EZH2 coupled with HOTAIR to silence MicroRNA-34a by the induction of heterochromatin formation in human pancreatic ductal adenocarcinoma.
MicroRNA-34a (miR-34a) is frequently downregulated in pancreatic ductal adenocarcinoma (PDAC) cells, however, the silencing mechanism remains unclear. Enhancer of zeste homolog 2 (EZH2) is overexpressed in PDAC, and our previous miRNA profiling showed that inhibition of EZH2 in PDAC cells led to the re-expression of a group of tumor suppressor miRNAs including miR-34a. Here, we studied the effect of ectopic EZH2 expression to the silencing of miR-34a, and identified HOTAIR as an interacting partner to induce heterochromatin formation during miR-34a repression. We identified EZH2 as a major player in silencing miR-34a. Inhibition of EZH2 upregulated miR-34a expression in PDAC cells, while EZH2 overexpression in human pancreatic ductal epithelial (HPDE) cells repressed miR-34a expression and decreased the miR-34a promoter activity. We then showed that HOTAIR played a critical role in EZH2-mediated repression of miR-34a, as knockdown of HOTAIR attenuated the miR-34a inhibition effect in EZH2-overexpressing HPDE cells. HOTAIR physically interacted with miR-34a promoter, and the EZH2-interacting region located at 5' HOTAIR RNA was essential in repressing miR-34a and promoting cell proliferation. More importantly, we showed that the interaction between EZH2 and HOTAIR underlay the silencing of miR-34a through induction of heterochromatin formation. We first showed that manipulation of EZH2 level interfered the occupancy of heterochromatin markers H3K9me2, heterochromatin associated protein 1α and 1γ in PDAC cells. In turn, we showed that knockdown of HOTAIR reduced the occupancy of EZH2 at miR-34a promoter. The identification of HOTAIR-guided miR-34a silencing opened a new avenue in miR-34a-oriented therapy against PDAC.
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Chi-Han
CH
Li
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Zhangang
Z
Xiao
Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
Joanna Hung-Man
JH
Tong
Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong.
Ka-Fai
KF
To
CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China.
Xiangdong
X
Fang
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.|State Key Laboratory of Digestive Diseases, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
Alfred Sl
AS
Cheng
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.|State Key Laboratory of Digestive Diseases, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.|Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China.
Yangchao
Y
Chen
D000818:Animals; D021441:Carcinoma, Pancreatic Ductal / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D000071221:Enhancer of Zeste Homolog 2 Protein / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006570:Heterochromatin / Q000235:genetics*; D006801:Humans; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D009368:Neoplasm Transplantation; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D062085:RNA, Long Noncoding / Q000235:genetics*
C561566:HOTAIR long untranslated RNA, human; D006570:Heterochromatin; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D062085:RNA, Long Noncoding; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein
enhancer of Zeste Homolog 2; long non-coding RNA; microRNA; microRNA-34a; pancreatic cancer