FIG. 2.

Localization of NP mutants. MDCK cells transfected with plasmids expressing mutant NP or wild-type NP were subjected to indirect immunofluorescence assays. NP and DNA were stained with an anti-NP antibody and DAPI (4′,6′-diamidino-2-phenylindole), respectively. Samples were observed under a confocal laser microscope. Nine hours after transfection, wild-type and mutant NP exclusively localized to the nucleus. Shown are wild-type NP (A) and mutant R175A as a representative example of the mutants tested (B). Twenty-four hours after transfection, wild-type NP and all mutant NPs tested localized to both the nucleus and the cytoplasm, regardless of the addition of the translational inhibitor cycloheximide at 9 h posttransfection. The localization of the mutant NP proteins was indistinguishable from that of wild-type NP. Scale bars, 20 μm.