FIG 3.

PRRSV infection shortens STAT2 half-life and mediates STAT2 reduction via the ubiquitin-proteasome degradation pathway. (A) PRRSV shortens STAT2 half-life. MARC-145 cells were infected with VR-2385 at an MOI of 1. The cells were treated with cycloheximide at 24 hpi and harvested at the indicated time (h) for WB and densitometry analysis. The average relative levels of STAT2 of five experiments for each time point are shown. Error bars represent the standard errors of the repeated experiments. Significant differences between mock and VR-2385-infected cells are denoted by asterisks (***, P < 0.001). (B) MG132 treatment restores STAT2 level in PRRSV-infected cells. MARC-145 cells were infected with VR-2385 at an MOI of 1. At 24 hpi, the cells were treated with MG132 for 6 h and then harvested for WB. Nontreated and mock-infected cells were included as controls. WB with an antibody against PRRSV nsp1β was also done. The relative levels of STAT2 are shown below the images. (C) Lactacystin treatment restores STAT2 levels in PRRSV-infected cells. The cells were treated with lactacystin at 24 hpi and harvested 6 h later. (D) Lactacystin treatment has minimal effect on the viability of MARC-145 cells during the 6-h treatment. LAC, lactacystin. DMSO was included as a solvent control. (E) Lactacystin treatment has minimal effect on PRRSV RNA level during the 6-h treatment. Error bars represent the standard errors of the results of three repeated experiments.