NPM1 and infection: Finally, it has been reported that the SUMOylation of NPM1 can be negatively regulated by SENP3 [26], we checked the expression levels of SENP3 in PCV2-infected PK-15 cells, the results showed that PCV2 infection upregulated the expression of SENP3 at 24 h post-infection, indicating that the decrease of the SUMOylation level of pNPM1 may be also relative to the deSUMOylation activity of SENP3.