Inhibition of EHMT2/G9a epigenetically increases the transcription of Beclin-1 via an increase in ROS and activation of NF-κB

// Sang Eun Park 1, 7 , Hye Jin Yi 1 , Nayoung Suh 9 , Yun-Yong Park 2, 5 , Jae-Young Koh 3, 4, 6 , Seong-Yun Jeong 1, 2, 5 , Dong-Hyung Cho 8 , Choung-Soo Kim 1, 4, 7 , Jung Jin Hwang 1, 2, 5 1 Institute for Innovative Cancer Research, Asan Medical Center, Seoul, Korea 2 Asan Institute for Life Sciences, Asan Medical Center, Seoul, Korea 3 Department of Neurology, Asan Medical Center, Seoul, Korea 4 Department of Urology, Asan Medical Center, Seoul, Korea 5 Department of Convergence Medicine, University of Ulsan, College of Medicine, Seoul, Korea 6 Neural Injury Research Lab, University of Ulsan, College of Medicine, Seoul, Korea 7 Department of Urology, University of Ulsan, College of Medicine, Seoul, Korea 8 Graduate School of East-West Medical Science, Kyung Hee University, Yongin, Korea 9 Department of Medicine Engineering, Soon Chun Hyang University, College of Medical Sciences, Asan, Korea Correspondence to: Jung Jin Hwang, e-mail: jjhwang@amc.seoul.kr Choung-Soo Kim, e-mail: cskim@amc.seoul.kr Keywords: EHMT2/G9a, histone methyltransferase, Beclin-1, autophagy, epigenetic regulation Received: October 14, 2015     Accepted: April 16, 2016     Published: May 11, 2016 ABSTRACT We previously reported that BIX-01294 (BIX), a small molecular inhibitor of euchromatic histone-lysine N-methyltransferase 2 (EHMT2/G9a), induces reactive oxygen species (ROS)-dependent autophagy in MCF-7 cells. Herein, we analyzed the epigenetic mechanism that regulates the transcription of Beclin-1 , a tumor suppressor and an autophagy-related gene (ATG). Inhibition of EHMT2 reduced dimethylation of lysine 9 on histone H3 (H3K9me2) and dissociated EHMT2 and H3K9me2 from the promoter of Beclin-1. To this promoter, RNA polymerase II and nuclear factor kappa B (NF-κB) were recruited in a ROS-dependent manner, resulting in transcriptional activation. Moreover, treatment with BIX reversed the suppression of Beclin-1 by the cooperative action of EHMT2 and DNA methyltransferase 1 (DNMT1). Accordingly, a combination treatment with BIX and 5-Aza-2’-deoxycytidine (5-Aza-Cd), a DNMT1 inhibitor, exerted a synergistic effect on Beclin-1 expression. Importantly, high levels of EHMT2 expression showed a significant association with low levels of Beclin-1 expression, which was related to a poor prognosis. These findings suggest that EHMT2 can directly repress Beclin-1 and that the inhibition of EHMT2 may be a useful therapeutic approach for cancer prevention by activating autophagy.