Identification of FET-oncoprotein-interacting proteins by immunoprecipitation and mass spectrometry analysis in sarcoma cell lines

The FET family of fusion oncogenes carry one of the three genes, FUS, EWSR1 or TAF15, as 5’‑partners juxtaposed to one of many different DNA binding transcription factor genes as 3’‑partners. FET fusion oncogenes are pathognomonic for many types of sarcoma and leukemia, such as FUS-DDIT3 in myxoid liposarcoma (MLS) and EWSR1-FLI1 in Ewing sarcoma (EWS). We used recombinant FET N-terminal domains in a pulldown screen to find interaction partners to the FET proteins and identified components of the SWI/SNF complex. The ~2 MDa SWI/SNF chromatin remodeling complex utilizes energy from ATP hydrolysis to remodel nucleosomes and expose DNA. We used immunoprecipitation followed by mass spectrometry or western blot analysis to extensively characterize the interaction between FET fusion oncoproteins and the SWI/SNF complex.