Sustained Mps1 activity is required in mitosis to recruit O-Mad2 to the Mad1-C-Mad2 core complex

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Mps1 (Monastrol-Plk1-sensitive kinase 1) is crucial for the spindle assembly checkpoint (SAC).
• Understanding Mps1's catalytic role is key to comprehending mitotic regulation and checkpoint function.

Purpose of the Study:

• To investigate the role of Mps1's catalytic activity in mitosis using a novel inhibitor.
• To elucidate Mps1's function in kinetochore-associated protein recruitment and SAC signaling.

Main Methods:

• Utilized a novel Mps1 inhibitor, AZ3146, to probe Mps1 activity during mitosis.
• Assessed the impact of Mps1 inhibition on the recruitment of SAC proteins (Mad1, Mad2) and CENP-E to kinetochores.
• Investigated Mps1 dimerization and transphosphorylation in cellular contexts.

Main Results:

• Mps1 inhibition before mitosis entry prevented Mad1/Mad2 kinetochore recruitment.
• Mps1 inhibition after mitosis entry blocked O-Mad2 recruitment but not Mad1-C-Mad2 core complex binding.
• Kinetochore recruitment of CENP-E was impaired, while aurora B activity was unaffected. Mps1 abundance at kinetochores increased upon inhibition.
• Demonstrated Mps1 dimerization and transphosphorylation in cells.

Conclusions:

• Mps1 catalytic activity is essential for timely O-Mad2 and CENP-E kinetochore recruitment.
• Mps1 transphosphorylation may regulate its release from kinetochores, facilitating SAC signaling and chromosome alignment.
• This study proposes a model for Mps1's dual role in checkpoint activation and chromosome congression.