kinetochor

Kinetochor is a term sometimes used as a variant spelling of kinetochore, the protein structure assembled at the centromere of each chromosome. In standard usage, kinetochore refers to a complex that mediates attachment between chromosomes and the mitotic or meiotic spindle, enabling proper segregation during cell division.

A typical kinetochor consists of an inner and an outer portion. The inner kinetochore forms on centromeric chromatin that contains CENP-A–containing nucleosomes and includes components of the constitutive centromere-associated network (CCAN), such as CENP-C and CENP-T. The outer kinetochore interfaces with microtubules and is organized around the KMN network, which comprises the KNL1 complex, the Mis12 complex, and the Ndc80 complex. Additional proteins, including those from the RZZ complex and motor proteins such as dynein and CENP-E, help regulate attachments and movement.

Functions of the kinetochor include establishing stable microtubule attachments, generating and transmitting forces that drive chromosome movement toward opposite poles, and ensuring proper tension across sister chromatids. The spindle assembly checkpoint monitors unattached or improperly attached kinetochores and delays anaphase onset until all chromosomes are correctly attached and under tension. Aurora B kinase and other checkpoint components correct faulty attachments by destabilizing erroneous microtubule contacts.

Kinetochor activity is conserved across eukaryotes, though organizational details vary with chromosome structure. Defects in kinetochore function can lead to aneuploidy and chromosomal instability, phenomena associated with developmental disorders and cancer.