Histone-lysine N-methyltransferase that acts as a regulator of cell proliferation, cell differentiation and inflammatory response (PubMed:31308046). Regulates the inflammatory response by mediating mono- and dimethylation of 'Lys-4' of histone H3 (H3K4me1 and H3K4me2, respectively), leading to activate the transcription of pro-inflammatory cytokines IL6 and TNF-alpha (By similarity). Also involved in the regulation of stem cell quiescence by catalyzing the trimethylation of 'Lys-20' of histone H4 (H4K20me3), thereby promoting heterochromatin formation (PubMed:31308046). Involved in proliferation, migration, paracrine and myogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) (By similarity). L-lysyl(4)-[histone H3] + S-adenosyl-L-methionine = H(+) + N(6)-methyl-L-lysyl(4)-[histone H3] + S-adenosyl-L-homocysteine N(6)-methyl-L-lysyl(4)-[histone H3] + S-adenosyl-L-methionine = H(+) + N(6),N(6)-dimethyl-L-lysyl(4)-[histone H3] + S-adenosyl-L-homocysteine L-lysyl(20)-[histone H4] + S-adenosyl-L-methionine = H(+) + N(6)-methyl-L-lysyl(20)-[histone H4] + S-adenosyl-L-homocysteine N(6)-methyl-L-lysyl(20)-[histone H4] + S-adenosyl-L-methionine = H(+) + N(6),N(6)-dimethyl-L-lysyl(20)-[histone H4] + S-adenosyl-L-homocysteine N(6),N(6)-dimethyl-L-lysyl(20)-[histone H4] + S-adenosyl-L-methionine = H(+) + N(6),N(6),N(6)-trimethyl-L-lysyl(20)-[histone H4] + S-adenosyl-L-homocysteine May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the class V-like SAM-binding methyltransferase superfamily. SETD4 family.