Interaction of DNA demethylase and histone methyltransferase upregulates Nrf2 in 5-fluorouracil-resistant colon cancer cells

// Kyoung Ah Kang 1 , Mei Jing Piao 1 , Yea Seong Ryu 1 , Hee Kyoung Kang 1 , Weon Young Chang 1 , Young Sam Keum 2 , Jin Won Hyun 1 1 School of Medicine, Jeju National University, Jeju 63243, Republic of Korea 2 Department of Biochemistry, College of Pharmacy, Dongguk University, Goyang 10326, Republic of Korea Correspondence to: Jin Won Hyun, email: jinwonh@jejunu.ac.kr Keywords: Nrf2 transcription factor, DNA demethylase, histone methyltransferase, 5-fluorouracil-resistance, oxidative stress Received: January 15, 2016 Accepted: May 09, 2016 Published: May 31, 2016 ABSTRACT We recently reported that DNA demethylase ten-eleven translocation 1 (TET1) upregulates nuclear factor erythroid 2-related factor 2 (Nrf2) in 5-fluorouracil-resistant colon cancer cells (SNUC5/5-FUR). In the present study, we examined the effect of histone modifications on Nrf2 transcriptional activation. Histone deacetylase (HDAC) and histone acetyltransferase (HAT) were respectively decreased and increased in SNUC5/5-FUR cells as compared to non-resistant parent cells. Mixed-lineage leukemia (MLL), a histone methyltransferase, was upregulated, leading to increased trimethylation of histone H3 lysine 4, while G9a was downregulated, leading to decreased dimethylation of histone H3 lysine 9. siRNA-mediated MLL knockdown decreased levels of Nrf2 and HO-1 to a greater extent than did silencing HAT1. Host cell factor 1 (HCF1) was upregulated in SNUC5/5-FUR cells, and we observed interaction between HCF1 and MLL. Upregulation of O-GlcNAc transferase (OGT), an activator of HCF1, was also associated with HCF1-MLL interaction. In SNUC5/5-FUR cells, a larger fraction of OGT was bound to TET1, which recruits OGT to the Nrf2 promoter region, than in SNUC5 cells. These findings indicate that SNUC5/5-FUR cells are under oxidative stress, which induces expression of histone methylation-related proteins as well as DNA demethylase, leading to upregulation of Nrf2 and 5-FU resistance.