Our ongoing studies aim to answer three questions:
What are the structural proteins of the mitotic chromosome and kinetochore and how do they direct chromosome segregation in mitosis?
In an ongoing collaboration with Juri Rappsilber, we have defined the complete proteome of vertebrate mitotic chromosomes (>4000 proteins) using a novel approach that we term Multi-Classifier Combinatorial Proteomics (MCCP). We now using MCCP to determine the comprehensive assembly pathway for the vertebrate kinetochore – the complex multi-protein assembly that directs chromosome segregation during mitosis.
What is the chromatin environment of the centromere that provides an epigenetic landscape permissive for kinetochore assembly?
We used synthetic biology approaches to design and build an artificial human chromosome whose centromere chromatin can be modified as desired by targeting chimeric protein “tools”. This was done in an a ongoing collaboration with Vladimir Larionov at the NIH in the USA and Hiroshi Masumoto at the Kazusa DNA Institute in Japan. Our recent studies with this system have focused on analysis of the role of transcription and “open chromatin” in kinetochore function. This system offers unique opportunities both for functional analysis of kinetochore epigenetics, but also for gene therapy.
How does the chromosomal passenger complex (CPC) regulate mitotic events?
We have recently combined genetic and biochemical studies in Drosophila and human cells to show that CPC component Aurora B kinase is responsible for Polo kinase activation at kinetochores. This is extremely interesting because the two kinases have opposite effects: Polo promotes microtubule binding by kinetochores and Aurora B promotes microtubule release. We believe that INCENP (the scaffolding component of the CPC) integrates and coordinates the activity of these two kinases, thereby enabling accurate chromosome segregation.