Kavli Affiliate: Vinothan N. Manoharan
| First 5 Authors: LaNell A. Williams, Andreas Neophytou, Rees F. Garmann, Dwaipayan Chakrabarti, Vinothan N. Manoharan
| Summary:
Self-assembly is a vital part of the life cycle of certain icosahedral RNA
viruses. Furthermore, the assembly process can be harnessed to make icosahedral
virus-like particles (VLPs) from coat protein and RNA in vitro. Although much
previous work has explored the effects of RNA-protein interactions on the
assembly products, relatively little research has explored the effects of
coat-protein concentration. We mix coat protein and RNA from bacteriophage MS2,
and we use a combination of gel electrophoresis, dynamic light scattering, and
transmission electron microscopy to investigate the assembly products. We show
that with increasing coat-protein concentration, the products transition from
well-formed MS2 VLPs to "monster" structures consisting of multiple partial
capsids to RNA-protein condensates consisting of large networks of RNA and
protein. We argue that the variation in structure arises because the assembly
follows a nucleation-and-growth pathway in which the nucleation rate depends
sensitively on the coat-protein concentration. At high coat-protein
concentration, multiple nuclei can form on each RNA strand, leading to
malformed structures. Monte Carlo simulations with coarse-grained models of
capsomers and RNA validate this physical picture. Our results provide insight
into an important biophysical process and could inform design rules for making
VLPs for various applications.
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