A labile subviral particle (‘the equestron’) is proposed as a multifunctional regulator of poliovirus growth, withaffinities for 45s ribosomal subunits and 5’ ends of viral RNA. These suggested properties suffice to explain suppression of hostprotein synthesis, synchronous synthesis of viral RNA and protein, and timing of maturation. The candidate for the equestron is a precursor to the virionstructural unit.