Fig. 2. Lack of evidence for a transferable NLS within IN. (A) HeLa cells were transiently transfected with pGFP-PK (a), pGFP-PK-Vpr^73-96 (b) or pGFP-PK-IN (c-f) and monitored by fluorescence microscopy. As expected (Sherman et al., 2001), GFP-PK was exclusively localized to the cytoplasm (a) and the NLS within Vpr actively transported GFP-PK-Vpr^73-96 to the cell nucleus (b). By contrast, GFP-PK-IN localized exclusively to the cytoplasm in most cells (c-e). In rare instances, some degree of nuclear staining was also observed (e,f, arrows). (B) Western-blot analysis of cells transiently transfected with the plasmids described in (A) or pEGFP-C1 (Clontech Laboratories). Fusion proteins were detected with an anti-GFP antibody. Molecular mass markers in kDa are indicated to the left of the blot.