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Prof. Dr. Sebastian Hiller

Department Biozentrum
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Projects & Collaborations

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Efficient Characterization of Biomolecular Interactions by Automated Isothermal Titration Calorimetry

Research Project  | 5 Project Members

Inhalt und Ziel des Forschungsprojekts Im Gegensatz zu anderen Methoden ist die isothermale Titrationskalorimetrie (ITC) in einzigartiger Weise geeignet, die Wechselwirkung von unmodifizierten Bindungspartnern anhand der aufgenommenen oder abgegebenen Bindungswärme zu messen. Messungen mittels ITC erlauben dabei eine thermodynamische Charakterisierung der Wechselwirkungen zwischen Bindungspartnern. Diese erlaubt, zusammen mit Strukturinformationen, die Mechanismen der Bindung im Detail zu verstehen und zu erklären, warum verschiedene Bindungspartner unterschiedlich stark interagieren. In diesem Projekt wird ein automatisiertes System für ITC Messungen aufgebaut, das hilft, wesentliche Nachteile von manuellen Messungen hinsichtlich des Durchsatzes und der Datenqualität zu überkommen. Das neue ITC System wird in der Biophysik Forschungsserviceeinheit (BF) des Biozentrums der Universität Basel installiert und betrieben, und steht dort auch externen Nutzern zur Verfügung. Erste Anwendungen des neuen Geräts sind in den Bereichen Antibiotikaentwicklung und Antibiotikaresistenzen, sowie der molekularen und zellulären Krebsforschung vorgesehen. Wissenschaftlicher und gesellschaftlicher Kontext Wir erwarten, dass dieses Projekt zu einem besseren Verständnis fundamentaler biologischer Prozesse beitragen wird und dass die entsprechenden Erkenntnisse einen wertvollen Beitrag zu der Entwicklung von Molekülen leisten, die als Werkzeuge in der Biologie oder als Vorstufen zukünftiger Medikamente dienen.

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Structure-function analysis of the RNA-binding protein PGC-1a in skeletal muscle

Research Project  | 2 Project Members

Plasticity of cells, tissues and organs relies on sensing of external and internal cues, integration of the engaged signaling pathways, and orchestration of a pleiotropic response. For example, contractile patterns, ambient temperature and oxygen levels, nutrient availability and composition, as well as other factors result in a massive remodeling of biochemical pathways, cellular metabolism and mechanical properties of skeletal muscle cells, most notably in the context of repeated bouts of exercise, ultimately leading to training adaptations. In turn, such adaptations of skeletal muscle trigger internal and external changes that contribute to the systemic effects of exercise with many health benefits, and strong preventative and therapeutic outcomes in a number of pathologies. Surprisingly, even though the physiological and clinical contributions of exercise-linked muscle plasticity are well recognized, the molecular mechanisms that control the corresponding biological programs are still poorly understood. In recent years, the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) has emerged as a central regulatory nexus of plasticity in various cell types. PGC-1α integrates upstream signaling pathways to coordinate the complex transcriptional networks encoding biological programs involved in mitochondrial function, cellular metabolism and more. In the case of endurance exercise-mediated plasticity of muscle cells, most, if not all of the adaptations are evoked by this stimulus. Accordingly, muscle-specific overexpression or knockout of PGC-1α elicits high endurance and pathologically sedentary phenotypes, respectively. Our proposal aims at elucidating the molecular underpinnings of the complex transcriptional control that is exerted by PGC-1α in a spatio-temporal manner. We have recently discovered that the binding of RNAs to PGC-1α contributes to full transcriptional activity, and is central for the inclusion of PGC-1α-containing multiprotein complexes in liquid-liquid phase separated nuclear condensates for the sequestration of transcription. We now plan to determine the list and common features of PGC-1α-bound RNAs, interrogate how RNA binding is brought about in a structure-function analysis, study the consequences on multiprotein complex formation, and ultimately investigate the physiological relevance in skeletal muscle cells in vitro and in vivo . To do so, novel animal models will be leveraged for single-end enhanced crosslinking and immunoprecipitation (seCLIP) experiments to identify PGC-1α-bound RNAs, structural information will be obtained by NMR spectroscopy, and validated using site-directed mutagenesis of key amino acids and nucleotides in PGC-1α and RNAs, respectively, to study PGC-1α-dependent liquid-liquid phase separation. Then, PGC-1α-containing multiprotein complexes will be co-purified to perform cryo-electron microscopy-based single particle structural analysis. Finally, the functional consequence of targeted mutagenesis of key residues will be assessed in muscle cells in culture and mouse muscle in vivo with state-of-the-art myotropic adeno-associated viral vectors (AAVMYO). The research plan thus a.) highly synergizes in terms of interdisciplinary approaches between the groups involved and b.) will result in hitherto unprecedented insights into molecular mechanisms that underlie complex spatio-temporal control of transcriptional networks with important implications for the understanding of cellular and tissue plasticity in health and disease.

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Bacterial Type IV Secretion (T4S): Cellular, Molecular and Evolutionary Basis of the Subversion of Host Cell Functions by Translocated Effector Proteins

Research Project  | 2 Project Members

In the ongoing funding period of SNSF grant 31003A-173119 we are studying the cellular, molecular and evolutionary basis of subversion of host cell functions by type IV secretion (T4S) effector proteins during chronic bacterial infection by the related zoonotic pathogens Bartonella and Brucella. The three-year pro rata temporis extension in the frame of the excellence grant will allow us to extend our studies towards a better understanding (i) of the evolutionary origin and function of these host cell-targeted effector proteins and (ii) of the nature of their signal for T4S-dependent translocation. In Subproject A we will continue the functional characterization of Bartonella effector proteins (Beps) translocated by the VirB T4S system and the structure/function analysis of the BID domain as principle constituent of their T4S signal. Furthermore, we will extend our multidisciplinary studies to an unrelated class of newly identified T4S effectors in Bartonella with homology to a family of widespread type III secretion (T3S) effectors. Furthermore, we will study the role of the Bartonella Gene Transfer Agent (BaGTA) in facilitating adaptive evolution of Beps and associated virulence factors in processes like host adaptation. Subproject B will focus on the functional analysis of effector proteins translocated by the distinct VirB T4S system of Brucella with particular emphasis on delineating the unknown T4S signal. Together, these studies will contribute fundamentally to our molecular understanding of the widespread T4S mechanism in the context of chronic bacterial infections.