Figure 2. Basic mechanistic principles behind selective stabilization of amphitelic attachments.

A. Geometric constraint. A pair of kinetochores linked through a geometric constraint (right) that interferes with attachment to microtubules coming from distal poles. The black box indicates the constraint, which may be promoted by the CPC at the centromere. In the absence of a geometric constraint (right), such as on paired homologous chromosomes during meiosis I, attachment from distal poles is enabled, resulting in merotelic attachment (and also syntelic attachment). B. Spontaneous microtubule turnovers. Each microtubule attachment has limited lifetime, and is spontaneously replaced by new attachment. A few aberrant attachments can be spontaneously replaced by correct attachment as the geometric constraint interferes with aberrant attachment. The turnover can be enhanced by Aurora B. C. Tension-induced enhancement of kinetochore-microtubule attachment (catch-bond mechanism). At a kinetochore under reduced tension (left), intrinsic microtubule binding is weak. At a kinetochore under tension (right), intrinsic microtubule binding is enhanced. Aurora B can weaken the microtubule-binding strength.