Les événements du mois
Séminaire
Génomes
Vendredi 2 avril 16:00-17:00 - Sebastian Lourido Defining transitions in a parasitic life cycle [note : CHANGE OF TIME] Résumé : For over half a billion years, members of the phylum Apicomplexa have existed as parasites and symbionts of all major animals on earth. The group includes major human pathogens like the etiological agents of malaria and toxoplasmosis. Our lab employs unbiased approaches in functional genomics and proteomics to delve into the major transitions of the apicomplexan life cycle and understand their molecular underpinnings. Here, I will discuss the implementation of genome-scale CRISPR-based screens to identify new components of the machinery for host cell invasion, and describe our recent discovery of the master regulator of chronic differentiation in Toxoplasma gondii. These vignettes will illustrate the possibilities brought about by new technologies to understand cell biology of apicomplexans. We hope such studies will provide insight into microbial pathogenesis and a reference point for the vast diversity of the eukaryotic radiation.
Contact : Joana SANTOS <joana.santos i2bc.paris-saclay.fr>Vendredi 16 avril 11:00-12:00 - Jose Antonio ESCUDERO - Universidad Complutense de Madrid Evolutionary History of Integrons Résumé : Integrons are genetic platforms that act as bacterial memories of adaptive functions, accelerating evolution in changing environments. They were discovered on conjugative plasmids for their role in the early rise of multidrug resistance, but they are naturally found in the chromosomes of many bacterial species, where they have driven their evolution for aeons. Integrons recruit, stockpile and modulate the expression of new genes encoded in small mobile structures named cassettes. The streamlined functionality of integrons is based on the DNA transactions performed by the integrase –that integrates, excises and reshuffles cassettes-, and the peculiarities of the recombination sites.
Yet integrons have an interesting evolutionary origin themselves. In this seminar, we will see how they have evolved from the tyrosine recombinase family of proteins through a process of evolutionary innovation. I will explain how the activity of these ancestors has been extensively modified to deliver the modern activity of today’s integrases through the co-evolution of the integrase and the attC recombination site. We will discuss the main biological implications of this evolutionary process in an attempt to establish the selective forces driving it, and the meaning of the coexistence of ancestral and modern activities. We will end by deciphering the structural basis of both activities and their trade-offs through an attempt to rewind the tape of evolutionary innovation.
Invited by Virginia Lioy Lioy <virginia.lioy i2bc.paris-saclay.fr>Lieu : visio
Vendredi 23 avril 16:00-17:00 - Josh Beck - Iowa State University Transcending a self-imposed barrier : EXP2/PTEX function in transport across the Malaria parasite vacuole membrane (NOTE : CHANGE OF TIME) Résumé : Obligate intracellular malaria parasites undergo development in their hepatocyte and erythrocyte host cells within a vacuolar compartment that is the principal interface between host and parasite. To create a niche for survival in these remarkably diverse cell types, these parasites coordinate a range of transport activities at the vacuole membrane including import of nutrients and export of effector proteins. These processes are best characterized in the blood stage where an arsenal of hundreds of effector proteins are exported into the erythrocyte by the Plasmodium translocon of exported proteins (PTEX) to dramatically remodel this terminally differentiated host cell. PTEX is comprised of the AAA+ unfoldase HSP101 which is coupled to a membrane pore formed by EXP2 via a flange-like adaptor called PTEX150. In addition to its role in protein export, EXP2 also functions in small molecule transport across the vacuole membrane. In contrast to the blood stage, few exported proteins have been identified in the liver stage and the nature of the export machinery is unknown. Curiously, while EXP2 and PTEX150 are both expressed by liver stage parasites, previous studies could not detect HSP101 by fluorescence microscopy. Using a proximity-labeling proteomic strategy, we were similarly unable to detect HSP101 in the liver stage vacuole. These observations indicate major differences in the export machinery and raise the question of EXP2 and PTEX150 function during hepatocyte infection. We are currently using a combination of reverse genetic and proteomic strategies to dissect PTEX roles across blood and liver stages.
Invited by Joana SantosLieu : visio
B3S
Vendredi 9 avril 17:00-18:00 - Walter Chazin - Vanderbilt University (TN) USA Structural biochemistry of action at the replication fork : On the road to understanding RADX Résumé : Walter Chazin from the Vanderbilt University (https://www.vanderbilt.edu/chemistry/faculty/chazin.php) is an American structural biologist, with an NMR background, focusing on DNA repair proteins.
He just published an exciting article on RADX destabilizing RAD51 filaments, in order to, together with BRCA2, regulate replication fork elongation rate & stability : https://www.sciencedirect.com/science/article/pii/S1097276520309576?via%3DihubLieu : Visio - Lien Visio disponible sur l’intranet ou sur demande (seminaires i2bc.paris-saclay.fr)
cytoskeleton club
Mardi 13 avril 11:30-13:00 - Guy Lippens - INSA, Toulouse Cytoskeleton club - To aggregate or not : a question of forgetting. A story of the Tau protein Lieu : Webinar