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

Area of Science:

• Virology
• Genetics
• Molecular Biology

Background:

• Orthoflaviviruses, including Zika virus (ZIKV), pose significant global health threats.
• Identifying host factors that restrict viral replication is crucial for developing antiviral strategies.

Purpose of the Study:

• To identify host restriction factors against Zika virus (ZIKV) and other orthoflaviviruses.
• To elucidate the molecular mechanism by which SPART restricts orthoflavivirus infection.

Main Methods:

• Genome-wide CRISPR activation screen to identify host restriction factors.
• Co-immunoprecipitation and immunofluorescence assays to study protein interactions and localization.
• Viral replication assays in gene-edited cell lines and mouse models.
• Infection studies using ZIKV and related orthoflaviviruses in SPART and ITCH knockout mice.

Main Results:

• Spartin (SPART) was identified as a host restriction factor against ZIKV and other orthoflaviviruses.
• SPART interacts with and disrupts the endosomal localization of the E3-ubiquitin ligase Itchy (ITCH).
• ITCH ubiquitinates the ZIKV capsid, promoting viral uncoating; SPART antagonizes this process.
• Loss of SPART enhances ZIKV replication, while loss of ITCH inhibits it.
• SPART deficiency exacerbates ZIKV-induced fetal abnormalities in mice, whereas ITCH deficiency is protective.

Conclusions:

• SPART acts as a broad-spectrum restriction factor against orthoflaviviruses.
• The SPART-ITCH-ZIKV capsid axis represents a novel antiviral target.
• Targeting SPART or its pathway could offer new therapeutic strategies against flaviviral diseases.