The novel mechanism of initiation of picornavirus RNA translation

The initiation of translation of picornaviral RNAs takes place by an unusual mechanism whereby ribosomes bind directly to an internal site rather than scan the RNA from the 5′-end. This internal entry mechanism requires a 450-nucleotide segment of the picornavirus 5′-untranslated region. The ribosome binds initially to a site at the 3′-end of this segment, and then may scan the RNA to reach the authentic initiation site. This novel mechanism may be of relevance to the translation of some cellular mRNAs.