FIGURE 7.

TPP1 is degraded in a proteasome-dependent manner, but its half-life is not changed upon USP7 depletion. A, cells stably expressing TPP1(WT)- or TPP1(10R)-3xHA were treated with cycloheximide (CHX) and MG132 or solvent (DMSO). TPP1 protein levels were analyzed by Western blotting for the indicated time points. B, quantification of six experiments as in A. TPP1(WT) half-life is prolonged by MG132 treatment, indicating proteasome-dependent degradation of TPP1(WT)-3xHA. The half-life of TPP1(10R)-3xHA is longer than of TPP1(WT)-3xHA but is still further increased by MG132 treatment. Average values and standard deviations (error bars) are indicated. C, cells stably expressing TPP1(WT)-3xHA were depleted for USP7. Western blot analysis and quantification from five independent experiments are shown. Average values, standard deviations (error bars), and p values as determined by t test are indicated. Efficient USP7 depletion slightly reduces TPP1–3xHA levels. D, cells from C were used for half-life analysis as in A. Quantification from five independent experiments is shown. Average values and standard deviations (error bars) are indicated. Efficient USP7 depletion does not significantly change TPP1–3xHA half-life. EV, empty vector.