Plays a role as a transcriptional activator or repressor. Specifically binds to the upstream regulatory region of type I IFN and IFN-inducible MHC class I genes (the interferon consensus sequence (ICS)). Plays a regulatory role in cells of the immune system (By similarity). In resting macrophages, localizes in the cytoplasm. Translocated in the nucleus upon IFN-gamma induction. Belongs to the IRF family.