Fig. 2: Structural basis for the interaction of KAP1_Hbox with HP1α_CSD.

a Domain architecture of HP1α: nte amino-terminal extension, CD chromodomain, CSD chromoshadow domain, cte carboxyl-terminal extension. Histone H3K9me2/3 mark recognized by CD is depicted as purple circle. b Binding curves used to determine binding affinity of HP1α_CSD for the KAP1_Hbox peptide by tryptophan fluorescence. K_d is represented as average ±SD of three independent experiments. n = 3. c The crystal structure of the HP1α_CSD dimer in complex with KAP1_Hbox’ is depicted as a ribbon diagram with one chromoshadow domain protomer labeled as CSD1 and colored pink and another protomer labeled as CSD2 and colored grey. Bound KAP1_Hbox’ is shown as a green ribbon that pairs with the C-terminal parts of CSD1 in a parallel manner and CSD2 in an antiparallel manner (both are in an extended conformation). d A schematic representation of the HP1α_CSD dimer in complex with KAP1_Hbox. e Surface representation of the HP1α_CSD-KAP1_Hbox’ complex colored as in (c). KAP1_Hbox’ is shown as green stick. Residues of KAP1_Hbox’ involved in the interaction with HP1α_CSD are labeled. f Close-up view of the KAP1_Hbox’-binding site of the HP1α_CSD dimer. Residues involved in the interaction between HP1α_CSD and KAP1_Hbox’ are labeled. Dashed lines represent hydrogen bonds. Source data are provided as a Source Data file.