  Single-stranded (ss) RNA viruses self-assemble spontaneously in solutions
that contain the viral RNA genome molecules and viral capsid proteins. The
self-assembly of empty capsids can be understood on the basis of free energy
minimization. However, during the self-assembly of complete viral particles in
the cytoplasm of an infected cell, the viral genome molecules must be selected
from a large pool of very similar host messenger RNA molecules and it is not
known whether this also can be understood by free energy minimization. We
address this question using a simple mathematical model recently proposed for
the assembly of small ssRNA viruses (submitted to PLOS Biocomputation). We
present a statistical physics analysis of the properties of the model finding
an effect kinetic RNA selection mechanism with selection taking place during
the formation of the nucleation complex. Surprisingly, kinetic selectivity is
greatly enhanced by a modest level of supersaturation and by reduced protein to
RNA concentration ratios. The mechanism is related to the Hopfield kinetic
proofreading scenario.
