Transcriptional regulator that specifically binds to the upstream regulatory region of type I IFN and IFN-inducible MHC class I genes (the interferon consensus sequence (ICS)) and activates those genes (By similarity). Acts as a tumor suppressor (By similarity). Phosphorylated by CK2 and this positively regulates its activity. Sumoylation represses the transcriptional activity and displays enhanced resistance to protein degradation. Inactivates the tumor suppressor activity. Elevated levels in tumor cells. Major site is Lys-271. Sumoylation is enhanced by PIAS3. Desumoylated by SENP1 in tumor cells and appears to compete with ubiquitination on C-terminal sites (By similarity). Ubiquitinated. Appears to compete with sumoylation on C-terminal sites (By similarity). Belongs to the IRF family.