TY - JOUR T1 - Fusion protein EWS-FLI1 is incorporated into a protein granule in cells JF - bioRxiv DO - 10.1101/2020.05.31.122028 SP - 2020.05.31.122028 AU - Nasiha S. Ahmed AU - Lucas M. Harrell AU - Daniel R. Wieland AU - Michelle A. Lay AU - Valery F. Thompson AU - Jacob C. Schwartz Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/05/05/2020.05.31.122028.abstract N2 - Ewing sarcoma is driven by fusion proteins containing a low complexity (LC) domain that is intrinsically disordered and a powerful transcriptional regulator. The most common fusion protein found in Ewing sarcoma, EWS-FLI1, takes its LC domain from the RNA-binding protein EWSR1 (Ewing Sarcoma RNA-binding protein 1) and a DNA-binding domain from the transcription factor FLI1 (Friend Leukemia Virus Integration 1). EWS-FLI1 can bind RNA polymerase II (RNA Pol II) and self-assemble through its low-complexity (LC) domain. The ability of RNA-binding proteins like EWSR1 to self-assemble or phase separate in cells has raised questions about the contribution of this process to EWS-FLI1 activity. We examined EWSR1 and EWS-FLI1 activity in Ewing sarcoma cells by siRNA-mediated knockdown and RNA-seq analysis. More transcripts were affected by the EWSR1 knockdown than expected and these included many EWS-FLI1 regulated genes. We reevaluated physical interactions between EWS-FLI1, EWSR1, and RNA Pol II, and employed a cross-linking based strategy to investigate protein assemblies associated with the proteins. The LC domain of EWS-FLI1 was required for the assemblies observed to form in cells. These results offer new insights into a protein assembly that may enable EWS-FLI1 to bind its wide network of protein partners and contribute to regulation of gene expression in Ewing sarcoma.Competing Interest StatementThe authors have declared no competing interest. ER -