Chromodomain: The chromodomain is the smallest member, consisting of four curved β-strands and an α-helix. The chromodomains of HP1 and Polycomb were found to recognize histone H3 trimethylated at K9 (H3K9me3) and H3K27me3, respectively, and these proteins were the first examples of readers specific for methyllysine. Chromodomains generally prefer trimethylated lysine, though some have been shown to bind dimethylated species. The aromatic cage of the chromodomain of mouse and fly HP1 contains an aspartate or glutamate residue, accounting for its ability to interact well with H3K9me3 and dimethylated H3K9 (H3K9me2). (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.
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.
