No description available.

Les protéine arginine méthyltransférases (PRMT) sont impliquées dans de nombreux processus cellulaires, incluant la régulation de l’expression des gènes, le contrôle de l’épissage, le maintien de l’intégrité du génome et la transduction du signal. De nombreuses études montrent que la dérégulation de l’activité des PRMT est associée au développement de pathologies, et en particulier de cancers. Les PRMT constituent ainsi une des nouvelles cibles potentielles en chimiothérapie. Les travaux présentés dans ce manuscrit portent sur trois cibles : PRMT2, PRMT3 et PRMT4/CARM1. Combinant des approches biochimiques, biophysiques et structurales (cristallographie et cryo- microscopie électronique), ces travaux comportent deux aspects : (I) comprendre au niveau atomique la régulation de la réaction de méthylation des protéines (reconnaissance protéines-protéines et interactions entre modifications post-traductionnelles) ; (II) découvrir des inhibiteurs spécifiques et puissants de plusieurs PRMT cibles. / Protein arginine methyltransferases (PRMT) are involved in many cellular processes, including gene expression regulation, splicing control, maintenance of genome integrity and signal transduction.Since deregulation of those biological processes appears to be implicated in the pathogenesis of different diseases, PRMTs have emerged as potential new targets for the development of novel therapeutic modulators. Despite the large amount of biological and structural data on PRMTs, two challenges remain to be solved by structural biology ; (I) understanding how PRMTs recognize and bind their full-length substrates ; (II) revealing how PRMTs achieve specific arginine methylation on different target sites. The works presented here focused on 3 targets: PRMT2, PRMT3 and PRMT4/ CARM1. We used biochemical, biophysical and structural methods (bio-crystallography and cryo- electron microscopy) to decipher structural clues that drive PRMT-substrate recognition. We developed new chemical probes that can be used in early drug discovery for the conception of PRMT inhibitors.

Les "protéine arginine méthyltransférases" (PRMT) sont impliquées dans de nombreux processus cellulaires : transcription, maturation et transport des ARN, traduction, transduction du signal, réplication et réparation de l'ADN, et apoptose. Différents travaux ont montré que des dérégulations de ces mécanismes impliquant les PRMT peuvent induire certains cancers, faisant de ces enzymes de nouvelles cibles potentielles en chimiothérapie. Il s'avère donc crucial de comprendre le mode d'action des PRMT à l'échelle atomique, à la fois au niveau fondamental et pour le développement de nouveaux médicaments. Les travaux décrits ici s'intéressent à la protéine PRMT4/CARM1 et s'appuient sur des études structurales par bio-cristallographie, pour comprendre les mécanismes de la réaction de méthylation catalysée par CARM1 et découvrir des inhibiteurs spécifiques, mais aussi sur des études en solution, pour caractériser l'interaction entre CARM1 et ses substrats.

For many enzymes to function correctly they must have the freedom to display a level of dynamics or communication during their catalytic cycle. The effects that protein dynamics and communication can have are wide ranging, from changes in substrate specificity or product profiles, to speed of reaction or switching activity on or off. This project investigates the protein dynamics and communication in two separate systems, a non-ribosomal peptide synthetase (NRPS), and a protein arginine methyltransferase (PRMT). PRMT1, the enzyme responsible for 80% of arginine methylation in humans, has been implicated in a variety of disease states when functioning incorrectly. For this reason, much focus has been placed on better understanding how PRMT1 determines which products it creates and at what times. This project aims to shed light on how dynamics and communication within PRMT1 dictate its activity. We have to this point developed a protocol for creating and purifying a linked PRMT1 construct which will enable us to conduct the necessary experiments capable of answering our larger questions about the PRMT1 catalytic mechanism. Our collaborators in the Zhan lab discovered the presence of a methyltransferase (Mt) in the two NRPS systems they study, which produce two different and medically relevant compounds, bassianolide and beauvericin. The Hevel lab is well suited to study methyltransferases and so were asked to help evaluate the role of these Mt domains and how they affect the production of the relevant natural products. Achieving a more complete understanding of these systems will move us closer toward the “holy grail” of being able to manipulate and harness NRPS systems for the engineering of novel medically relevant compounds. This project has found that the Mt domain substrate specificity is affected by the surrounding protein domains, or even small portions of them.

Proteinmethylierung spielt eine immer größere Rolle in der Regulierung zellulärer Prozesse. Die Entwicklung effizienter proteomweiter Methoden zur Detektion von Methylierung auf Proteinen ist limitiert und technisch schwierig. In dieser Arbeit haben wir einen neuen Hefe-Zwei-Hybrid-Ansatz (Y2H) entwickelt, der Proteine, die miteinander wechselwirken, mit Hilfe von Sequenzierungen der zweiten Generation identifiziert (Y2H-Seq). Der neue Y2H-Seq-Ansatz wurde systematisch mit dem Y2H-Seq-Ansatz verglichen. Dafür wurde ein Bait-Set von 8 Protein-Arginin-Methyltransferasen, 17 Protein-Lysin-Methyltransferasen und 10 Demethylasen gegen 14,268 Prey-Proteine getestet. Der Y2H-Seq-Ansatz ist weniger arbeitsintensiv, hat eine höhere Sensitivität als der Standard Y2H-Matrix-Ansatz und ist deshalb besonders geeignet, um schwache Interaktionen zwischen Substraten und Protein-Methyltransferasen zu detektieren. Insgesamt wurden 523 Wechselwirkungen zwischen 22 Bait-Proteinen und 324 Prey-Pr oteinen etabliert, darunter 11 bekannte Methyltransferasen-Substrate. Netzwerkanalysen zeigen, dass Methyltransferasen bevorzugt mit Transkriptionsregulatoren, DNA- und RNA-Bindeproteinen wechselwirken. Diese Daten repräsentieren das erste proteomweite Wechselwirkungsnetzwerk über Protein-Methyltransferasen und dienen als Ressource für neue potentielle Methylierungssubstrate. In einem in vitro Methylierungsassay wurden exemplarisch mit Hilfe massenspektrometrischer Analysen die methylierten Aminosäurereste einiger Kandidatenproteine bestimmt. Von neun getesteten Proteinen waren sieben methyliert, zu denen gehören SPIN2B, DNAJA3, QKI, SAMD3, OFCC1, SYNCRIP und WDR42A. Wahrscheinlich sind viele Methylierungssubstrate im Netzwerk vorhanden. Das vorgestellte Protein-Protein-Wechselwirkungsnetzwerk zeigt, dass Proteinmethylierung sehr unterschiedliche zelluläre Prozesse beeinflusst und ermöglicht die Aufstellung neuer Hypothesen über die Regulierung Molekularer Mechanismen durch Methylierung. / Protein methylation on arginine and lysine residues is a largely unexplored posttranslational modification which regulates diverse cellular processes. The development of efficient proteome-wide approaches for detecting protein methylation is limited and technically challenging. We developed a novel workload reduced yeast-two hybrid (Y2H) approach to detect protein-protein interactions utilizing second generation sequencing. The novel Y2H-seq approach was systematically evaluated against our state of the art Y2H-matrix screening approach and used to screen 8 protein arginine methyltransferases, 17 protein lysine methyltransferases and 10 demethylases against a set of 14,268 proteins. Comparison of the two approaches revealed a higher sensitivity of the new Y2H-seq approach. The increased sampling rate of the Y2H-seq approach is advantageous when assaying transient interactions between substrates and methyltransferases. Overall 523 interactions between 22 bait proteins and 324 prey proteins were identified including 11 proteins known to be methylated. Network analysis revealed enrichment of transcription regulator activity, DNA- and RNA-binding function of proteins interacting with protein methyltransferases. The dataset represents the first proteome-wide interaction network of enzymes involved in methylation and provides a comprehensively annotated resource of potential new methylation substrates. An in vitro methylation assay coupled to mass spectrometry revealed amino acid methylation of candidate proteins. Seven of nine proteins tested were methylated including SPIN2B, DNAJA3, QKI, SAMD3, OFCC1, SYNCRIP and WDR42A indicating that the interaction network is likely to contain many putative methyltransferase substrate pairs. The presented protein-protein interaction network demonstrates that protein methylation is involved in diverse cellular processes and can inform hypothesis driven investigation into molecular mechanisms regulated through methylation.