Checkpoints in the cell cycle of fission yeast.

When cell cycle progression in fission yeast is disrupted, checkpoint controls ensure that the normal sequence of cell cycle events is maintained. Activation of a checkpoint relies on monitoring signals that might involve assembly of macromolecular structures essential for specific cell cycle processes. The past year has seen further elucidation of two new checkpoints operating during the cell cycle of Schizosaccharomyces pombe. One involves the product of the rum1 gene and prevents cells from entering mitosis from the pre-Start G1 interval. The second checkpoint operates during the later stages of the cell cycle and is essential for coupling the events of mitosis and cell division.