Supplementary Figure 2: PRC2 complex purification and nucleosome reconstitution.

a,b, Full Coomassie blue-stained SDS–PAGE and the corresponding radiogram as shown in Fig. 2c, d. c, Coomassie blue-stained SDS-PAGE gel shows the purity of PRC2 complexes used for HMTase assays in Fig. 2c, d. d, Gel filtration chromatography (Sephacryl S-400 HR resin) of the PRC2 complexes that were used for HMTase assays in Fig. 2c, d. Only fractions corresponding to assembled PRC2 complexes were collected and used. e, Mononucleosomes used for HMTase assays in Fig. 2c, d were analyzed on a 4% polyacrylamide TBE gel and visualized by SYBR Green I post-staining. f, Mononucleosome homogeneity was assessed using negative stain electron microscopy (representative micrograph at x52,000 magnification). g, A Coomassie blue-stained SDS–PAGE gel shows the purity of PRC2-MTF2 and PRC2-MTF2-EPOP complexes. h, Fluorescence anisotropy was carried out to compare the RNA-binding affinities of PRC2-MTF2 and PRC2-MTF2-EPOP. Error bars represent standard deviation based on three independent experiments that were performed on different days. i, Resulting dissociation constants (Kd) and Hill coefficients are indicated, including the corresponding standard errors. Data for PRC2 was imported from Fig 2b, for a direct comparison. j-k, HMTase assays of the indicated complexes were carried out in the presence or absence of 8.0 μM G4 256 RNA. j, A representative Coomassie blue-stained SDS–PAGE and the corresponding radiograms. k, Quantification of HMTase activities from (j), with error bars representing standard deviation calculated from three independent experiments. P values were determined using unpaired two-tailed Student’s t-test; *, P < 0.05.