Molecular analysis of kinetochore architecture in fission yeast.

Kinetochore composition and structure are critical for understanding how kinetochores of different types perform similar functions in chromosome segregation. We used affinity purification to investigate the kinetochore composition and assembly in Schizosaccharomyces pombe. We identified a conserved DASH complex that functions to ensure precise chromosome segregation. Unlike DASH in budding yeast that is localized onto kinetochores throughout the cell cycle, SpDASH is localized onto kinetochores only in mitosis. We also identified two independent groups of kinetochore components, one of which, the Sim4 complex, contains several novel Fta proteins in addition to known kinetochore components. DASH is likely to be associated with the Sim4 complex via Dad1 protein. The other group, Ndc80-MIND-Spc7 complex, contains the conserved Ndc80 and MIND complexes and Spc7 protein. We propose that fission yeast kinetochore is comprised of at least two major structural motifs that are biochemically separable. Our results suggest a high degree of conservation between the kinetochores of budding yeast and fission yeast even though many individual protein subunits do not have a high degree of sequence similarity.