first malignant brain tumor (MBT) repeat found in Lethal(3)malignant brain tumor-like protein 3 (L3MBTL3)
L3MBTL3, also called L(3)mbt-like protein 3, or MBT-1, is a Polycomb group (PcG) protein that recognizes mono- and dimethylated lysine residues on histone tails. It also acts as a methyl-binding protein that binds the K142-methylated DNMT1 and recruits a novel CRL4(DCAF5) ubiquitin ligase to degrade DNMT1. L3MBTL3 contains three MBT (malignant brain tumor) repeats. The MBT repeat is a protein module that recognizes methylated lysine residues on histones. MBT repeats contain a semi-aromatic cage to accommodate methyllysine and show specificity towards the lower methylation states of lysine. This model corresponds to the first MBT repeat that contains the semi-aromatic cage that binds methylated lysine residues.