VP40 octamers are essential for Ebola virus replication

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Ebola virus matrix protein VP40 is crucial for virus assembly and budding.
• VP40 can form RNA-binding octamers, with Phe125 and Arg134 identified as key residues for RNA coordination.
• Previous studies established the structural basis for RNA binding in VP40 octamers.

Purpose of the Study:

• To investigate the role of VP40 RNA binding and octamer formation in Ebola virus assembly and replication.
• To determine if VP40 octamer formation is essential for virus-like particle (VLP) production.
• To assess the in vivo significance of VP40-RNA interactions for the Ebola virus life cycle.

Main Methods:

• Expression of full-length wild-type and mutant VP40 proteins in HEK 293 cells.
• Assessment of RNA binding and octamer formation using biochemical assays.
• Analysis of VLP morphology, abundance, and size.
• Introduction of VP40 mutations into the Ebola virus genome for rescue experiments.

Main Results:

• Wild-type VP40 octamers bind RNA in cells; Phe125 mutation reduced binding, while Arg134 mutation abolished binding and octamer formation.
• Octamer formation is dispensable for VLP production, with similar VLP morphology and size observed for wild-type and mutant VP40.
• Mutant VP40 proteins exhibited altered cellular localization compared to wild-type VP40.
• Recombinant Ebola virus could be rescued with wild-type VP40 and Phe125-mutant VP40, but not with Arg134-mutant VP40.

Conclusions:

• VP40 octamer formation is not required for the formation of virus-like particles.
• RNA binding and subsequent octamer formation by VP40 are essential for the Ebola virus life cycle.
• The Arg134 residue is critical for VP40 RNA binding and octamerization, impacting viral recovery.