WD-repeat domain 5 (WDR5) is a member of the WD repeat family. The WD repeat is defined by four or more repeating units of a conserved core of approximately 40 amino acids ending with tryptophan-aspartic acid (WD). WD repeats may serve as sites of protein-protein interaction for adaptor proteins and facilitate multiprotein complex formation. WDR5 contains 7 WD repeats and is a core subunit of the human MLL and SET1 histone H3 lys4 methyltransferase complexes. WDR5 functions in facilitating the assembly of MLL and SET1 chromatin-modifiying complexes.