Monitoring nuclear import with GFP-variant fusion proteins in digitonin-permeabilized cells.

A convenient assay for monitoring nuclear localization signal-mediated nuclear import of green fluorescent protein (GFP)-variant fusion proteins has been developed. This modified assay relies upon indirect immunofluorescence microscopy for visualization of transported substrates. The use of GFP-variant fusion proteins allows for the rapid assessment of optimal digitonin concentration and permits nuclear import to be monitored with minimal sample preparation in real time.