Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on June 11, 2009). Includes bibliographical references.

No description available.

We observed that platelets, which mediate thrombus formation, also enhance fibrinolysis by single-chain urokinase (scuPA).  Preliminary data suggested that this enhancement was due to platelet thrombospondin (TSP), which, depending upon the specifics of the environment, changed conformation, influencing its role in the fibrinolytic system.  Results showed that the activity of scuPA was enhanced by platelets, regardless of platelet treatment or protein release, and that TSP could not explain the platelet effect.  Investigation of the underlying mechanism, using the non-cleavable mutant scuPA (K158E) and protease inhibitors, showed that the platelet-dependent enhancement of scuPA arose from the activation to uPA by a serine protease.  Factor VII activating protease (FSAP) was not the protease responsible, since inhibition of platelet FSAP with function-blocking antibodies did not inhibit the platelet effect.  Comparison of plasminogen and plasma kallikrein, using an array of inhibitors, showed that both candidates mirrored the platelet effect.  Further results, including those from assessment of protease activity on platelets against chromogenic substrates and from the evaluation of uPA formation over time, were consistent with the involvement of plasminogen.  In addition, experiments with platelets from plasminogen-deficient mice showed that platelets lacking plasminogen no longer activated scuPA.  The enhancement of scuPA was found to be platelet-dependent, even in plasma; scuPA activation was more efficient when plasminogen was associated with the platelet membrane, compared to in solution; and the presence of membranes was essential to induce rapid lysis by scuPA.  Our findings indicate that platelets stimulate fibrinolysis by scuPA via local activation to uPA by platelet-associated plasminogen, which is activated by scuPA, consistent with a system of reciprocal activation.

Les Facteurs de transcription du groupe PEA3 (Pea3, Erm et Er81) font partie de la famille d’oncogènes ETS. Leur expression est souvent observée lors de la mise en place des organes par morphogenèse de branchement tels que les poumons ou encore la glande mammaire. De plus une expression aberrante de ces facteurs de transcription est corrélée au caractère cancéreux de nombreux tissus tels que le côlon, les poumons ou encore le sein. Ainsi, l’expression d’Erm dans les tumeurs du sein est associée à un mauvais pronostic pour les patientes et celle de Pea3 constitue un marqueur de l’agressivité tumorale. Enfin, en qualité de facteur de transcription Pea3 module l’expression de gènes spécifiques alors appelés gènes cibles. Même si certains de ces gènes sont déjà bien caractérisés beaucoup de choses restent à faire pour comprendre les mécanismes moléculaires régulés par Pea3. Dans ce contexte lors de ma thèse je me suis intéressé à l’étude du rôle du facteur de transcription Pea3 dans les processus de morphogenèse et de tumorigenèse mammaires selon deux approches complémentaires : 1- l’étude des propriétés morphogénétiques modulées par Pea3 lors des étapes de morphogenèse et de tumorigenèse mammaires, 2- la recherche et la caractérisation de gènes régulés par Pea3 dans ce même contexte, par une analyse transcriptomique à grande échelle en utilisant des puces à ADN. Ces deux points sont développés grâce à l’utilisation de modèles cellulaires dans lesquelles nous modulons l’expression de Pea3. Les cellules épithéliales mammaires TAC 2.1 modèle de morphogenèse mammaire dans lesquelles nous surexprimons Pea3 et les cellules mammaires transformées MMT, modèle de tumorigenèse mammaire dans lesquelles nous inhibons l’expression du facteur de transcription Pea3. Au cours de ma thèse nous avons ainsi pu montrer l’importance du facteur de transcription Pea3 dans le contrôle des propriétés de migration, d’invasion et de prolifération des cellules cancéreuses TAC et MMT. En accord avec ces données, la recherche des gènes dont l’expression est régulée par Pea3 dans nos deux modèles cellulaires suite à la modulation de Pea3, a permis d’identifier de nombreux gènes capables de réguler la prolifération, la migration et l’invasion des cellules. Parmi ces gènes nous nous sommes intéressés au gène cycline d2 bien connu pour son implication dans le contrôle de la progression du cycle cellulaire. Nous avons pu montrer que le gène cycline d2 est un gène cible direct du facteur de transcription Pea3 qui module l’expression dans le modèle cellulaire TAC des deux transcrits (cycline d2 et cycline d2 trc) issus de ce gène et décrits à ce jour. L’étude de la fonction des protéines Cycline D2 et Cycline D2 Trc dans les cellules TAC a été entreprise. Tout d’abord la surexpression de l’une ou l’autre de ces isoformes dans les cellules TAC 2.1 modifie de façon opposée leur capacité à s’organiser dans un gel de collagène mimant l’environnement d’une glande mammaire, la Cycline D2 réprimant cette capacité et la Cycline D2 Trc l’augmentant. L’utilisation de petits ARN interférents permettant de réprimer l’expression de ces deux protéines a permis de montrer une relation fonctionnelle, toujours opposée, des deux isoformes avec le facteur de transcription Pea3 pour le contrôle de la progression du cycle cellulaire mais aussi pour l’induction d’une transition épithélio-mésenchymateuse étroitement reliée au pouvoir de migration des cellules épithéliales lors du développement des organes comme la glande mammaire mais aussi lors de la progression tumorale. Notre étude a ainsi permis de mieux définir l’implication du facteur de transcription Pea3 lors des événements de morphogenèse et de tumorigenèse de la glande mammaire. De plus elle ouvre la réflexion sur le rôle du gène cycline d2 lors de ces événements. / "Proteins of the PEA3 group (Pea3, Erm and Er81) belong to the ETS family of transcription factors. They are expressed in organs that undergo an epithelial branching morphogenesis process such as the lungs and the mammary gland. Moreover, in these organs, they are aberrantly expressed during cancer progression. Indeed, during breast cancer high Pea3 or Erm expression is respectively associated with cancer metastatic potential and a lower patient survival rate. Finally, as transcription factors they control the expression of specific genes called target genes. Even though some of these genes are known, more work is needed to understand the molecular mechanism governed by the PEA3 transcription factors. The main topic of my PhD is the study of the role of the Pea3 transcription factor during mammary morphogenesis and tumorigenesis using two complementary approaches: 1- characterize the morphogenetic properties that are controlled by Pea3 during the mammary morphogenesis and tumorigenesis events 2- find and characterize the genes that are regulated by Pea3 using a large scale transcriptomic analysis based on a microarray technology. The strategy is based on the utilization of two main cell lines in which we modulate Pea3 expression: an epithelial cell line, model of mammary morphogenesis (TAC 2.1) in which we overexpress Pea3 and a cancer cell line, model of mammary tumorigenesis (MMT) in which Pea3 expression is knocked down by means of small interfering RNA sequences. During my PhD we showed that Pea3 controls the proliferation, invasion and migration properties of TAC 2.1 and MMT cells. In agreement with these data, the transcriptomic analysis after Pea3 expression modulation in these cells (overexpression or knockdown) demonstrate that a large proportion of the Pea3 regulated genes are already known players in the regulation of the proliferation, invasion and migration processes. Amongst these genes, we focused on the cyclin d2 gene which is a well characterized actor in cell cycle progression and cell proliferation. We showed that cyclin d2 is direct Pea3 target gene. The cyclin d2 gene gives rise to two different isoforms generated by a splicing event (Cyclin D2 and Cyclin D2 Trc) that are both regulated by Pea3 at the mRNA and protein levels. We then evaluated the function of these two isoforms in the mammary epithelial cell line TAC 2.1. Overexpression of these proteins in the TAC2.1 cells leads to a modification, in an opposite fashion, of their ability to grow and organize in 3D structures within a collagen envirronement. The Cyclin D2 and the Cyclin D2 Trc respectively repressing and enhancing these abilities. The use of small interfering RNA sequences targeting specifically one or the other isoform allowed us to show a functional link between both isoforms and the Pea3 transcription factor , again in an opposite way, especially during cell cycle progression and during epithelial to mesenchymal conversion, a hallmark of development and cancer progression. Thus, this study gives new clues to understand the involvement of the Pea3 transcription factor during mammary morphogenesis and tumorigenesis, events in which the cyclin d2 gene seems to be a major player. The characterization of the molecular events governed by Pea3 should help in defining new therapeutic strategies against breast cancer progression. "

No description available.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 73-90). Also available in print.

In 1999, the discovery of the Steroid Receptor RNA Activator (SRA) was unprecedented in the field of steroid receptor co-regulator research. It was the first time that an RNA molecule was demonstrated to function similarly to its protein counterpart and modulate the activity of steroid receptors. This peculiar steroid receptor co-activator thus attracted the attention of numerous research groups. Over the years, studies were reported deciphering SRA mechanisms of action, its role in co-regulating nuclear receptors and its possible implication in human diseases. While SRA was originally thought to exist solely as a non-coding RNA, our laboratory has identified longer SRA RNA isoforms with the theoretical capacity to encode for a protein. This discovery impelled us to investigate the existence of a Steroid Receptor RNA Activator Protein or SRAP. In this thesis, we first demonstrated the existence and function of endogenous evolutionary conserved SRA proteins. Based on these results we further explored SRAP expression in breast tumors. Interestingly, Western blot analysis of a small cohort of estrogen positive breast tumors suggested that SRAP expression correlates with a better overall survival in patients treated with tamoxifen. This observation prompted us to explore the biological role of SRAP. We found that MCF-7 cells stably expressing coding SRA isoforms had lower ligand dependent estrogen receptor alpha transcriptional activity. In order to dissect the function of the protein independently of its RNA counterpart, we separated the functions of the protein by introducing extensive silent mutations into the RNA sequence. Using this model, we established that SRAP, independent of its RNA counterpart, enhances estrogen receptor alpha activity in a ligand and response-element dependent manner. Furthermore, we showed for the first time that SRAP physically interacts with multiple transcription factors and is recruited to specific promoter regions. Moreover, by artificially recruiting SRAP to the promoter of a luciferase reporter gene under the control of the strong transcriptional activator VP16, we observed a decrease in transcription. These latter results suggest that SRA could function as a repressor through direct association with promoters. Overall, we believe that SRA is a very peculiar example of a bi-faceted system consisting of a functional RNA and its corresponding protein. Altogether our data suggest that SRAP, similarly to its RNA counterpart, is involved in many critical pathways that directly participate in gene expression regulation.

In 1999, the discovery of the Steroid Receptor RNA Activator (SRA) was unprecedented in the field of steroid receptor co-regulator research. It was the first time that an RNA molecule was demonstrated to function similarly to its protein counterpart and modulate the activity of steroid receptors. This peculiar steroid receptor co-activator thus attracted the attention of numerous research groups. Over the years, studies were reported deciphering SRA mechanisms of action, its role in co-regulating nuclear receptors and its possible implication in human diseases. While SRA was originally thought to exist solely as a non-coding RNA, our laboratory has identified longer SRA RNA isoforms with the theoretical capacity to encode for a protein. This discovery impelled us to investigate the existence of a Steroid Receptor RNA Activator Protein or SRAP. In this thesis, we first demonstrated the existence and function of endogenous evolutionary conserved SRA proteins. Based on these results we further explored SRAP expression in breast tumors. Interestingly, Western blot analysis of a small cohort of estrogen positive breast tumors suggested that SRAP expression correlates with a better overall survival in patients treated with tamoxifen. This observation prompted us to explore the biological role of SRAP. We found that MCF-7 cells stably expressing coding SRA isoforms had lower ligand dependent estrogen receptor alpha transcriptional activity. In order to dissect the function of the protein independently of its RNA counterpart, we separated the functions of the protein by introducing extensive silent mutations into the RNA sequence. Using this model, we established that SRAP, independent of its RNA counterpart, enhances estrogen receptor alpha activity in a ligand and response-element dependent manner. Furthermore, we showed for the first time that SRAP physically interacts with multiple transcription factors and is recruited to specific promoter regions. Moreover, by artificially recruiting SRAP to the promoter of a luciferase reporter gene under the control of the strong transcriptional activator VP16, we observed a decrease in transcription. These latter results suggest that SRA could function as a repressor through direct association with promoters. Overall, we believe that SRA is a very peculiar example of a bi-faceted system consisting of a functional RNA and its corresponding protein. Altogether our data suggest that SRAP, similarly to its RNA counterpart, is involved in many critical pathways that directly participate in gene expression regulation.

Diss. (sammanfattning) Göteborg : Göteborgs universitet , 2007. / Härtill 4 uppsatser.