Cell cycle checkpoints

Abstract

Abstract During each yeast cell cycle, chromosomes must be copied faithfully and segregated accurately between daughter cells. Surveillance systems termed ‘checkpoints’ ensure the fidelity of chromosome duplication by detecting abnormal structures and blocking cell cycle transitions while problems are corrected. Studies in Saccharomyces cerevisiae and Schizosaccharomyces pombe have identified a plethora of checkpoint genes and proteins. Remarkably, as was predicted in 1989 by Hartwell and Weinert (1), the same checkpoint proteins that maintain the yeast genomes play a crucial role in preventing cancer in mammals (2, 3). Thus studies in yeasts have helped to elucidate an important cause of genomic instability and cancer. Now that many checkpoint proteins have been identified, current investigations are aimed at understanding how these checkpoints work in molecular detail. As this review will detail, considerable progress has been made in this area in the last 10 years. Because many of the checkpoint proteins arc conserved in higher eukaryotes, yeasts will continue to prove their value as model systems for the study of mechanisms that maintain the genome.