Interferon regulator transcription factors (IRF) are a family characterized by a helix-turn-helix DNA binding domain enriched in tryptophan repeats. IRF family members show diverse cellular regulation of interferon-stimulated gene transcription, viral-mediated gene activation, apoptosis, differentiation, and cellular growth. IRF2 functions as a regulator of type I interferons influencing cellular proliferation and immune response through transcriptional regulation. IRF2 competitively inhibits IRF1 gene activation, as well as, stimulating transcription on its own.
Interferon response factor 3 (IRF3) is a 50 kDa, 427 amino acid, member of the IRF family of proteins. Human IRF3 is a transcription factor that binds the interferon-sensitive response element (ISRE) and is activated by Toll-like receptors, TLR3 and TLR4. Viral entry or engagement of TLR3 or TLR4 stimulates IRF3 phosphorylation, nuclear translocation and stimulation of IFN production. There are potential alternate splice forms affecting IRF3 structure, one including a deletion of aa 201 - 327, a second with the same deletion and an alternate Met147 start site, and a third with a 125 aa substitution of the C-terminal 100 aa.