Cdc2 Phosphorylation of the Fission Yeast Dis1 Ensures Accurate Chromosome Segregation

Shortened kinetochore microtubules take separated chromatids to the opposing spindle poles in anaphase. Fission yeast Dis1 belongs to the Dis1/XMAP215/TOG family that is required for proper microtubule dynamics. Here, we report that Dis1is regulated by Cdc2 phosphorylation and that this mitotic phosphorylation ensures the fidelity of chromosome segregation. Whereas mutants Dis16A and Dis16E that substitute all of the six Cdc2 sites for Ala or Glu, respectively, produce colonies at 22°C-36°C, Dis16A but not Dis16E loses a minichromosome and reveals aberrant chromosome segregation at significant frequencies. Dis1WT is recruited to two regions of the mitotic spindle: kinetochores (possibly also kinetochore microtubules) in metaphase and the pole-to-pole microtubule lattice in anaphase. Mutant Dis16E preferentially binds to metaphase kinetochores, whereas Dis16A, which is located along microtubules, fails in its accumulation at kinetochores. Dis16A displays synthetic lethality with the mis12-537, which is a mutant that compromises kinetochore function. Dis16E mimics the Cdc2-phosphorylated form of Dis1WT, whereas Dis16A can partially rescue the phenotype resulting form deletion of Mtc1/Alp14, another XMAP215-like protein. In anaphase, dephosphorylated Dis1 and Dis16A, but not Dis16E, move to the spindle microtubule lattice near the SPBs. Cdc2 thus directly phosphorylates Dis1, and this phosphorylation regulates Dis1 localization in both metaphase and anaphase and ensures high-fidelity segregation.