RNA Biology最新文献

Bacterial RNA polymerases (RNAP) utilize 6S RNAs as templates to synthesize ultrashort transcripts (up to ~14 nt), termed product RNAs (pRNAs), that play a key role in reversing the blockage of RNAP by 6S RNA. Here, we resolved the pRNA length profile of 6S-1 RNA from B. subtilis, a major model system for the study of 6S RNA biology, during outgrowth of cells from extended stationary phase. 9-mers were found to be a particularly abundant pRNA length species, followed by 8-/10-/11-mers and 13-/14-mers. Consistent with in vitro data from the Escherichia coli system, these findings support the mechanistic model according to which the housekeeping sigma factor (σ⁷⁰ or σ^A) dissociates from 6S RNA:RNAP complexes upon synthesis of pRNA 9-mers, followed by final dissociation of 6S RNA and RNAP upon synthesis of longer pRNAs (13-/14-mers). Methodologically, the identification of such ultrashort RNAs in total cellular extracts by RNA-Seq is inefficient with standard protocols using adapter ligation to RNA 3'-ends for reverse transcription and PCR-based cDNA sequencing. Here, we demonstrate that ultrashort RNAs can instead be incorporated into RNA-Seq libraries by polyA-, polyC- and potentially also polyU-tailing of their 3'-ends. At positions where a non-tailing nucleotide is followed by one or more tailing nucleotides, an algorithm that integrates RNA-Seq results from at least two different 3'-end tailings allows one to approximate the fraction of read counts at such ambiguous positions. Finally, methodological biases and potential applications of our approach to other short RNAs are discussed.

The mRNA translation defines the composition of the cell proteome in all forms of life and diseases. In this process, precise selection of the mRNA translation initiation site (TIS) is crucial, as it establishes the correct open reading frame for triplet decoding. We have gathered and curated all published TIS consensus context sequences. We also included the TIS consensus context from novel 538 fungal genomes available from NCBI's RefSeq database. To do so, we wrote ad hoc programs in PERL to find and extract the TIS for each annotated gene, plus ten bases upstream and three downstream. For each genome, the sequences around the TIS of each gene were obtained, and the consensus was further calculated according to the Cavener rules and by the LOGOS algorithm. We created AUGcontext DB, a portal with a comprehensive collection of TIS context sequences across eukaryotes in a range from -10 to + 6. The compilation covers species of 30 vertebrates, 17 invertebrates, 25 plants, 14 fungi, and 11 protists studied in silico; 23 experimental studies; data on biotechnology; and the discovery of 8 diseases associated with specific mutations. Additionally, TIS context sequences of cellular IRESs were included. AUGcontext DB belongs to the National Institute of Cancer (Instituto Nacional de Cancerología, INCan), Mexico, and is freely available at http://108.161.138.77:8096/. Our catalogue allows us to do comparative studies between species, may help improve the diagnosis of certain diseases, and will be key to maximize the production of recombinant proteins.

This study aimed to identify differentially expressed non-coding RNAs (ncRNAs) associated with preterm birth (PTB) and determine biological pathways being influenced in the context of PTB. We processed cell-free RNA sequencing data and identified seventeen differentially expressed (DE) ncRNAs that could be involved in the onset of PTB. Per the validation via customized RT-qPCR, the recorded variations in expressions of eleven ncRNAs were concordant with the in-silico analyses. The results of this study provide insights into the role of DE ncRNAs and their impact on pregnancy-related biological pathways that could lead to PTB. Further studies are required to elucidate the precise mechanisms by which these DE ncRNAs contribute to adverse pregnancy outcomes (APOs) and their potential as diagnostic biomarkers.

Sonneratia apetala is a pioneering species of mangrove plants, which has evolved various mechanisms to tolerate salt-stress due to their long-term exposure to a salinized environment as compared to the of terrestrial freshwater plants. However, limited attempt has been made to uncover the underlying molecular mechanism of their saline adaptation. Here, we integrated mRNA and microRNA (miRNA) sequencing to identify the genes and pathways that may be involved in salt stress-response in the roots of S. apetala. A comprehensive full‑length transcriptome containing 295,501 high‑quality unigenes was obtained by PacBio sequencing technology. Of these, 6,686 genes exhibited significantly differential accumulation after salt stress treatment (p < 0.001, Q < 0.01). They were mainly implicated in plant signal transduction and diverse metabolic pathways, such as those involving phenylpropanoid biosynthesis, plant-pathogen interaction and protein processing. Also, our results identified the regulatory interaction between miRNA-target counterparts during salt stress. Taken together, we present the first global overview of the transcriptome of S. apetala roots, and identify potentially important genes and pathways associated with salt tolerance for further investigation. This study is expected to deliver novel insights in understanding the regulatory mechanism in S. apetala response to salt stress.

RNA is fundamental for life, and its homoeostasis is a critical contributor to cellular growth and adaptation to stress. Key RNA species include messenger RNA (mRNA) and non-coding RNAs, such as transfer RNA (tRNA), or ribosomal RNA (rRNA), that are essential for ribosome formation and translation of the genetic code. Furthermore, various other non-coding RNAs are expressed at each growth stage. Given RNA's abundance and its role in all cellular processes, RNases - enzymes responsible for RNA degradation and processing - are central to RNA metabolism. In this review, we discuss the pivotal contribution of the 3' exonuclease RNase R to bacterial RNA homoeostasis. We focus on its functions in regulating and degrading components of the translation machinery, including the trans-translation system, and we take a look at recent structural studies that shed new light on the activities of this important enzyme.

Circular RNAs (circRNAs) are a unique class of covalently closed single-stranded RNA molecules that play diverse roles in normal physiology and pathology. Among the major types of circRNA, exon-intron circRNA (EIciRNA) distinguishes itself by its sequence composition and nuclear localization. Recent RNA-seq technologies and computational methods have facilitated the detection and characterization of EIciRNAs, with features like circRNA intron retention (CIR) and tissue-specificity being characterized. EIciRNAs have been identified to exert their functions via mechanisms such as regulating gene transcription, and the physiological relevance of EIciRNAs has been reported. Within this review, we present a summary of the current understanding of EIciRNAs, delving into their identification and molecular functions. Additionally, we emphasize factors regulating EIciRNA biogenesis and the physiological roles of EIciRNAs based on recent research. We also discuss the future challenges in EIciRNA exploration, underscoring the potential for novel functions and functional mechanisms of EIciRNAs for further investigation.

The germline genome serves as a crucial battleground for transposon expansion, as transposons can increase their copy numbers in offspring when activated within germ cells. Unexpectedly, during Drosophila spermatogenesis, the piRNA pathway, typically responsible for transposon silencing in female germ cells, is significantly downregulated, coinciding with a burst of transposon expression in spermatocytes. This suggests that germ cells might rely on alternative mechanisms for transposon suppression. By leveraging single-cell Smart-seq transcriptomic data, we found that transposon expression, Adar expression, and A-to-I RNA editing efficiency are markedly elevated in Drosophila spermatocytes. Adar mutant flies exhibit higher testicular TE expression, likely resulting from the loss of editing-mediated suppression. In the absence of a fully functional piRNA pathway in male germline, Adar-mediated RNA editing may act as an alternative mechanism for transposon silencing, highlighting a potential role for Adar in maintaining genome integrity.

Germ cells depend on specialized post-transcriptional regulation for proper development and function, much of which is mediated by dynamic RNA granules. These membrane-less organelles form through the condensation of RNA and proteins, governed by multivalent biomolecular interactions. RNA granules compartmentalize cellular components, selectively enriching specific factors and modulating biochemical reactions. Over recent decades, various types of RNA granules have been identified in germ cells across species, with extensive studies uncovering their molecular roles and developmental significance. This review explores the mRNA regulatory mechanisms mediated by RNA granules in germ cells. We discuss the distinct spatial organization of specific granule components and the variations in material states of germ granules, which contribute to the regulation of mRNA storage and translation. Additionally, we highlight emerging research on how changes in these material states, during developmental stages, reflect the dynamic nature of germ granules and their critical role in development.

The sources and degradation profiles of dissolved environmental RNAs from fish in water remain unknown. In this study, laboratory experiments and mathematical modelling were conducted to investigate the permeability of RNA extracted from zebrafish cells through filters, the release of dissolved environmental RNAs from live and dying zebrafish cells, and the degradation of RNA extracted from zebrafish cells in a non-sterile aqueous environment. This research aimed to provide biological and ecological insights into fish RNAs dissolved in water. The results showed that most of the RNA extracted from zebrafish cells was detected in the filtrates after passage through 0.45 µm filters. Over the course of the 6-day experiment, dynamic levels of the RNAs in the liquid environment containing live or dying zebrafish cells were determined. The release and degradation rates of dissolved environmental RNA from zebrafish cells were calculated using mathematical modelling. RNA extracted from zebrafish cells degraded in non-sterile water in the tubes, and after 2 months, more than 15% of the RNAs in the water remained detectable. The half-life of the RNA in the tubes was approximately 20 ~ 43 days. The modelling results suggest that the levels of the dissolved environmental fish RNAs in natural waters or aquariums could be so low that it would be difficult to detect them using current techniques. The results obtained in this study will help develop new methods for measuring the dynamics of dissolved environmental fish RNAs in water and determining their significance.

RNA cis elements play pivotal roles in regulatory processes, e.g. in transcriptional and translational regulation. Two stem-looped cis elements, the constitutive and alternative decay elements (CDE and ADE, respectively) are shape-specifically recognized in mRNA 3' untranslated regions (UTRs) by the immune-regulatory protein Roquin. Roquin initiates mRNA decay and contributes to balanced transcript levels required for immune homoeostasis. While the interaction of Roquin with several CDEs is described, our knowledge about ADE complex formation is limited to the mRNA of Ox40, a gene encoding a T-cell costimulatory receptor. The Ox40 3'UTR comprises both a CDE and ADE, each sufficient for Roquin-mediated control. Opposed to highly conserved and abundant CDE structures, ADEs are rarer, but predicted to exhibit a greater structural heterogeneity. This raises the question of how and when two structurally distinct cis elements evolved as equal target motifs for Roquin. Using an interdisciplinary approach, we here monitor the evolution of sequence and structure features of the Ox40 ADE across species. We designed RNA variants to probe en-detail determinants steering Roquin-RNA complex formation. Specifically, those reveal the contribution of a second RNA-binding interface of Roquin for recognition of the ADE basal stem region. In sum, our study sheds light on how the conserved Roquin protein selected ADE-specific structural features to evolve a second high-affinity mRNA target cis element relevant for adaptive immune regulation. As our findings also allow expanding the RNA target spectrum of Roquin, the approach can serve a paradigm for understanding RNA-protein specificity through back-tracing the evolution of the RNA element.