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. Author manuscript; available in PMC: 2016 May 1.
Published in final edited form as: Virology. 2015 Feb 11;0:66–74. doi: 10.1016/j.virol.2015.01.019

Figure 3. Viral mechanisms of Ifit1 evasion and antagonism.

Figure 3

Viruses generate cap 1 structures through (a) cap-snatching (orthomyxoviurses, bunyaviruses, arenaviruses) whereby cap 1 is cleaved from host mRNA transcripts and used as a primer for viral RNA transcription. In contrast to orthomyxoviruses, which cap-snatch from mRNA in the nucleus, bunyaviruses associate with and sequester cap 1 containing nonsense-mRNA transcripts in cellular P bodies where N protein protects cap 1 from degradation. Some viruses mimic cap 1 structures via virally-encoded 2′-O MTases (flaviviruses, coronaviruses, rhabdoviruses, paramyxoviruses, reoviruses, and poxviruses). Other viruses (picornaviruses, caliciviruses, and hepaciviruses) circumvent Ifit1-mediated restriction by using non-canonical cap-like structures (VPg) at their 5′ end or IRES-mediated cap-independent translation (b). Alphaviruses antagonize Ifit1 function directly by inhibiting association with viral RNA through the generation of stable secondary structures in the 5′-UTR (c).