H3K9me3 and H3K27me3 are the two most commonly studied sites of histone methylation that mediate gene silencing [36, 37], and related histone methyltransferases, including SUV39H1/2, SETDB1, and EZH2, are highly expressed in BC (Fig. S9C-F). The gene discussed is PRDM9; the disease is breast cancer.