%0 Thesis
%9 Doctoral
%A Hsu, K.-S.
%B Faculty of Life Sciences
%D 2012
%F discovery:1338563
%I UCL (University College London)
%P 244
%T Molecular mechanism of the kinetochore-microtubule  attachment in fission yeast
%U https://discovery-pp.ucl.ac.uk/id/eprint/1338563/
%X Kinetochore capture by the spindle microtubule is a crucial step required for  chromosome biorientation. Any errors in this process would result in production  of aneuploid progenies, a hallmark of human cancer. The Ndc80 complex, a  conserved outer kinetochore complex, comprising four components,  Ndc80/Hec1, Nuf2, Spc24 and Spc25, constitutes one of the core microtubulebinding  sites within the kinetochore. Despite this knowledge, molecular  mechanism by which this complex contributes to establishment of correct  bipolar attachment of the kinetochore to the spindle microtubule remains largely  elusive. Here I show that the conserved internal loop of fission yeast Ndc80  directly binds the Dis1/TOG microtubule-associated protein, thereby coupling  spindle microtubule dynamics with kinetochore capture. Ndc80 loop mutant  proteins fail to recruit Dis1 to kinetochores, imposing unstable attachment and  frequent spindle collapse. In these mutants, mitotic progression is halted  attributable to spindle assembly checkpoint activation, and chromosomes  remain in the vicinity of the spindle poles without congression. dis1 deletion  precisely phenocopies the loop mutants. Furthermore, forced targeting of Dis1  to the Ndc80 complex rescues loop mutant’s defects. I propose that Ndc80  comprises two microtubule-interacting interfaces; the N-terminal region directly  binds the microtubule lattice, whilst the internal loop interacts with the plus end  of microtubules via Dis1/TOG. Therefore, my results provide a crucial insight  into how the Ndc80 complex establishes stable bipolar attachment to the  spindle microtubule.  In addition, integrity of the Ndc80 complex is also required for the kinetochore  tethering to the SPB during interphase. Loss of Ndc80 results in kinetochore  declustering in the nucleus, and those scattered kinetochores are found to  colocalise with cytoplasmic microtubules and the tubulin nucleation factor γ-  TuC. Further investigation will be needed to understand how Ndc80 affects the  γ-TuC distribution and/or how Ndc80 and the γ-TuC participate in the SPBkinetochore  anchorage in interphase.
%Z A copyright restricted article with supplementary material has been removed from the digital copy of this thesis