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

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

The biogenesis pathway of tRNA-derived piRNAs in Bombyx germ cells.

Transfer RNAs (tRNAs) function in translational machinery and further serves as a source of short non-coding RNAs (ncRNAs). tRNA-derived ncRNAs show differential expression profiles and play roles in many biological processes beyond translation. Molecular mechanisms that shape and regulate their expression profiles are largely unknown. Here, we report the mechanism of biogenesis for tRNA-derived Piwi-interacting RNAs (td-piRNAs) expressed in Bombyx BmN4 cells. In the cells, two cytoplasmic tRNA species, tRNAAspGUC and tRNAHisGUG, served as major sources for td-piRNAs, which were derived from the 5\u27-part of the respective tRNAs. cP-RNA-seq identified the two tRNAs as major substrates for the 5\u27-tRNA halves as well, suggesting a previously uncharacterized link between 5\u27-tRNA halves and td-piRNAs. An increase in levels of the 5\u27-tRNA halves, induced by BmNSun2 knockdown, enhanced the td-piRNA expression levels without quantitative change in mature tRNAs, indicating that 5\u27-tRNA halves, not mature tRNAs, are the direct precursors for td-piRNAs. For the generation of tRNAHisGUG-derived piRNAs, BmThg1l-mediated nucleotide addition to -1 position of tRNAHisGUG was required, revealing an important function of BmThg1l in piRNA biogenesis. Our study advances the understanding of biogenesis mechanisms and the genesis of specific expression profiles for tRNA-derived ncRNAs

Sex hormone-dependent tRNA halves enhance cell proliferation in breast and prostate cancers.

Sex hormones and their receptors play critical roles in the development and progression of the breast and prostate cancers. Here we report that a novel type of transfer RNA (tRNA)-derived small RNA, termed Sex HOrmone-dependent TRNA-derived RNAs (SHOT-RNAs), are specifically and abundantly expressed in estrogen receptor (ER)-positive breast cancer and androgen receptor (AR)-positive prostate cancer cell lines. SHOT-RNAs are not abundantly present in ER(-) breast cancer, AR(-) prostate cancer, or other examined cancer cell lines from other tissues. ER-dependent accumulation of SHOT-RNAs is not limited to a cell culture system, but it also occurs in luminal-type breast cancer patient tissues. SHOT-RNAs are produced from aminoacylated mature tRNAs by angiogenin-mediated anticodon cleavage, which is promoted by sex hormones and their receptors. Resultant 5\u27- and 3\u27-SHOT-RNAs, corresponding to 5\u27- and 3\u27-tRNA halves, bear a cyclic phosphate (cP) and an amino acid at the 3\u27-end, respectively. By devising a cP-RNA-seq method that is able to exclusively amplify and sequence cP-containing RNAs, we identified the complete repertoire of 5\u27-SHOT-RNAs. Furthermore, 5\u27-SHOT-RNA, but not 3\u27-SHOT-RNA, has significant functional involvement in cell proliferation. These results have unveiled a novel tRNA-engaged pathway in tumorigenesis of hormone-dependent cancers and implicate SHOT-RNAs as potential candidates for biomarkers and therapeutic targets

Modulation of Aub-TDRD interactions elucidates piRNA amplification and germplasm formation.

Aub guided by piRNAs ensures genome integrity by cleaving retrotransposons, and genome propagation by trapping mRNAs to form the germplasm that instructs germ cell formation. Arginines at the N-terminus of Aub (Aub-NTRs) interact with Tudor and other Tudor domain-containing proteins (TDRDs). Aub-TDRD interactions suppress active retrotransposons via piRNA amplification and form germplasm via generation of Aub-Tudor ribonucleoproteins. Here, we show that Aub-NTRs are dispensable for primary piRNA biogenesis but essential for piRNA amplification and that their symmetric dimethylation is required for germplasm formation and germ cell specification but largely redundant for piRNA amplification

Sex Hormones Regulate The Expression of Short Non-Coding RNAs

Presentation: 29 minute