Investigating the molecular mechanisms of MPS1 localisation to mammalian kinetochores

Thesis

The accurate segregation of the genome during mitosis is necessary for successful cell division. Prior to anaphase the cell must ensure that all chromosomes are properly attached, via large proteinaceous structures called kinetochores, to microtubules of the mitotic spindle. Two related processes, spindle assembly checkpoint signalling and error correction, have an essential role in promoting the formation of proper microtubule attachments prior to anaphase onset. The kinase Monopolar Spindle 1 (MPS1) dynamically localises to kinetochores to initiate spindle checkpoint signalling in the absence of stable microtubule attachment, and additionally promotes error correction at improperly attached chromosomes. This thesis explores how the control of MPS1 localisation is controlled by kinase and phosphatase activity, and microtubule binding, to fulfil its role in checkpoint signalling and error correction. A new paradigm for how MPS1 localisation is coupled to microtubule binding is established wherein the balance between Aurora B kinase and Protein Phosphatase 2A-B56 determines MPS1 recruitment downstream of microtubule binding. Furthermore, the molecular mechanisms of MPS1 binding to the kinetochore are investigated, finding that auto-phosphorylation of the N-terminus of MPS1 controls its steady-state levels at kinetochores without microtubules bound. Beyond the mechanisms of MPS1 localisation to kinetochores, a detailed view of the involvement of MPS1 in error correction is developed. New evidence is provided that MPS1 participates directly in error correction, but that this attachment-destabilising function is balanced by MPS1-dependent recruitment of PP2A-B56. These findings highlight a complex interplay between MPS1, Aurora B, and PP2A-B56 which serves to control checkpoint signalling and microtubule attachment stability.

Authors: Roberts, E

• DOI: 10.5287/ora-az85jrowg
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: kinetochore; error correction; microtubule; MPS1; spindle; mitosis; checkpoint