Kinetochore function: molecular motors, switches and gates.

Kinetochores are essential for accurate chromosome segregation. Recent studies reveal that vertebrate kinetochores are sophisticated propulsion systems composed of not only force generators but also "navigation' and "fail-safe' mechanisms. Advances toward the understanding of the biochemical composition and activities of the components of the kinetochore have come from the molecular characterization of key proteins of the kinetochore complex.