cut11.1 lethality is not rescued by boosting Cdc25. (A) Serial dilutions (1 in 5) of the strains indicated were plated at the permissive (left) and restrictive temperature (right). In contrast to the rescue of cut12.1 by stabilizing cdc25 mRNA (cut12.1 cdc25.d1), cut11.1 lethality at 36°C is not suppressed in the same conditions (cut11.1 cdc25.d1). (B) Frequency of cells that display a defective karyokinesis, including the cut phenotype and asymmetric or no segregation of the nucleus (n = 50). (C) Indicated strains bearing NLS-GFP–β-Gal marker were grown at 25°C and mounted at 36°C for live cell imaging. Stacks of images were taken every 4 min to monitor karyokinesis. Both cdc25.d1 control and cdc25.d1 cut12.1 double mutant are able to divide the nucleus successfully, whereas in the majority of cdc25.d1 cut11.1 cells, GFP signal leaks into the cytoplasm in mitosis. Note that the cells are very small because of the elevated levels of Cdc25. (D) Frequency of cells that show leakage at any point in the process of nuclear division (n = 50). (E) Mean duration of the nucleoplasm efflux in cells that were assessed in D (n = 40). Error bars show standard deviation. wt, wild type. Bar, 2 µm.