PADI4 and infection: Furthermore, treatment of HSV-1-infected HFFs with the protein synthesis inhibitor CHX curbed the induction of PAD2, 3, and 4, as well as ICP27, protein expression and total levels of protein citrullination at 24 hpi, without altering total protein levels (Fig 3C and S2E Fig), indicating that de novo gene expression is required for PAD protein upregulation and citrullination profile modification during infection.