Putting mitosis in reverse

Cells exiting mitosis are able to undo their work and return to metaphase if cyclin B is preserved, as revealed by a new study from Tamara Potapova, Gary Gorbsky (Oklahoma Medical Research Foundation, Oklahoma City, OK), and colleagues.

The destruction of cyclin B at anaphase, and the resulting inactivation of Cdk1, ushers in mitotic exit and cytokinesis. By tinkering with these mitotic regulators, Gorbsky's group reversed mitotic exit in vertebrate cells.

The authors first inhibited proteasome activity to preserve cyclin B at anaphase onset, creating a mitotic stall. They then forced these cells into cytokinesis by inhibiting Cdk1 activity. If they then withdrew the Cdk1 inhibitor, the cells reverted back into mitosis. The cleavage furrow opened, the nuclear envelope dissolved, chromatin recondensed, and the mitotic spindle...