Basepairing with 18S ribosomal RNA in internal initiation of translation

In concert with the translation initiation factors 'trans-acting' factors function specifically during internal initiation on picornaviral mRNAs. Of these trans-acting factors, two have been identified as the La-protein and the polypyrimidine tract binding protein. Within the internal ribosomal entry site on the viral RNA, sequences are present that direct the ribosome to the initiation codon. We suggest that selection of the correct AUG initiation codon occurs through basepairing with a part of 18S ribosomal RNA.