Rgfp966

The HT1080 (male brosarcoma) cell lines with doxycycline inducible full length XIST cDNA constructs integrated into chromosome 8p have been described in previous publications (16, 17) . The XIST CRISPRmediated deletion constructs studied throughout this work were all created by targeted excision of speci c sequences from the Full length inducible XIST cDNA construct as described previously (13) . The additional deletion constructs Delta P MI, Exon 1, and Delta Delta, were generated through independent integration of partial XIST sequences into an 8p FRT integration site in the HT1080 cell line (17) . All XIST inducible constructs were under the control of a CMV promoter with a Tet repressor element as described previously (13, 17) . Induction of XIST was performed with 1µg/ml doxycycline, refreshed daily. All of the chemical inhibitors used in this assay were rst dissolved in DMSO and then added to culture media at the desired concentration. Inhibition of HDAC3 was performed using the chemical RGFP966 (Sigma-Aldrich) and the inhibition of all HDACs non-speci cally was performed using Trichostatin A (TSA;
Sigma-Aldrich). Inhibition of the catalytic activity of KMT5A (also known as PR-SET7/SET8/SETD8) was performed using the chemical ryuvidine from Abcam. Inhibition of PRC2 and PRC1 was performed using GSK343 and PRT4165 (both from Sigma-Aldrich) as described previously (13) .