RNA-BINDING PROPERTIES OF POLIOVIRUS SUBVIRAL PARTICLES

The mechanism of encapsidation of the RNA genome of poliovirus and oth er picornaviruses is unknown. To test whether any of the putative asse mbly intermediates of poliovirus could interact directly with the poli ovirus RNA genome, poliovirus RNA was attached to magnetic streptavidi n beads and incubated with partially purified extracts containing S-35 -labeled 14S pentamer and 75S empty-capsid subviral particles from inf ected cells. The amount of labeled protein bound to the beads was moni tored, thus testing the RNA-binding activities of only the labeled vir al proteins in the preparations. In this assay, nonspecific RNA-bindin g activity was displayed by the 14S pentameric particles and mature vi rions. 75S empty capsids displayed no propensity to associate with RNA . 14S pentamers were demonstrated to form rapidly sedimenting complexe s and to undergo a conformational alteration upon RNA binding. These f indings are consistent with a direct role for the 14S pentameric parti cles in RNA packaging during poliovirus morphogenesis.