Structural protein requirements in equine arteritis virus assembly.

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Equine arteritis virus (EAV) is an enveloped RNA virus with seven structural proteins.
• These proteins include major components (N, M, GP5) and minor components (GP2b, GP3, GP4, E).
• Understanding the role of these proteins in virus assembly is crucial for viral pathogenesis research.

Purpose of the Study:

• To investigate the essentiality of individual EAV structural proteins for virus particle formation.
• To elucidate the role of minor structural proteins (GP2b, GP3, GP4, E) in EAV assembly and particle composition.

Main Methods:

• Utilized a full-length EAV cDNA clone to systematically inactivate genes encoding structural proteins.
• Analyzed the effect of gene inactivation on virus assembly and protein incorporation into viral particles.
• Characterized EAV particles lacking specific proteins using techniques like buoyant density analysis, SDS-PAGE, and electron microscopy.

Main Results:

• The three major structural proteins (N, M, GP5) are essential for EAV particle formation.
• Minor proteins GP2b, GP3, GP4, and E are dispensable for particle formation but affect composition.
• Absence of E blocked incorporation of GP2b, GP3, and GP4; absence of any of GP2b, GP3, or GP4 blocked others and reduced E incorporation.
• EAV particles lacking GP2b, GP3, GP4, and E showed minimal differences from wild-type virions in key characteristics.

Conclusions:

• Propose a model where EAV particle assembly involves GP2b/GP3/GP4 heterotrimers and E molecules positioned around the nucleocapsid.
• Highlights the non-essential but regulatory role of minor structural proteins in EAV virion composition.