Demonstrates that ribosomes assembled on the Cricket paralysis virus IRES without initiation factors are true initiation complexes capable of elongation.
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Defines minimal ribosomal requirements for IRES-mediated elongation; leaves open relevance to mammalian viral pathogenesis or therapeutic targeting.
Reconstitution of translation elongation from purified components confirmed that ribosomes that assembled on the Cricket paralysis virus intercistronic internal ribosomal entry site (IRES) without the involvement of initiation factors or initiator tRNA were active in elongation and are, therefore, true initiation complexes. The first elongation cycle occurred without peptide bond formation on 80S ribosomes that did not contain tRNA in the P site. It required elongation factors 1A and 2 and A site-cognate aminoacylated tRNA. Cycloheximide arrested ribosomes on the IRES only after two cycles of elongation, when the first deacylated tRNA reached the E-site after translocation from the A-site.
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Pestova et al. (2003) studied this question.
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