Virus symmetry-breaking, elasticity and self-assembly

The process of formation of virus particles in which hundreds or thousands of the protein subunits encapsulate the genetic materials to form a stable, protective shell (capsid) is an essential step in the viral life cycle. The capsids of the majority of spherical viruses adopt structures with icosahedral symmetry, built of coat proteins assembled in special motifs involving a minimal number of inequivalent positions.  Since protein subunits assemble into error-free capsids with universal Icosahedral Order under a variety of in vivo and in vitro conditions, I first present our numerical and analytical work exploring the origin of this universality. In the second part of the talk, I discuss our efforts to understand the formation of SARS-CoV-2 particles in their host cells. In contrast to icosahedral viruses, the structures of coronaviruses are heterogeneous both in morphology and size, complicating significantly any theory of their formation. Further, they carry the largest single-stranded RNA genome. Through a combination of computer simulations and scaling theories, I describe our attempts to account for how SARS-CoV-2 condenses and organizes its 30 kb genome while budding from internal membranes of infected cells.