Sapovirus translation requires an interaction between VPg and the cap binding protein eIF4E

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Sapoviruses (family Caliciviridae) cause gastroenteritis but human strains are difficult to study in culture.
• Porcine sapovirus (PSaV) is cultivatable, serving as a model for sapovirus and enteric calicivirus research.
• Caliciviruses utilize a unique protein synthesis mechanism involving the viral protein genome (VPg) linked to the 5' RNA end and cellular translation factors.

Purpose of the Study:

• To investigate the role of the viral protein genome (VPg) in porcine sapovirus (PSaV) translation.
• To elucidate the mechanism by which PSaV VPg facilitates viral protein synthesis.
• To understand the interaction between PSaV VPg and host cell translation machinery.

Main Methods:

• Characterization of VPg linkage to the PSaV genome.
• Assessment of VPg's requirement for viral RNA translation and infectivity.
• Co-immunoprecipitation assays to detect interactions between PSaV VPg and eukaryotic translation initiation factors (eIFs).
• In vitro binding assays to confirm direct interaction between PSaV VPg and eIF4E.

Main Results:

• The PSaV genome is covalently linked to VPg, a crucial step for translation and infectivity.
• PSaV VPg interacts with the eukaryotic translation initiation factor 4F (eIF4F) complex in infected cells.
• Direct binding of PSaV VPg to the eIF4E protein was confirmed.
• PSaV translation requires eIF4E and its interaction with eIF4G, similar to other caliciviruses.

Conclusions:

• The VPg protein of porcine sapovirus is essential for viral translation initiation.
• PSaV VPg hijacks the host cell's translation machinery by interacting with the eIF4F complex, specifically eIF4E.
• This study reveals a novel mechanism of VPg-dependent translation initiation in sapoviruses, offering insights into calicivirus replication.