Updated project metadata. Expansion of a hexanucleotide repeat GGGGCC (G4C2) in C9ORF72 is the most common cause of amyotrophic lateral sclerosis and frontotemporal dementia. Transcripts carrying (G4C2) expansions undergo unconventional, non-ATG-dependent translation, generating toxic dipeptide repeat (DPR) proteins that are thought to contribute to disease. Here, we transfected HEK 293T cells with GFP-tagged dipeptides (GA, GR, PA, PG and PR) and performed LC-MS/MS to identify immunoprecipitated interactors.