Module 9: Figure spindle-assembly checkpoint
Spindle-assembly checkpoint signalling pathway.
During assembly of the spindle, the free kinetochores, which have not bound a microtubule, assemble a molecular complex (see box) that inhibits the Cdc20 protein which is responsible for activating the anaphase-promoting complex (APC) that initiates chromatid separation. This checkpoint is removed when the spindle is fully assembled. The inhibitory protein complex dissociates and Cdc20 is able to activate APC and anaphase begins as described in (Module 9: Figure chromosome separation). The hypothesis presented in this figure was developed by Stegmeier et al. 2007.