Figure 3.

A block in nuclear transport has no effect on the degradation of an ER membrane protein. (A) The indicated strains expressing the constitutively-degraded 6MYC-Hmg2p were grown at the permissive temperature of 23°C. Log phase (OD₆₀₀ = 0.1) cells were then shifted to the restrictive temperature of 37°C for 3.5 h before the addition of cycloheximide and subsequent chase at the indicated times. During this time, wild-type cells doubled at the normal rate, while the temperature-sensitive hrd4–1 and nup116Δ cells failed to complete even one additional doubling after temperature shift. Equal numbers of cells were collected at the indicated times following addition of cycloheximide and lysed. These lysates were then separated by SDS-PAGE, and immunoblotting for the myc epitope tag was performed. (B) Nup116 protein is absent in nup116Δ cells. Lysates from the indicated strains were subjected to SDS-PAGE and immunoblotting using anti-Nup116p antibodies.