This is an NSD-specific Cys-His rich region (C5HCH) domain. Family members include NSD3 (nuclear receptor SET domain-containing) proteins. This domain is located on the C-terminal of NSD1, 2 and 3 proteins. C5HCH domain lies adjacent to the fifth plant homeodomain (PHD5). The PHD5-C5HCH module of NSD3 (PHD5-C5HCHNSD3) recognises the H3 N-terminal peptide containing unmodified K4 and trimethylated K9. Moreover, it has been reported that the PHD5-C5HCH module of NSD1 (PHD5-C5HCH) was the sole region required for tight binding of the NUP98-NSD1 fusion protein to the HoxA9 gene promoter, implicating that PHD5-C5HCH might have chromatin targeting ability [1].

1: The methyltransferase NSD3 has chromatin-binding motifs, PHD5-C5HCH, that are distinct from other NSD (nuclear receptor SET domain) family members in their histone H3 recognition. He C, Li F, Zhang J, Wu J, Shi Y; J Biol Chem. 2013;288:4692-4703. PMID:23269674