The miR-17-5p microRNA is a key regulator of the G1/S phase cell cycle transition

Novel targets of the oncogenic miR-17-92 cluster have been identified and the mechanism of regulation of proliferation at the G1/S phase cell cycle transition via the miR-17-5p microRNA has been elucidated

miR-139-5p is a regulator of metastatic pathways in breast cancer

Metastasis is a complex, multistep process involved in the progression of cancer from a localized primary tissue to distant sites, often characteristic of the more aggressive forms of this disease. Despite being studied in great detail in recent years, the mechanisms that govern this process remain poorly understood. In this study, we identify a novel role for miR-139-5p in the inhibition of breast cancer progression. We highlight its clinical relevance by reviewing miR-139-5p expression across a wide variety of breast cancer subtypes using in-house generated and online data sets to show that it is most frequently lost in invasive tumors. A biotin pull-down approach was then used to identify the mRNA targets of miR-139-5p in the breast cancer cell line MCF7. Functional enrichment analysis of the pulled-down targets showed significant enrichment of genes in pathways previously implicated in breast cancer metastasis (P < 0.05). Further bioinformatic analysis revealed a predicted disruption to the TGFβ, Wnt, Rho, and MAPK/PI3K signaling cascades, implying a potential role for miR-139-5p in regulating the ability of cells to invade and migrate. To corroborate this finding, using the MDA-MB-231 breast cancer cell line, we show that overexpression of miR-139-5p results in suppression of these cellular phenotypes. Furthermore, we validate the interaction between miR-139-5p and predicted targets involved in these pathways. Collectively, these results suggest a significant functional role for miR-139-5p in breast cancer cell motility and invasion and its potential to be used as a prognostic marker for the aggressive forms of breast cancer

MicroRNA-182-5-p targets a network of genes involved in DNA repair

MicroRNAs are noncoding regulators of gene expression, which act by repressing protein translation and/or degrading mRNA. Many have been shown to drive tumorigenesis in cancer, but functional studies to understand their mode of action are typically limited to single-target genes. In this study, we use synthetic biotinylated miRNA to pull down endogenous targets of miR-182-5p. We identified more than 1000 genes as potential targets of miR-182-5p, most of which have a known function in pathways underlying tumor biology. Specifically, functional enrichment analysis identified components of both the DNA damage response pathway and cell cycle to be highly represented in this target cohort. Experimental validation confirmed that miR-182-5p-mediated disruption of the homologous recombination (HR) pathway is a consequence of its ability to target multiple components in that pathway. Although there is a strong enrichment for the cell cycle ontology, we do not see primary proliferative defects as a consequence of miR-182-5p overexpression. We highlight targets that could be responsible for miR-182-5p-mediated disruption of other biological processes attributed in the literature so far. Finally, we show that miR-182-5p is highly expressed in a panel of human breast cancer samples, highlighting its role as a potential oncomir in breast cancer

MicroRNAs and their isomiRs function cooperatively to target common biological pathways

Background: Variants of microRNAs (miRNAs), called isomiRs, are commonly reported in deep-sequencing studies; however, the functional significance of these variants remains controversial. Observational studies show that isomiR patterns are non-random, hinting that these molecules could be regulated and therefore functional, although no conclusive biological role has been demonstrated for these molecules. Results: To assess the biological relevance of isomiRs, we have performed ultra-deep miRNA-seq on ten adult human tissues, and created an analysis pipeline called miRNA-MATE to align, annotate, and analyze miRNAs and their isomiRs. We find that isomiRs share sequence and expression characteristics with canonical miRNAs, and are generally strongly correlated with canonical miRNA expression. A large proportion of isomiRs potentially derive from AGO2 cleavage independent of Dicer. We isolated polyribosome-associated mRNA, captured the mRNA-bound miRNAs, and found that isomiRs and canonical miRNAs are equally associated with translational machinery. Finally, we transfected cells with biotinylated RNA duplexes encoding isomiRs or their canonical counterparts and directly assayed their mRNA targets. These studies allow us to experimentally determine genome-wide mRNA targets, and these experiments showed substantial overlap in functional mRNA networks suppressed by both canonical miRNAs and their isomiRs. Conclusions: Together, these results find isomiRs to be biologically relevant and functionally cooperative partners of canonical miRNAs that act coordinately to target pathways of functionally related genes. This work exposes the complexity of the miRNA-transcriptome, and helps explain a major miRNA paradox: how specific regulation of biological processes can occur when the specificity of miRNA targeting is mediated by only 6 to 11 nucleotides

In vitro differentiation of murine embryonic stem cells toward a renal lineage

Embryonic stem (ES) cells have the capacity to differentiate into all cells of the developing embryo and may provide a renewable resource for future cell replacement therapies. The addition of bone morphogenetic protein 4 (BMP4) to serum-free ES cell culture has previously been shown to induce transcription factors, signaling molecules, and cell adhesion proteins expressed during mesoderm specification of the embryo. Here, we show the dynamics of primitive streak mesoderm differentiation in ES cells is comparable between serum and serum-free embryoid body (EB) cultures, supplemented with BMP4. Furthermore, we show a delayed wave of expression of a cohort of genes (Pax2, WT1, podocalyxin, pod-1, and nephrin), which play important roles during embryonic kidney development. The paired box transcription factor, Pax2, is one of the earliest genes expressed during kidney organogenesis and is required for normal urogenital development. ES cell lines containing either a modified Pax2 promoter-lacZ or bacterial artificial chromosome-green fluorescent protein (GFP) transgene were generated, which enabled the quantitative analysis of kidney rather than neuronal Pax2 expression within EBs. Both beta-galactosidase activity and GFP expression were detected by immunohistochemical and flow cytometric analysis following 16 days of EB culture, which correlated with an increase in Pax2 transcript levels. Together, these results suggest a spontaneous kidney gene expression program develops in mature EBs grown in both serum and serum-free conditions, when supplemented with BMP4. Further, the recombinant growth factors BMP2, BMP4, and BMP7 strongly influence gene expression within mesoderm induced EBs. BMP4 promotes ventral (blood) and intermediate (kidney) mesoderm gene expression, whereas BMP2 and BMP7 promote kidney outcomes at the expense of hematopoietic commitment. This induction assay and these unique ES cell lines will be useful for the generation of mesoderm-derived cell populations with implications for future cell therapeutic/integration assays

Imperfect centered miRNA binding sites are common and can mediate repression of target mRNAs

Background: MicroRNAs (miRNAs) bind to mRNAs and target them for translational inhibition or transcriptional degradation. It is thought that most miRNA-mRNA interactions involve the seed region at the 5′ end of the miRNA. The importance of seed sites is supported by experimental evidence, although there is growing interest in interactions mediated by the central region of the miRNA, termed centered sites. To investigate the prevalence of these interactions, we apply a biotin pull-down method to determine the direct targets of ten human miRNAs, including four isomiRs that share centered sites, but not seeds, with their canonical partner miRNAs.Results: We confirm that miRNAs and their isomiRs can interact with hundreds of mRNAs, and that imperfect centered sites are common mediators of miRNA-mRNA interactions. We experimentally demonstrate that these sites can repress mRNA activity, typically through translational repression, and are enriched in regions of the transcriptome bound by AGO. Finally, we show that the identification of imperfect centered sites is unlikely to be an artifact of our protocol caused by the biotinylation of the miRNA. However, the fact that there was a slight bias against seed sites in our protocol may have inflated the apparent prevalence of centered site-mediated interactions.Conclusions: Our results suggest that centered site-mediated interactions are much more frequent than previously thought. This may explain the evolutionary conservation of the central region of miRNAs, and has significant implications for decoding miRNA-regulated genetic networks, and for predicting the functional effect of variants that do not alter protein sequence

Koreans evaluate democracy A new Korea Barometer survey

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