subunit to the messenger RNA (mRNA). In most cases, this depends on recognition of a
modified nucleotide cap on the 5′ end of the mRNA. However, an alternate pathway uses a
structured RNA element in the 5′ untranslated region of the messenger or viral RNA called
an internal ribosomal entry site (IRES). Here, we present a cryo-electron microscopy map of
the hepatitis C virus (HCV) IRES bound to the 40 S ribosomal subunit at about 20 Å …