Figure 3.

The amino-terminal spc110–221 mutant remains viable. The carboxy-terminal mutants spc110–226, spc110–225, and spc110–220 suffer considerable lethality. spc110–220, spc110–221, spc110–226, and spc110–225 mutant cultures (strains HSY20, HSY21, HSY83, and HSY48, respectively) were synchronized in early G₁ by elutriation as described in MATERIALS AND METHODS and released at 37°C. At regular intervals, aliquots were removed, sonicated, and titered for colony-forming units on YPD at 21°C. Time zero is the midpoint of S phase and is the landmark chosen to align the data from different elutriation experiments. The fraction of viable cells in the spc110–220 mutant culture (□) is shown in each panel. (A) ▴, fraction of spc110–221 cells viable when plated at the permissive temperature. (B) •, fraction of spc110–225 cells viable when plated at the permissive temperature. (C) ▪, fraction of spc110–226 cells viable when plated at the permissive temperature.