Sense and Antisense Transcripts of Convergent Gene Pairs in Arabidopsis thaliana Can Share a Common Polyadenylation Region

The Arabidopsis genome contains a large number of gene pairs that encode sense and antisense transcripts with overlapping 3′ regions, indicative for a potential role of natural antisense transcription in regulating sense gene expression or transcript processing. When we mapped poly(A) transcripts of three plant gene pairs with long overlapping antisense transcripts, we identified an unusual transcript composition for two of the three gene pairs. Both genes pairs encoded a class of long sense transcripts and a class of short sense transcripts that terminate within the same polyadenylation region as the antisense transcripts encoded by the opposite strand. We find that the presence of the short sense transcript was not dependent on the expression of an antisense transcript. This argues against the assumption that the common termination region for sense and antisense poly(A) transcripts is the result of antisense-specific regulation. We speculate that for some genes evolution may have especially favoured alternative polyadenylation events that shorten transcript length for gene pairs with overlapping sense/antisense transcription, if this reduces the likelihood for dsRNA formation and transcript degradation

Translation and emerging functions of non‐coding RNAs in inflammation and immunity

Regulatory non-coding RNAs (ncRNAs) including small non-coding RNAs (sRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) have gained considerable attention in the last few years. This is mainly due to their condition- and tissue-specific expression and their various modes of action, which suggests them as promising biomarkers and therapeutic targets. One important mechanism of ncRNAs to regulate gene expression is through translation of short open reading frames (sORFs). These sORFs can be located in lncRNAs, in non-translated regions of mRNAs where upstream ORFs (uORFs) represent the majority, or in circRNAs. Regulation of their translation can function as a quick way to adapt protein production to changing cellular or environmental cues, and can either depend solely on the initiation and elongation of translation, or on the roles of the produced functional peptides. Due to the experimental challenges to pinpoint translation events and to detect the produced peptides, translational regulation through regulatory RNAs is not well studied yet. In the case of circRNAs, they have only recently started to be recognized as regulatory molecules instead of mere artifacts of RNA biosynthesis. Of the many roles described for regulatory ncRNAs, we will focus here on their regulation during inflammation and in immunity

The how and why of lncRNA function: An innate immune perspective.

Next-generation sequencing has provided a more complete picture of the composition of the human transcriptome indicating that much of the "blueprint" is a vastness of poorly understood non-protein-coding transcripts. This includes a newly identified class of genes called long noncoding RNAs (lncRNAs). The lack of sequence conservation for lncRNAs across species meant that their biological importance was initially met with some skepticism. LncRNAs mediate their functions through interactions with proteins, RNA, DNA, or a combination of these. Their functions can often be dictated by their localization, sequence, and/or secondary structure. Here we provide a review of the approaches typically adopted to study the complexity of these genes with an emphasis on recent discoveries within the innate immune field. Finally, we discuss the challenges, as well as the emergence of new technologies that will continue to move this field forward and provide greater insight into the biological importance of this class of genes. This article is part of a Special Issue entitled: ncRNA in control of gene expression edited by Kotb Abdelmohsen

Post-transcriptional Regulation through Long Noncoding RNAs (lncRNAs)

This book is a collection of eight articles, of which seven are reviews and one is a research paper, that together form a Special Issue that describes the roles that long noncoding RNAs (lncRNA) play in gene regulation at a post-transcriptional level

Translation and emerging functions of non-coding RNAs in inflammation and immunity

Regulatory non-coding RNAs (ncRNAs) including small non-coding RNAs (sRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) have gained considerable attention in the last few years. This is mainly due to their condition- and tissue-specific expression and their various modes of action, which suggests them as promising biomarkers and therapeutic targets. One important mechanism of ncRNAs to regulate gene expression is through translation of short open reading frames (sORFs). These sORFs can be located in lncRNAs, in non-translated regions of mRNAs where upstream ORFs (uORFs) represent the majority, or in circRNAs. Regulation of their translation can function as a quick way to adapt protein production to changing cellular or environmental cues, and can either depend solely on the initiation and elongation of translation, or on the roles of the produced functional peptides. Due to the experimental challenges to pinpoint translation events and to detect the produced peptides, translational regulation through regulatory RNAs is not well studied yet. In the case of circRNAs, they have only recently started to be recognized as regulatory molecules instead of mere artifacts of RNA biosynthesis. Of the many roles described for regulatory ncRNAs, we will focus here on their regulation during inflammation and in immunity. Keywords: immunology; inflammation; non-coding RNA; regulation; translatio

Generation of antisense RNAs at convergent gene loci in cells undergoing senescence

La sénescence, qui est un mécanisme antitumoral majeur, est définie comme un état d'arrêt irréversible de la prolifération cellulaire en réponse à un stress comme l'activation illégitime d'oncogènes. Les cellules qui entrent en sénescence subissent de profonds changements de leur épigénome. Les ARNs antisens sont suspectés de joue des rôles importants dans le contrôle du destin cellulaire et dans des processus cellulaires variés. Dans la levure, le variant d'histone H2A.Z co-opère avec les machineries du RNAi et de l'hétérochromatine pour réprimer sur les loci de gènes convergents l'apparition d'antisens dus à des défauts de terminaison de transcription de un des deux gènes. Chez les mammifères, l'existence et la régulation de tels transcrits antisens restent inconnues. De façon intéressante, la déplétion du variant d'histones H2A.Z est connue pour induire la sénescence. Nous nous sommes donc demandés si la sénescence est accompagnée de la régulation de tels transcrits antisens sur les gènes convergents, si la régulation par H2A.Z est conservée et si ces transcrits pouvaient avoir un rôle fonctionnel. Dans un modèle de sénescence induite par les oncogènes in vitro, nous avons identifiés par RNA-Seq brin spécifiques plusieurs loci de gènes convergents où des ARN antisens pourraient être générés par des défauts de terminaison de transcription sur le gène convergent. Des analyses en profondeurs sur deux loci ont confirmé que les transcrits antisens sont effectivement générés par un tel mécanisme (appelé "read-through transcriptionnel"). Nous avons appelé ces antisens START RNAs (pour " Senescence Triggered Antisense Read-through Transcripts). Nous avons par la suite montré que ces STARTs répriment l'expression du gène pour lequel ils sont antisens. Finalement, nous avons montré qu'ils sont réprimés par H2A.Z dans les cellules en prolifération. Nous proposons donc un modèle où la progression en sénescence s'accompagne d'une diminution de H2A.Z, ce qui se traduit par l'induction de transcrits antisens régulateurs sur une famille de loci de gènes convergents dus à des défauts de contrôle de la terminaison de la transcription.Cellular senescence represents one of the major fail-safe mechanisms that counteracts tumour development is defined as a state of irreversible cell cycle arrest as a consequence of stress response such as oncogenic challenge. Such cells undergoing Oncogene-induced Senescence (OIS) display profound alternation in their epigenome as their chromatin are largely decorated with prominent drivers of constitutive heterochromatin. Antisense RNA-mediated gene regulation has been attributed to play diverse roles in mediating various cellular processes and cell fates per-se. In yeast, histone variant H2A.Z cooperates with RNAi and heterochromatin machinery to regulate antisense transcription at convergent gene loci which can otherwise generate pervasive read-through transcripts owing to improper transcription termination. In mammals, whether such antisense transcripts (occurring by read-through transcription at convergent gene pairs) exist and how they are regulated remains unknown. Interestingly, the depletion of the human H2A.Z histone variant has been reported to induce cellular senescence. We thus wondered if the regulation of particular antisense transcripts at convergent gene pairs occurs in senescence, if their regulation by H2A.Z is conserved in mammals and, if so, if a functional significance can be attributed to these transcripts. To this end we took advantage of a well-established in-vitro OIS model Briefly, we analysed genome wide strand specific RNA-seq analysis of cells undergoing Oncogene Induced Senescence. This led us to identify numerous convergent gene loci associated with accumulation of transcripts downstream of the designated transcription termination site in senescent cells, and extending to generate an antisense to the next gene located in the opposite strand of the convergent gene pair. We confirmed the RNA-seq data at two of such convergent loci. An RNAi based approach revealed that at least two of these transcripts are generated by transcriptional read-throughs. Hence we designated such pervasive transcripts as Senescence Triggered Antisense Read-through Transcripts (START). Importantly, we further found that the two STARTs for which we performed in depth studies repress the expression of the gene for which they are antisense. Finally, we demonstrate that the histone variant H2A.Z suppresses the accumulation of STARTs in proliferative cells. Since it also prevents senescence induction, this suggests that expression of START is important for cellular senescence. This has lead us to propose a model that human cells undergoing OIS are associated with loss of H2A.Z that leads to the wide spread accumulation of read-through transcripts owing to impaired termination control

Post-Transcriptional Control of RNA Expression in Cancer

Approximately 80% of the human genome contains functional DNA, including protein coding genes, non-protein coding regulatory DNA elements and non-coding RNAs (ncRNAs). An altered transcriptional signature is not only a cause, but also a consequence of the characteristics known as the hallmarks of cancer, such as sustained proliferation, replicative immortality, evasion of growth suppression and apoptotic signals, angiogenesis, invasion, metastasis, evasion of immune destruction and metabolic re-wiring. Post-transcriptional events play a major role in determining this signature, which is evidenced by the fact that alternative RNA splicing takes place in more than half of the human genes, and, among protein coding genes, more than 60% contain at least one conserved miRNA-binding site. In this chapter, we will discuss the involvement of post-transcriptional events, such as RNA processing, the action of non-coding RNAs and RNA decay in cancer development, and how their machinery may be used in cancer diagnosis and treatment

Nonsense-mediated RNA decay and its bipolar function in cancer

ReviewNonsense-mediated decay (NMD) was first described as a quality-control mechanism that targets and rapidly degrades aberrant mRNAs carrying premature termination codons (PTCs). However, it was found that NMD also degrades a significant number of normal transcripts, thus arising as a mechanism of gene expression regulation. Based on these important functions, NMD regulates several biological processes and is involved in the pathophysiology of a plethora of human genetic diseases, including cancer. The present review aims to discuss the paradoxical, pro- and anti-tumorigenic roles of NMD, and how cancer cells have exploited both functions to potentiate the disease. Considering recent genetic and bioinformatic studies, we also provide a comprehensive overview of the present knowledge of the advantages and disadvantages of different NMD modulation-based approaches in cancer therapy, reflecting on the challenges imposed by the complexity of this disease. Furthermore, we discuss significant advances in the recent years providing new perspectives on the implications of aberrant NMD-escaping frameshifted transcripts in personalized immunotherapy design and predictive biomarker optimization. A better understanding of how NMD differentially impacts tumor cells according to their own genetic identity will certainly allow for the application of novel and more effective personalized treatments in the near future.Gonçalo Nogueira, Rafael Fernandes, and Juan Fernandez García-Moreno are recipients of a fellowship from BioSys PhD programme PD65-2012 (SFRH/PD/BD/130959/2017, SFRH/BD/114392/2016 and SFRH/PD/BD/142898/2018, respectively) from FCT. This work was partially supported by UID/MULTI/04046/2019 Research Unit grant (to BioISI).info:eu-repo/semantics/publishedVersio

The functions of the RNA polymerase II CTD in transcription and RNA processing

RNA polymerase II (RNAP II), transcribing messenger RNAs (mRNAs), small nuclear RNAs (snRNAs), and non-coding RNAs (ncRNAs), is composed of 12 subunits. Rpb1, the largest subunit with catalytic polymerase activity, possesses a unique c-terminal domain (CTD) that consists of tandem heptad repeats with the consensus sequence of Tyr-Ser-Pro-Thr-Ser-Pro-Ser (Y1S2P3T4S5P6S7). Somewhat reflecting the complexity of the organism, the number of repeats varies, from 26 in yeast to 52 in vertebrates. The CTD, intensively phosphorylated during transcription, serves a means to coordinate transcription and RNA processing- capping, splicing, and 3' end formation. For example, Ser 5, phosphorylated in the start of transcription, promotes the recruitment of capping enzyme, and Ser 2 phosphorylation facilitates RNA 3' end formation and transcription termination by acting as a landing pad for Pcf11. Detailed introduction is described in Chapter 1. Because of the importance of the CTD in these events, I created an Rpb1 conditional knock-out DT40 cell line (DT40-Rpb1) to further study the CTD with an initial focus on Thr 4, the function of which was unclear. Using DT40-Rpb1 system, we found that Thr 4 was phosphorylated in yeast, fly, chicken, and human cells, and cyclin-dependent kinase (CDK9) was likely the kinase to carry out this phosphorylation. We further provide evidence that Thr 4 functions in histone mRNA 3' end formation (presented mostly in chapter 2 of this thesis). Chapter 3 mainly describes the studies regarding Ser 2, Ser 5, and Ser 7. Based on the DT40-Rpb1 cell line, I created stable cell lines expressing an Rpb1 carrying a CTD with Ser 2, Ser 5, or Ser 7 mutated to alanine, and investigated the phenotypes of these cells. We found that cells expressing an Rpb1 with S2A or S5A mutation were defective in transcription and RNA processing. Contrary to previous findings, we found Ser 7 was not involved in snRNA expression and 3' end processing. In fact, no phenotypes associated with Ser 7 mutation were detected by our measurements. Extending previous Thr 4 studies, we showed in vitro and in vivo that Fcp1 dephosphorylated Thr 4. Finally, Chapter 4 describes what we have found the functions of CTD Tyr 1. Using the DT40-Rpb1 cells, I created stable cell lines expressing an Rpb1 with all Tyr residues mutated to phenylalanine (Phe). We found these cells were inviable, and the mutant Rpb1-Y1F was degraded to a CTD-less protein. Interestingly, the instability of Rpb1-Y1F was restored by reintroduction of one Tyr residue at the last heptad repeat. Further analysis provided evidence showing the involvement of Tyr phosphorylation in preventing Rpb1 from degradation by the 20S proteasome. Next, using ChIP assay, we showed Tyr phosphorylation was detected mostly at promoters, indicating a function of Tyr phosphorylation in transcription initiation. Indeed, transcription initiation defects were uncovered by assessing the recruitment of general transcription factors in cells with Y1F mutation. Extending this, we found an accumulation of upstream antisense RNAs in about one hundred reference genes by RNA-Seq analysis