Effect of Reversible Inhibition of Deoxyribonucleic Acid Synthesis on the Yeast Cell Cycle

Hydroxyurea (HU) preferentially inhibited deoxyribonucleic acid (DNA) replication and division in Saccharomyces cerevisiae. Growth, ribonucleic acid synthesis, and protein synthesis were less sensitive to this drug. Upon addition of HU, cells underwent one cycle of budding and the nuclei migrated into the necks between the mother cells and buds. Neither the nucleus nor the cells divided. Removal of HU allowed immediate resumption of DNA synthesis. Nuclear division, budding, and cell division occurred 1.5, 2, and 4 hr, respectively, after HU was removed. If protein synthesis was blocked at the time HU was removed, budding and cell division did not occur. These results were interpreted to indicate that HU prevents accumulation of the potential to initiate a new cell cycle.