Figure 3.

Ectopic expression of α7-CFP promotes recruitment of whole 20S proteasomes into the nuclear foci. Parental U₂OS-tTA cells (A) and U₂OS-tTA-α7-CFP cells induced for 48 h for α7-CFP expression (B) were subjected to indirect immunofluorescence using antibodies directed against the α4 and α6 subunits of the 20S proteasome (red). α7-CFP fusion protein was detected by CFP fluorescence. Wide-field overlay images and enlargements of marked area are shown. All observations were done with a 63× objective. Bar, 10 μm. (C) Expression of α7-CFP does not alter expression level of other 20S proteasome subunits. Thirty micrograms of total protein extract from U₂OS-tTA (U) and induced U₂OS-tTA-α7-CFP (α7) cells were separated by electrophoresis and analyzed by immunoblot (IB) using the indicated antibodies.