ISG20 and infection: Under these conditions, WT ISG20 inhibited VSV spread in the different cell lines tested, in contrast to a catalytically inactive ISG20 mutant (Fig 1A, M1, that corresponds to the already described D94 mutant, S2 Fig for infection with different viral multiplicities of infection, MOIs and S3 Fig for typical flow cytometry profiles and mean fluorescent intensities of GFP-positive cells).