Samenvatting

Ubiquitin (Ub) is a protein which post-translationally modifies other proteins (its target substrates) and determines their cellular fate. Ub can label substrates for degradation, it can also alter the location of their substrates within a cell or even affect their activity. Chains can be formed via different lysine linkage’s, translating differently chains into proper cellular responses. Through additional post-translational modification by Small Ubiquitin-Related Modifier (SUMO), hybrid Ub-SUMO chains can be generated. These chains can alter the primitive encoded message or generate a new one. The hybrid Ub-SUMO chains have been identified either by MS approaches (linkages and proteomic studies) or by biochemical techniques, however these chains are poorly defined. These chains also have their specific receptors, thus showing that there must be a reasoning in their cellular signaling pathway. Understanding these responses is crucial since these signals play a role in DNA repair, immune responses and regulation of membrane dynamics. Within the scope of this project, Ub-SUMO hybrid trimers are synthesized as chemical probes/interactive tools by equipping them with Biotin moieties. These moieties serve for pulldown assays where interactors are non-covalently pulled down. Trimers are obtained by synthesizing required precursors which consist of components that support the Huisgen 1,3-dipolar cycloaddition, also giving them interactive handle’s alongside temporary groups. Using this strategy, temporary groups to the C-terminus of the nonhydrolyzable dipeptides can be biorthogonal modified into warheads supporting another click reaction. Homotypic and hybrid trimers are synthesized using this novel chemical synthetic route which allows total control of the different linkage’s generated in the trimer chains.