The kinetochore is the protein structure in eukaryotes which assembles on the centromere and links the chromosome to the mitotic spindle during mitosis.The kinetochore contains two regions: an inner kinetochore, which is tightly associated with the centromere DNA; and an outer kinetochore, which interacts with microtubules. Even the simplest kinetochores consist of more than 45 different proteins. Many of these proteins are conserved throughout eukaryotes, including a specialized histone H3 variant (called CENP-A or CenH3) which helps the kinetochore associate with DNA.

Other proteins in the kinetochore attach it to the microtubules of the mitotic spindle. There are also motor proteins, including both dynein and kinesin, which generate forces that move chromosomes during mitosis. Other proteins monitor the microtubule attachment as well as the tension between sister kinetochores and activate the spindle checkpoint to arrest the cell cycle when either of these is absent.