FIG 7.

PRRSV nsp5 leads to STAT3 degradation by the ubiquitin-proteasomal pathway. (A) Presence of nsp5 leads to elevation of STAT3 polyubiquitination level. IP analyses with STAT3 antibody and then WB with antibodies against ubiquitin (Ub), STAT3, and HA were performed. Samples of whole-cell lysate (WCL) were included as controls. The relative levels of ubiquitinated STAT3 are shown below the images after normalization with STAT3 level. (B) nsp5 shortens STAT3 half-life from around 24 to 3.5 h. HEK293 cells were transiently cotransfected with 0.5 μg of STAT3 and nsp5 plasmids. The cells were treated with cycloheximide (CHX) at 100 μg/ml at 24 hpt and harvested at indicated times in hours posttreatment, followed by WB with antibodies against STAT3 and tubulin. The relative levels of STAT3 are shown below the images after normalization with tubulin.