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EZH 2 coupled with HOTAIR to silence Micro RNA ‐34a by the induction of heterochromatin formation in human pancreatic ductal adenocarcinoma
Author(s) -
Li ChiHan,
Xiao Zhangang,
Tong Joanna Hung–Man,
To KaFai,
Fang Xiangdong,
Cheng Alfred SL,
Chen Yangchao
Publication year - 2016
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.30414
Subject(s) - hotair , ezh2 , gene silencing , gene knockdown , microrna , cancer research , biology , heterochromatin , microbiology and biotechnology , downregulation and upregulation , cell culture , gene expression , long non coding rna , chromatin , genetics , gene
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.