Managing tension

Cells only exit metaphase if all their chromosomes are both attached and under tension from microtubules of the bipolar spindle, which pull on sister kinetochores that face in opposite directions. Now, Benjamin Pinsky, Sue Biggins, and colleagues (Fred Hutchinson Cancer Research Center, Seattle, WA) report that tension creation requires Mtw1p and associated proteins, and is sensed by the conserved Ipl1p/Aurora B protein kinase.

In the current model for Ipl1p action, many chromosomes initially have both kinetochores attached to a single pole. The resulting lack of tension turns on Ipl1p, which detaches kinetochores so that they are free to have another go at attaching to opposite poles. This detaching activity can be mimicked by adding low doses of microtubule-depolymerizing drugs to cells lacking Ipl1p....