MicroRNA destabilization enables dynamic regulation of the miR-16 family in response to cell-cycle changes

Advances in the study of epithelial mesenchymal transition in cancer progression: Role of miRNAs

Epithelial-mesenchymal transition (EMT) has been extensively studied for its roles in tumor metastasis, the generation and maintenance of cancer stem cells and treatment resistance. Epithelial mesenchymal plasticity allows cells to switch between various states within the epithelial-mesenchymal spectrum, resulting in a mixed epithelial/mesenchymal phenotypic profile. This plasticity underlies the acquisition of multiple malignant features during cancer progression and poses challenges for EMT in tumors. MicroRNAs (miRNAs) in the microenvironment affect numerous signaling processes through diverse mechanisms, influencing physiological activities. This paper reviews recent advances in EMT, the role of different hybrid states in tumor progression, and the important role of miRNAs in EMT. Furthermore, it explores the relationship between miRNA-based EMT therapies and their implications for clinical practice, discussing how ongoing developments may enhance therapeutic outcomes.

A review on gut microbiota and miRNA crosstalk: implications for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline and progressive neuronal damage. Recent research has highlighted the significant roles of the gut microbiota and microRNAs (miRNAs) in the pathogenesis of AD. This review explores the intricate interaction between gut microbiota and miRNAs, emphasizing their combined impact on Alzheimer's progression. First, we discuss the bidirectional communication within the gut-brain axis and how gut dysbiosis contributes to neuroinflammation and neurodegeneration in AD. Changes in gut microbiota composition in Alzheimer's patients have been linked to inflammation, which exacerbates disease progression. Next, we delve into the biology of miRNAs, focusing on their roles in gene regulation, neurodevelopment, and neurodegeneration. Dysregulated miRNAs are implicated in AD pathogenesis, influencing key processes like inflammation, tau pathology, and amyloid deposition. We then examine how the gut microbiota modulates miRNA expression, particularly in the brain, potentially altering neuroinflammatory responses and synaptic plasticity. The interplay between gut microbiota and miRNAs also affects blood-brain barrier integrity, further contributing to Alzheimer's pathology. Lastly, we explore therapeutic strategies targeting this gut microbiota-miRNA axis, including probiotics, prebiotics, and dietary interventions, aiming to modulate miRNA expression and improve AD outcomes. While promising, challenges remain in fully elucidating these interactions and translating them into effective therapies. This review highlights the importance of understanding the gut microbiota-miRNA relationship in AD, offering potential pathways for novel therapeutic approaches aimed at mitigating the disease's progression.

Widespread destabilization of Caenorhabditis elegans microRNAs by the E3 ubiquitin ligase EBAX-1

MicroRNAs (miRNAs) associate with Argonaute (AGO) proteins to form complexes that direct mRNA repression. miRNAs are also the subject of regulation. For example, some miRNAs are destabilized through a pathway in which pairing to specialized transcripts recruits the ZSWIM8 E3 ubiquitin ligase, which polyubiquitinates AGO, leading to its degradation and exposure of the miRNA to cellular nucleases. Here, we found that 22 miRNAs in Caenorhabditis elegans are sensitive to loss of EBAX-1, the ZSWIM8 ortholog in nematodes, implying that these 22 miRNAs might be subject to this pathway of target-directed miRNA degradation (TDMD). The impact of EBAX-1 depended on the developmental stage, with the greatest effect on the miRNA pool (14.5%) observed in L1 larvae, and the greatest number of different miRNAs affected (17) observed in germline-depleted adults. The affected miRNAs included the miR-35-42 family, as well as other miRNAs among the least stable in the worm, suggesting that TDMD is a major miRNA-destabilization pathway in the worm. The excess miR-35-42 molecules that accumulated in ebax-1 mutants caused increased repression of their predicted target mRNAs and underwent 3' trimming over time. In general, however, miRNAs sensitive to EBAX-1 loss had no consistent pattern of either trimming or tailing. Replacement of the 3' region of miR-43 substantially reduced EBAX-1 sensitivity, a result that differed from that observed previously for miR-35. Together, these findings broaden the implied biological scope of TDMD-like regulation of miRNA stability in animals, and indicate that a role for miRNA 3' sequences is variable in the worm.

What goes up must come down: off switches for regulatory RNAs

Small RNAs base pair with and regulate mRNA translation and stability. For both bacterial small regulatory RNAs and eukaryotic microRNAs, association with partner proteins is critical for the stability and function of the regulatory RNAs. We review the mechanisms for degradation of these RNAs: displacement of the regulatory RNA from its protein partner (in bacteria) or destruction of the protein and its associated microRNAs (in eukaryotes). These mechanisms can allow specific destruction of a regulatory RNA via pairing with a decay trigger RNA or function as global off switches by disrupting the stability or function of the protein partner.

An ALS-associated mutation dysregulates microglia-derived extracellular microRNAs in a sex-specific manner

Evidence suggests the presence of microglial activation and microRNA (miRNA) dysregulation in amyotrophic lateral sclerosis (ALS), the most common form of adult motor neuron disease. However, few studies have investigated whether the miRNA dysregulation originates from microglia. Furthermore, TDP-43 (encoded by TARDBP), involved in miRNA biogenesis, aggregates in tissues of ∼98% of ALS cases. Thus, this study aimed to determine whether expression of the ALS-linked TDP-43M337V mutation in a transgenic mouse model dysregulates microglia-derived miRNAs. RNA sequencing identified several dysregulated miRNAs released by transgenic microglia and a differential miRNA release by lipopolysaccharide-stimulated microglia, which was more pronounced in cells from female mice. We validated the downregulation of three candidate miRNAs, namely, miR-16-5p, miR-99a-5p and miR-191-5p, by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and identified their predicted targets, which primarily include genes involved in neuronal development and function. These results suggest that altered TDP-43 function leads to changes in the miRNA population released by microglia, which may in turn be a source of the miRNA dysregulation observed in the disease. This has important implications for the role of neuroinflammation in ALS pathology and could provide potential therapeutic targets.

microRNAs and thrombo-inflammation: relationship in sight

PURPOSE OF REVIEW

Thrombo-inflammation is a multifaceted pathologic process involving various cells such as platelets, neutrophils, and monocytes. In recent years, microRNAs have been consistently implicated as regulators of these cells.

RECENT FINDINGS

MicroRNAs play a regulatory role in several platelet receptors that have recently been identified as contributing to thrombo-inflammation and neutrophil extracellular trap (NET) formation. In addition, a growing body of evidence has shown that several intracellular and extracellular microRNAs directly promote NET formation.

SUMMARY

Targeting microRNAs is a promising therapeutic approach to control thrombosis in patients with both infectious and noninfectious inflammatory diseases. Future research efforts should focus on elucidating the specific roles of microRNAs in thrombo-inflammation and translating these findings into tangible benefits for patients.

Target-directed microRNA degradation: Mechanisms, significance, and functional implications

MicroRNAs (miRNAs) are small non-coding RNAs that play a fundamental role in enabling miRNA-mediated target repression, a post-transcriptional gene regulatory mechanism preserved across metazoans. Loss of certain animal miRNA genes can lead to developmental abnormalities, disease, and various degrees of embryonic lethality. These short RNAs normally guide Argonaute (AGO) proteins to target RNAs, which are in turn translationally repressed and destabilized, silencing the target to fine-tune gene expression and maintain cellular homeostasis. Delineating miRNA-mediated target decay has been thoroughly examined in thousands of studies, yet despite these exhaustive studies, comparatively less is known about how and why miRNAs are directed for decay. Several key observations over the years have noted instances of rapid miRNA turnover, suggesting endogenous means for animals to induce miRNA degradation. Recently, it was revealed that certain targets, so-called target-directed miRNA degradation (TDMD) triggers, can "trigger" miRNA decay through inducing proteolysis of AGO and thereby the bound miRNA. This process is mediated in animals via the ZSWIM8 ubiquitin ligase complex, which is recruited to AGO during engagement with triggers. Since its discovery, several studies have identified that ZSWIM8 and TDMD are indispensable for proper animal development. Given the rapid expansion of this field of study, here, we summarize the key findings that have led to and followed the discovery of ZSWIM8-dependent TDMD. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Turnover and Surveillance > Turnover/Surveillance Mechanisms RNA in Disease and Development > RNA in Development.

To kill a microRNA: emerging concepts in target-directed microRNA degradation

MicroRNAs (miRNAs) guide Argonaute (AGO) proteins to bind mRNA targets. Although most targets are destabilized by miRNA-AGO binding, some targets induce degradation of the miRNA instead. These special targets are also referred to as trigger RNAs. All triggers identified thus far have binding sites with greater complementarity to the miRNA than typical target sites. Target-directed miRNA degradation (TDMD) occurs when trigger RNAs bind the miRNA-AGO complex and recruit the ZSWIM8 E3 ubiquitin ligase, leading to AGO ubiquitination and proteolysis and subsequent miRNA destruction. More than 100 different miRNAs are regulated by ZSWIM8 in bilaterian animals, and hundreds of trigger RNAs have been predicted computationally. Disruption of individual trigger RNAs or ZSWIM8 has uncovered important developmental and physiologic roles for TDMD across a variety of model organisms and cell types. In this review, we highlight recent progress in understanding the mechanistic basis and functions of TDMD, describe common features of trigger RNAs, outline best practices for validating trigger RNAs, and discuss outstanding questions in the field.

Recent progress in miRNA biogenesis and decay

MicroRNAs are a class of small regulatory RNAs that mediate regulation of protein synthesis by recognizing sequence elements in mRNAs. MicroRNAs are processed through a series of steps starting from transcription and primary processing in the nucleus to precursor processing and mature function in the cytoplasm. It is also in the cytoplasm where levels of mature microRNAs can be modulated through decay mechanisms. Here, we review the recent progress in the lifetime of a microRNA at all steps required for maintaining their homoeostasis. The increasing knowledge about microRNA regulation upholds great promise as therapeutic targets.

Promise and Perils of MicroRNA Discovery Research: Working Toward Quality Over Quantity

Since the first microRNA (miRNA) was described in 1993 in the humble worm Caenorhabditis elegans, the miRNA field has boomed, with more than 100 000 related patents filed and miRNAs now in ongoing clinical trials. Despite an advanced understanding of the biogenesis and action of miRNAs, applied miRNA research faces challenges and irreproducibility due to a lack of standardization. This review provides guidelines regarding miRNA investigation, while focusing on the pitfalls and considerations that are often overlooked in prevailing applied miRNA research. These include miRNA annotation and quantification, to modulation, target prediction, validation, and the study of circulating miRNAs.

Target-directed microRNA degradation regulates developmental microRNA expression and embryonic growth in mammals

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression that play critical roles in development and disease. Target-directed miRNA degradation (TDMD), a pathway in which miRNAs that bind to specialized targets with extensive complementarity are rapidly decayed, has emerged as a potent mechanism of controlling miRNA levels. Nevertheless, the biological role and scope of miRNA regulation by TDMD in mammals remains poorly understood. To address these questions, we generated mice with constitutive or conditional deletion of Zswim8, which encodes an essential TDMD factor. Loss of Zswim8 resulted in developmental defects in the heart and lungs, growth restriction, and perinatal lethality. Small RNA sequencing of embryonic tissues revealed widespread miRNA regulation by TDMD and greatly expanded the known catalog of miRNAs regulated by this pathway. These experiments also uncovered novel features of TDMD-regulated miRNAs, including their enrichment in cotranscribed clusters and examples in which TDMD underlies "arm switching," a phenomenon wherein the dominant strand of a miRNA precursor changes in different tissues or conditions. Importantly, deletion of two miRNAs, miR-322 and miR-503, rescued growth of Zswim8-null embryos, directly implicating the TDMD pathway as a regulator of mammalian body size. These data illuminate the broad landscape and developmental role of TDMD in mammals.

Target-directed microRNA degradation regulates developmental microRNA expression and embryonic growth in mammals

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression that play critical roles in development and disease. Target-directed miRNA degradation (TDMD), a pathway in which miRNAs that bind to specialized targets with extensive complementarity are rapidly decayed, has emerged as a potent mechanism of controlling miRNA levels. Nevertheless, the biological role and scope of miRNA regulation by TDMD in mammals remains poorly understood. To address these questions, we generated mice with constitutive or conditional deletion of Zswim8 , which encodes an essential TDMD factor. Loss of Zswim8 resulted in developmental defects in heart and lung, growth restriction, and perinatal lethality. Small RNA sequencing of embryonic tissues revealed widespread miRNA regulation by TDMD and greatly expanded the known catalog of miRNAs regulated by this pathway. These experiments also uncovered novel features of TDMD-regulated miRNAs, including their enrichment in co-transcribed clusters and examples in which TDMD underlies 'arm switching', a phenomenon wherein the dominant strand of a miRNA precursor changes in different tissues or conditions. Importantly, deletion of two miRNAs, miR-322 and miR-503, rescued growth of Zswim8 null embryos, directly implicating the TDMD pathway as a regulator of mammalian body size. These data illuminate the broad landscape and developmental role of TDMD in mammals.

Palmitate alters miR-2137 and miR-503-5p to induce orexigenic Npy in hypothalamic neuronal cell models: Rescue by oleate and docosahexaenoic acid

MicroRNAs (miRNAs) are short noncoding RNA implicated in the pathogenesis of obesity. One cause of obesity is excess exposure to the saturated fatty acid palmitate that can alter miRNA levels in the periphery. Palmitate also promotes obesity by acting on the hypothalamus, the central coordinator of energy homeostasis, to dysregulate hypothalamic feeding neuropeptides and induce ER stress and inflammatory signaling. We hypothesized that palmitate would alter hypothalamic miRNAs that control genes involved in energy homeostasis thereby contributing to the obesity-promoting effects of palmitate. We found that palmitate upregulated 20 miRNAs and downregulated six miRNAs in the orexigenic NPY/AgRP-expressing mHypoE-46 cell line. We focused on delineating the roles of miR-2137 and miR-503-5p, as they were strongly up- and downregulated by palmitate, respectively. Overexpression of miR-2137 increased Npy mRNA levels and downregulated Esr1 levels, while increasing C/ebpβ and Atf3 mRNA. Inhibiting miR-2137 had the opposite effect, except on Npy, which was unchanged. The most downregulated miRNA by palmitate, miR-503-5p, negatively regulated Npy mRNA levels. Exposure to the unsaturated fatty acids oleate or docosahexaenoic acid completely or partially blocked the effects of palmitate on miR-2137 and miR-503-5p as well as Npy, Agrp, Esr1, C/ebpβ and Atf3. MicroRNAs may therefore contribute to palmitate actions in dysregulating NPY/AgRP neurons. Effectively combating the deleterious effects of palmitate is crucial to help prevent or reduce the impact of obesity.

Circulating miRNAs associated with nonalcoholic fatty liver disease

MicroRNAs (miRNAs) are secreted from cells as either protein-bound or enclosed in extracellular vesicles. Circulating liver-derived miRNAs are modifiable by weight-loss or insulin-sensitizing treatments, indicating that they could be important biomarker candidates for diagnosis, monitoring, and prognosis in nonalcoholic liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Unfortunately, the noninvasive diagnosis of NASH and fibrosis remains a key challenge, which limits case finding. Current diagnostic guidelines, therefore, recommend liver biopsies, with risks of pain and bleeding for the patient and substantial healthcare costs. Here, we summarize mechanisms of RNA secretion and review circulating RNAs associated with NAFLD and NASH for their biomarker potential. Few circulating miRNAs are consistently associated with NAFLD/NASH: miR-122, miR-21, miR-34a, miR-192, miR-193, and the miR-17-92 miRNA-cluster. The hepatocyte-enriched miRNA-122 is consistently increased in NAFLD and NASH but decreased in liver cirrhosis. Circulating miR-34a, part of an existing diagnostic algorithm for NAFLD, and miR-21 are consistently increased in NAFLD and NASH. MiR-192 appears to be prominently upregulated in NASH compared with NAFDL, whereas miR-193 was reported to distinguish NASH from fibrosis. Various members of miRNA cluster miR-17-92 are reported to be associated with NAFLD and NASH, although with less consistency. Several other circulating miRNAs have been reported to be associated with fatty liver in a few studies, indicating the existence of more circulating miRNAs with relevant as diagnostic markers for NAFLD or NASH. Thus, circulating miRNAs show potential as biomarkers of fatty liver disease, but more information about phenotype specificity and longitudinal regulation is needed.

PVT1/miR-16/CCND1 axis regulates gastric cancer progression

Long non-coding RNA plasmacytoma variant translocation 1 (PVT1) has been reported to be a vital modulator in tumorigenesis of gastric cancer (GC). However, the detailed regulatory mechanism of PVT1 in GC remains largely unclear. In this work, the expressions of PVT1 and microRNA-16 (miR-16) were detected by quantitative real-time PCR (qRT-PCR) in GC tissues and cell lines. GC cell lines NCI-N87 and MKN45 cell lines were chosen for the following assays. After PVT1 was overexpressed or depleted, CCK-8 and Transwell assays were performed to examine the cell viability and invasive capacity. Cell cycle was analyzed by flow cytometry. The expression of cyclin D1 (CCND1) at mRNA and protein levels was measured by qRT-PCR and western blot. The competitive endogenous RNA molecular mechanism among PVT1, miR-16 and CCND1 was verified by bioinformatics analysis, luciferase-reporter gene assay and RNA immunoprecipitation assay. In the present study, it was revealed that PVT1 expression was remarkably evaluated in GC tissues and cell lines than that in the corresponding control group. PVT1 positively regulated the proliferation, migration and cell cycle progression of GC cells. Besides, miR-16 was identified as a target of PVT1, and CCND1 was identified as a target of miR-16. The depletion of PVT1 promoted the expression of miR-16 and suppressed CCND1 expression. Moreover, either miR-16 inhibitor or CCND1 overexpression plasmid could reverse the promoting effects of PVT1 on the malignant biological behaviors of GC cells. In conclusion, PVT1 promoted CCND1 expression by negatively regulating miR-16 expression to enhance the viability, invasion and cell cycle progression of GC cells.

MicroRNA turnover: a tale of tailing, trimming, and targets

MicroRNAs (miRNAs) post-transcriptionally repress gene expression by guiding Argonaute (AGO) proteins to target mRNAs. While much is known about the regulation of miRNA biogenesis, miRNA degradation pathways are comparatively poorly understood. Although miRNAs generally exhibit slow turnover, they can be rapidly degraded through regulated mechanisms that act in a context- or sequence-specific manner. Recent work has revealed a particularly important role for specialized target interactions in controlling rates of miRNA degradation. Engagement of these targets is associated with the addition and removal of nucleotides from the 3' ends of miRNAs, a process known as tailing and trimming. Here we review these mechanisms of miRNA modification and turnover, highlighting the contexts in which they impact miRNA stability and discussing important questions that remain unanswered.

Using CRL3BPM E3 ligase substrate recognition sites as tools to impact plant development and stress tolerance in Arabidopsis thaliana

Cullin-based RING E3 ligases that use BTB/POZ-MATH (BPM) proteins as substrate receptors have been established over the last decade as critical regulators in plant development and abiotic stress tolerance. As such they affect general aspects of shoot and root development, flowering time, embryo development, and different abiotic stress responses, such as heat, drought and salt stress. To generate tools that can help to understand the role of CRL3BPM E3 ligases in plants, we developed a novel system using two conserved protein-binding motifs from BPM substrates to transiently block CRL3BPM activity. The work investigates in vitro and in planta this novel approach, and shows that it can affect stress tolerance in plants as well as developmental aspects. It thereby can serve as a new tool for studying this E3 ligase in plants.

The microRNA Lifecycle in Health and Cancer

MicroRNAs (miRNAs) are small non-coding RNAs of ~22 nucleotides that regulate gene expression at the post-transcriptional level. They can bind to around 60% of all protein-coding genes with an average of 200 targets per miRNA, indicating their important function within physiological and pathological cellular processes. miRNAs can be quickly produced in high amounts through canonical and non-canonical pathways that involve a multitude of steps and proteins. In cancer, miRNA biogenesis, availability and regulation of target expression can be altered to promote tumour progression. This can be due to genetic causes, such as single nucleotide polymorphisms, epigenetic changes, differences in host gene expression, or chromosomal remodelling. Alternatively, post-transcriptional changes in miRNA stability, and defective or absent components and mediators of the miRNA-induced silencing complex can lead to altered miRNA function. This review provides an overview of the current knowledge on the lifecycle of miRNAs in health and cancer. Understanding miRNA function and regulation is fundamental prior to potential future application of miRNAs as cancer biomarkers.

The developmentally timed decay of an essential microRNA family is seed-sequence dependent

MicroRNA (miRNA) abundance is tightly controlled by regulation of biogenesis and decay. Here, we show that the mir-35 miRNA family undergoes selective decay at the transition from embryonic to larval development in C. elegans. The seed sequence of the miRNA is necessary and largely sufficient for this regulation. Sequences outside the seed (3' end) regulate mir-35 abundance in the embryo but are not necessary for sharp decay at the transition to larval development. Enzymatic modifications of the miRNA 3' end are neither prevalent nor correlated with changes in decay, suggesting that miRNA 3' end display is not a core feature of this mechanism and further supporting a seed-driven decay model. Our findings demonstrate that seed-sequence-specific decay can selectively and coherently regulate all redundant members of a miRNA seed family, a class of mechanism that has great biological and therapeutic potential for dynamic regulation of a miRNA family's target repertoire.

CRISPR/Cas9-Induced Knockout of miR-24 Reduces Cholesterol and Monounsaturated Fatty Acid Content in Primary Goat Mammary Epithelial Cells

In nonruminants, microRNA (miRNA)-24 plays an important role in lipid metabolism in adipose tissue and the liver. Although the abundance of miR-24 in ruminant mammary glands is the highest during peak lactation, its potential role in regulating the synthesis and secretion of fat into milk is unclear. This study aimed to identify the function of miR-24 in these processes using CRISPR/Cas9 technology in primary goat mammary epithelial cells (GMEC). A single clone containing a 66-nucleotide deletion between two sgRNAs mediating double-strand break (DSB) sites was obtained. The abundance of miR-24-3p and miR-24-5p encoded by the deleted sequence was decreased, whereas the target genes INSIG1 and FASN increased. In addition, miR-24 knockout reduced the gene abundance of genes associated with fatty acid and TAG synthesis and transcription regulator. Similarly, the content of cholesterol and monounsaturated fatty acid (MUFA) C18:1 decreased, whereas that of polyunsaturated fatty acids (PUFA) C18:2, C20:3, C20:4 and C20:5 increased. Subsequently, knocking down of INSIG1 but not FASN reversed the effect of miR-24 knockout, indicating that miR-24 modulated cholesterol and fatty acid synthesis mainly by targeting INSIG1. Overall, the present in vitro data demonstrated a critical role for miR-24 in regulating lipid and fatty acid synthesis and highlighted the possibility of manipulating milk components in dairy goats.

Single-molecule FRET uncovers hidden conformations and dynamics of human Argonaute 2

Human Argonaute 2 (hAgo2) constitutes the functional core of the RNA interference pathway. Guide RNAs direct hAgo2 to target mRNAs, which ultimately leads to hAgo2-mediated mRNA degradation or translational inhibition. Here, we combine site-specifically labeled hAgo2 with time-resolved single-molecule FRET measurements to monitor conformational states and dynamics of hAgo2 and hAgo2-RNA complexes in solution that remained elusive so far. We observe dynamic anchoring and release of the guide’s 3’-end from the PAZ domain during the stepwise target loading process even with a fully complementary target. We find differences in structure and dynamic behavior between partially and fully paired canonical hAgo2-guide/target complexes and the miRNA processing complex formed by hAgo2 and pre-miRNA451. Furthermore, we detect a hitherto unknown conformation of hAgo2-guide/target complexes that poises them for target-directed miRNA degradation. Taken together, our results show how the conformational flexibility of hAgo2-RNA complexes determines function and the fate of the ribonucleoprotein particle.

Single-molecule FRET measurements provide detailed insights into the conformational states and dynamics of human Argonaute 2 that are required for its function at the core of the eukaryotic RNA silencing pathway.

MiR-144-3p inhibits the proliferation and metastasis of lung cancer A549 cells via targeting HGF

Aim

MicroRNAs have been confirmed as vital regulators in gene expression, which could affect multiple cancer cell biological behaviors. This study aims to elucidate the molecular mechanism of miR-144-3p in lung cancer cellular proliferation and metastasis.

Methods

MiR-144-3p expression in lung cancer tissues and cell lines was detected by qRT-PCR. HGF was predicted as the target gene of miR-144-3p using TargetScan and dual luciferase reporter assay. Immunohistochemistry and qRT-PCR were used to explore the impacts of HCF on lung cancer tissues and cell lines. Impacts of miR-144-3p and HGF on cancer cellular proliferation, migration and invasion were elucidated by CCK-8, Flow cytometry, Transwell invasion and Wound-healing assay. Moreover, nude mouse xenograft model was established to evaluate the effects of miR-144-3p on lung cancer cells.

Results

MiR-144-3p exhibited a reduction in both lung cancer tissues and cell lines. HGF was a direct target of miR-144-3p. In contrast to the miR-144-3p expression level, HGF showed a higher level in lung cancer tissues and cell lines. Overexpression miR-144-3p suppressed A549 and NCI-H1299 cell proliferation and metastasis, whereas this was reversed by HGF. MiR-144-3p exhibited an inhibitory effect on A549 cell-induced tumor growth of nude mice.

Conclusions

This study reveals miR-144-3p/HGF axis may be involved in the suppression of lung cancer cellular proliferation and development, and miR-144-3p may function as a potential therapeutic target in lung cancer treatment in the future.

A microRNA Cluster Controls Fat Cell Differentiation and Adipose Tissue Expansion By Regulating SNCG

The H19X-encoded miR-424(322)/503 cluster regulates multiple cellular functions. Here, it is reported for the first time that it is also a critical linchpin of fat mass expansion. Deletion of this miRNA cluster in mice results in obesity, while increasing the pool of early adipocyte progenitors and hypertrophied adipocytes. Complementary loss and gain of function experiments and RNA sequencing demonstrate that miR-424(322)/503 regulates a conserved genetic program involved in the differentiation and commitment of white adipocytes. Mechanistically, it is demonstrated that miR-424(322)/503 targets γ-Synuclein (SNCG), a factor that mediates this program rearrangement by controlling metabolic functions in fat cells, allowing adipocyte differentiation and adipose tissue enlargement. Accordingly, diminished miR-424(322) in mice and obese humans co-segregate with increased SNCG in fat and peripheral blood as mutually exclusive features of obesity, being normalized upon weight loss. The data unveil a previously unknown regulatory mechanism of fat mass expansion tightly controlled by the miR-424(322)/503 through SNCG.

miR-424-5p overexpression inhibits LPS-stimulated inflammatory response in bovine endometrial epithelial cells by targeting IRAK2

Endometritis is inflammation of endometrium due to various factors and is a common cause of infertility. Several remedies used for endometritis like antibiotics, hormones, and herbs. Studies confirm that microRNAs play a significant role in various inflammatory diseases. However, the role of miR-424-5p in endometritis is not clear. In our study, histopathology, real-time quantitative polymerase chain reaction, Western blot analysis, immunofluorescence, ELISA, and dual-luciferase reporter assay were used to elucidate the effect of miR-424-5p in lipopolysaccharide (LPS)-primed inflammatory response in bovine endometrial epithelial cells (BEECs) and clarify the potential mechanism. Our results revealed that miR-424-5p mimics noticeably decrease the production of proinflammatory cytokines (IL-1β, IL-6, and TNF-α), while miR-424-5p inhibitors have inverse effects in BEECs. Moreover, overexpression of miR-424-5p on BEECs cells also suppressed NF-κB p65 activation. Afterwards, we verified that miR-424-5p inhibited Interleukin 1 Receptor Associated Kinase 2 (IRAK2) expression by binding to the 3'-UTR of IRAK2 mRNA. Further, co-transfection of miR-424-5p inhibitors and siRNA-IRAK2 revealed that negative regulation of miR-424-5p on LPS-induced inflammatory response in BEECs was mediated by IRAK2.Mutually, miR-424-5p pharmacologic stabilization represents an entirely unique medical aid for cow endometritis and other inflammation-related diseases.

miR-424/503 modulates Wnt/β-catenin signaling in the mammary epithelium by targeting LRP6

During the female lifetime, the expansion of the epithelium dictated by the ovarian cycles is supported by a transient increase in the mammary epithelial stem cell population (MaSCs). Notably, activation of Wnt/β-catenin signaling is an important trigger for MaSC expansion. Here, we report that the miR-424/503 cluster is a modulator of canonical Wnt signaling in the mammary epithelium. We show that mammary tumors of miR-424(322)/503-depleted mice exhibit activated Wnt/β-catenin signaling. Importantly, we show a strong association between miR-424/503 deletion and breast cancers with high levels of Wnt/β-catenin signaling. Moreover, miR-424/503 cluster is required for Wnt-mediated MaSC expansion induced by the ovarian cycles. Lastly, we show that miR-424/503 exerts its function by targeting two binding sites at the 3'UTR of the LRP6 co-receptor and reducing its expression. These results unveil an unknown link between the miR-424/503, regulation of Wnt signaling, MaSC fate, and tumorigenesis.

H19X-encoded miR-322(424)/miR-503 regulates muscle mass by targeting translation initiation factors

BACKGROUND

Skeletal muscle atrophy is a debilitating complication of many chronic diseases, disuse conditions, and ageing. Genome-wide gene expression analyses have identified that elevated levels of microRNAs encoded by the H19X locus are among the most significant changes in skeletal muscles in a wide scope of human cachectic conditions. We have previously reported that the H19X locus is important for the establishment of striated muscle fate during embryogenesis. However, the role of H19X-encoded microRNAs in regulating skeletal mass in adults is unknown.

METHODS

We have created a transgenic mouse strain in which ectopic expression of miR-322/miR-503 is driven by the skeletal muscle-specific muscle creatine kinase promoter. We also used an H19X mutant mouse strain in which transcription from the locus is interrupted by a gene trap. Animal phenotypes were analysed by standard histological methods. Underlying mechanisms were explored by using transcriptome profiling and validated in the two animal models and cultured myotubes.

RESULTS

Our results demonstrate that the levels of H19X microRNAs are inversely related to postnatal skeletal muscle growth. Targeted overexpression of miR-322/miR-503 impeded skeletal muscle growth. The weight of gastrocnemius muscles of transgenic mice was only 54.5% of the counterparts of wild-type littermates. By contrast, interruption of transcription from the H19X locus stimulates postnatal muscle growth by 14.4-14.9% and attenuates the loss of skeletal muscle mass in response to starvation by 12.8-21.0%. Impeded muscle growth was not caused by impaired IGF1/AKT/mTOR signalling or a hyperactive ubiquitin-proteasome system, instead accompanied by markedly dropped abundance of translation initiation factors in transgenic mice. miR-322/miR-503 directly targets eIF4E, eIF4G1, eIF4B, eIF2B5, and eIF3M.

CONCLUSIONS

Our study illustrates a novel pathway wherein H19X microRNAs regulate skeletal muscle growth and atrophy through regulating the abundance of translation initiation factors, thereby protein synthesis. The study highlights how translation initiation factors lie at the crux of multiple signalling pathways that control skeletal muscle mass.

Screening by deep sequencing reveals mediators of microRNA tailing in C. elegans

microRNAs are frequently modified by addition of untemplated nucleotides to the 3' end, but the role of this tailing is often unclear. Here we characterize the prevalence and functional consequences of microRNA tailing in vivo, using Caenorhabditis elegans. MicroRNA tailing in C. elegans consists mostly of mono-uridylation of mature microRNA species, with rarer mono-adenylation which is likely added to microRNA precursors. Through a targeted RNAi screen, we discover that the TUT4/TUT7 gene family member CID-1/CDE-1/PUP-1 is required for uridylation, whereas the GLD2 gene family member F31C3.2-here named GLD-2-related 2 (GLDR-2)-is required for adenylation. Thus, the TUT4/TUT7 and GLD2 gene families have broadly conserved roles in miRNA modification. We specifically examine the role of tailing in microRNA turnover. We determine half-lives of microRNAs after acute inactivation of microRNA biogenesis, revealing that half-lives are generally long (median = 20.7 h), as observed in other systems. Although we observe that the proportion of tailed species increases over time after biogenesis, disrupting tailing does not alter microRNA decay. Thus, tailing is not a global regulator of decay in C. elegans. Nonetheless, by identifying the responsible enzymes, this study lays the groundwork to explore whether tailing plays more specialized context- or miRNA-specific regulatory roles.

Learning noncoding RNA biology from viruses

Insights into interactions between viral factors and the cellular machinery usually lead to discoveries concerning host cell biology. Thus, the gene expression field has historically relied on viral model systems to discover mechanisms underlying different cellular processes. In recent years, the functional characterization of the small nuclear noncoding RNAs expressed by the oncogenic Herpesvirus saimiri, called HSURs, resulted in the discovery of two mechanisms for the regulation of gene expression. HSUR1 and HSUR2 associate with host microRNAs, which are small noncoding RNAs that broadly regulate gene expression by binding to messenger RNAs. HSUR1 provided the first example of a process known as target-directed miRNA degradation that operates in cells to regulate miRNA populations. HSUR2 functions as a miRNA adaptor, uncovering an entirely new, indirect mechanism by which miRNAs can inhibit mRNA function. Here, I review the path that led to these discoveries and their implications and postulate new exciting questions about the functions of these fascinating viral noncoding RNAs.

The roles of microRNAs in mouse development

Hundreds of microRNAs (miRNAs) are expressed in distinct spatial and temporal patterns during embryonic and postnatal mouse development. The loss of all miRNAs through the deletion of critical miRNA biogenesis factors results in early lethality. The function of each miRNA stems from their cumulative negative regulation of multiple mRNA targets expressed in a particular cell type. During development, miRNAs often coordinate the timing and direction of cell fate transitions. In adults, miRNAs frequently contribute to organismal fitness through homeostatic roles in physiology. Here, we review how the recent dissection of miRNA-knockout phenotypes in mice as well as advances related to their targets, dosage, and interactions have collectively informed our understanding of the roles of miRNAs in mammalian development and adaptive responses.

MicroRNAs and thyroid hormone action

MicroRNAs (miRNAs) are small noncoding RNAs that post-transcriptionally repress gene expression by binding generally to the 3'-untranslated regions of their target mRNAs. miRNAs regulate a large fraction of the genome, playing a key role in most physiological and pathological processes. The thyroid hormones (T4 and T3) are major regulators of development, metabolism and cell growth. The thyroid hormones (THs) are synthetized in the thyroid gland and enter the cells through transporter proteins. In the cells, T4 and T3 are metabolized by deiodinase enzymes and bind to nuclear receptors (TRs), which have a higher affinity by T3. TRs act as hormone dependent transcription factors by binding to thyroid hormone response elements (TREs) in the target genes and recruiting transcriptional coregulators. There is increasing evidence that a variety of miRNAs target deiodinases and the receptor, thus regulating TH signaling is different tissues. In turn, the THs have been shown to modulate the expression of specific miRNAs and their mRNA targets in different cell types and organs. In many cases, the existence of TREs in the regulatory regions of these miRNAs has been identified, and the hormone bound receptors transcriptionally regulate expression of these molecules. Changes in the levels of miRNAs have been demonstrated to mediate some of the important actions of the THs in processes such as muscle and heart function, lipid liver metabolism or skin physiology. In addition, miRNA regulation is involved in the effects of TRs on cell proliferation and cancer.

Coordinated regulation of miR-27 by insulin/CREB/Hippo contributes to insulin resistance

MicroRNA-27 is a critical non-coding metabolic gene that is often aberrantly overexpressed in non-alcoholic fatty livers (NAFLD). However, the pathogenic role of miR-27 in NAFLD remains unknown. In this study, we attempted to identify the mechanism by which miR-27 was regulated in the context of insulin resistance, a predisposed metabolic disorder in NAFLD. Our data from cell culture and animal studies showed that insulin, CREB, and Hippo signalings coordinately regulated miR-27. First, miR-27 was upregulated in palmitate-treated cells and high fat diet-fed mouse livers, which exhibited insulin resistance and CREB overexpression. Second, miR-27 peaked in the mouse liver at the post-absorptive phase when CREB activity was increased. Also, miR-27 was increased rapidly in cell lines when CREB was deactivated by insulin treatment. Third, miR-27 was decreased in cultured cells when CREB was downregulated by siRNA or metformin treatment. In contrast, Forskolin-mediated activation of CREB promoted miR-27 expression. Fourth, Hippo signaling repressed miR-27 in a CREB-independent manner: miR-27 was reduced in cells at full confluence but was inhibited in cells transfected with siRNA against Lats2 and Nf2, which were two positive regulators of Hippo signaling. Lastly, bioinformatics and luciferase assay showed that miR-27 inhibited Akt phosphorylation by targeting Pdpk1 and Pik3r1. Overexpression of miR-27 impaired Akt phosphorylation in cell lines and primary mouse hepatocytes upon insulin stimulation. In conclusion, our data suggest that insulin, CREB, and Hippo signalings contribute to aberrant miR-27 overexpression and eventually lead to insulin resistance in NAFLD.

A ubiquitin ligase mediates target-directed microRNA decay independently of tailing and trimming

MicroRNAs (miRNAs) act in concert with Argonaute (AGO) proteins to repress target messenger RNAs. After AGO loading, miRNAs generally exhibit slow turnover. An important exception occurs when miRNAs encounter highly complementary targets, which can trigger a process called target-directed miRNA degradation (TDMD). During TDMD, miRNAs undergo tailing and trimming, suggesting that this is an important step in the decay mechanism. We identified a cullin-RING ubiquitin ligase (CRL), containing the substrate adaptor ZSWIM8, that mediates TDMD. The ZSWIM8 CRL interacts with AGO proteins, promotes TDMD in a tailing and trimming-independent manner, and regulates miRNA expression in multiple cell types. These findings suggest a model in which the ZSWIM8 ubiquitin ligase mediates TDMD by directing proteasomal decay of miRNA-containing complexes engaged with highly complementary targets.

Influence of microRNAs and exosomes in muscle health and diseases

microRNAs are short, (18-22 nt) non-coding RNAs involved in important cellular processes due to their ability to regulate gene expression at the post-transcriptional level. Exosomes are small (50-200 nm) extracellular vesicles, naturally secreted from a variety of living cells and are believed to mediate cell-cell communication through multiple mechanisms, including uptake in destination cells. Circulating microRNAs and exosome-derived microRNAs can have key roles in regulating muscle cell development and differentiation. Several microRNAs are highly expressed in muscle and their regulation is important for myocyte homeostasis. Changes in muscle associated microRNA expression are associated with muscular diseases including muscular dystrophies, inflammatory myopathies, and congenital myopathies. In this review, we aim to highlight the biology of microRNAs and exosomes as well as their roles in muscle health and diseases. We also discuss the potential crosstalk between skeletal and cardiac muscle through exosomes and their contents.

The ZSWIM8 ubiquitin ligase mediates target-directed microRNA degradation

MicroRNAs (miRNAs) associate with Argonaute (AGO) proteins to direct widespread posttranscriptional gene repression. Although association with AGO typically protects miRNAs from nucleases, extensive pairing to some unusual target RNAs can trigger miRNA degradation. We found that this target-directed miRNA degradation (TDMD) required the ZSWIM8 Cullin-RING E3 ubiquitin ligase. This and other findings support a mechanistic model of TDMD in which target-directed proteolysis of AGO by the ubiquitin-proteasome pathway exposes the miRNA for degradation. Moreover, loss-of-function studies indicated that the ZSWIM8 Cullin-RING ligase accelerates degradation of numerous miRNAs in cells of mammals, flies, and nematodes, thereby specifying the half-lives of most short-lived miRNAs. These results elucidate the mechanism of TDMD and expand its inferred role in shaping miRNA levels in bilaterian animals.

Mechanistic Actions of microRNAs in Diabetic Wound Healing

Wound healing is a complex biological process that is impaired under diabetes conditions. Chronic non-healing wounds in diabetes are some of the most expensive healthcare expenditures worldwide. Early diagnosis and efficacious treatment strategies are needed. microRNAs (miRNAs), a class of 18-25 nucleotide long RNAs, are important regulatory molecules involved in gene expression regulation and in the repression of translation, controlling protein expression in health and disease. Recently, miRNAs have emerged as critical players in impaired wound healing and could be targets for potential therapies for non-healing wounds. Here, we review and discuss the mechanistic background of miRNA actions in chronic wounds that can shed the light on their utilization as specific wound healing biomarkers.

The Oncogenic Kaposi's Sarcoma-Associated Herpesvirus Encodes a Mimic of the Tumor-Suppressive miR-15/16 miRNA Family

Many tumor viruses encode oncogenes of cellular origin. Here, we report an oncoviral mimic of a cellular tumor suppressor. The Kaposi’s sarcoma-associated herpesvirus (KSHV) microRNA (miRNA) miR-K6-5p shares sequence similarity to the tumor-suppressive cellular miR-15/16 miRNA family. We show that miR-K6-5p inhibits cell cycle progression, a hallmark function of miR-16. miR-K6-5p regulates conserved miR-15/16 family miRNA targets, including many cell cycle regulators. Inhibition of miR-K6-5p in KSHV-transformed B cells confers a significant growth advantage. Altogether, our data show that KSHV encodes a functional mimic of miR-15/16 family miRNAs. While it is exceedingly well established that oncogenic viruses encode oncogenes of cellular origin, this is an unusual example of an oncogenic virus that encodes a viral mimic of a cellular tumor suppressor. Encoding a tumor-suppressive miRNA could help KSHV balance viral oncogene expression and thereby avoid severe pathogenesis in the healthy host.

Morrison et al. report that the tumor virus KSHV encodes a mimic of a cellular tumor suppressor. KSHV miR-K6-5p phenocopies miR-16-induced cell cycle inhibition, shares mRNA targets and binding sites with miR-16, and negatively regulates proliferation in KSHV-infected cells.

MicroRNAs Responding to Space Radiation

High-energy and high-atom-number (HZE) space radiation poses an inevitable potential threat to astronauts on deep space exploration missions. Compared with low-LET radiation, high-energy and high-LET radiation in space is more efficient in inducing clustered DNA damage with more serious biological consequences, such as carcinogenesis, central nervous system injury and degenerative disease. Space radiation also causes epigenetic changes in addition to inducing damage at the DNA level. Considering the important roles of microRNAs in the regulation of biological responses of radiation, we systematically reviewed both expression profiling and functional studies relating to microRNAs responding to space radiation as well as to space compound environment. Finally, the directions for improvement of the research related to microRNAs responding to space radiation are proposed. A better understanding of the functions and underlying mechanisms of the microRNAs responding to space radiation is of significance to both space radiation risk assessment and therapy development for lesions caused by space radiation.

MicroRNA‑15b‑5p exerts its tumor repressive role via targeting GDI2: A novel insight into the pathogenesis of thyroid carcinoma

Thyroid carcinoma (THCA) is a malignant tumor of the endocrine system. Previous studies have revealed the vital roles of microRNAs (miRNAs/miRs) in THCA procession. The present study aimed to explore the effects of miR-15b-5p on the progression of THCA and its targeting mechanism. The data of THCA and healthy samples were firstly collected from starbase2.0 and used to analyze the relationship of miR-15b-5p with THCA. Dual-luciferase assay was performed to detect the direct interaction between miR-15b-5p and the predicted target gene GDP dissociation inhibitor 2 (GDI2). The effects of miR-15b-5p and GDI2 on the overall survival of patients with THCA were analyzed using Kaplan-Meier analysis with log rank test. Cell Counting Kit-8 and Transwell assays were conducted to assess the impacts of miR-15b-5p and GDI2 on the proliferation and invasion of THCA cells. Reverse transcription-quantitative PCR and western blot analyses were performed to analyze the expression levels of the related miRNAs and proteins, respectively. miR-15b-5p was found to be downregulated both in THCA tissues and cells, and the low expression of miR-15b-5p was associated with the short overall survival time of patients. Moreover, the upregulation or downregulation of miR-15b-5p could inhibit or enhance the proliferation and invasion of THCA cells, respectively. miR-15b-5p reduced the protein expression levels of matrix metalloproteinase (MMP)2 and MMP9, which were related to cell invasion. Furthermore, GDI2, which was enhanced in THCA and related to the poor prognosis of patients with THCA, was identified as the target gene of miR-15b-5p and negatively regulated by miR-15b-5p. Additional experiments demonstrated that GDI2 overexpression could significantly reduce the antitumor effect of miR-15b-5p and its inhibitory action on the expression levels of MMP2 and MMP9. Thus, the results indicated a potential tumor suppressive role of miR-15b-5p in THCA, which was mainly exerted by targeting GDI2 and modulating MMP2 and MMP9. These findings will increase the understanding on the pathogenesis of THCA and provide novel candidates for THCA therapy.

miR-15/107 microRNA Gene Group: Characteristics and Functional Implications in Cancer

The miR-15/107 group of microRNAs (miRNAs) encloses 10 annotated human members and is defined based on the presence of the sequence AGCAGC near the mature miRNAs’ 5′ end. Members of the miR-15/107 group expressed in humans are highly evolutionarily conserved, and seven of these miRNAs are widespread in vertebrate species. Contrary to the majority of miRNAs, which recognize complementary sequences on the 3′UTR region, some members of the miR-15/107 group are peculiarly characterized by the ability to target the coding sequence (CDS) of their target mRNAs, inhibiting translation without strongly affecting their mRNA levels. There is compelling evidence that different members of the miR-15/107 group regulate overlapping lists of mRNA targets but also show target specificity. The ubiquitously expressed miR-15/107 gene group controls several human cellular pathways, such as proliferation, angiogenesis, and lipid metabolism, and might be altered in various diseases, such as neurodegenerative diseases and cancer. Intriguingly, despite sharing the same seed sequence, different members of this family of miRNAs may behave as oncomiRs or as tumor suppressor miRNAs in the context of cancer cells. This review discusses the regulation and functional contribution of the miR-15/107 group to the control of gene expression. Moreover, we particularly focus on the contribution of specific miR-15/107 group members as tumor suppressors in breast cancer, reviewing literature reporting their ability to function as major controllers of a variety of cell pathways and to act as powerful biomarkers in this disease.

How Complementary Targets Expose the microRNA 3' End for Tailing and Trimming during Target-Directed microRNA Degradation

microRNAs (miRNAs) are crucial for posttranscriptional regulation of messenger RNAs. "Classical" miRNA targets predominantly interact with the miRNA seed sequence located near the miRNA 5' end. Interestingly, certain transcripts that exhibit extensive complementarity to the miRNAs 3' region, instead of being subjected to regulation, induce miRNA decay in a process termed target-directed miRNA degradation (TDMD). Here, we review recent advances in understanding the molecular mechanisms of TDMD. Specifically, we discuss how extensive miRNA complementarity to TDMD-inducing targets results in displacement of the miRNA 3' end from its protective pocket in the Argonaute protein. Unprotected miRNA 3' ends are then available for enzymatic attack by still-unidentified cellular enzymes. Identification of these cellular enzymes and discovery of additional TDMD-inducing transcripts are subjects for future research.

Global analyses of the dynamics of mammalian microRNA metabolism

Rates of production and degradation together specify microRNA (miRNA) abundance and dynamics. Here, we used approach-to-steady-state metabolic labeling to assess these rates for 176 miRNAs in contact-inhibited mouse embryonic fibroblasts (MEFs), 182 miRNAs in dividing MEFs, and 127 miRNAs in mouse embryonic stem cells (mESCs). MicroRNA duplexes, each comprising a mature miRNA and its passenger strand, are produced at rates as fast as 110 ± 50 copies/cell/min, which exceeds rates reported for any mRNAs. These duplexes are rapidly loaded into Argonaute, with <30 min typically required for duplex loading and silencing-complex maturation. Within Argonaute, guide strands have stabilities that vary by 100-fold. Half-lives also vary globally between cell lines, with median values ranging from 11 to 34 h in mESCs and contact-inhibited MEFs, respectively. Moreover, relative half-lives for individual miRNAs vary between cell types, implying the influence of cell-specific factors in dictating turnover rate. The apparent influence of miRNA regions most important for targeting, together with the effect of one target on miR-7 accumulation, suggest that targets fulfill this role. Analysis of the tailing and trimming of miRNA 3' termini showed that the flux was typically greatest through the isoform tailed with a single uridine, although changes in this flux did not correspond to changes in stability, which suggested that the processes of tailing and trimming might be independent from that of decay. Together, these results establish a framework for describing the dynamics and regulation of miRNAs throughout their life cycle.

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.

Time-Resolved Small RNA Sequencing Unravels the Molecular Principles of MicroRNA Homeostasis

Argonaute-bound microRNAs silence mRNA expression in a dynamic and regulated manner to control organismal development, physiology, and disease. We employed metabolic small RNA sequencing for a comprehensive view on intracellular microRNA kinetics in Drosophila. Based on absolute rate of biogenesis and decay, microRNAs rank among the fastest produced and longest-lived cellular transcripts, disposing up to 105 copies per cell at steady-state. Mature microRNAs are produced within minutes, revealing tight intracellular coupling of biogenesis that is selectively disrupted by pre-miRNA-uridylation. Control over Argonaute protein homeostasis generates a kinetic bottleneck that cooperates with non-coding RNA surveillance to ensure faithful microRNA loading. Finally, regulated small RNA decay enables the selective rapid turnover of Ago1-bound microRNAs, but not of Ago2-bound small interfering RNAs (siRNAs), reflecting key differences in the robustness of small RNA silencing pathways. Time-resolved small RNA sequencing opens new experimental avenues to deconvolute the timescales, molecular features, and regulation of small RNA silencing pathways in living cells.

miRBaseMiner, a tool for investigating miRBase content

microRNAs are small non-coding RNA molecules playing a central role in gene regulation. miRBase is the standard reference source for analysis and interpretation of experimental studies. However, the richness and complexity of the annotation is often underappreciated by users. Moreover, even for experienced users, the size of the resource can make it difficult to explore annotation to determine features such as species coverage, the impact of specific characteristics and changes between successive releases. A further consideration is that each new miRBase release contains entries that have had limited review and which may subsequently be removed in a future release to ensure the quality of annotation. To aid the miRBase user, we developed a software tool, miRBaseMiner, for investigating miRBase annotation and generating custom annotation sets. We apply the tool to characterize each release from v9.2 to v22 to examine how annotation has changed across releases and highlight some of the annotation features that users should keep in mind when using for miRBase for data analysis. These include: (1) entries with identical or very similar sequences; (2) entries with multiple annotated genome locations; (3) hairpin precursor entries with extremely low-estimated minimum free energy; (4) entries possessing reverse complementary; (5) entries with 3ʹ poly(A) ends. As each of these factors can impact the identification of dysregulated features and subsequent clinical or biological conclusions, miRBaseMiner is a valuable resource for any user using miRBase as a reference source.

Methylation-mediated repression of MiR-424/503 cluster promotes proliferation and migration of ovarian cancer cells through targeting the hub gene KIF23

Ovarian cancer is one type of gynecological malignancies with extremely high lethal rate. Abnormal proliferation and metastasis are regarded to play important roles in patients' death, whereas we know little about the underlying molecular mechanisms. Under this circumstance, our current study aims to investigate the role of hub genes in ovarian cancer. Bioinformatics analysis of the data from GEO and analyses of ovarian cancer samples were performed. Then, the results showed that KIF23, a hub gene, was mainly related to cell cycle and positively associated with poor prognosis. Meanwhile, both miR-424-5p and miR-503-5p directly targeted to 3'UTR of KIF23 to suppress the expression of KIF23 and inhibit ovarian cancer cell proliferation and migration. Furthermore, we discovered that miR-424/503 was epigenetically repressed by hypermethylation in the promoter regions, which directly modulated the expression of KIF23 to improve the oncogenic performance of cancer cells in vitro. Together, our research certifies that miR-424/503 cluster is silenced by DNA hypermethylation, which promotes the expression of KIF23, thereby regulating the proliferation and migration of ovarian cancer cells. Interposing this process might be a novel approach in cancer therapy.

MicroRNA-15b-5p Predicts Locoregional Relapse in Head and Neck Carcinoma Patients Treated With Intensity-modulated Radiotherapy

BACKGROUND/AIM

Head and neck cancers are a heterogenous group of epithelial tumors represented mainly by squamous cell carcinomas (HNSCC), which are the sixth most common type of cancer worldwide. Surgery together with radiotherapy (RT) is among the basic treatment modalities for most HNSCC patients. Various biomarkers aiming to predict patients' response to RT are currently investigated. The reason behind this effort is, on one hand, to distinguish radioresistant patients that show weak benefit from RT and, on the other hand, reduce the ionizing radiation dose in less aggressive radiosensitive HNSCC with possibly less acute or late toxicity.

MATERIALS AND METHODS

A total of 94 HNSCC patients treated by definitive intensity-modulated radiotherapy were included in our retrospective study. We used a global expression analysis of microRNAs (miRNAs) in 43 tumor samples and validated a series of selected miRNAs in an independent set of 51 tumors.

RESULTS

We identified miR-15b-5p to be differentially expressed between patients with short and long time of locoregional control (LRC). Kaplan-Meier analysis confirmed that HNSCC patients with higher expression of miR-15b-5p reach a significantly longer locoregional relapse-free survival compared to patients expressing low levels. Finally, multivariable Cox regression analysis revealed that miR-15b-5p is an independent predictive biomarker of LRC in HNSCC patients (HR=0.25; 95% CI=0.05-0.78; p<0.016).

CONCLUSION

miR-15b-5p represents a potentially helpful biomarker for individualized treatment decisions concerning the management of HNSCC patients.

Functional Screening Identifies MicroRNAs as Multi-Cellular Regulators of Heart Failure

Heart failure (HF) is the leading cause of death in the Western world. Pathophysiological processes underlying HF development, including cardiac hypertrophy, fibrosis and inflammation, are controlled by specific microRNAs (miRNAs). Whereas most studies investigate miRNA function in one particular cardiac cell type, their multicellular function is poorly investigated. The present study probed 194 miRNAs -differentially expressed in cardiac inflammatory disease - for regulating cardiomyocyte size, cardiac fibroblasts collagen content, and macrophage polarization. Of the tested miRNAs, 13%, 26%, and 41% modulated cardiomyocyte size, fibroblast collagen production, and macrophage polarization, respectively. Seventeen miRNAs affected all three cellular processes, including miRNAs with established (miR-210) and unknown roles in cardiac pathophysiology (miR-145-3p). These miRNAs with a multi-cellular function commonly target various genes. In-depth analysis in vitro of previously unstudied miRNAs revealed that the observed phenotypical alterations concurred with changes in transcript and protein levels of hypertrophy-, fibrosis- and inflammation-related genes. MiR-145-3p and miR-891a-3p were identified to regulate the fibrotic response, whereas miR-223-3p, miR-486-3p, and miR-488-5p modulated macrophage activation and polarisation. In conclusion, miRNAs are multi-cellular regulators of different cellular processes underlying cardiac disease. We identified previously undescribed roles of miRNAs in hypertrophy, fibrosis, and inflammation, and attribute new cellular effects to various well-known miRNAs.

H19X-encoded miR-424(322)/-503 cluster: emerging roles in cell differentiation, proliferation, plasticity and metabolism

miR-424(322)/-503 are mammal-specific members of the extended miR-15/107 microRNA family. They form a co-expression network with the imprinted lncRNA H19 in tetrapods. miR-424(322)/-503 regulate fundamental cellular processes including cell cycle, epithelial-to-mesenchymal transition, hypoxia and other stress response. They control tissue differentiation (cardiomyocyte, skeletal muscle, monocyte) and remodeling (mammary gland involution), and paradoxically participate in tumor initiation and progression. Expression of miR-424(322)/-503 is governed by unique mechanisms involving sex hormones. Here, we summarize current literature and provide a primer for future endeavors.