These results show that PCV2 infection upregulates Ubc9 expression to promote the interaction of TRIM24 with pNPM1, leading to the enhancement of pNPM1 SUMOylation at the early stage of infection, while increasing the expression level of SENP3 at a later stage that may mediate the reduction of the pNPM1 SUMOylation. This evidence concerns the gene UBE2I and infection.