The replication of the 2 μm DNA of Saccharomyces cerevisiae has been examined in cell division cycle (cdc) mutants. The 2 μm DNA does not replicate at the restrictive temperature in cells bearing the cdc28, cdc4, and cdc7 mutations which prevent passage of cells from the G1 phase into S phase. Plasmid replication also is prevented in a mating-type cells by α factor, a mating hormone which prevents cells from completing an event early in G1 phase. The 2 μm DNA ceases replication at 36 °C in a mutant harboring the cdc8 mutation, a defect in the elongation reactions of nuclear DNA replication. Plasmid replication continues at the restrictive temperature for approximately one generation in a cdc13 mutant defective in nuclear division. These results show that 2 μm DNA replication is controlled by the same genes that control the initiation and completion of nuclear DNA replication.
Bibliographical noteFunding Information:
WC thank Leland H. Hartwell for his interc~st and support of this work. This project was supported by a grant from the National Inst,itute of General Medical Sciences (GM17709) to Leland H. Hartwell. One of us (D.M.L.) is a postdoctoral fellow of the National Ca~~ccr Institllt,e (CA 00592).