p53-Binding protein 1 (53BP1) binds to dimethylated lysine 20 on histone 4 (H4K20me2) via tandem tudor domains on a 53BP1 homodimer.1 This interaction is an important part of the DNA damage response.1 UNC2170 is a micromolar ligand of 53BP1 that binds to a pocket formed by the tandem tudor domains.2 It displays at least 17-fold selectivity for 53BP1 over other methyl-lysine binding proteins.2 UNC2170 functions as a 53BP1 antagonist in cellular lysates and shows cellular activity by suppressing class switch recombination, a process which requires a functional 53BP1 tudor domain.2
1.Botuyan, M.V., Lee, J., Ward, I.M., et al.Structural basis for the methylation state-specific recognition for histone H4-K20 by 53BP1 and Crb2 in DNA repairCell127(7)1361-1373(2006) 2.Perfetti, M.T., Baughman, B.M., Dickson, B.M., et al.Identification of a fragment-like small molecule ligand for the methyl-lysine binding protein, 53BP1ACS Chem. Biol.10(4)1072-1081(2015)