Assembled coronavirus from complementation of two defective interfering RNAs

Area of Science:

• Virology
• Molecular Biology
• Cellular Biology

Background:

• Coronavirus assembly is a complex process.
• Defective interfering (DI) RNAs offer a unique tool to study viral replication and assembly.
• Mouse hepatitis virus (MHV) is a model coronavirus.

Purpose of the Study:

• To investigate the roles of specific viral proteins in the assembly and release of MHV particles.
• To understand the complementation mechanism between two different MHV DI RNAs.
• To identify the essential viral components for the formation of infectious MHV particles derived from DI RNAs.

Main Methods:

• Utilized temperature-sensitive (ts) mutant helper virus for complementation studies.
• Employed two types of MHV DI RNAs: DIssA (self-replicating, encoding N and gene 1 proteins) and a genetically engineered DI RNA (encoding sM and M proteins).
• Analyzed viral particle assembly and release at non-permissive temperatures, including mutational analysis of envelope protein genes.

Main Results:

• Coinfection with the two DI RNAs resulted in replication and transcription of both DI RNAs, but not the helper virus.
• MHV particles containing DI RNAs, N protein, and M protein were released, exclusively derived from the DI RNAs.
• Mutational analysis indicated that M and sM proteins are required for assembly and release of DI RNA-containing MHV particles, while S protein is not essential.

Conclusions:

• M and sM proteins play crucial roles in the assembly and release of MHV particles during DI RNA-mediated replication.
• The S protein is dispensable for the assembly and release of these specific MHV particles.
• Coronavirus assembly can be effectively studied using complemented DI RNAs, highlighting the importance of envelope proteins.