The BIR domain is crucial for Survivin function. (A) Location of C86 in the CPC form of Survivin. (B) Expression of Survivin^C86A-GFP and loss of wild-type (WT) Survivin expression from cultures grown in doxycycline. (C) Survivin^C86A-GFP fails to rescue the life of Survivin^OFF cells; cells expressing this protein as their sole form of Survivin die with kinetics essentially identical to those of Survivin^OFF cells. (D) Survivin^C86A-GFP fails to localize in Survivin^ON/OFF cells. INCENP localization is normal in Survivin^ON cells, so Survivin^C86A-GFP fails to act as a dominant-negative mutant. Panel a shows the normal localization of Survivin-GFP in a control experiment. (E) Location of C59 in the Survivin dimer. (F) Expression of Survivin^C59A-GFP and loss of wild-type Survivin expression from cultures grown in doxycycline. (G) Survivin ^C59A-GFP fails to rescue the life of Survivin^OFF cells. (H) Survivin^C59A-GFP fails to localize in Survivin^ON/OFF cells. INCENP localization is normal in Survivin^ON cells, so Survivin^C59A-GFP also fails to act as a dominant-negative mutant. Bars, 5 μm.