DCD: In the double chromodomain (DCD), both chromodomains share their general secondary structure elements with those previously seen in HP1 and Polycomb chromodomains. The linker segment forms a novel helix–turn–helix structure that juxtaposes the two chromodomains to form a continuous surface. A total of 350 Å is buried at the interface of these tandem chromodomains. (1)

Reference
1. John F. Flanagan, Li-Zhi Mi, Maksymilian Chruszcz, Marcin Cymborowski, Katrina L. Clines, Youngchang Kim, Wladek Minor, Fraydoon Rastinejad & Sepideh Khorasanizadeh.Double chromodomains cooperate to recognize the methylated histone H3 tail. Nature.2005;438:1181–1185. PMID: 16372014.

    PHD: Distinct from the Royal family is the PHD finger, a well-characterized reader of H3K4me3. It contains a C4HC3 motif that coordinates two zinc ions in a cross-brace manner. Such an arrangement produces a globular domain with a small β-sheet and an α-helix. PHD fingers make extensive contacts with H3K4me3, imparting a high degree of specificity. (1)

Reference
1. Musselman CA, Lalonde ME, Cote J, Kutateladze TG.Perceiving the epigenetic landscape through histone readers. Nat Struct Mol Biol.2012;19(12):1218-27. PMID: 23211769.

    Tudor: Tudor can exist as a single domain or in tandem, containing two β-barrels. The single Tudor domains of PHF1 and PHF19 have been shown to recognize H3K36me3, whereas the canonical TTD of 53BP1 associates with H4K20me2, and the hybrid TTD of JMJD2A binds H3K4me3 and H4K20me3. (1)

Reference
1. Musselman CA, Lalonde ME, Cote J, Kutateladze TG.Perceiving the epigenetic landscape through histone readers. Nat Struct Mol Biol.2012;19(12):1218-27. PMID: 23211769.

    ZF-CW: The zinc finger CW (ZF-CW) domain is a motif of about 60 residues that is frequently found in proteins involved in epigenetic regulation. The ZF-CW domain adopts a new fold in which a zinc ion is coordinated tetrahedrally by four conserved Cys ligand residues. The tertiary structure of the ZF-CW domain partially resembles that adopted by the plant homeo domain (PHD) finger bound to the histone tail, suggesting that the ZF-CW domain and the PHD finger have similar functions. (1)

Reference
1. He F, Umehara T, Saito K, Harada T, Watanabe S, Yabuki T, Kigawa T, Takahashi M, Kuwasako K, Tsuda K, Matsuda T, Aoki M, Seki E, Kobayashi N, Güntert P, Yokoyama S, Muto Y.Structural insight into the zinc finger CW domain as a histone modification reader. Structure.2010;18:1127–1139. PMID: 20826339 .