In vitro liquid-liquid phase separation induced by respiratory syncytial virus proteins and RNA

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Respiratory syncytial virus (RSV) causes significant respiratory illness.
• RSV replication occurs within cytoplasmic viral factories, structures formed by liquid-liquid phase separation (LLPS).
• The assembly of these viral factories involves interactions between RSV proteins (N, P, M2-1) and viral RNA.

Purpose of the Study:

• To systematically characterize the liquid-liquid phase separation (LLPS) processes involving RSV proteins and RNA.
• To elucidate the molecular mechanisms governing the formation and regulation of RSV viral factories.
• To identify potential targets for antiviral strategies focused on disrupting LLPS.

Main Methods:

• Utilized a microfluidic PhaseScan platform for high-throughput characterization of LLPS.
• Employed biochemical and cellular assays to analyze protein-RNA interactions and condensate formation.
• Investigated the role of specific RSV proteins (N, P, M2-1) and RNA in driving LLPS.

Main Results:

• Identified optimal concentrations of oligomeric N and P tetramers for in vitro condensate formation.
• Demonstrated that monomeric N protein inhibits LLPS, while M2-1 enhances it by increasing multivalency.
• Revealed that M2-1 preferentially binds 5' capped RNA, unlike N which binds uncapped RNA.

Conclusions:

• The study elucidates key molecular determinants governing RSV viral factory assembly and subcompartmentalization.
• Findings provide critical insights into the mechanisms of RSV replication.
• Results inform the development of novel antiviral strategies targeting LLPS processes in RSV infection.