FIGURE 6.

TDG destruction depends on its PIP degron. A, a p21 PIP box peptide prevents the destruction of TDG^WT. TDG destruction was measured as in Fig. 4B in extract supplemented with 200 μm WT or p21 peptide whose PIP box was mutated (ΔPIP). B, TDG PIP degron mutations used in this study. ΔPIP, Q128A/I131A/F135A; ΔB+4, R139A; ΔB+3/4, K138A/R139A; PIP*, A134F. C, mutation of the TDG PIP box or downstream basic residues stabilizes TDG^WT. Destruction of TDG^WT, TDG^ΔPIP, TDG^ΔB+4, and TDG^ΔB+3/4 was measured as in Fig. 4B. D, mutation of the TDG PIP box or downstream basic residues stabilizes TDG^ΔSUMO. The experiment was performed identically to that in Fig. 6C except that TDG^ΔSUMO replaced TDG^WT. Loading control for A was as in Fig. 4C. Loading controls for C and D were as in Fig. 4B.