Ludwig Institute for Cancer Research, La Jolla, California 92093, USA- icheeseman@ucsd-edu
Abstract: Kinetochores play an essential role in chromosome segregation by forming dynamic connections with spindle microtubules- Here, we identify a set of 10 copurifying kinetochore proteins from Caenorhabditis elegans, seven of which were previously uncharacterized- Using in vivo assays to monitor chromosome segregation, kinetochore assembly, and the mechanical stability of chromosome-microtubule attachments, we show that this copurifying protein network plays a central role at the kinetochore-microtubule interface- In addition, our analysis suggests that the network is comprised of three groups of proteins that contribute in distinct ways to this interface- KNL proteins act after the assembly of centromeric chromatin to generate the core of the microtubule-binding interface, MIS proteins control the rate and extent of formation of this interface, and NDC proteins are necessary to sustain tension during interactions with spindle microtubules- We also purify a similar set of associated proteins from human cells that includes four novel proteins and has recognizable homologs from each functional class- Thus, this protein network is a conserved constituent of the outer kinetochore, and the functions defined by our analysis in C- elegans are likely to be widely relevant-