Jmjd6 overexpression in MMTV-Myc driven tumor cell lines reduces expression of p19ARF, possibly by demethylating an activating H4R3me2a histone mark at the Cdkna2 promoter leading to reduced p53 expression and increased tumorigenic activity (Aprelikova et al., 2016). The gene discussed is TP53; the disease is neoplasm.