CENP-K and CENP-H may form coiled-coils in the kinetochores

Kinetochores are large proteinaceous structure on the surface of chromosomes' primary constriction during mitosis. They link chromosomes to spindle microtubules and also regulate the spindle assembly checkpoint, which is crucial for correct chromosome segregation in all eukaryotes. The better known core networks of kinetochores include the KMN network (K, KNL1; M, Mis12 complex; N, Ndc80 complex)and CCAN (constitutive centromere-associated network). However, the detailed molecular mechanism of the kinetochore protein network remains unclear. This study demonstrates that CENP-H and CENP-K form quite stable subcomplex by TAP (tandem affinity purification) with HEK 293 cells which express TAP-CENP-K, with the ratio of purified CENP-H and CENP-K being close to 1: 1 even with high salt. Bioinformatic analysis suggests that CENP-H and CENP-K are enriched with coiled-coil regions. This implies that CENP-H and CENP-K form heterodimeric coiled-coils. Furthermore, the functional regions which form the complex are respectively located on their N- and C-terminals, but the association between the C-terminals is more complex. It is possible that this is the first identified heterodimeric coiled-coils within the inner kinetochore, which is directly involved in the attachment between kinetochores and the spindle microtubules.