Figure 3.—

Temperature sensitivity of dpb2 strains. DPB2 (control) and dpb2 alleles were integrated into the DPB2 chromosomal locus of ΔI(-2)I-7B-YUNI300. (A) Viability of the dpb2 mutants grown at 23°, 30°, and 37°. Cells were grown overnight at 23° on SD plates supplemented with required amino acids and nucleotides. Cultures were diluted to identical initial concentrations and 10-fold serial dilutions were spotted in 10-μl portions on SD plates. The ability to grow was subsequently tested at different temperatures, as indicated. (B) Cellular and nuclear morphology of dpb2 strains. Cells were grown at permissive temperature (23°) to log phase and subsequently incubated for 6 hr at 37°. Differential interference microscopy (DIC) images of representative cells of the DPB2 and dpb2 strains and DAPI fluorescence images of cells with DAPI-stained DNA. (C) Cell-cycle analysis of cells carrying DPB2 and dpb2-103 alleles. Yeast cells were grown in YPDA medium at 23° to 0.4 OD. Cultures were synchronized with α-factor (3 hr at 23° and 1 hr at 37°). Samples of cells released from α-factor were collected every 15 min and subjected to flow cytometry analysis. DNA was stained with propidium iodide.