A novel mechanism of lncRNA and miRNA interaction: CCAT2 regulates miR-145 expression by suppressing its maturation process in colon cancer cells

Abstract

BackgroundAlthough both long and micro RNAs are emerging as important functional components in colorectal cancer (CRC) progression and metastasis, the mechanism of their interaction remains poorly understood. CCAT2 (Colon cancer-associated transcript-2), a long noncoding RNA (lncRNA), has been reported to be over-expressed in CRC and is found to promote tumor growth. miRNAs, a class of naturally occurring short RNAs negatively control the expression of target genes by cleaving mRNA or through translation repression. Recently, we reported that miR-145 and miR-21 cooperate to regulate colon cancer stem cell (CSC) proliferation and differentiation. Considering that CCAT2 is mainly located in the nucleus and miRNA maturation process begins in the nucleus, we hypothesize that CCAT2 selectively blocks miR-145 maturation process, resulting in decreased mature miR-145 affecting colon CSC proliferation and differentiation.MethodsThe levels of CCAT2 were manipulated by transfection of CCAT2 expression plasmid or knockdown by siRNA or by CRISPR/Cas9. Quantitative RT-PCR was performed to examine the expression of CCAT2 and pri-, pre- and mature miR-145/21. Fluorescence in situ hybridization (FISH) was used to visualize CCAT2 in the cells. In vitro processing of pri-miRNA-145 was performed using T7 RNA polymerase and recombinant human Dicer.ResultsWe have observed that modulated expression of CCAT2 regulates the expression of miR-145 in colon cancer HCT-116 and HT-29 cells. Knockout of CCAT2 increases miR-145 and negatively regulates miR-21 in HCT-116 cells, impairs proliferation and differentiation. In contrast, stable up-regulation of CCAT2 decreases mature miR-145 and increases the expression of several CSC markers in colon cancer cells. We have also observed that CCAT2 is enriched in the nucleus and correlates with the expression of pre-miR-145 but not pre-miR-21 in HCT-116 cells. These results indicate CCAT2 selectively blocks miR-145 maturation by inhibiting pre-miR-145 export to cytoplasm. Further, we revealed that CCAT2 blocks cleavage of pre-miR-145 by Dicer in vitro.ConclusionsOur results identify CCAT2 as a negative regulator of miRNA-145 biogenesis, and expose a novel mechanism of lncRNA-miRNA crosstalk.Electronic supplementary materialThe online version of this article (10.1186/s12943-017-0725-5) contains supplementary material, which is available to authorized users.

Downregulation of long non‐coding RNA Opa interacting protein 5‐antisense RNA 1 inhibits breast cancer progression by targeting sex‐determining region Y‐box 2 by microRNA‐129‐5p upregulation

“…In the present study, we investigated the role of lncRNA OIP5-AS1 in promoting breast cancer. OIP5-AS1 was increased in breast cancer Recent studies have shown that lncRNAs play a key role in regulating the development and growth of tumors 25 and some lncRNAs have been linked with breast cancer. lncRNAs have a mRNA-like structure and can function as a ceRNA to competitively bind miR-NAs to regulate the expression of mRNAs.…”

Colon Cancer‐Associated Transcripts 1 and 2: Roles and functions in human cancers

“…In addition, CCAT2 selectively inhibits miR-145 maturation by suppression of pre-miR-145 transfer to cytoplasm (Y. Yu et al, 2017;Figure 2 within the 8q24 genomic area in the determination of cancer risk have been evaluated by some studies. For instance, the rs6983267 within CCAT2 has been shown to alter expression level of this lncRNA and influences the risk of cancer (Ling et al, 2013).…”

RP11‐81H3.2 promotes gastric cancer progression through miR‐339‐HNRNPA1 interaction network

“…LncRNA might also regulate the expression of miRNA by controlling the maturation process of miRNA. For instance, lncRNA CCAT2 that is mainly located in the nucleus selectively blocks miR‐145 maturation by inhibiting pre‐miR‐145 export to cytoplasm . Here RP11‐81H3.2 might have the same mechanism regulating the expression of miR‐339.…”