title: The Dam1 kinetochore ring complex moves processively on depolymerizing microtubule ends.
abstract: Chromosomes interact through their kinetochores with microtubule plus ends and they are segregated to the spindle poles as the kinetochore microtubules shorten during anaphase A of mitosis. The molecular natures and identities of coupling proteins that allow microtubule depolymerization to pull chromosomes to poles during anaphase have long remained elusive. In budding yeast, the ten-protein Dam1 complex is a critical microtubule-binding component of the kinetochore that oligomerizes into a 50-nm ring around a microtubule in vitro. Here we show, with the use of a real-time, two-colour fluorescence microscopy assay, that the ring complex moves processively for several micrometres at the ends of depolymerizing microtubules without detaching from the lattice. Electron microscopic analysis of 'end-on views' revealed a 16-fold symmetry of the kinetochore rings. This out-of-register arrangement with respect to the 13-fold microtubule symmetry is consistent with a sliding mechanism based on an electrostatically coupled ring-microtubule interface. The Dam1 ring complex is a molecular device that can translate the force generated by microtubule depolymerization into movement along the lattice to facilitate chromosome segregation.
authors.affiliation: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California 94720-3202, USA.
authors.forename: Stefan
authors.initials: S
authors.lastname: Westermann
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Agustin
authors.initials: A
authors.lastname: Avila-Sakar
authors.forename: David G
authors.initials: DG
authors.lastname: Drubin
authors.forename: Eva
authors.initials: E
authors.lastname: Nogales
authors.forename: Georjana
authors.initials: G
authors.lastname: Barnes
mesh_terms: D018797:Cell Cycle Proteins / Q000502:physiology*; D020090:Chromosome Segregation / Q000502:physiology; D018386:Kinetochores / Q000502:physiology* / Q000648:ultrastructure; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000502:physiology*; D008870:Microtubules / Q000502:physiology* / Q000648:ultrastructure; D009068:Movement; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D008941:Spindle Apparatus / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D018797:Cell Cycle Proteins; C116003:DAM1 protein, S cerevisiae; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins