Quebec Network for Research on Protein Function, Structure, and Engineering 1 article published in JoVE Genetics Mass Spectrometry-Based Proteomics Analyses Using the OpenProt Database to Unveil Novel Proteins Translated from Non-Canonical Open Reading Frames Marie A. Brunet1,2, Xavier Roucou1,2 1Department of Biochemistry, Université de Sherbrooke, 2PROTEO, Quebec Network for Research on Protein Function, Structure, and Engineering OpenProt is a freely accessible database that enforces a polycistronic model of eukaryotic genomes. Here, we present a protocol for the use of OpenProt databases when interrogating mass spectrometry datasets. Using OpenProt database for analysis of proteomic experiments allows for discovery of novel and previously undetectable proteins.