Mutations in CDC14 result in high sensitivity to cyclin gene dosage in Saccharomyces cerevisiae

We screened for mutations that resulted in lethality when the G1 cyclin Cln 2p was overexpressed throughout the cell cycle in Saccharomyces cerevisiae. Mutations in five complementation groups were found to give this phenotype , and three of the mutated genes were identified as MEC1, NUP170, and CDC14 . Mutations in CDC14 may have been recovered in the screen because Cdc14p m ay reduce the cyclin B (Clb)-associated Cdc28 kinase activity in late mitos is, and Cln2p may normally activate Clb-Cdc28 kinase activity by related me chanisms. In agreement with the idea that cdc14 mutations elevate Clb-Cdc28 kinase activity, deletion of the gene for the Clb-Cdc28 inhibitor Sicl cau sed synthetic lethality with cdc14-1, as did the deletion of HCT1, which is required for proteolysis of Clb2p. Surprisingly, deletion of the gene for the major B-type cyclin, CLB2, also caused synthetic lethality with the cdc 14-1 mutation. The clb2 cdc14 strains arrested with replicated but unsepara ted DNA and unseparated spindle pole bodies; this phenotype is distinct fro m the late mitotic arrest of the sic1::TRP1 cdc14-1 and the cdc14-1 hctl::L EU2 double mutants and of the cdc14 CLN2 overexpressor. We found genetic in teractions between CDC14 and the replication initiator gene CDC6, extending previous observations of interactions between the late mitotic function of Cdc14p and control of DNA replication. We also describe genetic interactio ns between CDC28 and CDC14.