SPC24

SPC24 is a kinetochore-associated protein that serves as a core subunit of the Ndc80 complex, a conserved assembly essential for stable microtubule attachment to kinetochores during mitosis. It is found in a wide range of eukaryotes and is required for accurate chromosome segregation.

In the Ndc80 complex, SPC24 forms a heterodimer with SPC25 and, together with NDC80 (Hec1) and NUF2, constitutes the outer kinetochore microtubule-binding unit. SPC24 and SPC25 contribute to the complex’s structure and regulated interaction with microtubules.

Functionally, the complex mediates contact between kinetochores and microtubules, enabling proper bi-orientation of sister chromatids. The SPC24/25 subunits participate in the microtubule-binding interface and are subject to regulation by phosphorylation, notably by Aurora B kinase, which promotes error correction by destabilizing incorrect attachments; tension stabilizes correct links.

Structure and regulation: The complex is elongated, and the SPC24–SPC25 heterodimer forms a globular domain that anchors the Ndc80 core to microtubules.

Genetics and evolution: SPC24 is highly conserved among eukaryotes. In model organisms such as yeast, SPC24 is essential; depletion causes chromosome mis-segregation and aneuploidy.

Clinical relevance: In humans, altered SPC24 expression or mutations have been associated with chromosomal instability in some cancers. The precise role of SPC24 in tumorigenesis remains under investigation, and its utility as a biomarker or therapeutic target is not established.