How the genome modifies the stability and morphology of viral shells

Simple RNA viruses self-assemble spontaneously and encapsulate their genome into a shell called the capsid. This process is mainly driven by the attractive electrostatics interaction between the positive charges on capsid proteins and the negative charges on the genome. Despite its importance and many decades of intense research, how the virus selects and packages its native RNA inside the crowded environment of a host cell cytoplasm in the presence of an abundance of non-viral RNA and other anionic polymers, it has remained a mystery. In this research, we perform a series of simulations using coarse-grained models to monitor the growth of a viral shell andround a cargo. We find that RNA can completely modify the structure and stability of the capsid. The work suggests that capsid can assemble around non-viral RNA but forming non-icosahedral virion. We show that these structures are strained and can be split into fragments along the stress lines. These fragments can later be assembled into the stable native icosahedral structure if the viral genome becomes available, suggesting a new pathway for the formation of virion in the cell in the presence of other polyanionic species.