STRUCTURE DU COMPOSANT AVAL DE L'ORIGINE DE REPLICATION ORILYT DU VIRUS D'EPSTEIN-BARR ET CARACTERISATION DE LA PROTEINE K8 DU VIRUS HHV8 (DOCTORAT DIFFERENCIATION, GENETIQUE ET IMMUNOLOGIE)

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Conservation of the deadenylase activity of proteins of the Caf1 family in human

The yeast Pop2 protein, belonging to the eukaryotic Caf1 family, is required for mRNA deadenylation in vivo. It also catalyzes poly(A) degradation in vitro, even though this property has been questioned. Caf1 proteins are related to RNase D, a feature supported by the recently published structure of Pop2. Yeast Pop2 contains, however, a divergent active site while its human homologs harbor consensus catalytic residues. Given these differences, we tested whether its deadenylase activity is conserved in the human homologs Caf1 and Pop2. Our data demonstrate that both human factors degrade poly(A) tails indicating their involvement in mRNA metabolism

Les modifications post-traductionnelles orchestrent l’action du récepteur des œstrogènes εRα dans les tumeurs mammaires

Il apparaît de plus en plus évident que les modifications post-traductionnelles, par leur capacité à moduler de manière réversible les fonctions des protéines modifiées, sont les acteurs majeurs de la plasticité fonctionnelle des protéines. Le récepteur des œstrogènes (εRα), largement impliqué dans le développement du cancer mammaire, est également la cible de nombreuses modifications post-traductionnelles. Celles-ci modulent son activité en changeant sa localisation via la création de nouvelles surfaces d’interaction ou le masquage de surfaces existantes, modifiant ainsi la nature de ses partenaires. Certaines de ces modifications post-traductionnelles de εRα sont dérégulées dans les cancers mammaires et pourraient constituer de potentielles cibles thérapeutiques

Protein arginine methylation in estrogen signaling and estrogen-related cancers.

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Cracking the estrogen receptor's posttranslational code in breast tumors.

International audienceEstrogen signaling pathways, because of their central role in regulating the growth and survival of breast tumor cells, have been identified as suitable and efficient targets for cancer therapies. Agents blocking estrogen activity are already widely used clinically, and many new molecules have entered clinical trials, but intrinsic or acquired resistance to treatment limits their efficacy. The basic molecular studies underlying estrogen signaling have defined the critical role of estrogen receptors (ER) in many aspects of breast tumorigenesis. However, important knowledge gaps remain about the role of posttranslational modifications (PTM) of ER in initiation and progression of breast carcinogenesis. Whereas major attention has been focused on the phosphorylation of ER, many other PTM (such as acetylation, ubiquitination, sumoylation, methylation, and palmitoylation) have been identified as events modifying ER expression and stability, subcellular localization, and sensitivity to hormonal response. This article will provide an overview of the current and emerging knowledge on ER PTM, with a particular focus on their deregulation in breast cancer. We also discuss their clinical relevance and the functional relationship between PTM. A thorough understanding of the complete picture of these modifications in ER carcinogenesis might not only open new avenues for identifying new markers for prognosis or prediction of response to endocrine therapy but also could promote the development of novel therapeutic strategies

Transcriptional Repression of Estrogen Receptor α Signaling by SENP2 in Breast Cancer Cells.: ERα repression by SENP2

We wish to thank Drs Marc Piechaczyk and Guillaume Bossis for fruitful discussions. We are grateful to Dr Balaguer (IRCM, Montpellier) for providing ERE-β-globin-luciferase (EBL+), to Dr Khochbin (INSERM U823, Grenoble) for L8G5-luc and LexA-VP16, to Dr Chambon (IGBMC, Illkirch) for psg5-Erα, psg5-HE15, psg5-HEΔD and psg5-AF2, to Dr Dejean (Institut Pasteur, Paris) for pSG5-His-SUMO1, to Dr Hay (University of Dundee, Dundee) for pGEX-SUMO1 and to Dr Shuai (University of California, Los Angeles) for the pCMV-Flag PIAS1 expression vector.International audienceEstrogen receptors (ERs) are ligand-activated transcription factors involved in many physiological and pathological processes, including breast cancer. Their activity is fine-tuned by posttranslational modifications, notably sumoylation. In the present study, we investigated the role of the small ubiquitin-related modifier (SUMO) protease, SUMO1/sentrin/suppressor of Mif 2-specific peptidase 2 (SENP2), in the regulation of ERα activity. We first found SENP2 to significantly repress estradiol-induced transcriptional activity in breast cancer cells (MCF7 and T47D). This effect was observed with a reporter plasmid and on endogenous genes such as TFF1 and CTSD, which were shown to recruit SENP2 in chromatin immunoprecipitation experiments. Using glutathione S-transferase pull-down, coimmunoprecipitation and proximity ligation assays, SENP2 was found to interact with ERα and this interaction to be mediated by the amino-terminal region of the protease and the hinge region of the receptor. Interestingly, we demonstrated that ERα repression by SENP2 is independent of its SUMO protease activity and requires a transcriptional repressive domain located in the amino-terminal end of the protease. Using small interfering RNA assays, we evidenced that this domain recruits the histone deacetylase 3 (HDAC3), to be fully active. Furthermore, using both overexpression and knockdown strategies, we showed that SENP2 robustly represses estrogen-dependent and independent proliferation of MCF7 cells. We provided evidence that this effect requires both the proteolytic and transcriptional activities of SENP2. Altogether, our study unravels a new property for a SUMO protease and identifies SENP2 as a classical transcription coregulator

Generation of a conditional Flpo/FRT mouse model expressing constitutively active TGFβ in fibroblasts

International audienceTransforming growth factor (TGFβ) is a secreted factor, which accumulates in tissues during many physio- and pathological processes such as embryonic development, wound healing, fibrosis and cancer. In order to analyze the effects of increased microenvironmental TGFβ concentration in vivo, we developed a conditional transgenic mouse model (Flpo/Frt system) expressing bioactive TGFβ in fibroblasts, a cell population present in the microenvironment of almost all tissues. To achieve this, we created the genetically-engineered [Fsp1-Flpo; FSFTGFβCA] mouse model. The Fsp1-Flpo allele consists in the Flpo recombinase under the control of the Fsp1 (fibroblast-specific promoter 1) promoter. The FSFTGFβCA allele consists in a transgene encoding a constitutively active mutant form of TGFβ (TGFβCA) under the control of a Frt-STOP-Frt (FSF) cassette. The FSFTGFβCA allele was created to generate this model, and functionally validated by in vitro, ex vivo and in vivo techniques. [Fsp1-Flpo; FSFTGFβCA] animals do not present any obvious phenotype despite the correct expression of TGFβCA transgene in fibroblasts. This [Fsp1-Flpo; FSFTGFβCA] model is highly pertinent for future studies on the effect of increased microenvironmental bioactive TGFβ concentrations in mice bearing Cre-dependent genetic alterations in other compartments (epithelial or immune compartments for instance). These dual recombinase system (DRS) approaches will enable scientists to study uncoupled spatiotemporal regulation of different genetic alterations within the same mouse, thus better replicating the complexity of human diseases