THE SPINDLE-ASSEMBLY CHECKPOINT - AIMING FOR A PERFECT MITOSIS, EVERYTIME

Checkpoints reduce the frequency of errors in cell division by delayin g the progress of the cell cycle until certain processes are complete. The spindle-assembly checkpoint prevents the onset of anaphase until a bipolar spindle is present and all chromosomes are attached to the s pindle. Evidence from yeast and mammalian cells suggests that kinetoch ores are at least one source of the signal that stops the cell cycle. Recent studies in budding yeast have begun to define the signal-transd uction pathway involved in the spindle-assembly checkpoint, but detail s of the endpoint of the pathway, where these signals interact with th e cell-cycle machinery, remain to be characterized.