The DASH complex component Ask1 is a cell cycle-regulated Cdk substrate in Saccharomyces cerevisiae

The proper timing and fidelity of cell cycle transitions is critical for the survival of organisms. Cyclin-dependent kinases orchestrate many cell cycle transitions in eukaryotes including S phase entry and mitosis. Accurate chromosome segregation during mitosis is one of the key events regulated by the cell cycle and many proteins function together to ensure the fidelity of this process. In S. cerevisiae, the DASH complex is essential for chromosome segregation. The DASH complex binds to microtubules and kinetochores and regulates their association. Here we report that Askl, one component of DASH, is phosphorylated during the cell cycle. This phosphorylation is dependent on Cdks in vivo, and in vitro Cdc28 can phosphorylate Askl. We identify two Cdk phosphorylation sites in Askl and find that the phosphorylation of Askl is important for its full activity in vivo. Thus, the DASH complex is directly regulated by cyclin-dependent kinases to facilitate chromosome segregation.