The enhanced binding of the RBBP1 CD with H4K20me3 in the presence of dsDNA. A, 1H-15N HSQC spectra of the RBBP1 CD in the presence of dsDNA during titration with H4K20me3. The spectra with CD:H4K20me3 in molar ratios of 1:0, 1:0.5, 1:1.5, 1:3.5, and 1:5.0 are in black, cyan, blue, green, and red, respectively. B, KD values for binding of RBBP1 CD to H4K20me3 in the presence of dsDNA from NMR titration experiments. C and D, ITC results of H4K20me3 titration with RBBP1 CD in the absence (C) and presence (D) of dsDNA (CD:dsDNA = 1:1.5), respectively.