MSL3 resides in the MSL (male-specific lethal) complex, which upregulates 
transcription by spreading the histone H4 Lys16 (H4K16) acetyl mark. We 
discovered a DNA-dependent interaction of MSL3 chromodomain with the H4K20 
monomethyl mark. The structure of a ternary complex shows that the DNA minor 
groove accommodates the histone H4 tail, and monomethyllysine inserts in a 
four-residue aromatic cage in MSL3. H4K16 acetylation antagonizes MSL3 binding, 
suggesting that MSL function is regulated by a combination of post-translational 
modifications.