Functions as a E3 ubiquitin ligase and plays a role in the inhibition of innate immunity by preventing IFN-mediated signaling. Induces the ubiquitination and degradation of host STAT1, STAT2 and IRF9, resulting in the blockade of ISGF3 nuclear translocation. Protein modification; protein ubiquitination. Localizes in small nuclear bodies early in infection then moves to a more diffuse distribution in viral compartments as infection progresses. Tyrosine phosphorylated. ICP22 and protein US1.5 mRNAs are transcribed from two different promoters on the US1 gene. Belongs to the herpesviridae ICP22 family.