NPM1 knockdown abolished the nucleolar localization of PCV3 Cap. A NPM1-knocked down and shCON-transfected PK-15 cells were respectively transfected with mCherry-PCV3-Cap for 24 h, and cells were fixed and then subjected to confocal microscopy analysis. GFP signals indicate silenced PK-15 cells. Nuclei were stained with 4′, 6′-diamidino-2-phenylindole (DAPI). Scale bar, 10 μm. B, C Images of PK-15 cell line expressing shRNA mediated by lentivirus (B), and the knockdown efficiency of NPM1 in shCON-transfected and NPM1-silenced PK-15 cells (C). The cell lysates were subjected to immunoblotting using the indicated antibodies. D The nuclear DNA content of shRNA-control and NPM1-silenced cells were measured using PI staining and FACS analysis to analyze the cell cycle. E The histogram was analyzed quantitatively by a curve-fitting program to determine the percentage of cells in the S phase of both cells. Data are presented as means ± SD of three independent biological experiments. ns not significant.