Stabilization of S and M phase cyclins leads to constant Cdc14 release. (a–e) MET-CDC20 pds1Δ cdc15-as1 (Ry1558; a and b), MET-CDC20 pds1Δ cdc15-as1 clb5Δ (Ry1538; c and d), and cdc15-as1 (Ry1132; e) cells were arrested in G1 with α-factor in a synthetic complete medium lacking methionine. When arrest was complete, cells were released into YEPD media lacking the pheromone but with an added 8 mM methionine to repress the expression of Cdc20 in the presence (b, c, and e) or absence (a and d) of 5 µM Cdc15-as1 inhibitor (1NM-PP1 analogue 9; Bishop et al., 2001). The percentages of cells with metaphase spindles (closed squares), anaphase spindles (closed circles), and cells with Cdc14 released from the nucleolus (open circles) were determined at the indicated times. The presence or absence of the inhibitor is indicated as + or −, respectively.