Final Report Summary - KINETOCORE (Molecular Dissection of the Kinetochore – Microtubule Interface)
Every eukaryotic cell needs to faithfully duplicate and segregate their chromosomes in order to submit the genetic information from one generation to the next. At the heart of the process lie kinetochores, large multi-complex assemblies of proteins that physically link chromosome regions, termed centromeres, to the microtubules of the mitotic spindle. We have dissected the molecular mechanism of kinetochore function using the simple eukaryote Saccharomyces cerevisiae (budding yeast) as a model organism. In a synthetic approach we have asked if we can build simpler versions of kinetochores in vivo. To do this we have artificially recruited proteins to a piece of DNA and probed whether they can provide the function of kinetochores. Surprisingly, we could demonstrate that in yeast artificial recruitment of the microtubule-binding Dam1 complex is sufficient to let circular plasmids or authentic chromosomes segregate with high fidelity (Kiermaier et al., 2009). We could demonstrate that for native kinetochore function, the Dam1 complex co-operates with the conserved four-protein Ndc80 complex. Dam1 enhances the affinity of the Ndc80 complex for microtubules and allows persistent attachment to growing and shrinking microtubule plus ends – features that are essential for kinetochore function in vivo (Lampert et al., 2009, Lampert et al., 2013). We have furthermore characterized the conserved plus-end tracking protein EB1 (budding yeast Bim1p) and revealed molecular determinants of its activity. We could show that phosphorylation by the mitotic kinase Aurora B (budding yeast Ipl1p) is important for the regulation of the interaction with the mitotic spindle (Zimniak et al., 2009) and for control of Aurora B function itself (Zimniak et al, 2012). We have shown that the architecture of kinetochores is conserved between yeast and humans (Westermann and Schleiffer 2013, Hornung et al., 2011) and we have identified a conserved centromere receptor for the Ndc80 complex (Schleiffer et al., 2012). We have finally shown that yeast kinetochores are transported with the help of a non-canonical kinesin motor that uses a novel motility mechanism to move along microtubules (Mieck et al., manuscript in preparation).