IFIT1 and infection: In addition, we transfected HEK293T cells with the FLAG-XRN1 plasmid and observed that XRN1 overexpression repressed the expression of innate response-related genes, such as IFNB, IFIT1, IFIT3, and ISG15 in early stages of infection, 4 to 6 h.p.i. Moreover, at 8 h.p.i., the expression of these genes, in vector- or FLAG-XRN1-transfected cells was inhibited due to viral resistance (see Fig. S2A and B in the supplemental material).