Interferon regulatory factor 5 (IRF-5), belongs to the IRF family of DNA-binding factors, which includes IRF-1, IRF-2, IRF-3, IRF-4, IRF-6, IRF-7, ISGF-3γ p48 and IFN consensus sequence-binding protein (ICSBP). The IRF family regulate both interferon and interferon-inducible genes. IRF-5, like IRF-3 and IRF-7, is a direct transducer of virus-mediated signaling and plays a role in the expression of multiple cytokines/chemokines. Although IRF-5 is a direct target of p53, its cell cycle regulatory and proapoptotic effects are p53 independent.