This paper reviews the mechanisms of picornaviral polyprotein processing, highlighting the roles of peptide 2A, protease 3C, and a novel RNA-assisted autocatalytic mechanism.
May inform protease-targeted antivirals for enteroviral myocarditis; leaves open clinical validation of 2A/3C mechanisms.
Mature picornaviral proteins are derived by progressive, post-translational cleavage of a giant precursor polyprotein. At least three viral-encoded proteolytic activities are involved in the processing. The first cleavage takes place while the polyprotein is still nascent on a ribosome. In poliovirus, this event is probably catalyzed by peptide 2A, a protein from the middle portion of the genome. Most subsequent processing is effected by viral protease 3C, a thiol-type enzyme, responsible for eight to ten self-cleaving and autocatalytic reactions within the polyprotein. The final proteolytic processing event, maturation of the VPO peptide, may occur by a novel, autocatalytic, serine-type mechanism, where viral RNA serves as proton-acceptor during the cleavage reaction.
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Ann C. Palmenberg (1987) studied this question.
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