Cytoplasmic dynein, conserved in many eukaryotes, is involved in diverse cellular processes including vesicle and organelle transport, mitotic checkpoint signaling, and the organization and positioning of the nucleus. The budding yeast Saccharomyces cerevisiae is a useful model system for studying the mechanism of dynein function since this organism apparently employs dynein for a single task: positioning of the nucleus and mitotic spindle during cell division. This chapter describes our current understanding of how dynein contributes to this process. We describe the components of the yeast dynein complex along with accessory factors that are necessary for dynein function, and we discuss how comparison with this system might provide insight into the molecular details of dynein mechanisms in other eukaryotes. 15.1 INTRODUCTIONThe partitioning of the duplicated genome between the two progeny is an essential step in every cell division. Chromosomes are organized and ultimately separated by means of a bilateral microtubule (MT) network known as the mitotic spindle. In budding yeast, the spindle is contained within the nucleus, which remains intact throughout the cell cycle. Therefore, both the nucleus and the spindle must be positioned between the mother and bud in order for each cell to receive a copy of the genome. Dynein is an MT-based Handbook of Dynein Edited by Keiko Hirose and Linda A. Amos Copyright © 2012 Pan Stanford Publishing Pte. Ltd. www.panstanford.com

motor that contributes to the translocation of the spindle and the nucleus during yeast cell division. The study of yeast dynein provides the opportunity to understand the biology of this process and characterize dynein function at the molecular level. Yeast provides a classic genetic system allowing for the identification and characterization of genes necessary for dynein activity, many of which are conserved in higher eukaryotes and believed to function in a similar manner. Yeast cells also utilize a cytoskeleton that lends itself well to visualization due to the presence of relatively few cytoplasmic microtubules (cMTs) and actin cables. Therefore, the study of dynein and its role in spindle positioning in Saccharomyces cerevisiae should be extremely beneficial.