Regulation of chromosome attachment and dynamics by Saccharomyces cerevisiae kinetochores

Abstract

Kinetochores are large, multi-protein complexes that bind centromeric DNA to the microtubules of the mitotic spindle and mediate chromosome movement throughout the cell cycle. The proteins that regulate both force generation at kinetochores as well as and the cell-cycle-dependent changes in kinetochore architecture are largely unknown. The relative simplicity of centromere specification and kinetochore-microtubule attachment make Saccharomyces cerevisiae an attractive model organism for investigations into kinetochore-microtubule attachment and regulation. We used a combination of cell biology and biochemistry to study the roles of the four nuclear kinesin motor proteins at budding yeast kinetochores. We discovered that each of the four nuclear kinesins localizes to kinetochores. Three of these, Cin8p, Kip1p, and Kip3p are present at mature chromosome-microtubule attachments in metaphase. Cin8p and Kip1p align metaphase chromosomes into the characteristic bilobed configuration that is analogous to the metaphase plate in higher eukaryotes. Kip3p regulates microtubule dynamics throughout the cell cycle and regulates poleward movement during anaphase. Kar3p, the final nuclear kinesin, is recruited specifically to detached kinetochores.

(cont.) In addition, we have discovered that kinetochore-microtubule attachments alter during the cell cycle indicating that kinetochore function is temporally regulated.