Histone-lysine N-methyltransferase that acts as a regulator of cell proliferation, cell differentiation and inflammatory response (PubMed:31376731, PubMed:31794893, PubMed:33506343). 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 (PubMed:31376731). Also involved in the regulation of stem cell quiescence by catalyzing the trimethylation of 'Lys-20' of histone H4 (H4K20me3), thereby promoting heterochromatin formation (By similarity). Involved in proliferation, migration, paracrine and myogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) (PubMed:33506343). 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 No visible phenotype in normal physiological conditions (PubMed:33506343). Increased proliferation of bone marrow mesenchymal stem cells (BMSCs), impaired BMSCs migration and differentiation potentials of lineages of cardiacmyocyte and smooth muscle cell (PubMed:33506343). Conditional deletion in adult mice improves the survival from radiation-induced hematopoietic failure and thymic lymphoma (PubMed:31794893, PubMed:32259569). Extends survival from radiation-induced thymic lymphoma is likely due to slower tumor enlargement in the thymus (PubMed:31794893). Belongs to the class V-like SAM-binding methyltransferase superfamily. SETD4 family.