Generation of synthetic spindle checkpoint signals
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The spindle checkpoint ensures proper chromosome segregation by monitoring kinetochore-microtubule interactions: unattached kinetochores recruit checkpoint proteins that combine to form a diffusible inhibitor which delays anaphase, thus buying cells time to fix attachment errors. Although the major checkpoint proteins were identified some 25 years ago, we have only just begun to understand how they assemble at unattached kinetochores to generate the crucial checkpoint signal. Much of this can be attributed to the difficulty associated with studying these proteins at the kinetochores, which are highly complex and thus often make clean dissection of function impossible. To circumvent this problem, a synthetic version of the spindle checkpoint was engineered on an ectopic location on a chromosome arm away from kinetochores in S. pombe. This work describes how the co-targeting of only two checkpoint components, the outer kinetochore protein Spc7 and the checkpoint kinase Mph1, was found to be sufficient to successfully generate a checkpoint-dependent metaphase arrest and how this paves the way for a clearer, more joined-up understanding of how the checkpoint works.