Kinetochores hold on with a ring

A complex that links a budding yeast kinetochore to a microtubule (MT) forms a ring around the MT, based on structures from two groups. The ring may help kinetochores to keep hold of an MT, even as the MT shrinks towards the spindle pole during anaphase.

Stephen Harrison (Harvard Medical School, Boston, MA) and Peter Sorger (MIT, Cambridge, MA) are hoping to analyze the structure of the 60 or more yeast kinetochore proteins one subcomplex at a time. The current success with the 10-protein DASH complex, Harrison says, “came about on a dare to see if [first author JJ Miranda] could coexpress the whole thing in E. coli.” Happily, the bold experiment worked, the purified complex bound MTs, and the electron micrographs clearly showed rings of DASH complex encircling an MT.

The ring structure immediately suggests a...