From Proteopediaproteopedia link
Structure of KIAA1718, human Jumonji demethylase, in complex with N-oxalylglycine
[KDM7A_HUMAN] Histone demethylase required for brain development. Specifically demethylates dimethylated 'Lys-9' and 'Lys-27' (H3K9me2 and H3K27me2, respectively) of histone H3 and monomethylated histone H4 'Lys-20' residue (H4K20Me1), thereby playing a central role in histone code. Specifically binds trimethylated 'Lys-4' of histone H3 (H3K4me3), affecting histone demethylase specificity: in presence of H3K4me3, it has no demethylase activity toward H3K9me2, while it has high activity toward H3K27me2. Demethylates H3K9me2 in absence of H3K4me3. Has activity toward H4K20Me1 only when nucleosome is used as a substrate and when not histone octamer is used as substrate.  
Publication Abstract from PubMed
Combinatorial readout of multiple covalent histone modifications is poorly understood. We provide insights into how an activating histone mark, in combination with linked repressive marks, is differentially 'read' by two related human demethylases, PHF8 and KIAA1718 (also known as JHDM1D). Both enzymes harbor a plant homeodomain (PHD) that binds Lys4-trimethylated histone 3 (H3K4me3) and a jumonji domain that demethylates either H3K9me2 or H3K27me2. The presence of H3K4me3 on the same peptide as H3K9me2 makes the doubly methylated peptide a markedly better substrate of PHF8, whereas the presence of H3K4me3 has the opposite effect, diminishing the H3K9me2 demethylase activity of KIAA1718 without adversely affecting its H3K27me2 activity. The difference in substrate specificity between the two is explained by PHF8 adopting a bent conformation, allowing each of its domains to engage its respective target, whereas KIAA1718 adopts an extended conformation, which prevents its access to H3K9me2 by its jumonji domain when its PHD engages H3K4me3.
Enzymatic and structural insights for substrate specificity of a family of jumonji histone lysine demethylases.,Horton JR, Upadhyay AK, Qi HH, Zhang X, Shi Y, Cheng X Nat Struct Mol Biol. 2010 Jan;17(1):38-43. Epub 2009 Dec 20. PMID:20023638
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.