Figure 7.—

The rapid degradation of α1 requires an intact SUMO conjugation pathway. (A) Cycloheximide-chase analysis of α1^3HA turnover in wild-type, uba2-ts9, ubc9-1, and ulp1-333 cells. In these experiments, the temperature-sensitive strains and a congenic wild-type strain were shifted to 37° for 1 hr prior to the cycloheximide-chase assay and maintained at this temperature throughout the assay. A representative experiment is shown at the top, and the quantitative results of multiple experiments are shown below. (B) Measurement of the α1^3HA degradation rate at 30° in wild-type, siz1Δ siz2Δ, and mms21-ΔRING cells. A representative experiment is shown at the top, and the quantitative results of multiple experiments are shown below. In the mms21-ΔRING allele, the Mms21 ORF is truncated after L182 by replacing the RING domain with a stop codon, the terminator from ADH1, and a kanMX cassette. (C) A representative cycloheximide-chase assay of α1^3HA turnover at 30° in a wild-type and a smt3-allR strain is shown at the top, and the quantitative results of multiple experiments are shown below.