FIG 7.

Role of the IFITM1 C-terminal motifs in modulating the entry of HCoVs. (A) FLIP-IN T Rex cells expressing CAT or wild-type or mutant IFITM1 proteins were cultured in the presence of Tet for 24 h. The expression of FLAG-tagged IFITM1 proteins was detected by Western blotting assay using an anti-FLAG monoclonal antibody. β-Actin served as a loading control. (B to D) The above-mentioned cell lines were left untreated or treated with 1 μg/ml of Tet for 24 h to induce IFITM expression. The cells were then infected with SARSpp, NL63pp, or MLVpp (B); 229Epp (C); or MERSpp (D). Luciferase activities were determined at 48 hpi. Relative infection efficiency is the ratio of the luciferase activity in cells cultured in the presence of tetracycline over that in cells cultured in the absence of tetracycline. The error bars indicate standard deviations (n = 6). **, P < 0.001 compared to wild-type IFITM1.