Abstract
Upstream open reading frames (uORF) are small ORFs often found in 5' leader region of eukaryotic genes. The presence of uORF can negatively affect translational efficiency of the downstream main ORF. Although the effects of most uORFs are independent of their encoded peptide sequences, several uORFs have been shown to control translation of the main ORF in an amino acid sequence-dependent manner. In order to further identify such uORF-encoded regulatory peptides from Arabidopsis, we searched for uORFs whose amino acid sequences are conserved among eudicots by using a comparative genomic approach. We found 14 novel conserved uORFs, and tested whether these uORFs affect expression of the downstream ORF in a uORF peptide sequence-dependent manner. From this screen, we identified 5 novel genes whose expression is controlled by a uORF-encoded peptide. Some of these genes contain multiple uORFs in their 5'UTR. Mutational analyses revealed an involvement of the multiple uORFs in the translational regulation. It is also suggested that a uORF located upstream of the conserved uORF have a role to modulate translational efficiency of the conserved uORF.
