FIG. 2.

Loss of 3×GFP-NLS from nuclei of permeabilized poliovirus-infected but not mock-infected HeLa-3E cells. At 2 h p.i. (MOI of ∼100 PFU/cell), the monolayers of HeLa-3E cells were treated with digitonin, which by itself permeabilizes the plasma membrane but leaves the nuclear membrane intact, stained with Hoechst 33258, and inspected under fluorescence microscope by using the green (for 3×EGFP-NLS) and blue (for Hoechst) filter cubes. Note that this kind of Hoechst dye is not able to enter the cell through an intact plasma membrane, and therefore it stains only the permeabilized cells.