When two AUG codons were present, one at +63 and the other at either the +1 (wild-type) or -1 position, the upstream site took complete precedence over the +63 site ( Figure 6B, lanes 8 and 10) , and this precedence was maintained even when the stop codon was moved 12 codons downstream ( Figure 6B, lanes 11-13) . Thus the strongly preferred site for reinitiation is an AUG codon just downstream of the TURBS. If there is no AUG in this region, the reinitiation mechanism apparently seeks alternatives: either an acceptable non-AUG codon in this same region or an AUG codon further downstream. Reinitiation in the later case does not involve eIF4G/4A-dependent linear scanning, and so it is more likely to involve a direct transfer of the 40S subunit from the TURBS to the AUG, a transfer which might be facilitated by looping out the mRNA between the tethered 40S ribosomal subunit and the AUG.