Viperin, a member of the radical S-adenosyl-l-methionine (SAM) superfamily of enzymes, is an interferon-inducible protein implicated in the inhibition of replication of a broad range of RNA and DNA viruses, including dengue virus, West Nile virus, hepatitis C virus, influenza A virus, rabies virus and HIV. Viperin catalyses the conversion of cytidine triphosphate (CTP) to 3ʹ-deoxy-3′,4ʹ-didehydro-CTP (ddhCTP), a previously undescribed biologically relevant molecule, via a SAMdependent radical mechanism [1].
ddhCTP, can be produced in mammalian cytosol, is a chain terminator for the RNA-dependent RNA polymerases from multiple members of the Flavivirus genus, and directly inhibits replication of Zika virus in vivo[1].
Reference:
[1] Anthony S. Gizzi, Tyler L. Grove, Jamie J. Arnold, Joyce Jose, Rohit K. Jangra, Scott J. Garforth, Quan Du, Sean M. Cahill, Natalya G. Dulyaninova, James D. Love, Kartik Chandran, Anne R. Bresnick, Craig E. Cameron, Steven C. Almo. A naturally occurring antiviral ribonucleotide encoded by the human genome. Nature, 2018; DOI: 10.1038/s41586-018-0238-4.