FIG. 2.

Thermosensitive phenotype of rpn3-4 and rpn3-7 mutants. (A) YE100 (rpn3-4) and YE101 (rpn3-7) mutant strains transformed with either an RPN3 gene-containing plasmid (YCp50::RPN3) or an empty vector (YCp50) were streaked on synthetic medium and incubated at 37°C for 2 days. (B) Wild-type YE46 (RPN3) cells and YE100 mutant (rpn3-4) cells were grown at 25°C to the early log phase and shifted at time zero (arrow) to 37°C. At hourly intervals, cell density was determined for both strains and plotted against time. (C) Wild-type YE46 (RPN3) cells and YE100 mutant (rpn3-4) cells were incubated as described for panel B and scored for bud morphology. Bars represent the percentages scored for each category. (D) Microtubule and nuclear phenotypes of rpn3-4 mutant cells at the restrictive temperature. YE100 (rpn3-4) cells were grown to the early log phase in YEPD medium at 25°C, shifted to 37°C, and incubated for 5 h prior to fixation and staining for mitotic spindles (tubulin) and nuclei (DAPI).