PT  - JOURNAL ARTICLE
AU  - Banafsheh Etemad
AU  - Abel Vertesy
AU  - Timo E.F. Kuijt
AU  - Carlos Sacristan
AU  - Alexander van Oudenaarden
AU  - Geert J.P.L. Kops
TI  - Spindle checkpoint silencing at kinetochores with submaximal microtubule occupancy
AID  - 10.1101/472407
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 472407
4099  - http://biorxiv.org/content/early/2018/11/16/472407.short
4100  - http://biorxiv.org/content/early/2018/11/16/472407.full
AB  - The spindle assembly checkpoint (SAC) ensures proper chromosome segregation by monitoring kinetochore-microtubule interactions. SAC proteins are shed from kinetochores once stable attachments are achieved. Human kinetochores consist of hundreds of SAC protein recruitment modules and bind up to 20 microtubules, raising the question how the SAC responds to intermediate attachment states. We show that the ‘RZZS-MAD1/2’ module of the SAC is removed from kinetochores at low microtubule occupancy and remains absent at higher occupancies, while the ‘BUB1/R1’ module is retained at substantial levels irrespective of attachment states. Artificially tuning the affinity of kinetochores for microtubules further shows that ~50% occupancy is sufficient to shed MAD2 and silence the SAC. Kinetochores thus responds as a single unit to shut down SAC signaling at submaximal occupancy states, but retains one SAC module. This may ensure continued SAC silencing on kinetochores with fluctuating occupancy states while maintaining the ability for fast SAC re-activation.