Identification of PRRC2B methylation sites

It was hypothesized that the human PRRC2B protein (Uniprot accession Q5JSZ5) interacts with its RNA binding targets via methylated arginines. The protein contains at least two RG rich motifs (residues 1061-1080, and 1104-1124), in which the arginines are hypothesized to be methylated. The goal of the experiment was to identify such methylated PRRC2B arginines. To get a wide coverage of the RG rich domains, an immuno-precipitation experiment was performed, followed by digestion with chymotrypsin and LC-MS/MS analysis.