Protein–RNA interactions of the poliovirus CRE. (A) Electrophoretic mobility shift assay (EMSA) of the interaction of the 5′CL or CRE with poliovirus CDpro. The identity of the input probe is indicated below the autoradiograph, with the position of the free probe indicated with the label ‘‘Probe’’. The lanes labeled (−) contain no added 3CDpro, the relative concentration of which is indicated with a triangle. The 3CDpro-containing complex is indicated with an asterisk (*). (B) Specificity of the 3CDpro interaction with the CRE. Formation of the 3CDpro/CRE ribonucleoprotein complex (indicated *) was assayed in the presence of no competitor (lane labeled 0) or competing (10× and 100×) molar excess of the native CRE, the 5′CL, 3′ NCR, or the nonfunctional CRE variants, SL3, G19A/C22U, or G19A/C22U/U40C. All lanes contain 3CDpro, as indicated by the bar below the figure, with the exception of the lane containing probe alone, which is labeled (−).
