Structure and Function of the Chromosomal Passenger Complex

The Chromosomal Passenger Complex (CPC) is one of the key regulators of cell division. The activity of the CPC is essential for faithful chromosome segregation but also regulates cytokinesis. Proper coordination of these events, by the CPC, ensures an equal partitioning of DNA between two separating daughter cells while mistakes in this process can result in aneuploidy and chromosomal instability, two hallmarks of cancer. The CPC is described as a complex consisting of the protein kinase aurora B, and three scaffold proteins: survivin, borealin, INCENP. In addition, a potential fifth member of the complex, called TD-60, exists. The scaffold proteins not only mediate the dynamic localization of the CPC during the various stages of cell division, they are also required for full activity of aurora B. However, little is known about the three-dimensional structural organisation of the whole CPC and how this organisation affects CPC activity. Moreover, the exact stoichiometry of the complex is unclear and it is not known if and how this changes during mitosis. Finally, while it is clear that phosphorylation plays a key role in the regulation of the CPC, how this affects CPC structure and function is poorly understood. The aim of this project is to study the assembly and structure of the CPC. Using a novel expression system I plan to purify recombinant forms of the CPC, allowing me to study the complete full-length complex. I will analyse the CPC using a hybrid structural biology approach that combines cross-linking and mass spectrometry, X-ray crystallography, electron microscopy and small angle X-ray scattering. This approach should result in a complete, pseudo-atomic model of the CPC.