Oxygenase that can act as both a histone lysine demethylase and a ribosomal histidine hydroxylase. Is involved in the demethylation of trimethylated 'Lys-9' on histone H3 (H3K9me3), leading to an increase in ribosomal RNA expression. Also catalyzes the hydroxylation of 60S ribosomal protein L27a on 'His-39' (By similarity). May play an important role in cell growth and survival. May be involved in ribosome biogenesis, most likely during the assembly process of pre-ribosomal particles. 2-oxoglutarate + L-histidyl-[ribosomal protein uL15] + O2 = (3S)-3-hydroxy-L-histidyl-[ribosomal protein uL15] + CO2 + succinate Binds 1 Fe(2+) ion per subunit. Predominantly expressed in testis. Expressed at high levels in spleen, thymus, and colon, but barely detectable in brain, skeletal muscle, and seminal vesicle (at protein level). In testis, expressed in the nuclei of spermatogonia at all stages of the seminiferous epithelial cycle, and in meiotic prophase cells such as preleptotene, leptotene and zygotene, and weakly in early pachytene spermatocytes, but is absent in late pachytene spermatocytes, spermatids and mature sperm (at protein level). Up-regulated in experimentally-induced cryptorchid testis. Belongs to the ROX family. MINA53 subfamily.