FIGURE 4.
Cdc13 is ubiquitylated and partially degraded by the proteasome. A, Cdc13 ubiquitylation. GST-His6-Cdc13 was transformed with Myc-tagged Ub derivatives into wild-type cells. Cdc13 was precipitated with GST beads and blotted with anti-Myc antibody for ubiquitylated Cdc13 species (upper panel). The amounts of Cdc13 and Rpt5 in the extracts were also assessed by Western blotting (lower panels). B and C, compromised proteasomal activity partially stabilizes Cdc13. Cdc13 degradation was monitored as described for Fig. 3A in the presence or absence of the proteasome inhibitor MG132 or in cim5ts cells with compromised proteasome function.