Crystal structures of the L3MBTL1 MBT repeats in complex with histone H4 peptides dimethylated on Lys20 (H4K20me2) show that only the second of the three MBT repeats can bind mono- and dimethylated histone peptides. Its binding pocket
has similarities to that of 53BP1 and is able to recognize thedegree of histone lysine methylation. An unexpected mode of peptide-mediated dimerization suggests a possible mechanism for chromatin compaction by L3MBTL1.