Extensive translation of small Open Reading Frames revealed by Poly-Ribo-Seq

Area of Science:

• Genomics
• Molecular Biology
• Proteomics

Background:

• Genomes contain numerous small Open Reading Frames (smORFs) with unknown translation status and function.
• The roles of small peptides encoded by smORFs remain largely uncharacterized.

Purpose of the Study:

• To perform a genome-wide assessment of smORF translation in Drosophila.
• To identify and characterize actively translated smORFs and their encoded peptides.

Main Methods:

• Ribosomal profiling of polysomal fractions in Drosophila.
• Bioinformatic analysis of smORF sequences, conservation, and predicted peptide features.

Main Results:

• Detected two classes of translated smORFs: 'longer' (approx. 80 amino acids) and 'dwarf' (approx. 20 amino acids).
• 'Longer' smORFs exhibit canonical protein-like translational metrics, conservation, and transmembrane motifs.
• 'Dwarf' smORFs, often in 5'-UTRs and non-coding RNAs, are less conserved and lack clear peptide function indicators.

Conclusions:

• Thousands of smORFs are productively translated in metazoan genomes.
• smORFs represent an abundant and fundamental component of the genome with diverse characteristics.
• This study provides insights into the translational landscape of smORFs and their potential roles.