Figure 7.

Nuclear accumulation of β-catenin is saturable and competitively inhibited by importin β family proteins. Digitonin-permeabilized MDBK cells were incubated with 10 μl of testing solution containing 4 pmol of GFP-β-catenin (a–d) or 4 pmol of GFP-importin β (e–h) in the absence (a and e) or presence of 80 pmol of importin β (b and f), 80 pmol of GST-transportin (c and g), or 80 pmol of FLAG-β-catenin (d and h). After incubation for 10 min at 30°C, cells were fixed, and localization of the GFP fusion proteins was examined by Axiophoto microscopy (Zeiss).