Catalysis of the reaction: L-lysyl4- + 2 S-adenosyl-L-methionine = 2 H+ + N6,N6-dimethyl-L-lysyl4- + 2 S-adenosyl-L-homocysteine. This reaction is the successive addition of two methyl groups to the unmethylated lysine residue at position 4 of histone H3, producing histone H3K4me2.
histone H3-K4 dimethylation