Lengthening without letting go

Merotelic chromosome attachments present the cell with a particularly threatening scenario. With a single kinetochore attached to both spindle poles, the tension on this kinetochore ensures that no error message is sent out, as would be the case with a detached kinetochore. Most researchers presumed that the relatively lower tension on the “incorrect” attachment (the one that is relieved by the codirectional pull on the singly attached sister kinetochore) ensures detachment of that connection, followed by attachment to the correct pole.

But now Daniela Cimini, Lisa Cameron, and Ted Salmon (University of North Carolina, Chapel Hill, NC) show that this detachment process rarely makes it to completion. Instead, a tension-dependent elongation of the incorrect attachment allows the chromosome to reach the correct side during anaphase.

The group...