second malignant brain tumor (MBT) repeat found in the Lethal(3)malignant brain tumor-like protein 1 (L3MBTL1)-like family
The L3MBTL1-like family includes L3MBTL1, L3MBTL3, and L3MBTL4. L3MBTL1, also called L(3)mbt-like, or L(3)mbt protein homolog, is a Polycomb group (PcG) protein that functions as a 'reader' of a network of post-translational modifications by specifically recognizing and binding mono- and dimethyllysine residues on target proteins. It acts as a chromatin compaction factor by binding mono- and dimethylated histone H1b/HIST1H1E at 'Lys-26' (H1bK26me1 and H1bK26me2) and histone H4 at 'Lys-20' (H4K20me1 and H4K20me2), leading to condensed chromatin and repressed transcription. L3MBTL3, also called L(3)mbt-like protein 3, or MBT-1, is a 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. L3MBTL4, also called L(3)mbt-like protein 4, or L3mbt-like 4, is a PcG protein that may act as a tumor suppressor. Members of this family contain 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 second MBT repeat that contains the semi-aromatic cage that binds methylated lysine residues.
Jiyao W et al.(2023). "The conserved domain database in 2023.",