A CRISPR screen defines a signal peptide processing pathway required by flaviviruses

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Flaviviruses cause significant global health burdens with no available antiviral treatments.
• Understanding host-pathogen interactions is key to developing novel therapeutic strategies.

Purpose of the Study:

• To identify host genes essential for flavivirus replication using a genome-wide CRISPR/Cas9 screen.
• To investigate the role of identified host factors in the flavivirus life cycle.

Main Methods:

• Genome-wide CRISPR/Cas9 screening to identify host dependency factors.
• Validation of candidate genes involved in endoplasmic reticulum functions.
• Analysis of viral protein processing and particle secretion.

Main Results:

• Nine human genes essential for flavivirus infectivity were validated, primarily involved in endoplasmic reticulum functions.
• Signal peptidase complex (SPCS) proteins, particularly SPCS1, are critical for cleaving flavivirus structural proteins (prM and E) and viral particle secretion.
• Loss of SPCS1 significantly reduced infection across multiple Flaviviridae viruses (West Nile, Dengue, Zika, yellow fever, Japanese encephalitis, hepatitis C) but not other virus families.
• SPCS1 dependence was bypassed by altering viral protein leader sequences, indicating a specific reliance on this host pathway.

Conclusions:

• Flaviviruses exhibit a unique dependence on the SPCS1-mediated signal peptide processing pathway.
• SPCS1 and related proteins are potential pharmacological targets for broad-spectrum antiviral therapies against flaviviruses.