a A549 cells were infected with human respiratory syncytial virus (RSV) A2 for up to 6 days at MOI 0.02. Forty eight hours prior to infection, cells were transfected with a pool of siRNAs targeting RNF213 (siRNF213), a single siRNA targeting the RSV-nucleoprotein (siRSV-N) as positive control or a pool of scrambled siRNAs (siScramble) as negative control. The viral titer was determined by counting plaque-forming units (PFUs) after serial dilution (representative results from a single experiment, AVG ± SEM, n = 3 technical replicates, two-tailed unpaired t-test comparing siRNF213 to siScramble). b RSV infection experiment performed as in a, except that 42 h prior to infection cells were treated with interferon (IFN)-β (representative results from a single experiment, AVG ± SEM, n = 3 technical replicates, two-tailed unpaired t-test comparing siRNF213 to siScramble). Knockdown of RNF213 leads to significantly higher RSV titers. c A549 cells were infected with RSV-A2 at MOI 0.005 in combination with knockdown of RNF213 and RSV-N as described in a. Six days post infection, a plaque assay was performed and plaque sizes were quantified in pixels with Fiji (left panel, representative results from a single experiment, AVG ± SD, two-tailed Mann–Whitney test, siRSV-N n = 8, siScramble n = 267, and siRNF213 n = 183). Representative images showing plaques of siRNF213 and siScramble-treated cells (right panel). d RSV infection experiment performed as in c, except that 42 h prior to infection cells were treated with interferon-β (left panel, representative results from a single experiment, AVG ± SD, two-tailed Mann–Whitney test, siRSV-N n = 4, siScramble n = 123, and siRNF213 n = 99). Representative images showing plaques of siRNF213 and siScramble-treated cells (right panel). Knockdown of RNF213 leads to significantly larger RSV plaques. In a–d) asterisks indicate p values with *p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001. Source data are provided as a Source Data file.