Identification of RNF111 substrates by integrative ubiquitome and proteome analysis

In the present work, we sought to identify exhaustively the endogenous substrates ubiquitinated and degraded by the E3 ubiquitin ligase RNF111 in presence of TGF-β signaling by performing label free quantitative proteomics after enrichment of ubiquitinated proteins (ubiquitome) in parental U2OS cell line compared to U2OS CRISPR engineered clones expressing a truncated form of RNF111 devoid of C-terminal Ring domain. We compare two methods of enrichment for ubiquitinated proteins prior to mass spectrometry proteomics analysis, the diGly remnant peptide immunoprecipitation with a K-e-GG antibody and a novel approach using protein immunoprecipitation with an ubiquitin pan (Pan UB) nanobody that recognizes all ubiquitin chains and mono-ubiquitination. These ubiquitomes were compared to the corresponding proteome to identify proteins ubiquitinated and degraded by RNF111 upon TGF-β signaling pathway.