Figure 7.

Molecular Architecture of Kinetochores

(A) Molecular architecture of natural kinetochores. Centromere chromatin is crucial for centromere specification and kinetochore assembly at natural centromeres. At the base of the structure are CENP-A containing nucleosomes, centromere specific H3 nucleosomes, and a CENP-T-W-S-X nucleosome-like structure in centromere chromatin. Centromere-specific chromatin structure is established by coordination of these components. CCAN proteins assemble on the centromeric chromatin and the microtubule-binding complex is subsequently recruited to assemble the functional kinetochore.

(B) When the CENP-T N terminus or CENP-C N terminus is tethered at a noncentromere locus using the LacI-LacO system, an artificial kinetochore forms on the noncentromeric LacO site. Most centromeric chromatin proteins, including CENP-A, are not detected in the artificial kinetochores. However, the chromosome passenger complex (CPC) and Ndc80 complex are recruited and the artificial kinetochores are fully functional.

(C) Summary of studies on creation of artificial kinetochores. Tethering of CENP-T N terminus and/or CENP-C-N terminus can bypass the need for centromere-specific chromatin including CENP-A. CENP-A-mediated artificial kinetochores also have been created in human, chicken, and Drosophila cells and in Xenopus egg extracts.