Supplementary Figure 1: Preferential binding of PRC2 to G-tract RNA in conditions favoring G4 formation.

(a) The positional distribution of the top 10 PRC2 8-mers (by z-score) relative to PRC2 (bright red) or input (dark red) RNA crosslink sites, and the distribution of the A8 k-mer relative to PRC2 (bright blue) or input (dark blue) RNA crosslink sites, normalized by the mean frequency from 100 randomisations. G-tract-containing 8-mers peak around the crosslink site (the dip at the crosslink site (dashed line) is due to the known bias for UV-C crosslinking at uracil). The A-rich k-mer is depleted from PRC2 crosslink sites. (b) Native polyacrylamide gel electrophoresis of ³²P end-labeled [G₄A₄]₅ or [GA]₂₀ RNA oligonucleotides in folding or pull-down buffer in the presence of 150 mM K⁺ or Li⁺. RNA folded into a G4 structure is labeled. (c) Immunoblotting for EZH2 after pull-down of recombinant PRC2 (EZH2, SUZ12, EED, RBBP4/7; 1.5 ng/μl) with 10-fold dilutions of biotinylated G4-forming [G₄A₄]₅ or control [GA]₂₀ RNA oligonucleotides in 150 mM K⁺ or Li⁺ buffer. Representative of three independent experiments. (d) Immunoblotting for SUZ12 and H3 after incubation of recombinant PRC2 (1.5 ng/μl) with biotinylated nucleosomes (50 nM) in the presence of 2, 20 or 200 ng/μl G4-forming [G₄A₄]₅ or control [GA]₂₀ RNA in K+ or Li+ buffer. Representative of three independent experiments.