Fig. 3.

Downregulation of PML NBs by the nsp1β protein of PRRSV. (A), Numbers of PML-NBs were decreased in PRRSV nsp1β-expressing cells. HeLa cells were transfected with SARS-CoV-2 ORF3a, PRRSV-nsp1β, or empty vector pXJ41 for 24 h and stimulated by incubation with 1000 units/ml of IFN-β for 6 h. The cells were fixed and stained with anti-FLAG MAb (green) and anti-PML PAb (red). Nuclei were stained with DAPI (blue) as described in Materials and Methods. Long white arrows indicate nsp1β-expressing cells and short yellow arrows indicate uninfected cells. The images were taken by confocal microscopy (Nikon A1R). Scale bar represents 5 µm. (B), Quantification of the reduction of PML-NBs in nsp1β-expressing cells. Twenty cells expressing the nsp1β protein were randomly chosen, and numbers of PML-NB puncta per nucleus per cell were counted. The reduction of PML was quantified as described in Materials and Methods. Statistical significance is indicated as follows: ***P<0.01.