengthening our understanding of the mechanisms that involve histone demethylases in the regulation of cell proliferation genes. Understanding those mechanisms is crucial as it might help targeting those enzymes for the treatment of cell proliferation-associated diseases like cancer.