Localization of VP2/VP3, VP2, VP3, and their deletion mutants. (A) Expression vectors encoding VP2 and VP3 (VP2/VP3), VP2 alone (VP2/M120L), or VP3 alone (VP3) were transfected into COS-7 cells. The localization of VP2/VP3, VP2/M120L, and VP3 was examined by immunocytochemistry. (B) Two clusters of basic amino acids, GPNKKKRRK (cluster 1) and KRRSRSSRS (cluster 2), in the C-terminal sequence of VP2/VP3. The asterisk indicates the C terminus. Deletion mutants Del-1 and Del-2 were constructed for these clusters, and the localization of the mutant proteins was examined by immunocytochemistry. Both Del-1 and Del-2 were diffusely localized to the nucleus. (C) Percentages of cells showing exclusively nuclear localization of VP2/VP3, Del-1, and Del-2.