This entry describes enzymes that successively methylate the L-lysine4 residue of histone H3 (H3K4) twice, ultimately generating a dimethylated form. These modifications influence the binding of chromatin-associated proteins. The human NSD3 protein also catalyses the activity of EC 2.1.1.hq, [histone H3]-lysine27 N-dimethyltransferase. cf. EC 188.8.131.524, [histone H3]-lysine4 N-methyltransferase, and EC 184.108.40.2064, [histone H3]-lysine4 N-trimethyltransferase.