FIG. 3.

Piccolo variants containing Esa1 chromodomain mutations. (a) Space-filling representation of H3 peptide containing trimethylated K9 bound to Drosophila HP1 chromodomain. The HP1 chromodomain is shown in light blue, while the H3 peptide backbone and the trimethylated K9 are shown in pink and maroon, respectively. The residues that create or line the hydrophobic cage are displayed as follows: Y24 in light blue, Y48 in dark blue, W45 in yellow, and T54 in green. The corresponding Esa1 residues are also provided. Figure prepared using MidasPlus molecular graphics software (10) and PDB coordinates 1KNE (16). (b) Effect of Esa1 chromodomain point mutations on Piccolo HAT activity. Piccolo v55 and v68 to v74 each contain an N-terminal hexahistidine-tobacco etch virus nuclear inclusion a (NIa) protease site tag (HISN) on the Epl1 component, and all complexes were expressed and purified to similar levels. The preference for nucleosome ratio shown on the right side is the ratio of nucleosomal HAT activity to naked histone HAT activity, with Piccolo v55 set to 1.00 for all eight Piccolo variants.