Figure 2

The chromosomal passenger complex influences spindle checkpoint activity indirectly, through the creation of unattached kinetochores. Upon entry into mitosis chromosomes start to make random connections with microtubules from the mitotic spindle. To finally obtain bipolar spindle attachments, improper attachments (syntelic – depicted here-, and merotelic attachments) need to be corrected to prevent chromosome segregation errors. Aurora B in complex with its fellow passenger proteins is necessary for this correction process. Through the phosphorylation of kinetochore proteins that bind microtubules it modifies the stability or affinity of the kinetochore-microtubule interaction. As a consequence microtubules detach from the kinetochore allowing new rounds of attachments until bipolarity is obtained. However, during this correction process unattached are created capable of inhibiting the APC/C [33]. As such Aurora B's role in checkpoint function can be considered an indirect consequence of its microtubule destabilising activity.