Figure 4.

Model of Kinetochore-Spindle Interactions

A model illustrating the different states of kinetochore-spindle interactions in prometaphase and anaphase. Chromosomes are shown in blue, microtubules in black, kinetochores in yellow, and the AuroraB/INCENP complex in red. (A) In prometaphase, destabilization of inappropriate attachments by the AuroraB/INCENP complex allows interconversion of the different attachment states until bipolar attachment is achieved. At that point tension pulls the sister kinetochores away from the AuroraB/INCENP complex, more microtubules are recruited, and the bipolar state is stabilized (as previously proposed [3]). (B) After the metaphase/anaphase transition in the wild-type, the AuroraB/INCENP complex dissociates from the kinetochores, ensuring stable attachment during anaphase. (C) In the presence of CYC-B^S, the AuroraB/INCENP complex does not dissociate from the kinetochores, and the instability that characterizes prometaphase kinetochore-spindle interaction now persists. Because the disjoined kinetochores are unpaired, attachments interconvert without the option of normal bipolar attachment. As is the case with unreplicated prometaphase chromosomes in the double parked mutant, this interconversion (gray double-headed arrows at the right) leads to disorderly chromosome movements and merotelic attachments.