5\u27-Terminal nucleotide variations in human cytoplasmic tRNAHisGUG and its 5\u27-halves.

Transfer RNAs (tRNAs) are fundamental adapter components of translational machinery. tRNAs can further serve as a source of tRNA-derived noncoding RNAs that play important roles in various biological processes beyond translation. Among all species of tRNAs, tRNA(HisGUG) has been known to uniquely contain an additional guanosine residue at the -1 position (G-1) of its 5\u27-end. To analyze this -1 nucleotide in detail, we developed a TaqMan qRT-PCR method that can distinctively quantify human mature cytoplasmic tRNA(HisGUG) containing G-1, U-1, A-1, or C-1 or lacking the -1 nucleotide (starting from G1). Application of this method to the mature tRNA fraction of BT-474 breast cancer cells revealed the presence of tRNA(HisGUG) containing U-1 as well as the one containing G-1 Moreover, tRNA lacking the -1 nucleotide was also detected, thus indicating the heterogeneous expression of 5\u27-tRNA(HisGUG) variants. A sequence library of sex hormone-induced 5\u27-tRNA halves (5\u27-SHOT-RNAs), identified via cP-RNA-seq of a BT-474 small RNA fraction, also demonstrated the expression of 5\u27-tRNA(HisGUG) halves containing G-1, U-1, or G1 as 5\u27-terminal nucleotides. Although the detected 5\u27-nucleotide species were identical, the relative abundances differed widely between mature tRNA and 5\u27-half from the same BT-474 cells. The majority of mature tRNAs contained the -1 nucleotide, whereas the majority of 5\u27-halves lacked this nucleotide, which was biochemically confirmed using a primer extension assay. These results reveal the novel identities of tRNA(HisGUG) molecules and provide insights into tRNA(HisGUG) maturation and the regulation of tRNA half production

tRNA-Derived Short Non-coding RNA as Interacting Partners of Argonaute Proteins.

The advent of next-generation sequencing technologies has not only accelerated findings on various novel non-coding RNA (ncRNA) species but also led to the revision of the biological significance and versatility of fundamental RNA species with canonical function, such as transfer RNAs (tRNAs). Although tRNAs are best known as adapter components of translational machinery, recent studies suggest that tRNAs are not always end products but can further serve as a source for short ncRNAs. In many organisms, various tRNA-derived ncRNA species are produced from mature tRNAs or their precursor transcripts as functional molecules involved in various biological processes beyond translation. In this review, we focus on the tRNA-derived ncRNAs associated with Argonaute proteins and summarize recent studies on their conceivable biogenesis factors and on their emerging roles in gene expression regulation as regulatory RNAs

YAMAT-seq: an efficient method for high-throughput sequencing of mature transfer RNAs.

Besides translation, transfer RNAs (tRNAs) play many non-canonical roles in various biological pathways and exhibit highly variable expression profiles. To unravel the emerging complexities of tRNA biology and molecular mechanisms underlying them, an efficient tRNA sequencing method is required. However, the rigid structure of tRNA has been presenting a challenge to the development of such methods. We report the development of Y-shaped Adapter-ligated MAture TRNA sequencing (YAMAT-seq), an efficient and convenient method for high-throughput sequencing of mature tRNAs. YAMAT-seq circumvents the issue of inefficient adapter ligation, a characteristic of conventional RNA sequencing methods for mature tRNAs, by employing the efficient and specific ligation of Y-shaped adapter to mature tRNAs using T4 RNA Ligase 2. Subsequent cDNA amplification and next-generation sequencing successfully yield numerous mature tRNA sequences. YAMAT-seq has high specificity for mature tRNAs and high sensitivity to detect most isoacceptors from minute amount of total RNA. Moreover, YAMAT-seq shows quantitative capability to estimate expression levels of mature tRNAs, and has high reproducibility and broad applicability for various cell lines. YAMAT-seq thus provides high-throughput technique for identifying tRNA profiles and their regulations in various transcriptomes, which could play important regulatory roles in translation and other biological processes

Infection-induced 5′-half molecules of tRNAHisGUG activate Toll-like receptor 7

Toll-like receptors (TLRs) play a crucial role in the innate immune response. Although endosomal TLR7 recognizes single-stranded RNAs, their endogenous RNA ligands have not been fully explored. Here, we report 5 '-tRNA half molecules as abundant activators of TLR7. Mycobacterial infection and accompanying surface TLR activation up-regulate the expression of 5 '-tRNA half molecules in human monocyte-derived macrophages (HMDMs). The abundant accumulation of 5 '-tRNA halves also occur in HMDM-secreted extracellular vehicles (EVs); the abundance of EV-5 '-tRNA(HisGUG) half molecules is >200-fold higher than that of the most abundant EV-microRNA (miRNA). Sequence identification of the 5 '-tRNA halves using cP-RNA-seq revealed abundant and selective packaging of specific 5 '-tRNA half species into EVs. The EV-5 '-tRNA(HisGUG) half was experimentally demonstrated to be delivered into endosomes in recipient cells and to activate endosomal TLR7. Up-regulation of the 5 '-tRNA half molecules was also observed in the plasma of patients infected with Mycobacterium tuberculosis. These results unveil a novel tRNA-engaged pathway in the innate immune response and assign the role of "immune activators" to 5 '-tRNA half molecules

Making Invisible RNA Visible: Discriminative Sequencing Methods for RNA Molecules with Specific Terminal Formations

Next generation sequencing of RNA molecules (RNA-seq) has become a common tool to characterize the expression profiles of RNAs and their regulations in normal physiological processes and diseases. Although increasingly accumulating RNA-seq data are widely available through publicly accessible sites, most of the data for short non-coding RNAs (sncRNAs) have been obtained for microRNA (miRNA) analyses by standard RNA-seq, which only capture the sncRNAs with 5′-phosphate (5′-P) and 3′-hydroxyl (3′-OH) ends. The sncRNAs with other terminal formations such as those with a 5′-hydroxyl end (5′-OH), a 3′-phosphate (3′-P) end, or a 2′,3′-cyclic phosphate end (2′,3′-cP) cannot be efficiently amplified and sequenced by standard RNA-seq. Due to the invisibility in standard RNA-seq data, these non-miRNA-sncRNAs have been a hidden component in the transcriptome. However, as the functional significances of these sncRNAs have become increasingly apparent, specific RNA-seq methods compatible with various terminal formations of sncRNAs have been developed and started shedding light on the previously unrecognized sncRNAs that lack 5′-P/3′-OH ends. In this review, we summarize the expanding world of sncRNAs with various terminal formations and the strategic approaches of specific RNA-seq methods to distinctively characterize their expression profiles

Increasing cell density globally enhances the biogenesis of Piwi-interacting RNAs in Bombyx mori germ cells.

Piwi proteins and their bound Piwi-interacting RNAs (piRNAs) are predominantly expressed in the germline and play crucial roles in germline development by silencing transposons and other targets. Bombyx mori BmN4 cells are culturable germ cells that equip the piRNA pathway. Because of the scarcity of piRNA-expressing culturable cells, BmN4 cells are being utilized for the analyses of piRNA biogenesis. We here report that the piRNA biogenesis in BmN4 cells is regulated by cell density. As cell density increased, the abundance of Piwi proteins and piRNA biogenesis factors was commonly upregulated, resulting in an increased number of perinuclear nuage-like granules where Piwi proteins localize. Along with these phenomena, the abundance of mature piRNAs also globally increased, whereas levels of long piRNA precursor and transposons decreased, suggesting that increasing cell density promotes piRNA biogenesis pathway and that the resultant accumulation of mature piRNAs is functionally significant for transposon silencing. Our study reveals a previously uncharacterized link between cell density and piRNA biogenesis, designates cell density as a critical variable in piRNA studies using BmN4 cell system, and suggests the alteration of cell density as a useful tool to monitor piRNA biogenesis and function

Angiogenin mRNA Expression Levels in Prostate Cancer Tissue

Introduction: Prostate cancer is the most commonly diagnosed cancer in men and second leading cause of cancer deaths. Studies have shown that tRNA fragments are upregulated in prostate cancers and play important roles in carcinogenesis. This project looks at how tRNA cleaving enzyme angiogenin expression is regulated in prostate cancer tissues. Methods: Clinical data and mRNA expression levels of selected tRNA cleaving enzymes were extracted from the TCGA website. mRNAs were sequenced using IlluminaGA_RNASeqV2 at University of North Carolina. Results: 546 samples from 494 patients, with normal tissue from 53 patients were collected. ANG mRNA levels were lower in patients with higher Gleason scores(Intercept=1321.787362, regression coefficient= -87.05499452, R2=0.038). ANG mRNA levels were inconclusive in different clinical T grade(p=0.15), but were lower in higher pathologic T grade(intercept=1100.484695, x variable=-166.9047227, R2=0.038); ANG expression was lower in patients with nodal involvement versus without(539.56 vs 673.58, p=0.005). Discussion: Overall trend we found from the results were ANG mRNA expression levels are down regulated in patients that have more advanced disease versus early disease. This supports the hypothesis that ANG expression plays an interesting role in prostate cancer biology. This trend might be due to the negative feedback due to high levels of tRNA fragments however there is no single theory available to answer this question

MINTbase v2.0: a comprehensive database for tRNA-derived fragments that includes nuclear and mitochondrial fragments from all The Cancer Genome Atlas projects.

MINTbase is a repository that comprises nuclear and mitochondrial tRNA-derived fragments (\u27tRFs\u27) found in multiple human tissues. The original version of MINTbase comprised tRFs obtained from 768 transcriptomic datasets. We used our deterministic and exhaustive tRF mining pipeline to process all of The Cancer Genome Atlas datasets (TCGA). We identified 23 413 tRFs with abundance of ≥ 1.0 reads-per-million (RPM). To facilitate further studies of tRFs by the community, we just released version 2.0 of MINTbase that contains information about 26 531 distinct human tRFs from 11 719 human datasets as of October 2017. Key new elements include: the ability to filter tRFs on-the-fly by minimum abundance thresholding; the ability to filter tRFs by tissue keywords; easy access to information about a tRF\u27s maximum abundance and the datasets that contain it; the ability to generate relative abundance plots for tRFs across cancer types and convert them into embeddable figures; MODOMICS information about modifications of the parental tRNA, etc. Version 2.0 of MINTbase contains 15x more datasets and nearly 4x more distinct tRFs than the original version, yet continues to offer fast, interactive access to its contents. Version 2.0 is available freely at http://cm.jefferson.edu/MINTbase/

Generation of 2′,3′-Cyclic Phosphate-Containing RNAs as a Hidden Layer of the Transcriptome

Cellular RNA molecules contain phosphate or hydroxyl ends. A 2′,3′-cyclic phosphate (cP) is one of the 3′-terminal forms of RNAs mainly generated from RNA cleavage by ribonucleases. Although transcriptome profiling using RNA-seq has become a ubiquitous tool in biological and medical research, cP-containing RNAs (cP-RNAs) form a hidden transcriptome layer, which is infrequently recognized and characterized, because standard RNA-seq is unable to capture them. Despite cP-RNAs’ invisibility in RNA-seq data, increasing evidence indicates that they are not accumulated simply as non-functional degradation products; rather, they have physiological roles in various biological processes, designating them as noteworthy functional molecules. This review summarizes our current knowledge of cP-RNA biogenesis pathways and their catalytic enzymatic activities, discusses how the cP-RNA generation affects biological processes, and explores future directions to further investigate cP-RNA biology

Infection-induced 5\u27-half molecules of tRNAHisGUG activate Toll-like receptor 7.

Toll-like receptors (TLRs) play a crucial role in the innate immune response. Although endosomal TLR7 recognizes single-stranded RNAs, their endogenous RNA ligands have not been fully explored. Here, we report 5\u27-tRNA half molecules as abundant activators of TLR7. Mycobacterial infection and accompanying surface TLR activation up-regulate the expression of 5\u27-tRNA half molecules in human monocyte-derived macrophages (HMDMs). The abundant accumulation of 5\u27-tRNA halves also occur in HMDM-secreted extracellular vehicles (EVs); the abundance of EV-5\u27-tRNAHisGUG half molecules is \u3e200-fold higher than that of the most abundant EV-microRNA (miRNA). Sequence identification of the 5\u27-tRNA halves using cP-RNA-seq revealed abundant and selective packaging of specific 5\u27-tRNA half species into EVs. The EV-5\u27-tRNAHisGUG half was experimentally demonstrated to be delivered into endosomes in recipient cells and to activate endosomal TLR7. Up-regulation of the 5\u27-tRNA half molecules was also observed in the plasma of patients infected with Mycobacterium tuberculosis. These results unveil a novel tRNA-engaged pathway in the innate immune response and assign the role of immune activators to 5\u27-tRNA half molecules