Figure 2.

NEDD8 can substitute for RUB1 in yeast. Yeast mutants were streaked out on agar plates and incubated at 23°, 33°, or 37°C. Conditional cdc34-1 mutants are inviable at 37°C. Combined with the rub1-1 null mutation the double mutant (cdc34-1 rub1-1) is inviable even at 33°C. Viability could be restored by NEDD8 expression from a glucose-repressible GAL1-10 promoter (pGAL–NEDD8). The promoter is “off” on glucose (Upper) and “on” on galactose plates (Lower).