The role of cyclin F in Motor Neurone Disease

Abstract

of a thesis for a Doctorate of Philosophy submitted to Macquarie University, Sydney Mo Neurone Disease (MND) is characterised by the loss of motor neurons in the brain and spinal cord. Most patients with MND develop proteinaceous inclusions within affected neurons of the central nervous system, suggesting overall] dysregulation of protein degradation systems. Our team identified mutations in CCNF, the gene encoding cyclin F. Cyclin F is a substrate binding component of a multi-protein ubiquitin ligase (denoted SCFo«linF) | which mediates the ubiquitylation of substrates in order to influence the cell cycle. Overarching aims of this thesis concern the impact of CCNF mutations on the ubiquitin ligase activity of SCFeelin F and the downstream impact within cells. Addressing these aims involved using a series of biochemical assays (including in VItTO ubiquitylation assays, immunoprecipi-tations, proximity-ligation assays and mass spectrometry). Results demonstrate that an MND-linked mutation in cyclin F leads to defective ubiquitylation activity, ultimately leading to the accumulation of proteins tagged for degradation. Overall, the work provides insight into how the precise control of cyclin F ligase activity is dysregulated when cyclin F carries a disease-causing mutation. Furthermore, outcomes from this work provide novel links between cyclin F (a cell cycle regulator) and a devastating disease involving the degeneration of post-mitotic neurons.