Checkpoints controlling mitosis.

Each year many reviews deal with checkpoint control.((1-5)) Here we discuss checkpoint pathways that control mitosis. We address four checkpoint systems in depth: budding yeast DNA damage, the DNA replication checkpoint, the spindle assembly checkpoint and the mammalian G2 topoisomerase II-dependent checkpoint. A main focus of the review is the organization of these checkpoint pathways. Recent work has elucidated the order-of-function of several checkpoint components, and has revealed that the S phase, DNA damage and spindle assembly checkpoints each have at least two parallel branches. These steps forward have largely come from kinetic studies of checkpoint-defective mutants. Copyright 2000 John Wiley & Sons, Inc.