Differential phosphorylation and n-terminal configuration of capsid subunits in parvovirus assembly and viral...

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Icosahedral nuclear viruses, such as parvoviruses, assemble within the host cell nucleus.
• Capsid subunit structure, including phosphorylation and N-terminal (Nt) domain configuration, is critical for viral assembly.
• The Minute Virus of Mice (MVM) serves as a model for studying these processes.

Purpose of the Study:

• To investigate the roles of phosphorylation and N-terminal domain exposure in MVM capsid assembly.
• To understand how these modifications influence viral nuclear translocation and maturation.
• To elucidate the connection between parvovirus assembly and the host cell cycle.

Main Methods:

• Synchronous MVM infection of host cells.
• Analysis of capsid subunit phosphorylation levels and N-terminal domain exposure during different stages of infection.
• Characterization of cytoplasmic and nuclear viral intermediates.
• Investigation of endosomal processing of viral particles.

Main Results:

• Cytoplasmic MVM capsid subunits (trimeric intermediates) exhibit high VP1 phosphorylation and hidden N-terminal domains.
• Nuclear translocation during S phase exposes VP1 N-terminal domains in heterotrimers and subviral intermediates.
• Empty capsids show restored VP1:VP2 phosphorylation stoichiometry with concealed N-terminal domains.
• Mature ssDNA-filled virions (S/G2 phase) lack VP1 phosphorylation, have reduced VP2 phosphorylation, and expose VP2 N-terminal domains.
• Endosomal cleavage of VP2 N-terminal domains yields VP3 subunits, indicating incoming virions have low phosphorylation.

Conclusions:

• Phosphorylation status and N-terminal domain exposure are dynamically regulated during MVM assembly.
• These modifications are crucial for coordinating parvovirus nuclear assembly with the host cell cycle.
• Phosphorylation acts as a mechanistic link between viral assembly and cell cycle progression.