A CRISPR activation screen identifies SPART as a pan-orthoflavivirus restriction factor

Orthoflaviviruses, including Zika (ZIKV), dengue, Japanese encephalitis, and West Nile viruses, cause diverse clinical syndromes and threaten human health. Identifying factors that inhibit orthoflavivirus infection could lead to antiviral countermeasures. Here, we conducted a genome-wide CRISPR activation screen and identified the host gene SPART (Spartin/SPG20) as a restriction factor against ZIKV and other orthoflaviviruses. SPART interacts with and disrupts the endosomal localization of Itchy E3-ubiquitin ligase (ITCH), which we determine ubiquitinates the ZIKV capsid, thereby triggering uncoating. Loss of SPART enhances ZIKV replication, an effect not observed in SPART-ITCH double knockout mutants. Maternal ZIKV infection of Spg20^-/- mice results in heightened maternal and fetal viral loads and greater fetal abnormalities, whereas infection of Itch^-/- mice yields opposite outcomes. Similar results were observed in these gene-edited mice upon infection with related orthoflaviviruses. Overall, this approach identified a broad orthoflavivirus restriction factor, providing a potential target against these emerging pathogenic viruses.