Proteomic Detection and Validation of Translated Small Open Reading Frames

Area of Science:

• Proteomics
• Molecular Biology
• Bioinformatics

Background:

• Small open reading frames (smORFs) encode short proteins with regulatory or functional roles.
• These smORF-encoded proteins are often unannotated and undetectable by standard proteomic methods due to initiation at non-AUG codons and limited peptide generation.
• Discovering these small proteins is crucial for identifying novel biological regulators and potential therapeutic targets.

Purpose of the Study:

• To outline a comprehensive procedure for the mass spectrometry-based detection of translated smORFs in human cells.
• To establish a workflow for validating the translation and origin of smORF-encoded peptides.
• To facilitate the annotation and functional characterization of previously undiscovered small proteins.

Main Methods:

• Protein extraction, size selection, and trypsin digestion.
• Two-dimensional liquid chromatography-tandem mass spectrometry (LC-MS/MS) with ERLIC fractionation.
• Construction of transcriptomic databases and identification of non-annotated peptides.
• Validation using siRNA, overexpression, and synthetic peptide standards.

Main Results:

• A detailed protocol for detecting translated smORFs using mass spectrometry was established.
• The workflow allows for the identification of peptides originating from unannotated smORFs.
• Methods for validating smORF translation and assigning peptides to specific genomic loci were demonstrated.

Conclusions:

• The presented workflow enables the discovery and validation of smORF-encoded proteins.
• This approach overcomes limitations of standard proteomics for small protein detection.
• The method is adaptable for various cell types and physiological contexts, advancing the study of smORF functions.