The Role of Viral RNA and Membrane Proteins in the Assembly and Budding of SARS-CoV-2

Viral assembly and budding required for the replication of SARS-CoV-2 involves interactions between structural proteins along the surface of the ER-Golgi intermediate compartment membrane and viral RNA in the cytoplasm. Adsorption of viral RNA to the surface is followed by the membrane enveloping the genetic material, completing assembly and budding. However, it is unknown whether the viral RNA complex evolves with protein density and membrane shape throughout this process. To answer this question, we consider viral RNA as an adsorbed polymer attracted to membrane proteins along the surface. We develop a continuum model that accounts for the spatial distribution of curvature inducing membrane proteins, membrane shape, and viral RNA's competition between confinement entropy and polymer-surface interactions. From this, we determine the coupled evolution of protein density, membrane height, and viral RNA adsorption thickness, finding that the polymer is capable of locally inducing membrane curvature and enriching the protein density. This in turn increases polymer-surface interactions, ultimately leading to budding. Our work enables us to define regimes for the onset of assembly and budding, with or without viral RNA, and to classify viral RNA's impact on virion formation.