Polycomb repressor complex 2, of which EZH2 is the catalytic component, mediates trimethylation of histone 3 at lysine K27 (H3K27) and subsequent repression of target genes [24] including miR-31 expression in adult T cell leukemia and prostate cancer [33, 35], and ENCODE ChipSeq data indicates an enrichment of trimethylated H3K27 at the miR-31 promoter region. This evidence concerns the gene EZH2 and adult T-cell leukemia/lymphoma.