A coronaviral pore-replicase complex links RNA synthesis and export from double-membrane vesicles

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• Coronavirus-infected cells feature double-membrane vesicles (DMVs) crucial for viral RNA replication and transcription.
• These DMVs contain hexameric pores that connect the lumen to the cytoplasm, but their formation and function remain unclear.
• Understanding DMV organization is vital for developing antiviral therapies.

Purpose of the Study:

• To elucidate the mechanism of pore formation within DMVs during coronavirus infection.
• To identify the viral proteins responsible for organizing RNA synthesis and transport.
• To explore potential therapeutic targets for broad-spectrum antiviral activity.

Main Methods:

• Utilized structure prediction algorithms to model viral protein structures.
• Performed functional assays to validate predicted protein roles.
• Investigated protein-protein interactions between viral components.

Main Results:

• Identified the nonstructural viral membrane protein nsp4 as the primary organizer of the hexameric pores.
• Nsp4 spans the double membrane, forming the pore lining and interacting with nsp3 and the viral replicase.
• A conserved nsp4 residue ring restricts mRNA passage, suggesting modified nucleobases can block viral RNA export.

Conclusions:

• Nsp4 is essential for forming functional pores in DMVs, facilitating viral RNA replication and transcription.
• The pore structure, particularly the nsp4 residue ring, acts as a gate for mRNA export.
• Targeting this pore with modified nucleobases offers a promising strategy for broad-spectrum antiviral drug development.