A single nucleotide is a sufficient 5' untranslated region for translation in an eukaryotic in vitro system.

The 5' untranslated region of an RNA molecule is thought to play an important role in the regulation of translation. Following a recent report that a single nucleotide is sufficient to act in this role in the unicellular organism Giardia, we show that this is also the case for a mammalian in vitro system. These results also demonstrate that an RNA can initiate translation from a start codon where an ideal translational consensus sequence is impossible.