Recruitment Of miRNAs Research Articles

The Ago2-miRNA-co-IP Assay to Study TGF- β1 Mediated Recruitment of miRNA to the RISC in CFBE Cells.

Micro(mi)RNAs are short, non-coding RNAs that mediate the RNA interference (RNAi) by post-transcriptional mechanisms. Specific miRNAs are recruited to the cytoplasmic RNA induced silencing complex (RISC). Argonaute2 (Ago2), an essential component of RISC, facilitates binding of miRNA to the target-site on mRNA, followed by cleaving the miRNA-mRNA duplex with its endonuclease activity. RNAi is mediated by a specific pool of miRNAs recruited to RISC, and thus is referred to as the functional pool. The cellular levels of many miRNAs are affected by the cytokine Transforming Growth Factor-β1 (TGF-β1). However, little is known about whether the TGF-β1 affects the functional pools of these miRNAs. The Ago2-miRNA-co-IP assay, discussed in this manuscript, is designed to examine effects of TGF-β1 on the recruitment of miRNAs to RISC and it helps to determine whether changes in the cellular miRNA levels correlate with changes in the RISC-associated, functional pools. The general principles of the assay are as follows. Cultured cells treated with TGF-β1 or vehicle control are lysed and the endogenous Ago2 is immunoprecipitated with immobilized anti-Ago2 antibody, and the active miRNAs complexed with Ago2 are isolated with a RISC immunoprecipitation (RIP) assay kit. The miRNAs are identified with quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) using miRNA-specific stem-looped primers during reverse transcription, followed by PCR using miRNA-specific forward and reverse primers, and TaqMan hydrolysis probes.

Transforming Growth Factor-β1 Selectively Recruits microRNAs to the RNA-Induced Silencing Complex and Degrades CFTR mRNA under Permissive Conditions in Human Bronchial Epithelial Cells.

Mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene lead to cystic fibrosis (CF). The most common mutation F508del inhibits folding and processing of CFTR protein. FDA-approved correctors rescue the biosynthetic processing of F508del-CFTR protein, while potentiators improve the rescued CFTR channel function. Transforming growth factor (TGF-β1), overexpressed in many CF patients, blocks corrector/potentiator rescue by inhibiting CFTR mRNA in vitro. Increased TGF-β1 signaling and acquired CFTR dysfunction are present in other lung diseases. To study the mechanism of TGF-β1 repression of CFTR, we used molecular, biochemical, and functional approaches in primary human bronchial epithelial cells from over 50 donors. TGF-β1 destabilized CFTR mRNA in cells from lungs with chronic disease, including CF, and impaired F508del-CFTR rescue by new-generation correctors. TGF-β1 increased the active pool of selected micro(mi)RNAs validated as CFTR inhibitors, recruiting them to the RNA-induced silencing complex (RISC). Expression of F508del-CFTR globally modulated TGF-β1-induced changes in the miRNA landscape, creating a permissive environment required for degradation of F508del-CFTR mRNA. In conclusion, TGF-β1 may impede the full benefit of corrector/potentiator therapy in CF patients. Studying miRNA recruitment to RISC under disease-specific conditions may help to better characterize the miRNAs utilized by TGF-β1 to destabilize CFTR mRNA.

Viral miRNA adaptor differentially recruits miRNAs to target mRNAs through alternative base-pairing.

HSUR2 is a viral non-coding RNA (ncRNA) that functions as a microRNA (miRNA) adaptor. HSUR2 inhibits apoptosis in infected cells by recruiting host miRNAs miR-142-3p and miR-16 to mRNAs encoding apoptotic factors. HSUR2's target recognition mechanism is not understood. It is also unknown why HSUR2 utilizes miR-16 to downregulate only a subset of transcripts. We developed a general method for individual-nucleotide resolution RNA-RNA interaction identification by crosslinking and capture (iRICC) to identify sequences mediating interactions between HSUR2 and target mRNAs in vivo. Mutational analyses confirmed identified HSUR2-mRNA interactions and validated iRICC as a method that confidently determines sequences mediating RNA-RNA interactions in vivo. We show that HSUR2 does not display a 'seed' region to base-pair with most target mRNAs, but instead uses different regions to interact with different transcripts. We further demonstrate that this versatile mode of interaction via variable base-pairing provides HSUR2 with a mechanism for differential miRNA recruitment.

256 - Luteolin regulates AR-V7 expression via miRNA recruitment in castration-resistant prostate cancer

256 - Luteolin regulates AR-V7 expression via miRNA recruitment in castration-resistant prostate cancer

A Feed-Forward Regulatory Loop between HuR and the Long Noncoding RNA HOTAIR Promotes Head and Neck Squamous Cell Carcinoma Progression and Metastasis

Background/Aims: The lncRNA Homeobox (HOX) transcript antisense RNA (HOTAIR) is overexpressed in numerous cancers. HuR is also overexpressed during tumourigenesis and is abnormally present within the cytoplasm, where it binds to AU-rich elements in the 3′UTRs of target mRNA and post-transcriptionally regulates the expression of its target genes. However, whether HOTAIR is regulated and the mechanisms by which it affects head and neck squamous cell carcinoma (HNSCC) are not well understood. Methods: MTT, cell cycle arrest and apoptotic assays were used to examine the effects of HOTAIR and HuR on cell viability in SCC25 and FaDu cells. Wound healing and transwell invasion analysis were performed to detect the effects of HOTAIR and HuR on cell migration and invasion. The interaction between HuR and HOTAIR was confirmed via qRT-PCR, western blots, luciferase reporter and RIP assays. Finally, qRT-PCR analysis was used to detect the levels of HuR and HOTAIR in HNSCC tumours and adjacent normal tissues. Results: Knockdown of HOTAIR and HuR decreased cell viability, cellular migration and invasion. Moreover, HuR interacted and stabilized HOTAIR stability and thus promoted HOTAIR expression. Notably, HOTAIR acted as a miRNA sponge for HuR. HuR also reinforced HOTAIR sponge activity through miRNA recruitment, thus enhancing HuR expression in turn. Finally, HuR and HOTAIR levels were positively correlated and significantly up-regulated in tumours samples. Conclusion: We demonstrated the existence of a regulatory loop in which the expression of HOTAIR and HuR is reciprocally and temporally regulated during the metastasis and progression of HNSCC.

Commitment of Annexin A2 in recruitment of microRNAs into extracellular vesicles

Extracellular vesicles (EVs) contain microRNAs (miRNAs). However, the exact molecular mechanisms of the recruitment of miRNAs in EVs are not well characterized. Based on proteomic analysis, we identified that silencing of Annexin A2 (ANXA2) significantly decreased the amount of miRNAs in EVs. In addition, microarray analysis revealed that ANXA2 regulated the loading of miRNAs into EVs in a sequence independent manner. Lastly, immunoprecipitation analysis confirmed that ANXA2 could bind miRNAs in EVs in the presence of Ca2+. These observations demonstrate that ANXA2 plays an important role in the packaging process of miRNAs into EVs.

A Feedforward Regulatory Loop between HuR and the Long Noncoding RNA linc-MD1 Controls Early Phases of Myogenesis

SummaryThe muscle-specific long noncoding RNA linc-MD1 was shown to be expressed during early phases of muscle differentiation and to trigger the switch to later stages by acting as a sponge for miR-133 and miR-135. Notably, linc-MD1 is also the host transcript of miR-133b, and their biogenesis is mutually exclusive. Here, we describe that this alternative synthesis is controlled by the HuR protein, which favors linc-MD1 accumulation through its ability to bind linc-MD1 and repress Drosha cleavage. We show that HuR is under the repressive control of miR-133 and that the sponging activity of linc-MD1 consolidates HuR expression in a feedforward positive loop. Finally, we show that HuR also acts in the cytoplasm, reinforcing linc-MD1 sponge activity by cooperating for miRNA recruitment. An increase in miR-133 synthesis, mainly from the two unrelated miR-133a coding genomic loci, is likely to trigger the exit from this circuitry and progression to later differentiation stages.

Dynamic recruitment of microRNAs to their mRNA targets in the regenerating liver

BackgroundValidation of physiologic miRNA targets has been met with significant challenges. We employed HITS-CLIP to identify which miRNAs participate in liver regeneration, and to identify their target mRNAs.ResultsmiRNA recruitment to the RISC is highly dynamic, changing more than five-fold for several miRNAs. miRNA recruitment to the RISC did not correlate with changes in overall miRNA expression for these dynamically recruited miRNAs, emphasizing the necessity to determine miRNA recruitment to the RISC in order to fully assess the impact of miRNA regulation. We incorporated RNA-seq quantification of total mRNA to identify expression-weighted Ago footprints, and developed a microRNA regulatory element (MRE) prediction algorithm that represents a greater than 20-fold refinement over computational methods alone. These high confidence MREs were used to generate candidate ‘competing endogenous RNA’ (ceRNA) networks.ConclusionHITS-CLIP analysis provide novel insights into global miRNA:mRNA relationships in the regenerating liver.