Investigating the Role of the Chromosomal Passenger Complex and Putative Interactors in Drosophila Spindle and Central Spindle Formation

Abstract

Mitosis and meiosis, cellular processes leading to the production of diploid and haploid daughter cells respectively, are tightly regulated to ensure faithful chromosome segregation is coupled to cytokinesis. Defects in these processes can lead to many diseases, including the promotion of tumourogenesis and sterility. The Chromosomal Passenger Complex (CPC) orchestrates mitosis and meiosis through regulating the activity of many cellular proteins, including those involved in kinetochore-microtubule interactions and in central spindle formation. There are four known members of the CPC; the kinase Aurora B, Borealin, Survivin (Deterin) and the inner centromere protein, INCENP. All four subunits show the same localisation throughout the cell cycle; associating with chromatin during interphase and the centromeres during metaphase before transferring to the central spindle mid-zone and equatorial cortex during anaphase. An additional CPC interactor, TD60, has been described in humans. However, the mechanism by which the CPC facilitates cytokinesis and the potential role of TD60 as a CPC component has not been fully explored. The purpose of this research project was twofold: (i) to investigate the role of the CPC in central spindle formation and cytokinesis and (ii) to investigate the function of TD60, in the model organism Drosophila melanogaster. I show that although the CPC is not required for the microtubule (MT) association of two proteins, Pavarotti and Polo - a kinesin-like protein and kinase, respectively - during anaphase, it is required for the accumulation of Pavarotti to the plus ends of these microtubules (MTs). This work therefore sheds light on the relationship between key cytokinetic proteins. Through the 4 purification and injection of interfering antibodies raised against TD60, I also demonstrate an essential role for this protein in regulating the length of the metaphase mitotic spindle, kinetochore-MT interactions, chromosome segregation and mitotic exit timing, possibly through regulating the localisation of the CPC. Together, the work in this thesis advances our understanding of these important effectors of cell division, raising further questions as to their cellular roles and relationships to each other.