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'. 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. {ECO:0000269|PubMed:12091391, ECO:0000269|PubMed:14695334, ECO:0000269|PubMed:15534111, ECO:0000269|PubMed:15819408, ECO:0000269|PubMed:15897898, ECO:0000269|PubMed:17317935, ECO:0000269|PubMed:19502796, ECO:0000269|PubMed:23103944}. This is the function of Ensembl gene identifier ENSG00000170854 (RIOX2, ribosomal oxygenase 2).