We report a crystallographic analysis of small-molecule ligands of the human
YTHDC1 domain that recognizes N6-methylated adenine (m6A) in RNA. The
30 binders are fragments (molecular weight < 300 g mol-1) that
represent 10 different chemotypes identified by virtual screening. Despite the
structural disorder of the binding site loop (residues 429-439), most of the 30
fragments emulate the two main interactions of the -NHCH3 group of
m6A. These interactions are the hydrogen bond to the backbone
carbonyl of Ser378 and the van der Waals contacts with the tryptophan cage.
Different chemical groups are involved in the conserved binding motifs. Some of
the fragments show favorable ligand efficiency for YTHDC1 and selectivity
against other m6A reader domains. The structural information is
useful for the design of modulators of m6A recognition by YTHDC1.