Plasmid-based reverse genetics for probing phosphorylation-dependent viroplasm formation in rotaviruses.

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Rotavirus (RV) replication occurs in viroplasms, cytoplasmic compartments essential for virus production.
• Viroplasm formation depends on RV proteins NSP2 and NSP5, and cellular lipid droplets (LDs).
• The precise mechanisms governing viroplasm assembly are not fully understood.

Purpose of the Study:

• To investigate the role of cellular kinase CK1α-mediated phosphorylation of NSP2 on viroplasm formation.
• To analyze the early events of viroplasm assembly using a phosphomimetic NSP2 mutant.

Main Methods:

• Generation of recombinant rotavirus (rRV) with a phosphomimetic NSP2 mutation (NSP2 S313D) using plasmid-based reverse genetics.
• Analysis of viroplasm formation, virus replication, and protein localization in infected cells.
• Co-infection experiments to assess interference with wild-type RV replication.

Main Results:

• The rRV NSP2 S313D mutant exhibited significantly delayed viroplasm formation and virus replication.
• This mutant interfered with wild-type RV replication during co-infection.
• vNSP2 S313D co-localized with RV-induced LDs independently of NSP5, suggesting a role in LD recruitment.

Conclusions:

• CK1α-mediated phosphorylation of NSP2 is crucial for efficient rotavirus viroplasm assembly and replication.
• The NSP2 S313D mutation provides a tool to study early viroplasm and LD formation events.
• Phosphorylated NSP2 may be the viral factor initiating the interaction with and formation of LDs during RV infection.