Amplification of SETDB1, a methyltransferase for H3K9, was recently reported to play an accelerating role in melanoma onset [13], while knockout of Suv39h1, another histone methyltransferase for H3K9, caused escape from senescence of lymphocytes [43], suggesting necessity of adequate control of H3K9 methylation. The gene discussed is PRDM9; the disease is melanoma.