IRF-1 (D5E4) XP^® Rabbit mAb #8478

Interferon regulatory factors (IRFs) comprise a family of transcription factors that function within the Jak/Stat pathway to regulate interferon (IFN) and IFN-inducible gene expression in response to viral infection (1). IRFs play an important role in pathogen defense, autoimmunity, lymphocyte development, cell growth, and susceptibility to transformation. The IRF family includes nine members: IRF-1, IRF-2, IRF-9/ISGF3γ, IRF-3, IRF-4 (Pip/LSIRF/ICSAT), IRF-5, IRF-6, IRF-7, and IRF-8/ICSBP. All IRF proteins share homology in their amino-terminal DNA-binding domains. IRF family members regulate transcription through interactions with proteins that share similar DNA-binding motifs, such as IFN-stimulated response elements (ISRE), IFN consensus sequences (ICS), and IFN regulatory elements (IRF-E) (2).

The IRF-1 transcription factor was originally identified as a regulator of virus-inducible enhancer-like elements of the IFN-β gene (3). IRF-1 is widely expressed and upregulated by viral infection or stimulation with IFN or other cytokines. IRF-1 is serine-phosphorylated by casein kinase II (CKII) at two clustered sites, one in the DNA-binding domain (amino acids 138-150) and another in the transactivation domain (amino acids 219-231) (4). Mutation analysis of the latter site suggests that these phosphorylation sites help regulate IRF-1 activity. Tyrosine phosphorylation has also been shown to be important in IFN-γ-mediated differentiation of myeloid cell lines (5). C-terminal SUMOylated IRF-1 inhibits apoptosis in tumor cells by repression of its transcriptional activity (6).