Cleavage of the cap binding protein complex polypeptide p220 is not effected by the second poliovirus protease 2A

Poliovirus protein 2A contains a short amino acid sequence that also occurs in the putative active site of the known viral proteinase, 3C, previously shown to be responsible for glutamine/glycine cleavages in the poliovirus polyprotein precursor. Experimental evidence indicates that 2A is a second viral proteinase that mediates the cleavage of two tyrosine/glycine cleavages in the generation of virus-specific proteins. Since poliovirus inhibition of host cell protein synthesis correlates with the specific cleavage of the 220,000-Da component of the cap binding protein complex, we have tested whether viral protein 2A contains the p220 cleavage activity. The results show that (1) 2A does not copurify with p220 cleavage activity, (2) partially purified fractions containing high p220 cleavage activity contain no detectable 2A sequences in the form of either mature or precursor protein, and (3) anti-2A serum or IgG does not inhibit p220 cleavage in vitro.