Mitosis has always been near and dear to my heart, and there are enough proteins at the kinetochore to keep me fascinated for eternity. A recent study teases apart the roles of two proteins in mediating the attachment between microtubules and kinetochores.
Kinetochores are multi-protein complexes on chromosomes that serve as sites for microtubule attachment during mitosis. Other jobs of the kinetochore include relaying signals for mitotic progression and generating force that drives chromosome movement during anaphase. The Ndc80 complex is a group of proteins essential to providing stable microtubule-kinetochore interactions, and a recent paper adds to our understanding of two of these proteins, Hec1 (aka Ndc80) and Nuf2. Sundin and colleagues found that two specific domains of the Hec1 protein (the CH and tail domains, for those keeping track) are important for generating these stable microtubule-kinetochore attachments, while the CH domain of Nuf2 is not. Images above are of mitotic spindles in normal mammalian cells (top row) and Hec1 mutants (bottom two rows). Spindles with either of the domains in Hec1 mutated had many unaligned chromosomes (left column). Kinetochores (middle left, green in merged) and spindle microtubules (middle right, red in merged) can also be seen.
Sundin, L., Guimaraes, G., & DeLuca, J. (2011). The NDC80 complex proteins Nuf2 and Hec1 make distinct contributions to kinetochore-microtubule attachment in mitosis Molecular Biology of the Cell, 22 (6), 759-768 DOI: 10.1091/mbc.E10-08-0671