Interferon regulatory factor, conserved site <p>The expression of type I interferon genes (interferons alpha and beta) is induced by many agents, including viral attack [<cite idref="PUB00000818"/>]. Induction is mediated by the binding of interferon regulatory factor 1 (IRF-1) to a region known as the interferon consensus sequence (ICS), located upstream of the interferon genes [<cite idref="PUB00002752"/>]. Other factors may also bind to the ICS, including IRF-2, which does not function as an activator, but rather suppresses the function of IRF-1 under certain circumstances [<cite idref="PUB00000832"/>]. IRF proteins contain a conserved N-terminal DNA-binding region of about 120 amino acids, which folds into a structure that binds specifically to the ICS; the remaining parts of the sequences vary depending on the precise function of the protein [<cite idref="PUB00002752"/>]. This region contains five conserved tryptophans and is known as a 'tryptophan pentad repeat'. </p><p>The signature of this entry spans the region from the second to the fourth of the five conserved tryptophans.</p>