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EHMT2/G9a (euchromatic histone-lysine N-methyltransferase 2;EHMT2) is highly expressed in various human cancers, including aggressive breast cancer, prostate cancer, lung cancer,leukemia, and hepatocellular carcinoma.Its increased expression has been known to related with tumorigenesis, metastasis, and poor prognosis.Previously, we reported that BIX-01294 (BIX), a small molecular inhibitor of EHMT2, induces reactive oxygen species (ROS)-dependent autophagy and cell death in MCF-7 cells.Although the cytoplasmic machinery that orchestrates autophagy induction has been widely studied, the key epigenetic events that initiate and maintain the autophagy process remain unknown.In this study, we revealed that inhibition of EHMT2 by BIX and EHMT2 siRNA induced expression of autophagy-related genes (ATGs),especially a tumor suppressor gene, BECN1, using PCR array (RT2 profiler PCR array) and ingenuity pathway analysis (IPA).BIX and EHMT2 siRNA decreased dimethylation of lysine 9 of histone H3 (H3K9me2) and recruited RNA polymerase Ⅱ on promoter of BECN-1.Increase in ROS by BIX activated NF-KB and translocated it onto the promoter of BECN1, leading to transcriptional activation.Recently, it was reported that EHMT2 coordinates with DNA methyltransferase 1 (DNMT1) to downregulate tumor suppressor genes epigenetically in cancer cells.Thus, to further elucidate this possibility, we treated the cells with BIX in the presence of 5-aza-2-deoxycytidine(5-Aza-dC), a DNA methyltransferase inhibitor.This combination treatment had synergistic effect on transcriptional activation of BECN-1.These findings suggest that EHMT2 directly represses ATGs and tumor suppressor genes and the inhibition of EHMT2 may be an important mechanism of cancer prevention by activating autophagy.