FIGURE 2.

Proteasome-mediated degradation of MBP in mammalian cells is not affected by UbK0 co-transfection. A, HEK293 cells were transfected with cDNAs coding for MBP, ODC, and c-Myc, along with cDNAs coding for the respective ubiquitin species. After 24 h, the cells were subjected to cycloheximide (CHX) chase followed by Western blotting (WB) analysis. The percentage of protein remaining was calculated as the ratio of protein at the time points indicated relative to the initial protein. The data are represented as the mean ± S.E. from three separate experiments. B, the Ub K0/WT-transfected samples were additionally stained for Myc tag to visualize the accumulation of low molecular weight (LMW) and high molecular weight (HMW) polyubiquitin conjugates, which are marked by arrows. Ub conj., ubiquitin conjugates.