Evidence for a new viral late-domain core sequence, FPIV, necessary for budding of a paramyxovirus

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Enveloped virus budding is associated with cellular ubiquitin-proteasome and vacuolar protein-sorting pathways.
• The SV5 matrix (M) protein lacks known late domains crucial for recruiting cellular factors during budding.

Purpose of the Study:

• To investigate the mechanisms of enveloped virus budding for the paramyxovirus SV5.
• To identify novel motifs involved in SV5 matrix protein budding.
• To understand the role of the identified motif in virus replication and adaptation.

Main Methods:

• Treatment with proteasome inhibitors and dominant-negative VPS4(E228Q) ATPase.
• Mutagenesis of the SV5 matrix (M) protein, including identification and functional analysis of a novel budding motif.
• Assay of virus-like particle (VLP) budding and recombinant SV5 virus replication.
• Analysis of viral adaptation through sequencing of evolved viral genomes.

Main Results:

• Proteasome inhibitors and VPS4(E228Q) ATPase expression blocked SV5 budding.
• A novel budding motif, O-P-x-V (core FPIV), was identified in the SV5 M protein.
• This motif functionally compensated for the absence of a PTAP late domain in HIV-1 VLPs.
• Mutating the proline residue in the O-P-x-V motif severely impaired SV5 VLP budding and virus replication.
• Mutant viruses rapidly adapted by acquiring new proline residues in the M protein, suggesting the formation of suboptimal late domains.

Conclusions:

• The O-P-x-V motif is a novel and critical late domain for SV5 enveloped virus budding.
• The proline residue within this motif is essential for efficient budding and viral replication.
• Viral adaptation involves the generation of compensatory proline residues to restore budding efficiency.