Discovery and function of transfer RNA-derived fragments and their role in disease

Co-targeting of glial activation and inflammation by tsRNA-Gln-i-0095 for treating retinal ischemic pathologies

Ischemic retinopathies are the major causes of blindness, yet effective early-stage treatments remain limited due to an incomplete understanding of the underlying molecular mechanisms. Significant changes in gene expression often precede structural and functional alterations. Transfer RNA (tRNA)-derived small RNAs (tsRNAs) are emerging as novel gene regulators, involved in various biological processes and human diseases. In this study, tsRNA-Gln-i-0095 was identified as a novel regulator, which was significantly upregulated in retinal ischemia/reperfusion (I/R) injury. Reducing the levels of tsRNA-Gln-i-0095 suppressed reactive gliosis, lowered inflammatory cytokine levels, and protected retinal ganglion cells from I/R injury. These effects led to reduced structural and functional damage, inhibited glial activation and inflammation, and enhanced neuronal function. Mechanistically, tsRNA-Gln-i-0095 downregulated the expression of NFIA and TGFBR2 through a miRNA-like mechanism. Collectively, this study highlights the potential of targeting tsRNA-Gln-i-0095 as a novel therapeutic approach to reduce retinal I/R injury and preserve visual function.

Unravelling tRNA fragments in DENV pathogenesis: Insights from RNA sequencing

Small non-coding RNAs (sncRNAs) derived from tRNAs are known as tRNA-derived small RNAs (tsRNAs). These tsRNAs are further categorized into tRNA-derived fragments (tRFs) and tRNA halves (tiRNAs), which play significant roles in the various molecular mechanisms underlying certain human diseases. However, the generation of tsRNAs and their potential roles during Dengue virus (DENV) infection is not yet known. Here, we performed small RNA sequencing to identify the generation and alterations in tsRNAs expression profiles of DENV-infected Huh7 cells. Upon DENV infection, tRNA fragmentation was found to be increased. We identified a significant number of differentially expressed tsRNAs during DENV infection. Interestingly, the 3'tRF population showed upregulation, while the i-tRF population exhibited downregulation. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis was performed to analyze the impact of differentially expressed tsRNAs on DENV pathogenesis. Our results suggest that differentially expressed tsRNAs are involved in transcriptional regulation via RNA polymerase II promoter and metabolic pathways. Overall, our study contributes significantly to our understanding of the roles played by tsRNAs in the complex dynamics of DENV infection.

tiRNA-Gly-GCC-001 in major depressive disorder: Promising diagnostic and therapeutic biomarker

BACKGROUND AND PURPOSE

In major depressive disorder (MDD), exploration of biomarkers will be helpful in diagnosing the disorder as well as in choosing a treatment and predicting the treatment response. Currently, tRNA-derived small ribonucleic acids (tsRNAs) have been established as promising non-invasive biomarker candidates that may enable a more reliable diagnosis or monitoring of various diseases. Herein, we aimed to explore tsRNA expression together with functional activities in MDD development.

EXPERIMENTAL APPROACH

Serum samples were obtained from patients with MDD and healthy controls, and small RNA sequencing (RNA-Seq) was used to profile tsRNA expression. Dysregulated tsRNAs in MDD were validated by quantitative real-time polymerase chain reaction (qRT-PCR). The diagnostic utility of specific tsRNAs and the expression of these tsRNAs after antidepressant treatment were analysed.

KEY RESULTS

In total, 38 tsRNAs were significantly differentially expressed in MDD samples relative to healthy individuals (34 up-regulated and 4 down-regulated). qRT-PCR was used to validate the expression of six tsRNAs that were up-regulated in MDD (tiRNA-1:20-chrM.Ser-GCT, tiRNA-1:33-Gly-GCC-1, tRF-1:22-chrM.Ser-GCT, tRF-1:31-Ala-AGC-4-M6, tRF-1:31-Pro-TGG-2 and tRF-1:32-chrM.Gln-TTG). Interestingly, serum tiRNA-Gly-GCC-001 levels exhibited an area under the ROC curve of 0.844. Moreover, tiRNA-Gly-GCC-001 is predicted to suppress brain-derived neurotrophic factor (BDNF) expression. Furthermore, significant tiRNA-Gly-GCC-001 down-regulation was evident following an 8-week treatment course and served as a promising baseline predictor of patient response to antidepressant therapy.

CONCLUSION AND IMPLICATIONS

Our current work reports for the first time that tiRNA-Gly-GCC-001 is a promising MDD biomarker candidate that can predict patient responses to antidepressant therapy.

Structural determinants for tRNA selective cleavage by RNase 2/EDN

tRNA-derived fragments (tRFs) have emerged as key players of immunoregulation. Some RNase A superfamily members participate in the shaping of the tRFs population. By comparing wild-type and knockout macrophage cell lines, our previous work revealed that RNase 2 can selectively cleave tRNAs. Here, we confirm the in vitro protein cleavage pattern by screening of synthetic tRNAs, single-mutant variants, and anticodon-loop DNA/RNA hairpins. By sequencing of tRF products, we identified the cleavage selectivity of recombinant RNase 2 with base specificity at B1 (U/C) and B2 (A) sites, consistent with a previous cellular study. Lastly, protein-hairpin complexes were predicted by MD simulations. Results reveal the contribution of the α1, loop 3 and loop 4, and β6 RNase 2 regions, where residues Arg36/Asn39/Gln40/Asn65/Arg68/Arg132 provide interactions, spanning from P-1 to P2 sites that are essential for anticodon loop recognition. Knowledge of RNase 2-specific tRFs generation might guide new therapeutic approaches for infectious and immune-related diseases.

tRFtarget 2.0: expanding the targetome landscape of transfer RNA-derived fragments

tRFtarget 1.0 (http://trftarget.net/) is a platform consolidating both computationally predicted and experimentally validated binding sites between transfer RNA-derived fragments (tRFs) and target genes (or transcripts) across multiple organisms. Here, we introduce a newly released version of tRFtarget 2.0, in which we integrated 6 additional tRF sources, resulting in a comprehensive collection of 2614 high-quality tRF sequences spanning across 9 species, including 1944 Homo sapiens tRFs and one newly incorporated species Rattus norvegicus. We also expanded target genes by including ribosomal RNAs, long non-coding RNAs, and coding genes >50 kb in length. The predicted binding sites have surged up to approximately 6 billion, a 20.5-fold increase than that in tRFtarget 1.0. The manually curated publications relevant to tRF targets have increased to 400 and the gene-level experimental evidence has risen to 232. tRFtarget 2.0 introduces several new features, including a web-based tool that identifies potential binding sites of tRFs in user's own datasets, integration of standardized tRF IDs, and inclusion of external links to contents within the database. Additionally, we enhanced website framework and user interface. With these improvements, tRFtarget 2.0 is more user-friendly, providing researchers a streamlined and comprehensive platform to accelerate their research progress.

Sex-specific declines in cholinergic-targeting tRNA fragments in the nucleus accumbens in Alzheimer's disease

INTRODUCTION

Females with Alzheimer's disease (AD) suffer accelerated dementia and loss of cholinergic neurons compared to males, but the underlying mechanisms are unknown. Seeking causal contributors to both these phenomena, we pursued changes in transfer RNS (tRNA) fragments (tRFs) targeting cholinergic transcripts (CholinotRFs).

METHODS

We analyzed small RNA-sequencing (RNA-Seq) data from the nucleus accumbens (NAc) brain region which is enriched in cholinergic neurons, compared to hypothalamic or cortical tissues from AD brains; and explored small RNA expression in neuronal cell lines undergoing cholinergic differentiation.

RESULTS

NAc CholinotRFs of mitochondrial genome origin showed reduced levels that correlated with elevations in their predicted cholinergic-associated mRNA targets. Single-cell RNA seq from AD temporal cortices showed altered sex-specific levels of cholinergic transcripts in diverse cell types; inversely, human-originated neuroblastoma cells under cholinergic differentiation presented sex-specific CholinotRF elevations.

DISCUSSION

Our findings support CholinotRFs contributions to cholinergic regulation, predicting their involvement in AD sex-specific cholinergic loss and dementia.

Hyperglycemia-regulated tRNA-derived fragment tRF-3001a propels neurovascular dysfunction in diabetic mice

Neurovascular dysfunction is a preclinical manifestation of diabetic complications, including diabetic retinopathy (DR). Herein, we report that a transfer RNA-derived RNA fragment, tRF-3001a, is significantly upregulated under diabetic conditions. tRF-3001a downregulation inhibits Müller cell activation, suppresses endothelial angiogenic effects, and protects against high-glucose-induced retinal ganglion cell injury in vitro. Furthermore, tRF-3001a downregulation alleviates retinal vascular dysfunction, inhibits retinal reactive gliosis, facilitates retinal ganglion cell survival, and preserves visual function and visually guided behaviors in STZ-induced diabetic mice and db/db diabetic mice. Mechanistically, tRF-3001a regulates neurovascular dysfunction in a microRNA-like mechanism by targeting GSK3B. Clinically, tRF-3001a is upregulated in aqueous humor (AH) samples of DR patients. tRF-3001a downregulation inhibits DR-induced human retinal vascular endothelial cell and Müller cell dysfunction in vitro and DR-induced retinal neurovascular dysfunction in C57BL/6J mice. Thus, targeting tRF-3001a-mediated signaling is a promising strategy for the concurrent treatment of vasculopathy and neuropathy in diabetes mellitus.

Non-Coding RNA in Salivary Extracellular Vesicles: A New Frontier in Sjögren's Syndrome Diagnostics?

Sjögren's syndrome is an autoimmune rheumatic disease characterized by inflammation of the salivary and lacrimal glands, often manifesting as dry mouth and dry eyes. To simplify diagnostics of primary Sjögren's syndrome (pSS), a non-invasive marker is needed. The aim of the study was to compare the RNA content of salivary extracellular vesicles (EVs) between patients with pSS and healthy controls using microarray technology. Stimulated whole saliva was collected from 11 pSS patients and 11 age-matched controls. EV-RNA was isolated from the saliva samples using a Qiagen exoRNeasy Midi Kit and analyzed using Affymetrix Clariom D™ microarrays. A one-way ANOVA test was used to compare the mean signal values of each transcript between the two groups. A total of 9307 transcripts, coding and non-coding RNA, were detected in all samples. Of these transcripts, 1475 showed statistically significant differential abundance between the pSS and the control groups, generating two distinct EV-RNA patterns. In particular, tRNAs were downregulated in pSS patients, with the transcript tRNA-Ile-AAT-2-1 showing a 2-fold difference, and a promise as a potential biomarker candidate. This study therein demonstrates the potential for using salivary EV-RNA in pSS diagnostics.

Role of tRNA-derived small RNAs(tsRNAs) in the diagnosis and treatment of malignant tumours

Malignant tumours area leading cause of death globally, accounting for approximately 13% of all deaths. A detailed understanding of the mechanism(s) of the occurrence and development of malignant tumours and identification of relevant therapeutic targets are therefore key to tumour treatment. tsRNAs(tRNA-derived small RNAs)-also known as TRFs (tRNA-derived fragments), tiRNAs (tRNA-derived stress-induced RNAs), tRNA halves, etc.-are a recently identified class of small noncoding RNAs that are generated from mature tRNA or tRNA precursors through cleavage by enzymes such as angiogenin, Dicer, RNase Z, and RNase P. Several studies have confirmed that dysregulation of tsRNAs is closely related to the tumorigenesis of breast cancer, nasopharyngeal cancer, lung cancer, and so on. Furthermore, research indicates that tsRNAs can be used as clinical diagnostic markers and therapeutic targets for cancer. In our review, we summarized the recent research progress on the role and clinical application of tsRNAs in tumorigenesis and progression. Video Abstract.

An old friend with a new face: tRNA-derived small RNAs with big regulatory potential in cancer biology

Transfer RNAs (tRNAs) are small non-coding RNAs (sncRNAs) essential for protein translation. Emerging evidence suggests that tRNAs can also be processed into smaller fragments, tRNA-derived small RNAs (tsRNAs), a novel class of sncRNAs with powerful applications and high biological relevance to cancer. tsRNAs biogenesis is heterogeneous and involves different ribonucleases, such as Angiogenin and Dicer. For many years, tsRNAs were thought to be just degradation products. However, accumulating evidence shows their roles in gene expression: either directly via destabilising the mRNA or the ribosomal machinery, or indirectly via regulating the expression of ribosomal components. Furthermore, tsRNAs participate in various biological processes linked to cancer, including apoptosis, cell cycle, immune response, and retroviral insertion into the human genome. It is emerging that tsRNAs have significant therapeutic potential. Endogenous tsRNAs can be used as cancer biomarkers, while synthetic tsRNAs and antisense oligonucleotides can be employed to regulate gene expression. In this review, we are recapitulating the regulatory roles of tsRNAs, with a focus on cancer biology.

Cerebrospinal fluid and blood profiles of transfer RNA fragments show age, sex, and Parkinson's disease-related changes

Transfer RNA fragments (tRFs) have recently been shown to be an important family of small regulatory RNAs with diverse functions. Recent reports have revealed modified tRF blood levels in a number of nervous system conditions including epilepsy, ischemic stroke, and neurodegenerative diseases, but little is known about tRF levels in the cerebrospinal fluid (CSF). To address this issue, we studied age, sex, and Parkinson's disease (PD) effects on the distributions of tRFs in the CSF and blood data of healthy controls and PD patients from the NIH and the Parkinson's Progression Markers Initiative (PPMI) small RNA-seq datasets. We discovered that long tRFs are expressed in higher levels in the CSF than in the blood. Furthermore, the CSF showed a pronounced age-associated decline in the level of tRFs cleaved from the 3'-end and anti-codon loop of the parental tRNA (3'-tRFs, i-tRFs), and more pronounced profile differences than the blood profiles between the sexes. In comparison, we observed moderate age-related elevation of blood 3'-tRF levels. In addition, distinct sets of tRFs in the CSF and in the blood segregated PD patients from controls. Finally, we found enrichment of tRFs predicted to target cholinergic mRNAs (Cholino-tRFs) among mitochondrial-originated tRFs, raising the possibility that the neurodegeneration-related mitochondrial impairment in PD patients may lead to deregulation of their cholinergic tone. Our findings demonstrate that the CSF and blood tRF profiles are distinct and that the CSF tRF profiles are modified in a sex-, age-, and disease-related manner, suggesting that they reflect the inter-individual cerebral differences and calling for incorporating this important subset of small RNA regulators into future studies.

tncRNA Toolkit: A pipeline for convenient identification of RNA (tRNA)-derived non-coding RNAs

Insights into the eukaryotic gene regulation networks have improved due to the advent of diverse classes of non-coding RNAs. The transfer RNA (tRNA)-derived non-coding RNAs or tncRNAs is a novel class of non-coding RNAs, shown to regulate gene expression at transcription and translation levels. Here, we present a pipeline 'tncRNA Toolkit' for accurately identifying tncRNAs using small RNA sequencing (sRNA-seq) data. Previously, we identified tncRNA in six major angiosperms by utilizing our pipeline and highlighted the significant points regarding their generation and functions. The 'tncRNA Toolkit' is available at the URL: http://www.nipgr.ac.in/tncRNA. The scripts are written in bash and Python3 programming languages. The program can be efficiently run as a standalone command-line tool and installed in any Linux-based Operating System (OS). The user can run this program by providing the input of sRNA-seq data and genome file.The various features of the 'tncRNA Toolkit' are as follows:•Major tncRNA classes identified by this tool include tRF-5, tRF-3, tRF-1, 5'tRH, 3'tRH, and leader tRF. Also, it categorizes miscellaneous tncRNAs as other tRF.•It provides the following information for each identified tncRNA viz. tncRNA class, raw and normalized read count (RPM), read length, progenitor tRNA information (amino acid, anticodon, locus, strand), tncRNA sequence, and tRNA modification sites.•We hope to facilitate quick and reliable tncRNA identification, which will boost the exploration of this novel class of non-coding RNAs and their relevance in the living world, including plants.

Expression profiles of tRNA‑derived fragments in high glucose‑treated tubular epithelial cells

Transfer RNA-derived fragments (tRFs), a novel class of small non-coding RNA produced by the cleavage of pre- and mature tRNAs, are involved in various diseases. Renal tubulointerstitial fibrosis is a common final pathway in diabetic nephropathy (DN) in which hyperglycemia-induced tubular extracellular matrix (ECM) accumulation serves a vital role. The present study aimed to detect and investigate the role of tRFs in the accumulation of tubular ECM. Differentially expressed tRFs were analysed with high-throughput sequencing in primary mouse tubular epithelial cells treated with high glucose (HG). The Gene Ontology (GO) was used to analyze the potential molecular functions of these differentially expressed tRFs, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyze the associated signaling pathways involved in these differentially expressed tRFs. tRF-1:30-Gln-CTG-4 was overexpressed using tRF-1:30-Gln-CTG-4 mimic, followed by HG treatment. A total of 554 distinct tRFs were detected and 64 differentially expressed tRFs (fold change >2; P<0.05) were identified in tubular epithelial cells following high glucose (HG) treatment, among which 27 were upregulated and 37 were downregulated. Ten selected tRFs with the greatest difference (fold change >2; P<0.05) were verified to be consistent with small RNA-sequencing data, of which tRF-1:30-Gln-CTG-4 showed the most pronounced difference in expression and was significantly decreased in response to HG. GO analysis indicated that the differentially expressed tRFs were associated with 'cellular process', 'biological regulation' and 'metabolic process'. An analysis of the KEGG database suggested that these differentially expressed tRFs were involved in 'autophagy' and signaling pathways for 'forkhead box O', 'the mammalian target of rapamycin' and 'mitogen-activated protein kinase'. Finally, the overexpression of tRF-1:30-Gln-CTG-4 ameliorated HG-induced ECM accumulation in tubular epithelial cells. Therefore, the present study demonstrated that there may be a significant association between tRFs and HG-induced ECM accumulation in tubular epithelial cells; these differentially expressed tRFs warrant further study to explore the pathogenesis of DN.

tRNA‑derived fragment tRF‑Glu49 inhibits cell proliferation, migration and invasion in cervical cancer by targeting FGL1

A transfer RNA (tRNA)-derived fragment (tRF) was found to be a new possible biological marker and target in carcinoma therapy. However, the effect exerted by tRFs on cervical carcinoma remains unclear. In the present study, the potential tumor suppressor gene tRF-Glu49 was identified in cervical carcinoma through tRF and tiRNA microarray investigation. A reverse transcription-quantitative PCR assay then demonstrated that tRF-Glu49 was downregulated in the cervical carcinoma tissue. Further clinicopathological analysis proved that tRF-Glu49 was associated with less aggressive clinical features and improved prognosis. Cell Counting Kit-8 tests, Transwell and Matrigel tests, and xCELLigence system tests revealed that tRF-Glu49 inhibited cervical cell proliferation, migration and invasion processes. Mechanistic investigation revealed that tRF-Glu49 directly regulated the oncogene, fibrinogen-like protein-1 (FGL1). In general, according to the result achieved in the present study, tRF-Glu49 can modulate cervical cell proliferation, migration, and invasion processes through the target process for FGL1, and tRF-Glu49 is likely to be a possible prognostic biological marker in patients with cervical carcinoma.

Cloning and Sequencing Eukaryotic Small RNAs

Small RNAs are ubiquitous regulators of gene expression that participate in nearly all aspects of physiology in a wide range of organisms. There are many different classes of eukaryotic small RNAs that play regulatory roles at every level of gene expression, including transcription, RNA stability, and translation. While eukaryotic small RNAs display diverse functions across and within classes, they are generally grouped functionally based on the machinery required for their biogenesis, the effector proteins they associate with, and their molecular characteristics. The development of techniques to clone and sequence small RNAs has been critical for their identification, yet the ligation-dependent addition of RNA adapters and the use of reverse transcriptase to generate cDNA in traditional library preparation protocols can be unsuitable to detect certain small RNA subtypes. In particular, 3' or 5' chemical modifications that are characteristic of specific types of small RNAs can impede the ligation-dependent addition of RNA adapters, while internal RNA modifications can interfere with accurate reverse transcription. The inability to clone certain small RNA subtypes with traditional protocols results in an inaccurate assessment of small RNA abundance and diversity, where some RNAs appear over-represented and others are not detected. This overview aims to guide users on how to design small RNA cloning workflows in eukaryotes to more accurately capture specific small RNAs of interest. Hence, we discuss the molecular biology underlying the identification and quantitation of small RNAs, explore the limitations of commonly used protocols, and detail the alternative approaches that can be used to enrich specific small RNA classes. © 2022 Wiley Periodicals LLC.

PtncRNAdb: plant transfer RNA-derived non-coding RNAs (tncRNAs) database

Specific endonucleolytic cleavage of tRNA molecules leads to the biogenesis of heterogeneously sized fragments called tRNA-derived non-coding RNAs (tncRNAs). The role of tncRNAs is well studied in human processes, and diseases including different types of cancers and other ailments. They are also generated under stress conditions in plants. Considering the potential role of tncRNAs in the plant system, we have developed a user-friendly, open-access web resource, PtncRNAdb (https://nipgr.ac.in/PtncRNAdb). PtncRNAdb consists of 4,809,503 tncRNA entries identified from ~ 2500 single-end small RNA-seq libraries from six plants, viz., Arabidopsis thaliana, Cicer arietinum, Zea mays, Oryza sativa, Medicago truncatula, and Solanum lycopersicum. It is provided with assorted options to search, browse, visualize, interpret, and download tncRNAs data. Users can perform query search using 'BLASTN' against PtncRNAdb entries. Highcharts have been included for better statistical PtncRNAdb data readability to the users. Additionally, PtncRNAdb includes 'DE tncRNAs' module for differentially expressed tncRNAs under various conditions. Their secondary structure, putative targets, interactive networks of target enrichment, and related publications are also incorporated for further interpretation of their biological functions. PtncRNAdb is an efficient, user-friendly, and exhaustive database, which will aid the ongoing research in plant tncRNAs as well as help in deciphering their role in gene regulation. We hope that it provides a promising platform for researchers to facilitate the understanding of tncRNAs, and their involvement in numerous pathways related to plant development and stress tolerance.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03174-7.

tRNAGlyGCC-Derived Internal Fragment (i-tRF-GlyGCC) in Ovarian Cancer Treatment Outcome and Progression

Epithelial ovarian cancer (EOC) remains a highly-lethal gynecological malignancy, characterized by frequent recurrence, chemotherapy resistance and poor 5-year survival. Identifying novel predictive molecular markers remains an overdue challenge in the disease's clinical management. Herein, in silico analysis of TCGA-OV highlighted the tRNA-derived internal fragment (i-tRF-GlyGCC) among the most abundant tRFs in ovarian tumors, while target prediction and gene ontology (GO) enrichment analysis predicted its implication in key biological processes. Thereafter, i-tRF-GlyGCC levels were quantified in a screening EOC (n = 98) and an institutionally-independent serous ovarian cancer (SOC) validation cohort (n = 100, OVCAD multicenter study). Disease progression and patient death were used as clinical endpoints for the survival analysis. Internal validation was performed by bootstrap analysis and the clinical net benefit was estimated by decision curve analysis. The analysis highlighted the significant association of i-tRF-GlyGCC with advanced FIGO stages, suboptimal debulking and most importantly, with early progression and poor overall survival of EOC patients. The OVCAD validation cohort corroborated the unfavorable predictive value of i-tRF-GlyGCC in EOC. Ultimately, evaluation of i-tRF-GlyGCC with the established/clinically used prognostic markers offered superior patient risk-stratification and enhanced clinical benefit in EOC prognosis. In conclusion, i-tRF-GlyGCC assessment could aid towards personalized prognosis and support precision medicine decisions in EOC.

Deciphering the tRNA-derived small RNAs: origin, development, and future

Transfer RNA (tRNA)-derived small RNAs (tsRNAs), a novel category of small noncoding RNAs, are enzymatically cleaved from tRNAs. Previous reports have shed some light on the roles of tsRNAs in the development of human diseases. However, our knowledge about tsRNAs is still relatively lacking. In this paper, we review the biogenesis, classification, subcellular localization as well as action mechanism of tsRNAs, and discuss the association between chemical modifications of tRNAs and the production and functions of tsRNAs. Furthermore, using immunity, metabolism, and malignancy as examples, we summarize the molecular mechanisms of tsRNAs in diseases and evaluate the potential of tsRNAs as new biomarkers and therapeutic targets. At the same time, we compile and introduce several resource databases that are currently publicly available for analyzing tsRNAs. Finally, we discuss the challenges associated with research in this field and future directions.

Expression profiles of tRNA-derived small RNA and their potential roles in oral submucous fibrosis

BACKGROUND

Although transfer RNA (tRNA) has been found to be the main source of a rich class of noncoding RNA, the tRNA-derived small RNA (tsRNA) has been proved to play an irreplaceable role in the human body, and its dynamic imbalance could affect the progress of the disease. However, the research on tsRNA in oral submucous fibrosis (OSF) is still scarce.

METHODS

We sequenced the OSF and validated it by PCR. We found that there were significant differences in their expression levels in OSF. Furthermore, bioinformatic analysis was performed to explore the roles of these fragments in oral submucous fibrosis.

RESULTS

Of 126 tsRNAs in OSF were dysregulated, including 73 upregulated tsRNAs and 53 downregulated tsRNAs. The downregulated tiRNA-Val-CAC-002, tRF-Asn-GTT-005, tRF-Trp-CCA-007 and upregulated tRF-Gly-TCC-016, tRF-Pro-TGG-009 showed significant differences by qRT-PCR validation, which were consistent with the results of RNA sequencing. Gene ontology and pathway analysis revealed that tRF-Gly-TCC-016 would possibly promote the formation and progress of OSF through cytokine-cytokine receptor interaction and cAMP signal pathway, while tiRNA-Val-CAC-002 could be primarily concerned with the transition from OSF to oral squamous cell carcinoma (OSCC).

CONCLUSION

tRNA-derived fragments are dysregulated and could be involved in the pathogenesis of oral submucous fibrosis. tRF-Gly-TCC-016 and tiRNA-Val-CAC-002 may be new regulatory molecules that could affect the process of OSF by regulating signal pathways through interacting with multiple genes.

Transfer RNA-derived non-coding RNAs (tncRNAs): Hidden regulation of plants' transcriptional regulatory circuits

The emergence of distinct classes of non-coding RNAs has led to better insights into the eukaryotic gene regulatory networks. Amongst them, the existence of transfer RNA (tRNA)-derived non-coding RNAs (tncRNAs) demands exploration in the plant kingdom. We have designed a methodology to uncover the entire perspective of tncRNAome in plants. Using this pipeline, we have identified diverse tncRNAs with a size ranging from 14 to 50 nucleotides (nt) by utilizing 2448 small RNA-seq samples from six angiosperms, and studied their various features, including length, codon-usage, cleavage pattern, and modified tRNA nucleosides. Codon-dependent generation of tncRNAs suggests that the tRNA cleavage is highly specific rather than random tRNA degradation. The nucleotide composition analysis of tncRNA cleavage positions indicates that they are generated through precise endoribonucleolytic cleavage machinery. Certain nucleoside modifications detected on tncRNAs were found to be conserved across the plants, and hence may influence tRNA cleavage, as well as tncRNA functions. Pathway enrichment analysis revealed that common tncRNA targets are majorly enriched during metabolic and developmental processes. Further distinct tissue-specific tncRNA clusters highlight their role in plant development. Significant number of tncRNAs differentially expressed under abiotic and biotic stresses highlights their potential role in stress resistance. In summary, this study has developed a platform that will help in the understanding of tncRNAs and their involvement in growth, development, and response to various stresses. The workflow, software package, and results are freely available at http://nipgr.ac.in/tncRNA.

Modeling a human CLP1 mutation in mouse identifies an accumulation of tyrosine pre-tRNA fragments causing pontocerebellar hypoplasia type 10

Cleavage factor polyribonucleotide kinase subunit 1 (CLP1), an RNA kinase, plays essential roles in protein complexes involved in the 3'-end formation and polyadenylation of mRNA and the tRNA splicing endonuclease complex, which is involved in precursor tRNA splicing. The mutation R140H in human CLP1 causes pontocerebellar hypoplasia type 10 (PCH10), which is characterized by microcephaly and axonal peripheral neuropathy. Previously, we reported that RNA fragments derived from isoleucine pre-tRNA introns (Ile-introns) accumulate in fibroblasts of patients with PCH10. Therefore, it has been suggested that this intronic RNA fragment accumulation may trigger PCH10 onset. However, the molecular mechanism underlying PCH10 pathogenesis remains elusive. Thus, we generated knock-in mutant mice that harbored a CLP1 mutation consistent with R140H. As expected, these mice showed progressive loss of the upper motor neurons, resulting in impaired locomotor activity, although the phenotype was milder than that of the human variant. Mechanistically, we found that the R140H mutation causes intracellular accumulation of Ile-introns derived from isoleucine pre-tRNAs and 5' tRNA fragments derived from tyrosine pre-tRNAs, suggesting that these two types of RNA fragments were cooperatively or independently involved in the onset and progression of the disease. Taken together, the CLP1-R140H mouse model provided new insights into the pathogenesis of neurodegenerative diseases, such as PCH10, caused by genetic mutations in tRNA metabolism-related molecules.

Ozone-induced changes in the murine lung extracellular vesicle small RNA landscape

Inhalation exposure to ozone (O3 ) causes adverse respiratory health effects that result from airway inflammation, a complex response mediated in part by changes to airway cellular transcriptional programs. These programs may be regulated by microRNAs transferred between cells (e.g., epithelial cells and macrophages) via extracellular vesicles (EV miRNA). To explore this, we exposed female C57BL/6J mice to filtered air (FA), 1, or 2 ppm O3 by inhalation and collected bronchoalveolar lavage fluid (BALF) 21 h later for markers of airway inflammation, EVs, and EV miRNA. Both concentrations of O3  significantly increased markers of inflammation (neutrophils), injury (total protein), and the number of EV-sized particles in the BALF. Imagestream analysis indicated a substantial portion of particles was positive for canonical EV markers (CD81, CD51), and Siglec-F, a marker of alveolar macrophages. Using high-throughput small RNA sequencing, we identified several differentially expressed (DE) BALF EV miRNAs after 1 ppm (16 DE miRNAs) and 2 ppm (99 DE miRNAs) O3 versus FA exposure. O3 concentration-response patterns in EV miRNA expression were apparent, particularly for miR-2137, miR-126-3p, and miR-351-5p. Integrative analysis of EV miRNA expression and airway cellular mRNA expression identified EV miR-22-3p as a candidate regulator of transcriptomic responses to O3 in airway macrophages. In contrast, we did not identify candidate miRNA regulators of mRNA expression data from conducting airways (predominantly composed of epithelial cells). In summary, our data show that O3 exposure alters EV release and EV miRNA expression, suggesting that further investigation of EVs may provide insight into their effects on airway macrophage function and other mechanisms of O3 -induced respiratory inflammation.

tRNA derived fragment (tRF)-3009 participates in modulation of IFN-α-induced CD4+ T cell oxidative phosphorylation in lupus patients

BACKGROUND

Accumulating evidence suggests tRNA-derived fragments (tRFs) play important roles in cellular homeostasis. Here we aimed to explore aberrant expression of tRFs in CD4+ T cells from patients with systemic lupus erythematosus (SLE) and their potential function in the SLE pathogenesis.

METHODS

First, small RNA sequencing was performed on CD4+ T cells from four SLE patients and three healthy controls (HCs). Candidate tRFs were then validated in CD4+ T cells from 97 SLE patients and their relevant disease controls using qRT-PCR. Then sequencing was used to investigate the profiles of HC-derived CD4+ T cells transfected with tRF-3009. Lastly, tRF-3009 siRNA or tRF-3009 mimics were transfected into CD4+ T cells with/without IFN-α. Changes in oxygen consumption rate (OCR), ATP, and ROS production were analyzed.

RESULTS

We identified 482 differentially expressed tRFs from SLE CD4+ T cells and chose tRF-3009 for further analysis due to its upregulation and the positive correlations between its expression and SLEDAI, active lupus nephritis and serum IFN-α levels. In vitro, tRF-3009 over-expressing CD4+ T cell profiling and putative analysis linked this product to the type I IFN and oxidative phosphorylation (OXPHOS) pathways. Interestingly, IFN-α is capable of inducing ROS and ATP production in CD4+ T cells, while knockdown of tRF-3009 reversed this process. Overexpression of tRF-3009 in CD4+ T cells alone was sufficient to upregulate OCR, ROS, and ATP production.

CONCLUSIONS

Our study is the first to link aberrant tRF expression and SLE. tRF-3009 may participate in metabolic modulation of IFN-α-induced CD4+ T cell OXPHOS in lupus.

The RNA landscape of the human placenta in health and disease

The placenta is the interface between mother and fetus and inadequate function contributes to short and long-term ill-health. The placenta is absent from most large-scale RNA-Seq datasets. We therefore analyze long and small RNAs (~101 and 20 million reads per sample respectively) from 302 human placentas, including 94 cases of preeclampsia (PE) and 56 cases of fetal growth restriction (FGR). The placental transcriptome has the seventh lowest complexity of 50 human tissues: 271 genes account for 50% of all reads. We identify multiple circular RNAs and validate 6 of these by Sanger sequencing across the back-splice junction. Using large-scale mass spectrometry datasets, we find strong evidence of peptides produced by translation of two circular RNAs. We also identify novel piRNAs which are clustered on Chr1 and Chr14. PE and FGR are associated with multiple and overlapping differences in mRNA, lincRNA and circRNA but fewer consistent differences in small RNAs. Of the three protein coding genes differentially expressed in both PE and FGR, one encodes a secreted protein FSTL3 (follistatin-like 3). Elevated serum levels of FSTL3 in pregnant women are predictive of subsequent PE and FGR. To aid visualization of our placenta transcriptome data, we develop a web application ( https://www.obgyn.cam.ac.uk/placentome/ ).

Toward an Understanding of Extracellular tRNA Biology

Extracellular RNAs (exRNAs) including abundant full length tRNAs and tRNA fragments (tRFs) have recently garnered attention as a promising source of biomarkers and a novel mediator in cell-to-cell communication in eukaryotes. Depending on the physiological state of cells, tRNAs/tRFs are released to the extracellular space either contained in extracellular vesicles (EVs) or free, through a mechanism that is largely unknown. In this perspective article, we propose that extracellular tRNAs (ex-tRNAs) and/or extracellular tRFs (ex-tRFs) are relevant paracrine signaling molecules whose activity depends on the mechanisms of release by source cells and capture by recipient cells. We speculate on how ex-tRNA/ex-tRFs orchestrate the effects in target cells, depending on the type of sequence and the mechanisms of uptake. We further propose that tRNA modifications may be playing important roles in ex-tRNA biology.

Clinical diagnostic values of transfer RNA-derived fragment tRF-19-3L7L73JD and its effects on the growth of gastric cancer cells

Background and aim: Medicine has made great progress, but gastric cancer is still one of the most common malignant tumors worldwide. tRNA-derived fragments (tRFs), a type of small non-coding RNA, have been found to play important roles in cancers. Due to an abundance of modifications, tRFs have the potential to serve as cancer biomarkers. However, the relationship between tRFs and gastric cancer is still largely unclear. We have identified a new tRF, tRF-19-3L7L73JD, found to be expressed at a lower level in gastric cancer patients than healthy controls. Our study aims to explore the diagnostic value of tRF-19-3L7L73JD screening in gastric cancer and to investigate its effects on the growth of gastric cancer cells.

Methods: Using quantitative reverse transcription-polymerase chain reaction, we identified tRF-3L7L73JD as differentially expressed in plasma from gastric cancer patients compared to healthy controls. We measured tRF-3L7L73JD levels in plasma from 40 gastric cancer patients and healthy controls. Furthermore, we tested another cohort containing 89 gastric cancer patients and 98 healthy controls to validate our findings. Next, we analyzed the relationship between levels of tRF-19-3L7L73JD in plasma and clinicopathological data of gastric cancer patients, and then evaluated the effects of tRF-19-3L7L73JD on gastric cancer cell growth. Cell proliferation was measured by the Cell Counting Kit‐8 and clone formation experiments after transfer with tRF-19-3L7L73JD mimics. The changes in cell migration ability were explored through the scratch and Transwell experiments. Finally, we explored changes in apoptosis and cell cycle by flow cytometry.

Results: tRF-19-3L7L73JD showed lower expression in the tested gastric cancer patients. In the validation cohort tRF-19-3L7L73JD was also expressed at low levels in the pre-operative plasma group compared with healthy plasma and post-operative plasma groups. Additionally, a comparison of gastric cancer cell lines with normal gastric epithelial cell lines produced the same result. We found that tRF-19-3L7L73JD expression in patients was related to tumor size. The area under the curve (AUC) was 0.6230, with sensitivity and specificity of 0.4045 and 0.7959, respectively. Cellular function studies revealed that tRF-19-3L7L73JD inhibited cell proliferation and migration, induced apoptosis, and arrested cells at G₀/G₁ phases, suggesting it may suppress the development of gastric cancer.

Conclusion: The results suggest that tRF-19-3L7L73JD may be useful as a biomarker of gastric cancer.

Differential Expression Profiles and Function Prediction of Transfer RNA-Derived Fragments in High-Grade Serous Ovarian Cancer

Background

The present study is aimed at providing systematic insight into the composition and expression of transfer RNA (tRNA) derivative transcription in high-grade serous ovarian cancer (HGSOC).

Methods

tRNA derivative expression profiles in three pairs of HGSOC and adjacent normal ovarian tissues were conducted by tRNA-derived small RNA fragment (tRF) and tRNA half (tiRNA) sequencing. The differentially expressed tRFs and tiRNAs between HGSOC and paired adjacent normal samples were screened. The targeted genes of differentially expressed tRFs and tiRNAs were screened. The Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) of target genes of tRFs and tiRNAs were analyzed.

Results

There are a total of 20 significantly upregulated and 15 significantly downregulated tRFs and tiRNAs between the cancer group and the paracarcinoma group. The upregulated tRFs and tiRNAs are mucin-type O-glycan biosynthesis, glycosphingolipid biosynthesis, the glucagon signaling pathway, the AMPK signaling pathway, maturity-onset diabetes of the young, glycosphingolipid biosynthesis, the insulin signaling pathway, insulin resistance, leukocyte transendothelial migration, starch, and sucrose metabolism. The downregulated tRFs and tiRNAs are other glycan degradation, vitamin digestion and absorption, fatty acid elongation, and biosynthesis of unsaturated fatty acids.

Conclusions

There are significantly expressed tRFs and tiRNAs in HGSOC tissues, and these may provide potential diagnostic biomarkers and therapeutic targets for HGSOC.

Molecular mechanisms of β-cell dysfunction and death in monogenic forms of diabetes

Monogenetic forms of diabetes represent 1%-5% of all diabetes cases and are caused by mutations in a single gene. These mutations, that affect genes involved in pancreatic β-cell development, function and survival, or insulin regulation, may be dominant or recessive, inherited or de novo. Most patients with monogenic diabetes are very commonly misdiagnosed as having type 1 or type 2 diabetes. The severity of their symptoms depends on the nature of the mutation, the function of the affected gene and, in some cases, the influence of additional genetic or environmental factors that modulate severity and penetrance. In some patients, diabetes is accompanied by other syndromic features such as deafness, blindness, microcephaly, liver and intestinal defects, among others. The age of diabetes onset may also vary from neonatal until early adulthood manifestations. Since the different mutations result in diverse clinical presentations, patients usually need different treatments that range from just diet and exercise, to the requirement of exogenous insulin or other hypoglycemic drugs, e.g., sulfonylureas or glucagon-like peptide 1 analogs to control their glycemia. As a consequence, awareness and correct diagnosis are crucial for the proper management and treatment of monogenic diabetes patients. In this chapter, we describe mutations causing different monogenic forms of diabetes associated with inadequate pancreas development or impaired β-cell function and survival, and discuss the molecular mechanisms involved in β-cell demise.

Transfer RNA-derived fragment tRF-28-QSZ34KRQ590K in plasma exosomes may be a potential biomarker for atopic dermatitis in pediatric patients

Atopic dermatitis (AD) is a common chronic relapsing inflammatory disease. There is substantial evidence suggesting that noncoding RNAs have indispensable roles in the pathogenesis of AD. Exosomal transfer RNA-derived fragments (tRFs) have been identified as potential biomarkers for various disorders. However, the role of tRFs in AD has remained to be elucidated, which was thus the aim of the present study. Plasma samples from 23 pediatric patients with AD and 23 healthy controls were collected. Exosomes were successfully isolated from plasma according to the manufacturer's protocol. Small RNA sequencing was performed in 3 patients with AD and 3 controls, and 135 significantly differentially expressed plasma exosomal tRFs were identified, including 36 upregulated and 99 downregulated tRFs. Using the miRanda and RNAhybrid databases, 58,227 target genes of these 135 differentially expressed tRFs were predicted. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses suggested that these target genes of tRFs are involved in multiple functions and pathways associated with AD. Downregulation of tRF-28-QSZ34KRQ590K and tRF-33-Q99P9P9NH57SD3 were validated in 20 patients with AD and 20 controls by reverse transcription-quantitative PCR and tRF-28-QSZ34KRQ590K exhibited significance in the receiver operating characteristic curve analysis. The present study was the first to provide a tRF profile in AD and implied that plasma exosomal tRF-28-QSZ34KRQ590K may be a potential biomarker for pediatric patients with AD. The present study enhanced the understanding of the pathogenesis of AD and provided a novel marker for the diagnosis and targeted treatment of AD.

A 3' tRNA-derived fragment produced by tRNALeuAAG and tRNALeuTAG is associated with poor prognosis in B-cell chronic lymphocytic leukemia, independently of classical prognostic factors

OBJECTIVE

3' tRNA-derived fragments (3' tRFs) are important epigenetic regulators in normal and pathological conditions. In this study, we aimed to explore the potential value of a 3' tRF as a prognostic and/or screening biomarker for B-cell chronic lymphocytic leukemia (B-CLL).

METHODS

Publicly available next-generation sequencing data from 20 B-CLL cases were analyzed, followed by prediction of targets of the most abundantly and ubiquitously expressed 3' tRFs, leading to selection of tRF-Leu^AAG/TAG . PBMCs were isolated from blood samples of 91 B-CLL patients and 43 non-leukemic donors, followed by total RNA extraction, in-vitro polyadenylation, and first-strand cDNA synthesis. Next, a real-time quantitative PCR (qPCR) assay was developed for the accurate quantification of tRF-Leu^AAG/TAG and applied in all samples, prior to biostatistical analysis.

RESULTS

High tRF-Leu^AAG/TAG levels are associated with inferior overall survival (OS) of B-CLL patients. The unfavorable significance of tRF-Leu^AAG/TAG was independent of established prognostic factors in B-CLL. Stratified Kaplan-Meier OS analysis uncovered the unfavorable prognostic role of high tRF-Leu^AAG/TAG levels for patients in Binet A or Rai I stage, negative CD38 expression, mutated, or unmutated IGHV genomic locus.

CONCLUSION

Our approach revealed the independent prognostic value of a particular 3' tRF, derived from tRNA^LeuAAG and tRNA^LeuTAG (tRF-Leu^AAG/TAG ) in B-CLL.

m5U54 tRNA Hypomodification by Lack of TRMT2A Drives the Generation of tRNA-Derived Small RNAs

Transfer RNA (tRNA) molecules contain various post-transcriptional modifications that are crucial for tRNA stability, translation efficiency, and fidelity. Besides their canonical roles in translation, tRNAs also originate tRNA-derived small RNAs (tsRNAs), a class of small non-coding RNAs with regulatory functions ranging from translation regulation to gene expression control and cellular stress response. Recent evidence indicates that tsRNAs are also modified, however, the impact of tRNA epitranscriptome deregulation on tsRNAs generation is only now beginning to be uncovered. The 5-methyluridine (m⁵U) modification at position 54 of cytosolic tRNAs is one of the most common and conserved tRNA modifications among species. The tRNA methyltransferase TRMT2A catalyzes this modification, but its biological role remains mostly unexplored. Here, we show that TRMT2A knockdown in human cells induces m⁵U54 tRNA hypomodification and tsRNA formation. More specifically, m⁵U54 hypomodification is followed by overexpression of the ribonuclease angiogenin (ANG) that cleaves tRNAs near the anticodon, resulting in accumulation of 5′tRNA-derived stress-induced RNAs (5′tiRNAs), namely 5′tiRNA-Gly^GCC and 5′tiRNA-Glu^CTC, among others. Additionally, transcriptomic analysis confirms that down-regulation of TRMT2A and consequently m⁵U54 hypomodification impacts the cellular stress response and RNA stability, which is often correlated with tiRNA generation. Accordingly, exposure to oxidative stress conditions induces TRMT2A down-regulation and tiRNA formation in mammalian cells. These results establish a link between tRNA hypomethylation and ANG-dependent tsRNAs formation and unravel m⁵U54 as a tRNA cleavage protective mark.

tRNA 3' shortening by LCCR4 as a response to stress in Trypanosoma brucei

Sensing of environmental cues is crucial for cell survival. To adapt to changes in their surroundings cells need to tightly control the repertoire of genes expressed at any time. Regulation of translation is key, especially in organisms in which transcription is hardly controlled, like Trypanosoma brucei. In this study, we describe the shortening of the bulk of the cellular tRNAs during stress at the expense of the conserved 3' CCA-tail. This tRNA shortening is specific for nutritional stress and renders tRNAs unsuitable substrates for translation. We uncovered the nuclease LCCR4 (Tb927.4.2430), a homologue of the conserved deadenylase Ccr4, as being responsible for tRNA trimming. Once optimal growth conditions are restored tRNAs are rapidly repaired by the trypanosome tRNA nucleotidyltransferase thus rendering the recycled tRNAs amenable for translation. This mechanism represents a fast and efficient way to repress translation during stress, allowing quick reactivation with a low energy input.

tRNA-derived fragments: Mechanisms underlying their regulation of gene expression and potential applications as therapeutic targets in cancers and virus infections

tRNA-derived fragments (tRFs) are a new category of regulatory noncoding RNAs with distinct biological functions in cancers and stress-induced diseases. Herein, we first summarize the classification and biogenesis of tRFs. tRFs are produced from pre-tRNAs or mature tRNAs. Based on the incision loci, tRFs are classified into several types: tRF-1, tRF-2, tRF-3, tRF-5, and i-tRF. Some tRFs participate in posttranscriptional regulation through microRNA-like actions or by displacing RNA binding proteins and regulating protein translation by promoting ribosome biogenesis or interfering with translation initiation. Other tRFs prevent cell apoptosis by binding to cytochrome c or promoting virus replication. More importantly, the dysregulation of tRFs has important clinical implications. They are potential diagnostic and prognostic biomarkers of gastric cancer, liver cancer, breast cancer, prostate cancer, and chronic lymphocytic leukemia. tRFs may become new therapeutic targets for the treatment of diseases such as hepatocellular carcinoma and respiratory syncytial virus infection. Finally, we point out the existing problems and future research directions associated with tRFs. In conclusion, the current progress in the research of tRFs reveals that they have important clinical implications and may constitute novel molecular therapeutic targets for modulating pathological processes.

The emerging role of small non-coding RNA in renal cell carcinoma

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SncRNAs contribute to the progress of renal cell carcinoma.

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SncRNAs are promising biomarkers for diagnosis and prognosis of renal cell carcinoma.

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Despite the potential of sncRNA-based cancer therapy, some obstacles remain, including several severe adverse effect.

Noncoding RNAs are transcribed in the most regions of the human genome, divided into small noncoding RNAs (less than 200 nt) and long noncoding RNAs (more than 200 nt) according to their size. Compelling evidences suggest that small noncoding RNAs play critical roles in tumorigenesis and tumor progression, especially in renal cell carcinoma. MiRNA, the most famous small noncoding RNA, has been comprehensively explored for its fundamental role in cancer. And several miRNA-based therapeutic strategies have been applied to several ongoing clinical trials. However, piRNAs and tsRNAs, have not received as much research attention, because of several technological limitations. Nevertheless, some studies have revealed the presence of aberration of piRNAs and tsRNAs in renal cell carcinoma, highlighting a potentially novel mechanism for tumor onset and progression. In this review, we provide an overview of three classes of small noncoding RNA: miRNAs, piRNAs and tsRNAs, that have been reported dysregulation in renal cell carcinoma and have the potential for advancing diagnosis, prognosis and therapeutic applications of this disease.

Differential expression of transfer RNA-derived small RNAs in IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is one of the most common forms of primary glomerulonephritis. Recent studies have indicated that small noncoding RNAs, such as tRNA-derived small RNAs (tsRNAs), might be novel biomarkers for glomerulonephritis. We therefore investigated the potential roles and possible functions of the tsRNAs in IgAN.

METHOD

Peripheral blood mononuclear cells (PBMCs) were extracted from blood samples of the patients with IgAN and healthy control groups. The expression profiles of tsRNAs were assessed by small RNA sequencing (RNA-Seq) in PBMCs of the IgAN and control groups. Dysregulated tsRNAs were selected for validation by quantitative real-time polymerase chain reaction (qRT-PCR). Target gene prediction and enrichment were performed by bioinformatics analysis.

RESULTS

The results revealed that 143 significantly upregulated and 202 significantly downregulated tsRNAs were differentially altered in the IgAN group compared with the control group. Five upregulated tsRNAs (tRF-Val-AAC-007, tRF-Ala-AGC-063, tRF-Gln-CTG-010, tRF-Tyr-GTA-011 and tRF-Thr-AGT-007) and 3 downregulated tsRNAs (tiRNA-Val-TAC-004, tRF-Gly-CCC-005 and tRF-His-GTG-006) were selected for validation by qRT-PCR; the results were consistent with the sequencing data. Gene Ontology (GO) analysis revealed that the target genes predicted by upregulated tsRNAs were mostly enriched in "nucleic acid metabolic process,' "intracellular part,' and "ion binding,' whereas the target genes predicted by downregulated tsRNAs were mostly enriched in "regulation of cellular component organization,' "membrane-bound organelle,' and "ion binding.' Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that the target genes predicted by upregulated tsRNAs were mostly enriched in "herpes simplex virus 1 infection,' whereas the target genes predicted by downregulated tsRNAs were mostly enriched in "circadian rhythm CONCLUSIONS:: The present study confirmed the differential expression of tsRNAs in patients with IgAN, and these dysregulated tsRNAs might be novel potential targets for the diagnosis and treatment of IgAN.

The role of Transfer RNA-Derived Small RNAs (tsRNAs) in Digestive System Tumors

Transfer RNA-derived small RNA(tsRNA) is a type of non-coding tRNA undergoing cleavage by specific nucleases such as Dicer. TsRNAs comprise of tRNA-derived fragments (tRFs) and tRNA halves (tiRNAs). Based on the splicing site within the tRNA, tRFs can be classified into tRF-1, tRF-2, tRF-3, tRF-5, and i-tRF. TiRNAs can be classified into 5′-tiRNA and 3′-tiRNA. Both tRFs and tiRNAs have important roles in carcinogenesis, especially cancer of digestive system. TRFs and tiRNAs can promote cell proliferation and cell cycle progression by regulating the expression of oncogenes, combining with RNA binding proteins such as Y-box binding protein 1 (YBX1) to prevent transcription. Despite many reviews on the basic biological function of tRFs and tiRNAs, few have described their correlation with tumors especially gastrointestinal tumor. This review focused on the relationship of tRFs and tiRNAs with the biological behavior, clinicopathological characteristics, diagnosis, treatment and prognosis of digestive system tumors, and would provide novel insights for the early detection and treatment of digestive system tumors.

Integrative analysis of transcriptomes highlights potential functions of transfer-RNA-derived small RNAs in experimental intracerebral hemorrhage

Transfer-RNA-derived small RNAs (tsRNAs) are a novel class of short non-coding RNAs, that possess regulatory functions. However, their biological roles in hemorrhagic stroke are not understood. In this study, by RNA sequencing, we investigated the tsRNA expression profiles of intracerebral hemorrhagic rat brains in the chronic phase. A total of 331 tsRNAs were identified (308 in sham and 309 in intracerebral hemorrhage). Among them, the validation revealed that 7 tsRNAs (1 up-regulated and 6 down-regulated) were significantly changed. Subsequently, we predicted the target mRNAs of the 7 tsRNAs. Through integrative analysis, the predicted targets were validated by mRNA microarray data. Moreover, we confirmed the functions of tsRNAs targeting mRNAs in vitro. Furthermore, using bioinformatics tools and databases, we developed a tsRNA-mRNA-pathway interaction network to visualize their potential functions. Bioinformatics analyses and confirmatory experiments indicated that the altered genes were mainly enriched in several signaling pathways. These pathways were interrelated with intracerebral hemorrhage, such as response to oxidative stress, endocytosis, and regulation of G protein-coupled receptor signaling pathway. In summary, this study systematically revealed the profiles of tsRNAs after an experimental intracerebral hemorrhage. These results may provide novel therapeutic targets following a hemorrhagic stroke in the chronic phase.

On the expanding roles of tRNA fragments in modulating cell behavior

The fragments that derive from transfer RNAs (tRNAs) are an emerging category of regulatory RNAs. Known as tRFs, these fragments were reported for the first time only a decade ago, making them a relatively recent addition to the ever-expanding pantheon of non-coding RNAs. tRFs are short, 16-35 nucleotides (nts) in length, and produced through cleavage of mature and precursor tRNAs at various positions. Both cleavage positions and relative tRF abundance depend strongly on context, including the tissue type, tissue state, and disease, as well as the sex, population of origin, and race/ethnicity of an individual. These dependencies increase the urgency to understand the regulatory roles of tRFs. Such efforts are gaining momentum, and comprise experimental and computational approaches. System-level studies across many tissues and thousands of samples have produced strong evidence that tRFs have important and multi-faceted roles. Here, we review the relevant literature on tRF biology in higher organisms, single cell eukaryotes, and prokaryotes.

Mechanisms of tRNA-derived fragments and tRNA halves in cancer treatment resistance

The tRNA-derived fragments (tRFs) and tRNA halves (tiRNAs) are newly discovered noncoding RNAs in recent years. They are derived from specific cleavage of mature and pre-tRNAs and expressed in various cancers. They enhance cell proliferation and metastasis or inhibit cancer progression. Many studies have investigated their roles in the diagnosis, progression, metastasis, and prognosis of various cancers, but the mechanisms through which they are involved in resistance to cancer treatment are unclear. This review outlines the classification of tRFs and tiRNAs and their mechanisms in cancer drug resistance, thus providing new ideas for cancer treatment.

tRNA Fragments Populations Analysis in Mutants Affecting tRNAs Processing and tRNA Methylation

tRNA fragments (tRFs) are a class of small non-coding RNAs (sncRNAs) derived from tRNAs. tRFs are highly abundant in many cell types including stem cells and cancer cells, and are found in all domains of life. Beyond translation control, tRFs have several functions ranging from transposon silencing to cell proliferation control. However, the analysis of tRFs presents specific challenges and their biogenesis is not well understood. They are very heterogeneous and highly modified by numerous post-transcriptional modifications. Here we describe a bioinformatic pipeline (tRFs-Galaxy) to study tRFs populations and shed light onto tRNA fragments biogenesis in Drosophila melanogaster. Indeed, we used small RNAs Illumina sequencing datasets extracted from wild type and mutant ovaries affecting two different highly conserved steps of tRNA biogenesis: 5'pre-tRNA processing (RNase-P subunit Rpp30) and tRNA 2'-O-methylation (dTrm7_34 and dTrm7_32). Using our pipeline, we show how defects in tRNA biogenesis affect nuclear and mitochondrial tRFs populations and other small non-coding RNAs biogenesis, such as small nucleolar RNAs (snoRNAs). This tRF analysis workflow will advance the current understanding of tRFs biogenesis, which is crucial to better comprehend tRFs roles and their implication in human pathology.

Processing by RNase 1 forms tRNA halves and distinct Y RNA fragments in the extracellular environment

Extracellular RNAs participate in intercellular communication, and are being studied as promising minimally invasive diagnostic markers. Several studies in recent years showed that tRNA halves and distinct Y RNA fragments are abundant in the extracellular space, including in biofluids. While their regulatory and diagnostic potential has gained a substantial amount of attention, the biogenesis of these extracellular RNA fragments remains largely unexplored. Here, we demonstrate that these fragments are produced by RNase 1, a highly active secreted nuclease. We use RNA sequencing to investigate the effect of a null mutation of RNase 1 on the levels of tRNA halves and Y RNA fragments in the extracellular environment of cultured human cells. We complement and extend our RNA sequencing results with northern blots, showing that tRNAs and Y RNAs in the non-vesicular extracellular compartment are released from cells as full-length precursors and are subsequently cleaved to distinct fragments. In support of these results, formation of tRNA halves is recapitulated by recombinant human RNase 1 in our in vitro assay. These findings assign a novel function for RNase 1, and position it as a strong candidate for generation of tRNA halves and Y RNA fragments in biofluids.

Production and purification of endogenously modified tRNA-derived small RNAs

During particular stress conditions, transfer RNAs (tRNAs) become substrates of stress-induced endonucleases, resulting in the production of distinct tRNA-derived small RNAs (tsRNAs). These small RNAs have been implicated in a wide range of biological processes, but how isoacceptor and even isodecoder-specific tsRNAs act at the molecular level is still poorly understood. Importantly, stress-induced tRNA cleavage affects only a few tRNAs of a given isoacceptor or isodecoder, raising the question as to how such limited molecule numbers could exert measurable biological impact. While the molecular function of individual tsRNAs is likely mediated through association with other molecules, addressing the interactome of specific tsRNAs has only been attempted by using synthetic RNA sequences. Since tRNAs carry post-transcriptional modifications, tsRNAs are likely modified but the extent of their modifications remains largely unknown. Here, we developed a biochemical framework for the production and purification of specific tsRNAs using human cells. Preparative scale purification of tsRNAs from biological sources should facilitate experimentally addressing as to how exactly these small RNAs mediate the multitude of reported molecular functions.

Identification of tRNA-derived fragments and their potential roles in diabetic cataract rats

Aim: To illustrate the expression profile of transfer RNA-derived fragments and reveal their putative role in the pathogenesis of diabetic cataract (DC) rats. Materials & methods: Small RNA sequencing was conducted in the lens epithelium of rats lens. The data were validated by quantitative real-time PCR, and bioinformatic analysis was performed to explore the roles of the fragments in DC pathogenesis. Results: A total of 213 differentially expressed tRNA-related fragments were identified, in which 111 were upregulated and 102 were downregulated in DC rats. Bioinformatics analysis revealed that several associated pathways might participate in the development of DC rats. Conclusion: tRNA-derived fragments may be involved in the pathogenesis of DC rats.

Role of the RNA-binding protein La in cancer pathobiology

RNA-binding proteins are important regulators of RNA metabolism and are of critical importance in all steps of the gene expression cascade. The role of aberrantly expressed RBPs in human disease is an exciting research field and the potential application of RBPs as a therapeutic target or a diagnostic marker represents a fast-growing area of research.Aberrant overexpression of the human RNA-binding protein La has been found in various cancer entities including lung, cervical, head and neck, and chronic myelogenous leukaemia. Cancer-associated La protein supports tumour-promoting processes such as proliferation, mobility, invasiveness and tumour growth. Moreover, the La protein maintains the survival of cancer cells by supporting an anti-apoptotic state that may cause resistance to chemotherapeutic therapy.The human La protein represents a multifunctional post-translationally modified RNA-binding protein with RNA chaperone activity that promotes processing of non-coding precursor RNAs but also stimulates the translation of selective messenger RNAs encoding tumour-promoting and anti-apoptotic factors. In our model, La facilitates the expression of those factors and helps cancer cells to cope with cellular stress. In contrast to oncogenes, able to initiate tumorigenesis, we postulate that the aberrantly elevated expression of the human La protein contributes to the non-oncogenic addiction of cancer cells. In this review, we summarize the current understanding about the implications of the RNA-binding protein La in cancer progression and therapeutic resistance. The concept of exploiting the RBP La as a cancer drug target will be discussed.

The Emerging Role of Exosomal Non-coding RNAs in Musculoskeletal Diseases

Exosomes are phospholipid bilayer-enclosed membrane vesicles derived and constitutively secreted by various metabolically active cells. They are capable of mediating hetero- and homotypic intercellular communication by transferring multiple cargos from donor cells to recipient cells. Nowadays, non-coding RNAs (ncRNAs) have emerged as novel potential biomarkers or disease-targeting agents in a variety of diseases. However, the lack of effective delivery systems may impair their clinical application. Recently, accumulating evidence demonstrated that ncRNAs could be efficiently delivered to recipient cells using exosomes as a carrier, and therefore can exert a critical role in musculoskeletal diseases including osteoarthritis, rheumatoid arthritis, osteoporosis, muscular dystrophies, osteosarcoma and other diseases. Herein, we present an extensive review of biogenesis, physiological relevance and clinical implication of exosome-derived ncRNAs in musculoskeletal diseases.

Relationship between tRNA-derived fragments and human cancers

tRNA-derived fragments, a class of small noncoding RNAs (sncRNAs), have been identified in numerous studies in recent years. tRNA-derived fragments are classified into two main groups, including tRNA halves (tiRNAs) and tRNA-derived small RNA fragments (tRFs), according to different cleavage positions of the precursor or mature tRNAs. Instead of random tRNA degradation debris, a growing body of evidence has shown that tRNA-derived fragments are precise products of specific tRNA modifications and play important roles in biological activities, such as regulating protein translation, affecting gene expression, and altering immune signaling. Recently, the relations between tRNA-derived fragments and the occurrence of human diseases, especially cancers, have generated wide interest. It has been demonstrated that tRNA-derived fragments are involved in cancer cell proliferation, metastasis, progression and survival. In this review, we will describe the biogenesis of tRNA-derived fragments, the distinct expression and function of tRNA-derived fragments in the development of cancers, and their emerging roles as diagnostic and prognostic biomarkers and precise targets of future treatments.

Emerging Roles of tRNAs in RNA Virus Infections

Viruses rely on the host cell translation machinery for efficient synthesis of their own proteins. Emerging evidence highlights different roles for host transfer RNAs (tRNAs) in the process of virus replication. For instance, different RNA viruses manipulate host tRNA pools to favor viral protein translation. Interestingly, specific host tRNAs are used as reverse transcription primers and are packaged into retroviral virions. Recent data also demonstrate the formation of tRNA-derived fragments (tRFs) upon infection to facilitate viral replication. Here, we comprehensively discuss how RNA viruses exploit distinct aspects of the host tRNA biology for their benefit. In light of the recent advances in the field, we propose that host tRNA-related pathways and mechanisms represent promising cellular targets for the development of novel antiviral strategies.

Modulation of mammalian translation by a ribosome-associated tRNA half

Originally considered futile degradation products, tRNA-derived RNA fragments (tdRs) have been shown over the recent past to be crucial players in orchestrating various cellular functions. Unlike other small non-coding RNA (ncRNA) classes, tdRs possess a multifaceted functional repertoire ranging from regulating transcription, apoptosis, RNA interference, ribosome biogenesis to controlling translation efficiency. A subset of the latter tdRs has been shown to directly target the ribosome, the central molecular machine of protein biosynthesis. Here we describe the function of the mammalian tRNA^Pro 5ʹ half, a 35 residue long ncRNA associated with ribosomes and polysomes in several mammalian cell lines. Addition of tRNA^Pro halves to mammalian in vitro translation systems results in global translation inhibition and concomitantly causes the upregulation of a specific low molecular weight translational product. This tRNA^Pro 5ʹ half-dependent translation product consists of both RNA and amino acids. Transfection of the tRNA^Pro half into HeLa cells leads to the formation of the same product in vivo. The migration of this product in acidic gels, the insensitivity to copper sulphate treatment, the resistance to 3ʹ polyadenylation, and the association with 80S monosomes indicate that the accumulated product is peptidyl-tRNA. Our data thus suggest that binding of the tRNA^Pro 5ʹ half to the ribosome leads to ribosome stalling and to the formation of peptidyl-tRNA. Our findings revealed a so far unknown functional role of a tdR thus further enlarging the functional heterogeneity of this emerging class of ribo-regulators.

Novel insights into the emerging roles of tRNA-derived fragments in mammalian development

tRNA-derived fragments or tRFs were long considered merely degradation intermediates of full-length tRNAs; however, emerging research is highlighting unanticipated new and highly distinct functions in epigenetic control, metabolism, immune activity and stem cell fate commitment. Importantly, recent studies suggest that RNA epitranscriptomic modifications may provide an additional regulatory layer that dynamically directs tRF activity in stem and cancer cells. In this review, we explore current work illustrating unanticipated roles of tRFs in mammalian stem cells with a focus on the impact of post-transcriptional RNA modifications for the biogenesis and function of this growing class of small noncoding RNAs.

Pathological significance of tRNA-derived small RNAs in neurological disorders

Non-coding RNAs (ncRNAs) are a type of RNA that is not translated into proteins. Transfer RNAs (tRNAs), a type of ncRNA, are the second most abundant type of RNA in cells. Recent studies have shown that tRNAs can be cleaved into a heterogeneous population of ncRNAs with lengths of 18–40 nucleotides, known as tRNA-derived small RNAs (tsRNAs). There are two main types of tsRNA, based on their length and the number of cleavage sites that they contain: tRNA-derived fragments and tRNA-derived stress-induced RNAs. These RNA species were first considered to be byproducts of tRNA random cleavage. However, mounting evidence has demonstrated their critical functional roles as regulatory factors in the pathophysiological processes of various diseases, including neurological diseases. However, the underlying mechanisms by which tsRNAs affect specific cellular processes are largely unknown. Therefore, this study comprehensively summarizes the following points: (1) The biogenetics of tsRNA, including their discovery, classification, formation, and the roles of key enzymes. (2) The main biological functions of tsRNA, including its miRNA-like roles in gene expression regulation, protein translation regulation, regulation of various cellular activities, immune mediation, and response to stress. (3) The potential mechanisms of pathophysiological changes in neurological diseases that are regulated by tsRNA, including neurodegeneration and neurotrauma. (4) The identification of the functional diversity of tsRNA may provide valuable information regarding the physiological and pathophysiological mechanisms of neurological disorders, thus providing a new reference for the clinical treatment of neurological diseases. Research into tsRNAs in neurological diseases also has the following challenges: potential function and mechanism studies, how to accurately quantify expression, and the exact relationship between tsRNA and miRNA. These challenges require future research efforts.