Isolation of Genes Required for the Regulated Separation of Sister Chromatids

摘要

Failure in cell cycle checkpoint controls causes aneuploidy which is a significant factor in the tumorogenic progression of breast cancer cells. We identified and characterised a novel Pdsl-dependent checkpoint pathway that prevents aneuploidy by coordinating DNA replication with mitotic anaphase. The yeast anaphase inhibitor Pdsl is critically involved in this regulation. It is a distinct checkpoint control system from the previously described S-phase checkpoint pathway. Two more genes required for regulated chromosome segregation were identified, Rad23 and Ddil. When overproduced, these proteins suppress the S-phase checkpoint defect of a pdsl mutant strain. Structure/function studies revealed a likely mechanism through which Rad23 and Ddil may regulate Pdsl (by binding to ubiqutinated Pdsl) . Fad23 and Ddil contain a novel protein interaction domain (UBA) that binds to ubiquitin and ubiquitinated proteins. Rad23 and Ddil UBAs are essential for suppression of the pdsl mutant. These genes have closely related human homologues that are likely to be required for human checkpoint controls. Failure in such checkpoint mechanisms are a potential cause of aneuploidy that contributes to the etiology of breast cancer.