miRNA Decoy Research Articles

EIF4A3-negatively driven circular RNA β-catenin (circβ-catenin) promotes colorectal cancer progression via miR-197-3p/CTNND1 regulatory axis.

Circβ-catenin, our first reported circRNA, has been reported to mediate tumorigenesis in various cancers. However, its biological functions and underlying mechanisms in colorectal cancer (CRC) remain unknown. The qRT-PCR examination was used to detect the expression of circβ-catenin, miR-197-3p, and CTNND1 in cells and human tissues. Western blot was conducted to detect the protein expression levels. The biological function of circβ-catenin was verified by MTT, colony formation, wound healing, and transwell assays. The in vivo effects of circβ-catenin were verified by nude mice xenograft and metastasis models. The regulatory network of circβ-catenin/miR-197-3p/CTNND1 was confirmed via dual-luciferase reporter and RIP assays. In the present study, circβ-catenin was found to promote CRC cell proliferation and metastasis in vitro and in vivo. Mechanistically, circβ-catenin served as miRNA decoy to directly bind to miR-197-3p, then antagonized the repression of the target gene CTNND1, and eventually promoted the malignant phenotype of CRC. More interestingly, the inverted repeated Alu pairs termed AluJb1/2 and AluY facilitated the biogenesis of circβ-catenin, which could be partially reversed by EIF4A3 binding to Alu element AluJb2. Our findings illustrated a novel mechanism of circβ-catenin in modulating CRC tumorigenesis and metastasis, which provides a potential therapeutic target for CRC patients.

G-U base-paired hpRNA confers potent inhibition of small RNA function in plants.

MicroRNA (miRNA) target mimicry technologies, utilizing naturally occurring miRNA decoy molecules, represent a potent tool for analyzing miRNA function. In this study, we present a highly efficient small RNA (sRNA) target mimicry design based on G-U base-paired hairpin RNA (hpG:U), which allows for the simultaneous targeting of multiple sRNAs. The hpG:U constructs consistently generate high amounts of intact, polyadenylated stem-loop (SL) RNA outside the nuclei, in contrast to traditional hairpin RNA designs with canonical base pairing (hpWT), which were predominantly processed resulting in a loop. By incorporating a 460-bp G-U base-paired double-stranded stem and a 312-576 nt loop carrying multiple miRNA target mimicry sites (GUMIC), the hpG:U construct displayed effective repression of three Arabidopsis miRNAs, namely miR165/166, miR157, and miR160, both individually and in combination. Additionally, a GUMIC construct targeting a prominent cluster of siRNAs derived from cucumber mosaic virus (CMV) Y-satellite RNA (Y-Sat) effectively inhibited Y-Sat siRNA-directed silencing of the chlorophyll biosynthetic gene CHLI, thereby reducing the yellowing symptoms in infected Nicotiana plants. Therefore, the G-U base-paired hpRNA, characterized by differential processing compared to traditional hpRNA, acts as an efficient decoy for both miRNAs and siRNAs. This technology holds great potential for sRNA functional analysis and the management of sRNA-mediated diseases.

Long non-coding RNA LINC00992 promotes hepatocellular carcinoma cell proliferation, metastasis, and invasiveness by downregulating MicroRNA miR-361-5p expression to increase levels of the transcription factor twist1.

Hepatocellular carcinoma (HCC) is one of the most common cancers, and has an extremely poor prognosis. Our previous study confirmed that the microRNA miR-361-5p inhibited the proliferation, metastasis, invasiveness, and epithelial-to-mesenchymal transition (EMT) process of HCC by targeting the transcription factor Twist1. Long non-coding RNAs (lncRNAs) are key regulators of processes such as cell differentiation, inflammation, tumor formation, and immune escape. However, the underlying interactions between the lncRNA LINC00992, miR-361-5p, and Twist1 in HCC progression is still elusive. In the current study, the DIANA-lncBase database was used to identify regulatory genes upstream of miR-361-5p. Reverse transcription-quantitative PCR (RT-qPCR) was used to quantify the expression of the genes encoding LINC00992, miR-361-5p, and Twist1 in HCC cells. The cell counting kit-8 (CCK-8) was used to measure HCC cell proliferation and Transwell was used to measure HCC cell migration and invasion. The dual-luciferase reporter assay and RNA pull-down assay were performed to examine the interaction between LINC00992 and miR-361-5p. Western blotting was used to detect the levels of Twist1 protein. The result confirmed that, among three lncRNAs tested, miR-361-5p was the one most significantly affected by LINC00992. RT-qPCR revealed that LINC00992 was highly expressed in HCC tissues and cells. The follow-up results showed that the expression of LINC00992 and miR-361-5p in HCC tissues were closely correlated with the rate of metastasis or recurrence of the HCC patients. Our result showed that the expression of miR-361-5p was lower in the LINC00992 (+) group than in the LINC00992 (-) group. CCK-8 and Transwell showed that LINC00992 promoted HCC cell proliferation, migration, and invasion, whereas dual-luciferase reporter assay and RNA pull-down assay showed that LINC00992 combined with miR-361-5p to act as a miRNA decoy in HCC. RT-qPCR and Western blotting confirmed that LINC00992 upregulated the expression of the Twist1 gene in HCC cells by downregulating expression of miR-361-5p. CCK-8 and Transwell assays confirmed that LINC00992 promoted the proliferation, metastasis, and invasiveness of HCC cells by downregulating miR-361-5p levels and consequently upregulating Twist1 expression, implying that these three elements may be promising targets for HCC therapy.

In Vivo miRNA Decoy Screen Reveals miR-124a as a Suppressor of Melanoma Metastasis.

Melanoma is a highly prevalent cancer with an increasing incidence worldwide and high metastatic potential. Brain metastasis is a major complication of the disease, as more than 50% of metastatic melanoma patients eventually develop intracranial disease. MicroRNAs (miRNAs) have been found to play an important role in the tumorigenicity of different cancers and have potential as markers of disease outcome. Identification of relevant miRNAs has generally stemmed from miRNA profiling studies of cells or tissues, but these approaches may have missed miRNAs with relevant functions that are expressed in subfractions of cancer cells. We performed an unbiased in vivo screen to identify miRNAs with potential functions as metastasis suppressors using a lentiviral library of miRNA decoys. Notably, we found that a significant fraction of melanomas that metastasized to the brain carried a decoy for miR-124a, a miRNA that is highly expressed in the brain/neurons. Additional loss- and gain-of-function in vivo validation studies confirmed miR-124a as a suppressor of melanoma metastasis and particularly of brain metastasis. miR-124a overexpression did not inhibit tumor growth in vivo, underscoring that miR-124a specifically controls processes required for melanoma metastatic growth, such as seeding and growth post-extravasation. Finally, we provide proof of principle of this miRNA as a promising therapeutic agent by showing its ability to impair metastatic growth of melanoma cells seeded in distal organs. Our efforts shed light on miR-124a as an antimetastatic agent, which could be leveraged therapeutically to impair metastatic growth and improve patient survival.

In Vivo miRNA Decoy Screen Reveals miR-124a as a Suppressor of Melanoma Metastasis

In Vivo miRNA Decoy Screen Reveals miR-124a as a Suppressor of Melanoma Metastasis

Circular RNA Cwc27 contributes to Alzheimer's disease pathogenesis by repressing Pur-α activity.

Circular RNAs (circRNAs) have gained growing attention in participating in various biological processes and referring to multiply kinds of diseases. Although differentially expressed circRNA profiling in Alzheimer's disease (AD) has been established, little is known about the precise characteristic and functions of key circRNAs with direct relevance to AD in gene expression and disease-related cognition. Herein, we screened and identified circCwc27 as a novel circRNA implicated in AD. CircCwc27 was a neuronal-enriched circRNA that abundantly expressed in the brain and significantly upregulated in AD mice and patients. Knockdown of circCwc27 markedly improved AD-related pathological traits and ameliorated cognitive dysfunctions. Mechanistically, we excluded the miRNA decoy mechanism and focused on the important function of circRNA-RNA-binding protein (RBP) interaction in AD. CircCwc27 directly bound to purine-rich element-binding protein A (Pur-α), increased retention of cytoplasmic Pur-α, and suppressed Pur-α recruitment to the promoters of a cluster of AD genes, including amyloid precursor protein (APP), dopamine receptor D1 (Drd1), protein phosphatase 1, regulatory inhibitor subunit1B (Ppp1r1b), neurotrophic tyrosine kinase, receptor, type 1 (Ntrk1), and LIM homeobox 8 (Lhx8). Downregulation of circCwc27 enhanced the affinity of Pur-α binding to these promoters, leading to altered transcription of Pur-α targets. Moreover, Pur-α overexpression largely phenocopied circCwc27 knockdown in preventing Aβ deposition and cognitive decline. Together, our findings suggest significant functional consequences of a circRNA-protein interaction, that circCwc27, by associating with the regulatory protein Pur-α, may act as a crucial player in AD pathogenesis and represent a promising AD therapeutic target with clinical translational potential.

The Roles of Long Noncoding RNAs HNF1α-AS1 and HNF4α-AS1 in Drug Metabolism and Human Diseases.

Long noncoding RNAs (lncRNAs) are RNAs with a length of over 200 nucleotides that do not have protein-coding abilities. Recent studies suggest that lncRNAs are highly involved in physiological functions and diseases. lncRNAs HNF1α-AS1 and HNF4α-AS1 are transcripts of lncRNA genes HNF1α-AS1 and HNF4α-AS1, which are antisense lncRNA genes located in the neighborhood regions of the transcription factor (TF) genes HNF1α and HNF4α, respectively. HNF1α-AS1 and HNF4α-AS1 have been reported to be involved in several important functions in human physiological activities and diseases. In the liver, HNF1α-AS1 and HNF4α-AS1 regulate the expression and function of several drug-metabolizing cytochrome P450 (P450) enzymes, which also further impact P450-mediated drug metabolism and drug toxicity. In addition, HNF1α-AS1 and HNF4α-AS1 also play important roles in the tumorigenesis, progression, invasion, and treatment outcome of several cancers. Through interacting with different molecules, including miRNAs and proteins, HNF1α-AS1 and HNF4α-AS1 can regulate their target genes in several different mechanisms including miRNA sponge, decoy, or scaffold. The purpose of the current review is to summarize the identified functions and mechanisms of HNF1α-AS1 and HNF4α-AS1 and to discuss the future directions of research of these two lncRNAs.

CircNAPEPLD is expressed in human and murine spermatozoa and physically interacts with oocyte miRNAs

ABSTRACTCircular RNAs (circRNAs) have a critical role in the control of gene expression. Their function in spermatozoa (SPZ) is unknown to date. Twenty-eight genes, involved in SPZ/testicular and epididymal physiology, were given in circBase database to find which of them may generate circular transcripts. We focused on circNAPEPLDiso1, one of the circular RNA isoforms of NAPEPLD transcript, because expressed in human and murine SPZ. In order to functionally characterize circNAPEPLDiso1 as potential microRNA (miRNA) sponge, we performed circNAPEPLDiso1-miR-CATCH and then profiled the expression of 754 miRNAs, by using TaqMan® Low Density Arrays. Among them, miRNAs 146a-5p, 203a-3p, 302c-3p, 766-3p and 1260a (some of them previously shown to be expressed in the oocyte), resulted enriched in circNAPEPLDiso1-miR-CATCHed cell lysate: the network of interactions generated from their validated targets was centred on a core of genes involved in the control of cell cycle. Moreover, computational analysis of circNAPEPLDiso1 sequence also showed its potential translation in a short form of NAPEPLD protein. Interestingly, the expression analysis in murine-unfertilized oocytes revealed low and high levels of circNAPEPLDiso1 and circNAPEPLDiso2, respectively. After fertilization, circNAPEPLDiso1 expression significantly increased, instead circNAPEPLDiso2 expression appeared constant.Based on these data, we suggest that SPZ-derived circNAPEPLDiso1 physically interacts with miRNAs primarily involved in the control of cell cycle; we hypothesize that it may represent a paternal cytoplasmic contribution to the zygote and function as a miRNA decoy inside the fertilized oocytes to regulate the first stages of embryo development. This role is proposed here for the first time.

Androgen receptor regulates ASS1P3/miR-34a-5p/ASS1 signaling to promote renal cell carcinoma cell growth

Recent studies have demonstrated that the androgen receptor (AR) could play important roles to promote renal cell carcinoma (RCC) cell proliferation, and other studies have also indicated that suppressing the argininosuccinate synthase 1 (ASS1) could promote proliferation of various tumors. The potential of AR promoting cell proliferation in RCC via altering ASS1, however, remains unclear. Here we found that the expression of ASS1 was lower in RCC tissues than in adjacent normal renal tissues, and a lower ASS1 expression was linked to a worse prognosis in RCC patients. Mechanism dissection showed that AR could decrease ASS1 expression to promote RCC cell proliferation via ASS1P3, a pseudogene of ASS1. The results of RIP assay and AGO2 assay revealed that AR could bind ASS1P3 to increase RCC cell proliferation via altering miR-34a-5p function, which could bind to the 3′UTR of ASS1 to suppress its protein expression. ASS1P3 could function as a miRNA decoy for miR-34a-5p to regulate ASS1 in RCC. Preclinical study also supports the in vitro data. Together, these results demonstrated that ASS1P3 could function as a competing endogenous RNA to suppress RCC cell progression, and targeting this newly identified AR-mediated ASS1P3/miR-34a-5p/ASS1 signaling might help in blocking proliferation.

MEG3-4 is a miRNA decoy that regulates IL-1β abundance to initiate and then limit inflammation to prevent sepsis during lung infection.

Long noncoding RNAs (lncRNAs) regulate gene expression. We investigated the role of lncRNAs in the inflammatory response to bacterial infection in the lungs. We identified the lncRNA MEG3 as a tissue-specific modulator of inflammatory responses during bacterial infection. Among the 10 transcript isoforms of MEG3, transcript 4 (referred to as MEG3-4) encodes the isoform with the lowest abundance in mouse lungs. Nonetheless, we found that MEG3-4 bound to the microRNA miR-138 in a competitive manner with mRNA encoding the proinflammatory cytokine interleukin-1β (IL-1β), thereby increasing IL-1β abundance and intensifying inflammatory responses to bacterial infection in alveolar macrophages and lung epithelial cells in culture and in lung tissue in mice. MEG3-4-mediated sponging of miR-138 in the cytoplasm increased the autocrine activity of IL-1β that subsequently induced a negative feedback mechanism mediated by nuclear factor κB that decreased MEG3-4 abundance and inflammatory cytokine production. This timely reduction in MEG3-4 abundance tempered proinflammatory responses in mice with pulmonary bacterial infection, preventing the progression to sepsis. Together, these findings reveal that MEG3-4 dynamically modulates pulmonary inflammatory responses through transcriptional regulation of immune response genes, extending the decoy and sponge mechanism associated with lncRNAs to antibacterial immunity, which affects both response and disease progression.

HMGA1P7-pseudogene regulates H19 and Igf2 expression by a competitive endogenous RNA mechanism.

Recent studies have revealed that pseudogene transcripts can function as competing endogenous RNAs, and thereby can also contribute to cancer when dysregulated. We have recently identified two pseudogenes, HMGA1P6 and HMGA1P7 for the HMGA1 gene whose overexpression has a critical role in cancer progression. These pseudogenes work as competitive endogenous RNA decoys for HMGA1 and other cancer related genes suggesting their role in carcinogenesis. Looking for new HMGA1 pseudogene ceRNAs, we performed RNA sequencing technology on mouse embryonic fibroblasts deriving from transgenic mice overexpressing HMGA1P7. Here, we report that HMGA1P7 mRNA sustains the H19 and Igf2 overexpression by acting as miRNA decoy. Lastly, the expression of HMGA1P7 was significantly correlated with H19 and IGF2 levels in human breast cancer thereby suggesting a role for HMGA1P7 deregulation in this neoplasia.

Inhibiting plant microRNA activity: molecular SPONGEs, target MIMICs and STTMs all display variable efficacies against target microRNAs.

Elucidation of microRNA (miRNA) function through a loss-of-function approach has proven difficult due to extensive genetic redundancy among most plant and animal miRNA families. Consequently, miRNA decoy technologies such as target MIMICs (MIMs) and short tandem target MIMICs (STTMs) in plants or molecular SPONGEs (SPs) in animals have been developed to generate loss-of-function phenotypes by perturbing endogenous miRNA activity. To test whether SPs can inhibit plant miRNA activity, synthetic SP transgenes containing multiple miRNA binding sites targeting different Arabidopsis miRNA families were generated. Additionally, their silencing efficacies were compared to the corresponding MIM and STTM transgenes via scoring the frequency and severity of phenotypic abnormalities elicited by each transgene. While SPs with wild-type miRNA binding sites have no apparent impact, SPs containing miRNA binding sites with two central mismatches (cmSPs) can generate strong loss-of-function phenotypes. However, their efficacy varied dramatically, from inducing strong loss-of-function phenotypes to failing to produce any phenotypic impact. Variability was also observed when MIMs and STTMs were compared to cmSPs. While cmSP165/166 and STTM165/166 showed a stronger efficacy than MIM165/166, MIM159 was stronger than cmSP159 and STTM159. Although increasing the number of miRNA binding sites or strengthening the free energy of the miRNA binding site interaction can improve decoy efficacy, clearly additional unknown overriding factors are at play. In conclusion, we demonstrate that no one approach guarantees the strongest miRNA inhibition, but rather distinct miRNA families respond differently to the various approaches, suggesting that multiple approaches may need to be taken to generate the desired loss-of-function outcome.

LncRNAMap: A map of putative regulatory functions in the long non-coding transcriptome

BackgroundRecent studies have demonstrated the importance of long non-coding RNAs (lncRNAs) in chromatin remodeling, and in transcriptional and post-transcriptional regulation. However, only a few specific lncRNAs are well understood, whereas others are completely uncharacterized. To address this, there is a need for user-friendly platform to studying the putative regulatory functions of human lncRNAs. DescriptionlncRNAMap is an integrated and comprehensive database relating to exploration of the putative regulatory functions of human lncRNAs with two mechanisms of regulation, by encoding siRNAs and by acting as miRNA decoys. To investigate lncRNAs producing siRNAs that regulate protein-coding genes, lncRNAMap integrated small RNAs (sRNAs) that were supported by publicly available deep sequencing data from various sRNA libraries and constructed lncRNA-derived siRNA–target interactions. In addition, lncRNAMap demonstrated that lncRNAs can act as targets for miRNAs that would otherwise regulate protein-coding genes. Previously studies indicated that intergenic lncRNAs (lincRNAs) either positive or negative regulated neighboring genes, therefore, lncRNAMap surveyed neighboring genes within a 1Mb distance from the genomic location of specific lncRNAs and provided the expression profiles of lncRNA and its neighboring genes. The gene expression profiles may supply the relationship between lncRNA and its neighboring genes. ConclusionslncRNAMap is a powerful user-friendly platform for the investigation of putative regulatory functions of human lncRNAs with producing siRNAs and acting as miRNA decoy. lncRNAMap is freely available on the web at http://lncRNAMap.mbc.nctu.edu.tw/.

RNA decoys

The role of non-coding RNAs (ncRNAs), both short and long ncRNAs, in the regulation of gene expression has become evident in recent years. Non-coding RNA-based regulation is achieved through a variety of mechanisms; some are relatively well-characterized, while others are much less understood. MicroRNAs (miRNAs), a class of endogenous small RNAs, function as master regulators of gene expression in eukaryotic organisms. A notable, recently discovered role for long ncRNAs is that of miRNA decoys, also referred to as target mimics or sponges, in which long ncRNAs carry a short stretch of sequence sharing homology to miRNA-binding sites in endogenous targets. As a consequence, miRNA decoys are able to sequester and inactivate miRNA function. Engineered miRNA decoys are also efficacious and useful tools for studying gene function. We recently demonstrated that the potential of miRNA decoys to inactivate miRNAs in the model plants Arabidopsis thaliana and Nicotiana benthamiana is dependent on the level of sequence complementarity to miRNAs of interest. The flexibility of the miRNA decoy approach in sequence-dependent miRNA inactivation, backbone choice, ability to simultaneously inactivate multiple miRNAs, and more importantly, to achieve a desirable level of miRNA inactivation, makes it a potentially useful tool for crop improvement. This research addendum reports the functional extension of miRNA decoys from model plants to crops. Furthermore, endogenous miRNA decoys, first described in plants, have been proposed to play a significant role in regulating the transcriptome in eukaryotes. Using computational analysis, we have identified numerous endogenous sequences with potential miRNA decoy activity for conserved miRNAs in several plant species. Our data suggest that endogenous miRNA decoys can be widespread in plants and may be a component of the global gene expression regulatory network in plants.

High-throughput assessment of microRNA activity and function using microRNA sensor and decoy libraries

We introduce two large-scale resources for functional analysis of microRNA—a decoy/sponge library for inhibiting microRNA function and a sensor library for monitoring microRNA activity. To take advantage of the sensor library, we developed a high-throughput assay called Sensor-seq, which permits the activity of hundreds of microRNAs to be quantified simultaneously. Using this approach, we show that only the most abundant microRNAs within a cell mediate significant target suppression. Over 60% of detected microRNAs had no discernible activity, indicating that the functional ‘miRNome’ of a cell is considerably smaller than currently inferred from profiling studies. Moreover, some highly expressed microRNAs exhibit relatively weak activity, which in some cases correlated with a high target-to-microRNA ratio or increased nuclear localization of the microRNA. Finally, we show that the microRNA decoy library can be used for pooled loss-of-function studies. These tools provide valuable resources for studying microRNA biology and for microRNA-based therapeutics.

Regulation of Gene Expression in Plants through miRNA Inactivation

Eukaryotic organisms possess a complex RNA-directed gene expression regulatory network allowing the production of unique gene expression patterns. A recent addition to the repertoire of RNA-based gene regulation is miRNA target decoys, endogenous RNA that can negatively regulate miRNA activity. miRNA decoys have been shown to be a valuable tool for understanding the function of several miRNA families in plants and invertebrates. Engineering and precise manipulation of an endogenous RNA regulatory network through modification of miRNA activity also affords a significant opportunity to achieve a desired outcome of enhanced plant development or response to environmental stresses. Here we report that expression of miRNA decoys as single or heteromeric non-cleavable microRNA (miRNA) sites embedded in either non-protein-coding or within the 3′ untranslated region of protein-coding transcripts can regulate the expression of one or more miRNA targets. By altering the sequence of the miRNA decoy sites, we were able to attenuate miRNA inactivation, which allowed for fine regulation of native miRNA targets and the production of a desirable range of plant phenotypes. Thus, our results demonstrate miRNA decoys are a flexible and robust tool, not only for studying miRNA function, but also for targeted engineering of gene expression in plants. Computational analysis of the Arabidopsis transcriptome revealed a number of potential miRNA decoys, suggesting that endogenous decoys may have an important role in natural modulation of expression in plants.

Smoke and miRrors: pseudogenes tricking miRNAs

Smoke and miRrors: pseudogenes tricking miRNAs