IFNA1 and infection: To determine directly whether CMTR1 contributed to viral restriction by type I IFN, we measured the ability of type I IFN to restrict infection by another IFN-sensitive virus, vesicular stomatitis virus (VSV), a negative-sense RNA virus which also encodes its own Cap 1 2′-O-methyltransferase (37, –, 39), following CMTR1 depletion.