Figure 4.

The effect of brn1 mutation on cell cycle progression. (A) Relative viability of brn1-60 cells. Midlog phase cultures were split into two halves, and one half was shifted to the restrictive temperature (37°C). At indicated time points, portions of each culture were plated out at a density of 50–500 cells per plate, and the numbers of resulting colonies, divided by the corresponding number of colonies at time zero, were plotted on the graph. (B) Cell cycle stage distribution (% of total; 200 cells scored) of brn1–60 cells at the restrictive temperature, compared with wild-type (BRN1) cells. Asynchronous cultures were incubated at 37°C for 3 h. (C) DNA content of BRN1 and brn1-60 cells arrested at the G1 phase with α-factor and released at the restrictive temperature. Samples of cells were fixed at the indicated time points, stained with propidium iodide, and analyzed by flow cytometry. (D) Pulse-field electrophoresis of chromosomal DNA of BRN1 (lanes 1, 2) and brn1–60 mutant cells (lanes 3, 4) grown at 23°C (lanes 1, 3) or incubated at 37°C for 3 h. Lane 5, BRN1 cells treated with 100 mM hydroxyurea for 3 h.