SETDB1/KMT2G

SETDB1 (SET domain bifurcated 1) and KMT2G (also known as SETD1B) are histone lysine methyltransferases that catalyze H3K9 and H3K4 methylation, respectively, regulating chromatin compaction and transcriptional repression or activation^[1][2][3]. Mechanistically, SETDB1 silences tumor suppressor genes through H3K9 trimethylation, promoting proliferation, migration, and metastasis in multiple cancers, including melanoma and glioma^{[1][2][4][5][6][7][8]}. KMT2G mediates H3K4 methylation, influencing enhancer activity, neuronal plasticity, and T-cell proliferation^{[9][10][3][11]}. In disease models, SETDB1 overexpression enhances tumor growth by activating pathways such as AKT/mTOR and modulating macrophage recruitment, whereas cytoplasmic SETDB1 contributes to the Warburg effect and epithelial-mesenchymal transition^[4][7]. KMT2G dysfunction is associated with genome instability, leukemogenesis, and impaired memory function, distinguishing its tumor suppressor and neurodevelopmental roles from other KMT2 family isoforms^{[10][12][11][13]}. Compared with closely related isoforms, SETDB1 uniquely targets H3K9 residues and exerts both nuclear and cytoplasmic functions, while KMT2G focuses on H3K4 methylation and enhancer regulation^{[9][2][3][11]}. Experimental modulation of SETDB1 using inhibitors like APQ or mithramycin restores epigenetic balance and suppresses tumorigenic phenotypes, offering translational potential for cancer and neurodegenerative diseases^[14][5][8]. KMT2G-related interventions, including PROTACs and menin-KMT2A inhibitors, demonstrate isoform-specific effects on proliferation, differentiation, and immune checkpoint responses, providing insights for precision therapeutics^[18][12]. Therefore, SETDB1 and KMT2G represent complementary epigenetic regulators with distinct substrate specificity, cellular localization, and therapeutic relevance in cancer, neurodevelopment, and immune modulation^{[1][4][3][11]}.

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