Brd4 regulates the expression of essential autophagy genes and Keap1 in AML cells

// Min Huang 1 , Li Zhu 2 , Jacqueline S. Garcia 3 , Michael X. Li 4 , Andrew J. Gentles 5 and Beverly S. Mitchell 1 1 Department of Medicine, Stanford Cancer Institute, Stanford University, Stanford, California, USA 2 Department of Pathology, Stanford University School of Medicine, Stanford, California, USA 3 Department of Medicine, Dana-Farber Cancer Institute, Boston, Massachusetts, USA 4 Department of Electrical Engineering and Computer Science, College of Engineering, Oregon State University, Corvallis, Oregon, USA 5 Department of Medicine, Biomedical Informatics Research, Stanford University, Stanford, California, USA Correspondence to: Beverly S. Mitchell, email: bmitchell@stanford.edu Keywords: Brd4; autophagy; AML; Keap1 Received: October 26, 2017      Accepted: January 19, 2018      Published: February 07, 2018 ABSTRACT We have recently reported that activation of Brd4 is associated with the presence of autophagy in NPMc+ and MLL AML cells. In order to determine the mechanisms underlying this relationship, we have examined the role of Brd4 in regulating the expression of several genes that are central to the process of autophagy. We found that Brd4 binds to the promoters of ATG 3, 7 and CEBPβ, and expression of these genes is markedly reduced by inhibitors of Brd4, as well as by Brd4-shRNA and depletion of CEBPβ. Inhibitors of Brd4 also dramatically suppress the transcription of Keap1, thereby increasing the expression of anti-oxidant genes through the Nrf2 pathway and reducing the cytotoxicity induced by Brd4 inhibitors. Elimination of ATG3 or KEAP1 expression using CRISPR-cas9 mediated genomic editing markedly reduced autophagy. We conclude that Brd4 plays a significant role in autophagy activation through the direct transcriptional regulation of genes essential for it, as well as through the Keap1-Nrf2 axis in NPMc+ and MLL-fusion AML cells.