When assayed for bivalent marks individually, we not only find promoter regions of CDO1, SFRP1 and SOX17, genes (also known to be frequently DNA hypermethylated in cancer cells [20–22]), to be enriched for both H3K27me3 and H3K4me3 but also to display these marks concomitantly at the same mononucleosome when assayed for by sequential pull-down using 1°H3K27me3 → 2°H3K4me3 (Fig. 1g). The gene discussed is CDO1; the disease is cancer.