Poliovirus proteins associated with ribosomal structures in infected cells

Some poliovirus-specific protein in infected cell cytoplasm was found to have the same sedimentation coefficient and buoyant density in CsCl as the native 45 S subunits (1.48 g/cc), as viral ribonucleoprotein (1.40 g/cc) and as 60–80 S mono- or oligoribosome/vRNA complexes (1.50 to 1.54 g/cc). Cross-fixation artifacts resulting from glutaraldehyde treatment in the CsCl procedure could be controlled in these cases. Other structures carrying viral protein (1.44 and 1.47 g/cc) may be earlier polysome precursors or may be cross-fixation artifacts. The viral proteins found in each case were those of the 65 S empty capsids (VP0, VP1, and VP3, in equimolar ratio), but were not due to empty capsid contamination. The label attached to the 45 S subunit was removed by EDTA and could be recovered as a 6 S particle by RNase, EDTA, LiCl, and deoxycholate treatment; similar treatments of the other structures yielded only large ill-defined [VP0, VP1, VP3] aggregates. The presence of guanidine suppressed the addition of [VP0, VP1, VP3] to the 45 S and 70–80 S complexes, but induced the formation of an unidentified labile [VP0, VP1, VP3] multimer cosedimenting with empty capsids. The findings are discussed in terms of the equestron model for poliovirus regulation.