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ASSESSMENT OF APPROACHES TO STUDY UBIQUITIN BINDING INTERFACESKristos Negron (17584017) 10 December 2023 (has links)
<p dir="ltr">The process of ubiquitination is an important regulatory process that helps modulate eukaryotic signaling inside the cell. This process is described as the formation of an isopeptide linkage between the C-terminal residue of ubiquitin to the lysine residue of a target protein, a process catalyzed by the E1, E2, and E3 enzyme cascade. As mentioned, this process has only been observed in eukaryotes, although recently, prokaryotic pathogens have been shown to possess enzymes that affect the ubiquitination pathway in their hosts. While some of these enzymes have well known mechanisms, there are still many that are unknown and are novel when compared to other well documented enzymes. The studies conducted in this Thesis involve biochemical, structural, and bioinformatic studies involving both prokaryotic and eukaryotic enzymes as an approach to develop methodologies that help study processes involving ubiquitin. Among the insights provided in this document, the importance of a unique insertion found in the <i>Legionella </i>effector MavC, that is important for substrate recognition. The use of disulfide bridge formation to obtain Ub-DUB complexes through the design of a simple cysteine mutation on Ub. Finally, utilizing AlphaFold, in combination with other bioinformatic processes, to help study large, protein family data sets, like the USP family DUBs that is studied in this Thesis. Altogether, these findings show that through a combination of multiple techniques, we can have a more streamlined way of studying these new, exciting protein pathways.</p>
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SCF cdc4 regulates msn2 and msn4 dependent gene expression to counteract hog1 induced lethalityVendrell Arasa, Alexandre 16 January 2009 (has links)
L'activació sostinguda de Hog1 porta a una inhibició del creixement cel·lular. En aquest treball, hem observat que el fenotip de letalitat causat per l'activació sostinguda de Hog1 és parcialment inhibida per la mutació del complexe SCFCDC4. La inhibició de la mort causada per l'activació sostinguda de Hog1 depèn de la via d'extensió de la vida. Quan Hog1 s'activa de manera sostinguda, la mutació al complexe SCFCDC4 fa que augmenti l'expressió gènica depenent de Msn2 i Msn4 que condueix a una sobreexpressió del gen PNC1 i a una hiperactivació de la deacetilassa Sir2. La hiperactivació de Sir2 és capaç d'inhibir la mort causada per l'activació sostinguda de Hog1. També hem observat que la mort cel·lular causada per l'activació sostinguda de Hog1 és deguda a una inducció d'apoptosi. L'apoptosi induïda per Hog1 és inhibida per la mutació al complexe SCFCDC4. Per tant, la via d'extensió de la vida és capaç de prevenir l'apoptosi a través d'un mecanisme desconegut. / Sustained Hog1 activation leads to an inhibition of cell growth. In this work, we have observed that the lethal phenotype caused by sustained Hog1 activation is prevented by SCFCDC4 mutants. The prevention of Hog1-induced cell death by SCFCDC4 mutation depends on the lifespan extension pathway. Upon sustained Hog1 activation, SCFCDC4 mutation increases Msn2 and Msn4 dependent gene expression that leads to a PNC1 overexpression and a Sir2 deacetylase hyperactivation. Then, hyperactivation of Sir2 is able to prevent cell death caused by sustained Hog1 activation. We have also observed that cell death upon sustained Hog1 activation is due to an induction of apoptosis. The apoptosis induced by Hog1 is decreased by SCFCDC4 mutation. Therefore, lifespan extension pathway is able to prevent apoptosis by an unknown mechanism.
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