ZMPSTE24 and severe acute respiratory syndrome: In addition to demonstrating that human cells in which ZMPSTE24 is knocked out, or its expression knocked down, are sensitized to SARS-CoV-2 pseudovirus infection (Fig. 2), we have also provided evidence that mouse Zmpste24−/− knockout fibroblasts are more sensitive than WT fibroblasts to a bona fide viral infection, using the mouse betacoronavirus MHV and assaying viral production by plaque assay as well as cell viability upon infection (Fig. 6).