microtubule-based motor Kar3 and plus end-binding protein Bim1 provide structural support for the anaphase spindle

• Published in: The Journal of cell biology Vol. 180; no. 1; pp. 91 - 100
• Main Authors: Gardner, Melissa K, Haase, Julian, Mythreye, Karthikeyan, Molk, Jeffrey N, Anderson, MaryBeth, Joglekar, Ajit P, O'Toole, Eileen T, Winey, Mark, Salmon, E.D, Odde, David J, Bloom, Kerry
• Format: Journal Article
• Language: English
• Published: United States The Rockefeller University Press 14-01-2008; Rockefeller University Press
• Subjects: Anaphase; Anaphase - genetics; Anaphase - physiology; Biochemistry; Bundling; Cell cycle; Cell Cycle Proteins - genetics; Cell Cycle Proteins - physiology; Cell division; Cellular biology; Centromeres; Chromosome Segregation; Chromosomes; Deoxyribonucleic acid; DNA; Fluorescence; Kinetochores; Microtubule Proteins - genetics; Microtubule Proteins - physiology; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - physiology; Microtubules - metabolism; Microtubules - physiology; Mitotic spindle apparatus; Models, Genetic; Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - physiology; Spindle Apparatus - genetics; Spindle Apparatus - metabolism; Spindle Apparatus - ultrastructure; Spindle pole body; Tubulin - metabolism; Viability; Yeast
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.200710164

In budding yeast, the mitotic spindle is comprised of 32 kinetochore microtubules (kMTs) and ~8 interpolar MTs (ipMTs). Upon anaphase onset, kMTs shorten to the pole, whereas ipMTs increase in length. Overlapping MTs are responsible for the maintenance of spindle integrity during anaphase. To dissect the requirements for anaphase spindle stability, we introduced a conditionally functional dicentric chromosome into yeast. When centromeres from the same sister chromatid attach to opposite poles, anaphase spindle elongation is delayed and a DNA breakage-fusion-bridge cycle ensues that is dependent on DNA repair proteins. We find that cell survival after dicentric chromosome activation requires the MT-binding proteins Kar3p, Bim1p, and Ase1p. In their absence, anaphase spindles are prone to collapse and buckle in the presence of a dicentric chromosome. Our analysis reveals the importance of Bim1p in maintaining a stable ipMT overlap zone by promoting polymerization of ipMTs during anaphase, whereas Kar3p contributes to spindle stability by cross-linking spindle MTs.