IFIT1 [MD54R]

IFIT1, also known as GARG-16, Glucocorticoid-attenuated response gene 16 protein or Interferon-induced 56 kDa protein, IFI-56K, or P56, and encoded by the gene lfit1/Garg16, Ifi56, Isg56, is an interferon-induced antiviral RNA-binding protein that specifically binds single-stranded RNA bearing a 5′-triphosphate group (PPP-RNA), thereby acting as a sensor of viral single-stranded RNAs and inhibiting expression of viral messenger RNAs. Single-stranded PPP-RNAs, which lack 2′-O-methylation of the 5′ cap and bear a 5′-triphosphate group instead, are specific from viruses, providing a molecular signature to distinguish between self and non-self mRNAs by the host during viral infection. IFIT1 directly binds PPP-RNA in a non-sequence-specific manner. Viruses evolved several ways to evade this restriction system such as encoding their own 2′-O-methylase for their mRNAs or by stealing host cap containing the 2′-O-methylation (cap snatching mechanism). IFIT1 is a component of an interferon-dependent multiprotein complex that is at least composed of IFIT1, IFIT2 and IFIT3 and interacts with EIF3F, RPL15, TMEM173 and EEF1A1 and is important in antiviral defense, and innate immune response. IFIT1 is localized to the cytoplasm and expressed by most cells, particularly in the immune system and epithelial cells.