The Ipl1/Aurora Protein Kinase and Glc7 Protein Phosphatase Regulate The Metaphase to Anaphase Transition

Accurate cell division depends on the proper coordination of a number of events. Once all of the chromosomes align on the metaphase plate, anaphase is initiated so that chromosomes are equally segregated to daughter cells. The metaphase to anaphase transition is controlled by the anaphase promoting complex (APC), a ubiquitin ligase that targets the anaphase inhibitor Pds1 for destruction. This process is controlled by the Cdc20 activator protein. We have found that the budding yeast protein kinase Ipl1/Aurora inhibits the metaphase to anaphase transition independently of its role in the spindle checkpoint. Cells arrested in metaphase due to a defect in Cdc20 activity will progress into anaphase due to low Pds1 levels when Ipl1 function is impaired. Consistent with this, the overexpression of the opposing phosphatase drives metaphase‐arrested cells into anaphase. We are currently determining whether Pds1, Cdc20 or the APC are direct targets of Ipl1 and Glc7. This work was supported by grants from the NIH, Leukemia and Lymphoma Society and the Department of Defense.