Regulation and Functions of the Ipll/Aurora Kinase

Ipllp is the budding yeast member of the Aurora family of protein kinases, critical regulators of genomic stability that are required for chromosome segregation, the spindle checkpoint and cytokinesis. We had previously found that Ipllp localized at the midzone in anaphase cells. Using time lapse microscopy, we found that Ipll-GFP localizes to kinetochores from Gi to metaphase, transfers to the spindle after metaphase and accumulates at the spindle midzone late in anaphase. As the spindle disassembles, Ipllp follows the plus ends of the depolymerizing spindle microtubules. This prompted us to test whether Ipllp played a role in mitotic spindle disassembly. We found that it was the case and we further showed that this new function is separable from its previously identified roles. In addition ipll mutants can stabilize fragile spindles. Many Ipllp substrates co-localize with Ipllp to the spindle midzone, identifying additional proteins that may regulate spindle disassembly. We propose that Ipllp regulates both the kinetochore and interpolar microtubule plus ends to regulate its various mitotic functions. We found that Ipllp acts in the same pathway that the microtubule destabilizing kinesin, Kip3p. And Chitra Kotwaliwale the graduate student taking over the project is currently testing whether Iplpl regulates Kip3p.