microtubulekinetochore

The microtubule-kinetochore interface is a specialized protein structure that links spindle microtubules to the kinetochores at the centromere of each chromosome. This connection is essential for proper chromosome alignment, bi-orientation, and segregation during cell division in both mitosis and meiosis.

The core attachment is built from the KMN network, which comprises the KNL1 complex, the Mis12 complex, and the Ndc80 complex. The Ndc80 complex, including Ndc80 (Hec1 in vertebrates), Nuf2, Spc24, and Spc25, forms the primary microtubule-binding site at the kinetochore plus end. Additional factors such as the Dam1/DASH complex in yeast and the Ska complex in many vertebrates enhance attachment to depolymerizing microtubules, enabling robust coupling as microtubules grow and shrink.

Functionally, kinetochores capture dynamic microtubules and convert microtubule shortening into pulling forces that move chromosomes toward the spindle poles. Tension generated by correct microtubule-kinetochore attachments stabilizes the interaction, facilitating accurate alignment. The kinetochore also tracks microtubule ends, influenced by a network of plus-end–tracking proteins and motor-independent mechanisms driven by microtubule interface dynamics.

Regulation is tightly controlled by the spindle assembly checkpoint. If attachments are incorrect or lacking tension, Aurora B kinase phosphorylation destabilizes the improper contacts, enabling error correction. Once proper bi-orientation and tension are achieved, checkpoint signaling is satisfied, allowing progression to anaphase. Dysfunctions at the microtubule-kinetochore interface can lead to chromosome missegregation and aneuploidy.