The microtubule-based motor Kar3 and plus end-binding protein Bim1 provide structural support for the anaphase spindle.
In budding yeast, the mitotic spindle is comprised of 32 kinetochore microtubules (kMTs) and approximately 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.
Gardner
Melissa K
MK
Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
Haase
Julian
J
Mythreye
Karthikeyan
K
Molk
Jeffrey N
JN
Anderson
Marybeth
M
Joglekar
Ajit P
AP
O'Toole
Eileen T
ET
Winey
Mark
M
Salmon
E D
ED
Odde
David J
DJ
Bloom
Kerry
K
D000705:Anaphase / Q000235:genetics / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D020090:Chromosome Segregation; D008868:Microtubule Proteins / Q000235:genetics / Q000502:physiology*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism / Q000502:physiology; D008957:Models, Genetic; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism
C472767:Ase1 protein, S cerevisiae; C119683:BIM1 protein, S cerevisiae; D018797:Cell Cycle Proteins; C063504:KAR3 protein, S cerevisiae; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin