The JmjC domain belongs to the Cupin superfamily [3]. JmjC-domain proteins may be protein hydroxylases that catalyse a novel histone modification [4]. This is confirmed to be a hydroxylase: the human JmjC protein named Tyw5p unexpectedly acts in the biosynthesis of a hypermodified nucleoside, hydroxy-wybutosine, in tRNA-Phe by catalysing hydroxylation [5].

1: Evidence of domain swapping within the jumonji family of transcription factors. Balciunas D, Ronne H; Trends Biochem Sci 2000;25:274-276. PMID:10838566

2: A novel jmjC domain protein modulates heterochromatization in fission yeast. Ayoub N, Noma K, Isaac S, Kahan T, Grewal SI, Cohen A; Mol Cell Biol 2003;23:4356-4370. PMID:12773576

3: JmjC: cupin metalloenzyme-like domains in jumonji, hairless and phospholipase A2beta. Clissold PM, Ponting CP; Trends Biochem Sci 2001;26:7-9. PMID:11165500

4: Methylation: lost in hydroxylation?. Trewick SC, McLaughlin PJ, Allshire RC; EMBO Rep 2005;6:315-320. PMID:15809658

5: Expanding role of the jumonji C domain as an RNA hydroxylase. Noma A, Ishitani R, Kato M, Nagao A, Nureki O, Suzuki T; J Biol Chem. 2010;285:34503-34507. PMID:20739293