An Upstream Open Reading Frame (uORF) is an Open Reading Frame (ORF) within the 5'UTR (5' untranslated region) of a mRNA. uORFs can regulate eukaryotic gene expression. Translation of the uORF typically inhibits downstream expression of the primary ORF. In bacteria, uORFs are called leader peptides, and were originally discovered on the basis of their impact on the regulation of genes involved in the synthesis or transport of amino acids.
In humans, peptides derived from translated uORFs were detected with a mass spectrometer.
References
Upstream open reading frame Wikipedia(Text) CC BY-SA