Unlocking the therapeutic potential of E3 ubiquitin ligases through structure-function studies and Cryo-EM

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All cells within our body need to discard waste material such as damaged or no longer wanted proteinsto ensure that cells remain healthy and functional. The small protein ubiquitin is essential in thisprocess by functioning as an identification tag. Ubiquitin is the most versatile post-translationalmodification, it can exist as a single moiety on proteins, and this is important in protein trafficking andendocytosis, but also as a ubiquitin chain. It is only in the last decade that we have come to appreciatethe complexity of the ubiquitin system. We now know for instance that ubiquitin can use any of itsseven lysine residues, or its N-terminal Met, to assemble two ubiquitin chains together in order toform chains. Therefore, as many as eight linkage types have been found on proteins (i.e. Met1, K6,K11, K27, K29, K33, K48 and K63) in yeast and human cells.E3 ubiquitin ligases plays a key role in protein ubiquitination, by mediating the transfer of ubiquitinonto protein substrates. Depending on the type of ubiquitin signal added, this can trigger recognitionby the Ubiquitin-Proteasome System. Therefore, preventing the degradation of important proteins inage-related diseases could in theory be achieved through the targeted inhibition of the ligase activityof specific E3s, rather than the current and general/unspecific approach of inhibiting the proteasome.E3 HECT ligases are very good candidates for drug discovery given their Cys-based enzyme activity.However, the limited structural information and biochemical knowledge of these large enzymes hashindered their potential as therapeutic targets, despite mounting evidence for their importance inhuman health.In this project, the student will undertake structure-function studies of E3 HECT ubiquitin ligases. Thestudent will be trained in protein expression and purification, ubiquitination assays, biophysicaltechniques, protein crystallography and state-of-the-art Cryo-EM. An important goal will be to alsoestablish strategies for the expression and purification of full-length HECT E3 enzymes in eukaryoticsystems, for Cryo-EM studies and future drug discovery projects. This project will benefit from ongoinginternational collaboration with experts in proteomics and chemical biology as well as supportive anddynamic research environments at Bath and Bristol. Because of our combined expertise in proteinubiquitination, structure-function studies and Cryo-EM, the student will be in an ideal position to makean impact on the ubiquitin field.