Microtubule motors in mitosis

The mitotic spindle uses microtubule-based motor proteins to assemble itsel f and to segregate sister chromatids. It is becoming clear that motors invo ke several distinct mechanisms to generate the forces that drive mitosis. M oreover, in carrying out its function, the spindle appears to pass through a series of transient steady-state structures, each established by a delica te balance of forces generated by multiple complementary and antagonistic m otors. Transitions from one steady state to the next can occur when a chang e in the activity of a subset of mitotic motors tips the balance.