IE1 co-transfection with each Sp100 isoform was shown to reduce their SUMOylation (Tavalai et al., 2011); this effect is especially evident for Sp100A (Dimitropoulou et al., 2010; Tavalai et al., 2011), but unSUMOylated Sp100A levels also decrease at later times post HCMV infection (Tavalai et al., 2011). This evidence concerns the gene SP100 and cytomegalovirus infection.