C. SWI/SNF opposes the Polycomb complex PRC2. The catalytic subunit of PRC2, EZH2, catalyzes the trimethylation of Lys27 on histone H3 (H3K27me3), a chromatin modification associated with closed chromatin, leading to downregulation of polycomb-regulated genes. FET-fusion binding to SWI/SNF might compromise the function of SWI/SNF, including polycomb opposition. In particular, genes downregulated when FUS-DDIT3 is overexpressed in HT1080 cells (RNA-seq data, n=3, compared to control, n=4) overlap with upregulated gene-sets after EZH2 knockdown, NIPP1 knockdown and HDAC knockdown, and BAF57 (SMARCE1) reconstitution in a SMARCE1 null cell line. RNA-seq data of HT1080 wt (n=4), HT1080 EGFP (n=4), HT1080 FUS-DDIT3-EGFP (n=3) and HT1080 EWSR1-FLI1-EGFP (n=4) were generated and genes > two-fold regulated were analyzed using the molecular signature database (MSigDB). Gene lists were compared to the gene-set collection "chemical and genetic perturbations" and top 20 gene sets for each comparison are shown in the source data. q‑values (FDR-adjusted p‑values) are indicated in parentheses. 