Given the likely importance of the interaction between motif 1 and 18S rRNA, we previously carried out RNA structure mapping and minimal free energy predictions to assess whether motif 1 was in basepaired or single stranded conformation in the native mRNA. This work implicated two potential structures, mfold 1 and mfold 2 ( Figure 8A ; [11] ). In mfold 1 the 18S complementary region is sequestered in a base-paired region of stem 2. We previously hypothesised that translation through the segment 7 mRNA and termination of ribosomes at the M1 stop codon would prevent these interactions, creating a structure similar to mfold 2 ( Figure 8B ). In this structure, the 18S complementary region would then be presented to helix 26 of the 18S rRNA on the apical loop of a metastable stem-loop structure.