Emerging Roles of RNA 3'-end Cleavage and Polyadenylation in Pathogenesis, Diagnosis and Therapy of Human Disorders

Genotoxic stress impacts pre-mRNA 3'-end processing

Genotoxic stress, arising from various environmental sources and endogenous cellular processes, pose a constant threat to genomic stability. Cells have evolved intricate mechanisms to detect and repair DNA damage, orchestrating a robust genotoxic stress response to safeguard the integrity of the genome. Recent research has shed light on the crucial role of co- and post-transcriptional regulatory mechanisms in modulating the cellular response to genotoxic stress. Here we highlight recent advances illustrating the intricate interplay between pre-mRNA processing, with a focus on 3'-end processing, and genotoxic stress response.

Advances in Nonviral mRNA Delivery Materials and Their Application as Vaccines for Melanoma Therapy

Messenger RNA (mRNA) vaccines are promising platforms for cancer immunotherapy because of their potential to encode for a variety of tumor antigens, high tolerability, and capacity to induce strong antitumor immune responses. However, the clinical translation of mRNA cancer vaccines can be hindered by the inefficient delivery of mRNA in vivo. In this review, we provide an overview of mRNA cancer vaccines by discussing their utility in treating melanoma. Specifically, we begin our review by describing the barriers that can impede mRNA delivery to target cells. We then review native mRNA structure and discuss various modification methods shown to enhance mRNA stability and transfection. Next, we outline the advantages and challenges of three nonviral carrier platforms (lipid nanoparticles, polymeric nanoparticles, and lipopolyplexes) frequently used for mRNA delivery. Last, we summarize preclinical and clinical studies that have investigated nonviral mRNA vaccines for the treatment of melanoma. In writing this review, we aim to highlight innovative nonviral strategies designed to address mRNA delivery challenges while emphasizing the exciting potential of mRNA vaccines as next-generation therapies for the treatment of cancers.

NSUN4 mediated RNA 5-methylcytosine promotes the malignant progression of glioma through improving the CDC42 mRNA stabilization

5-Methylcytosine (m5C) methylation is a significant post-transcriptional modification that play a crucial role in the development and progression of numerous cancers. Whereas the functions and molecular mechanisms underlying m5C methylation in gliomas remain unclear. This study dedicated to explore changes of m5C levels and the clinical significance of the m5C writer NSUN4 in gliomas. We found that high m5C levels were negatively related to prognosis of patients with glioma. Moreover, gain- and loss-of-function experiments revealed the role of NSUN4 in enhancing m5C modification of mRNA to promote the malignant progression of glioma. Mechanistically speaking, NSUN4-mediated m5C alterations regulated ALYREF binding to CDC42 mRNA, thereby impacting the mRNA stability of CDC42. We also demonstrated that CDC42 promoted glioma proliferation, migration, and invasion by activating the PI3K-AKT pathway. Additionally, rescue experiments proved that CDC42 overexpression weaken the inhibitory effect of NSUN4 knockdown on the malignant progression of gliomas in vitro and in vivo. Our findings elucidated that NSUN4-mediated high m5C levels promote ALYREF binding to CDC42 mRNA and regulate its stability, thereby driving the malignant progression of glioma. This provides theoretical support for targeted the treatment of gliomas.

Research Progress of Caspase in Endometriosis

Endometriosis, a common chronic gynecological disease, refers to the presence and proliferation of endometrial tissue in locations other than the uterine cavity. Approximately 6 to 10% of the population of women of childbearing age are known to have endometriosis; the most common clinical signs are pelvic pain and infertility. Although endometriosis is a benign disease, it exhibits some typical features of malignant tumors, such as proliferation, invasion, metastasis, and recurrence. Endometriosis is considered a chronic, inflammatory, and estrogen-dependent disease, and multiple factors contribute to its occurrence and development. In recent years, increasing attention has been given to the role of apoptosis in the pathogenesis of this disease. Some researchers believe that spontaneous apoptosis of the endometrium is critical in maintaining its normal structure and function, and abnormal apoptosis can promote the occurrence and development of endometriosis. Inflammation is another likely process in the pathogenesis of endometriosis. Inflammation mediates the adhesion, proliferation, differentiation, and invasion of ectopic lesions of endometriosis, primarily by regulating the function of immune cells and increasing the level of proinflammatory cytokines in body fluids. The ultimate initiators of apoptosis and inflammatory cell death (pyroptosis) are the caspase family proteases. In this article, we review the progress in recent years in caspase function as well as the possible role of these enzymes in the pathogenesis of endometriosis, indicating potential treatment strategies.

RNA-binding proteins in cardiovascular biology and disease: the beat goes on

Cardiac development and function are becoming increasingly well understood from different angles, including signalling, transcriptional and epigenetic mechanisms. By contrast, the importance of the post-transcriptional landscape of cardiac biology largely remains to be uncovered, building on the foundation of a few existing paradigms. The discovery during the past decade of hundreds of additional RNA-binding proteins in mammalian cells and organs, including the heart, is expected to accelerate progress and has raised intriguing possibilities for better understanding the intricacies of cardiac development, metabolism and adaptive alterations. In this Review, we discuss the progress and new concepts on RNA-binding proteins and RNA biology and appraise them in the context of common cardiovascular clinical conditions, from cell and organ-wide perspectives. We also discuss how a better understanding of cardiac RNA-binding proteins can fill crucial knowledge gaps in cardiology and might pave the way to developing better treatments to reduce cardiovascular morbidity and mortality.

Alternative Polyadenylation Regulatory Factors Signature for Survival Prediction in Kidney Renal Cell Carcinoma

Background

Alternative polyadenylation (APA) plays a vital regulatory role in various diseases. It is widely accepted that APA is regulated by APA regulatory factors.

Objective

Whether APA regulatory factors affect the prognosis of renal cell carcinoma remains unclear, and this is the main topic of this study.

Methods

We downloaded the transcriptome and clinical data from The Cancer Genome Atlas (TCGA) database. We used the Lasso regression system to construct an APA model for analyzing the relationship between common APA regulatory factors and renal cell carcinoma. We also validated our APA model using independent GEO datasets (GSE29609, GSE76207).

Results

It was found that the expression levels of 5 APA regulatory factors (CPSF1, CPSF2, CSTF2, PABPC1, and PABPC4) were significantly associated with tumor gene mutation burden (TMB) score in renal clear cell carcinoma, and the risk score constructed using the expression level of 5 key APA regulatory factors could be used to predict the outcome of renal clear cell carcinoma. The TMB score is associated with the remodeling of the immune microenvironment.

Conclusions

By identifying key APA regulatory factors in renal cell carcinoma and constructing risk scores for key APA regulatory factors, we showed that key APA regulators affect prognosis of renal clear cell carcinoma patients. In addition, the risk score level is associated with TMB, indicating that APA may affect the efficacy of immunotherapy through immune microenvironment-related genes. This helps us better understand the mRNA processing mechanism of renal clear cell carcinoma.

An AluYa5 Insertion in the 3'UTR of COL4A1 and Cerebral Small Vessel Disease

Importance

Cerebral small vessel diseases (CSVDs) account for one-fifth of stroke cases. Numerous familial cases remain unresolved after routine screening of known CSVD genes.

Objective

To identify novel genes and mechanisms associated with familial CSVD.

Design, Setting, and Participants

This 2-stage study involved linkage analysis and a case-control study; linkage analysis and whole exome and genome sequencing were used to identify candidate gene variants in 2 large families with CSVD (9 patients with CSVD). Then, a case-control analysis was conducted on 246 unrelated probands, including probands from these 2 families and 244 additional probands. All probands (clinical onset

Main Outcomes and Measures

A pathogenic AluYa5 insertion was identified within the COL4A1 3'UTR in the 2 large families with CSVD. Reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR), Western blot, and long-read RNA sequencing were used to investigate outcomes associated with the insertion using patient fibroblasts. Clinical and magnetic resonance imaging features of probands with variants and available relatives were assessed.

Results

Among 246 probands (141 females [57.3%]; median [IQR] age at referral, 56 [49-64] years), 7 patients of French ancestry carried the insertion. This insertion was absent in 467 healthy French individuals in a control group (odds ratio, ∞; 95% CI, 2.78 to ∞; P = 5 × 10-4) and 10 847 individuals from the gnomAD structural variant database (odds ratio, ∞; 95% CI, 64.77 to ∞; P = 2.42 × 10-12). In these 7 patients' families, 19 family members with CSVD carried the insertion. RT-qPCR and Western blot showed an upregulation of COL4A1 mRNA (10.6-fold increase; 95% CI, 1.4-fold to 17.1-fold increase) and protein levels (2.8-fold increase; 95% CI, 2.1-fold to 3.5-fold increase) in patient vs control group fibroblasts. Long-read RNA sequencing data showed that the insertion was associated with perturbation in the use of canonical COL4A1 polyadenylation signals (approximately 87% of isoforms transcribed from the wild type allele vs 5% of isoforms transcribed from the allele with the insertion used the 2 distal canonical polyadenylation signals). The main clinical feature of individuals with CSVD was the recurrence of pontine ischemic lesions starting at an early age (17 of 19 patients [89.5%]).

Conclusions and relevance

This study found a novel mechanism associated with COL4A1 upregulation and a highly penetrant adult-onset CSVD. These findings suggest that quantitative alterations of the cerebrovascular matrisome are associated with CSVD pathogenesis, with diagnostic and therapeutic implications.

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Key Words Collapse

MESH Headings

• Adult
• Female
• Humans
• Middle Aged
• 3' Untranslated Regions/genetics
• Alleles
• Case-Control Studies
• Cerebral Small Vessel Diseases/genetics
• Collagen Type IV/metabolism
• Protein Isoforms
• Mutagenesis, Insertional

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Affiliation(s)

Chaker Aloui NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France
Lisa Neumann NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France
Françoise Bergametti NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France
Eric Sartori Service de Neurologie, Centre Hospitalier Bretagne Sud, Lorient, France
Marc Herbreteau Service de Neurologie, Centre Hospitalier Bretagne Sud, Lorient, France
Arnaud Maillard Assistance Publique-Hôpitaux de Paris, Service de Génétique Moléculaire Neurovasculaire, Hôpital Saint-Louis, Paris, France
Thibault Coste NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France Assistance Publique-Hôpitaux de Paris, Service de Génétique Moléculaire Neurovasculaire, Hôpital Saint-Louis, Paris, France
Hélène Morel NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France Assistance Publique-Hôpitaux de Paris, Service de Génétique Moléculaire Neurovasculaire, Hôpital Saint-Louis, Paris, France
Dominique Hervé NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France Assistance Publique-Hôpitaux de Paris, Service de Neurologie, Hôpital Lariboisière, Paris, France
Hugues Chabriat NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France Assistance Publique-Hôpitaux de Paris, Service de Neurologie, Hôpital Lariboisière, Paris, France
Serge Timsit Service de Neurologie Vasculaire, Centre Hospitalier Régional Universitaire de Brest, Brest, France
Irina Viakhireva Service de Neurologie Vasculaire, Centre Hospitalier Régional Universitaire de Brest, Brest, France
Yves Denoyer Service de Neurologie, Centre Hospitalier Bretagne Sud, Lorient, France Université de Rennes, Laboratoire Traitement du Signal et de l'Image, Institut National de la Santé Et de la Recherche Médicale Unité Mixte de Recherche 1099, Rennes, France
Rémi Allibert Service de Neurologie, Unité Neurovasculaire, Centre Hospitalier Universitaire de Saint Etienne, Saint Etienne, France
Florence Demurger Service de Neurologie, Unité Neurovasculaire, Centre Hospitalier Bretagne Atlantique, Vannes, France
Cedric Gollion Service de Neurologie, Centre Hospitalier Universitaire de Toulouse, Toulouse, France
Patrick Vermersch Univ. Lille, Institut National de la Santé Et de la Recherche Médicale Unité Mixte de Recherche 1172 LilNCog, Centre Hospitalier Universitaire Lille, Fédérations Hospitalo-Universitaire Precise, Lille, France
Florence Marchelli Assistance Publique-Hôpitaux de Paris, Service de Génétique Moléculaire Neurovasculaire, Hôpital Saint-Louis, Paris, France
Corinne Blugeon GenomiqueENS, Institut de Biologie de l’Ecole Normale Supérieur, Département de biologie, École Normale Supérieure, Centre National de la Recherche Scientifique, Institut National de la Santé Et de la Recherche Médicale, Université Paris Sciences et Lettres, Paris, France
Sophie Lemoine GenomiqueENS, Institut de Biologie de l’Ecole Normale Supérieur, Département de biologie, École Normale Supérieure, Centre National de la Recherche Scientifique, Institut National de la Santé Et de la Recherche Médicale, Université Paris Sciences et Lettres, Paris, France
Claire Tourtier-Bellosta Service de Neurologie, Centre Hospitalier Bretagne Sud, Lorient, France
Alexis Brouazin Service de neurologie, Centre Hospitalier de Cornouaille, Quimper, France
Anne-Louise Leutenegger NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France
Eva Pipiras NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France Assistance Publique-Hôpitaux de Paris, Hôpitaux Jean Verdier et Armand Trousseau, Université Sorbonne Paris Nord, Bobigny, France
Elisabeth Tournier-Lasserve NeuroDiderot, Université Paris Cité, Institut National de la Santé Et de la Recherche Médicale, Unité Mixte de Recherche 1141, Paris, France Assistance Publique-Hôpitaux de Paris, Service de Génétique Moléculaire Neurovasculaire, Hôpital Saint-Louis, Paris, France

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Improved discovery of RNA-binding protein binding sites in eCLIP data using DEWSeq

Enhanced crosslinking and immunoprecipitation (eCLIP) sequencing is a method for transcriptome-wide detection of binding sites of RNA-binding proteins (RBPs). However, identified crosslink sites can deviate from experimentally established functional elements of even well-studied RBPs. Current peak-calling strategies result in low replication and high false positive rates. Here, we present the R/Bioconductor package DEWSeq that makes use of replicate information and size-matched input controls. We benchmarked DEWSeq on 107 RBPs for which both eCLIP data and RNA sequence motifs are available and were able to more than double the number of motif-containing binding regions relative to standard eCLIP processing. The improvement not only relates to the number of binding sites (3.1-fold with known motifs for RBFOX2), but also their subcellular localization (1.9-fold of mitochondrial genes for FASTKD2) and structural targets (2.2-fold increase of stem-loop regions for SLBP. On several orthogonal CLIP-seq datasets, DEWSeq recovers a larger number of motif-containing binding sites (3.3-fold). DEWSeq is a well-documented R/Bioconductor package, scalable to adequate numbers of replicates, and tends to substantially increase the proportion and total number of RBP binding sites containing biologically relevant features.

Post-transcriptional control of haemostatic genes: mechanisms and emerging therapeutic concepts in thrombo-inflammatory disorders

The haemostatic system is pivotal to maintaining vascular integrity. Multiple components involved in blood coagulation have central functions in inflammation and immunity. A derailed haemostasis is common in prevalent pathologies such as sepsis, cardiovascular disorders, and lately, COVID-19. Physiological mechanisms limit the deleterious consequences of a hyperactivated haemostatic system through adaptive changes in gene expression. While this is mainly regulated at the level of transcription, co- and posttranscriptional mechanisms are increasingly perceived as central hubs governing multiple facets of the haemostatic system. This layer of regulation modulates the biogenesis of haemostatic components, for example in situations of increased turnover and demand. However, they can also be 'hijacked' in disease processes, thereby perpetuating and even causally entertaining associated pathologies. This review summarizes examples and emerging concepts that illustrate the importance of posttranscriptional mechanisms in haemostatic control and crosstalk with the immune system. It also discusses how such regulatory principles can be used to usher in new therapeutic concepts to combat global medical threats such as sepsis or cardiovascular disorders.

Genome-wide screening for genetic variants in polyadenylation signal (PAS) sites in mouse selection lines for fatness and leanness

Alternative polyadenylation (APA) determines mRNA stability, localisation, translation and protein function. Several diseases, including obesity, have been linked to APA. Studies have shown that single nucleotide polymorphisms in polyadenylation signals (PAS-SNPs) can influence APA and affect phenotype and disease susceptibility. However, these studies focussed on associations between single PAS-SNP alleles with very large effects and phenotype. Therefore, we performed a genome-wide screening for PAS-SNPs in the polygenic mouse selection lines for fatness and leanness by whole-genome sequencing. The genetic variants identified in the two lines were overlapped with locations of PAS sites obtained from the PolyASite 2.0 database. Expression data for selected genes were extracted from the microarray expression experiment performed on multiple tissue samples. In total, 682 PAS-SNPs were identified within 583 genes involved in various biological processes, including transport, protein modifications and degradation, cell adhesion and immune response. Moreover, 63 of the 583 orthologous genes in human have been previously associated with human diseases, such as nervous system and physical disorders, and immune, endocrine, and metabolic diseases. In both lines, PAS-SNPs have also been identified in genes broadly involved in APA, such as Polr2c, Eif3e and Ints11. Five PAS-SNPs within 5 genes (Car, Col4a1, Itga7, Lat, Nmnat1) were prioritised as potential functional variants and could contribute to the phenotypic disparity between the two selection lines. The developed PAS-SNPs catalogue presents a key resource for planning functional studies to uncover the role of PAS-SNPs in APA, disease susceptibility and fat deposition.

Post-transcriptional polyadenylation site cleavage maintains 3'-end processing upon DNA damage

The recognition of polyadenylation signals (PAS) in eukaryotic pre-mRNAs is usually coupled to transcription termination, occurring while pre-mRNA is chromatin-bound. However, for some pre-mRNAs, this 3'-end processing occurs post-transcriptionally, i.e., through a co-transcriptional cleavage (CoTC) event downstream of the PAS, leading to chromatin release and subsequent PAS cleavage in the nucleoplasm. While DNA-damaging agents trigger the shutdown of co-transcriptional chromatin-associated 3'-end processing, specific compensatory mechanisms exist to ensure efficient 3'-end processing for certain pre-mRNAs, including those that encode proteins involved in the DNA damage response, such as the tumor suppressor p53. We show that cleavage at the p53 polyadenylation site occurs in part post-transcriptionally following a co-transcriptional cleavage event. Cells with an engineered deletion of the p53 CoTC site exhibit impaired p53 3'-end processing, decreased mRNA and protein levels of p53 and its transcriptional target p21, and altered cell cycle progression upon UV-induced DNA damage. Using a transcriptome-wide analysis of PAS cleavage, we identify additional pre-mRNAs whose PAS cleavage is maintained in response to UV irradiation and occurring post-transcriptionally. These findings indicate that CoTC-type cleavage of pre-mRNAs, followed by PAS cleavage in the nucleoplasm, allows certain pre-mRNAs to escape 3'-end processing inhibition in response to UV-induced DNA damage.

Comparative genomics and interactomics of polyadenylation factors for the prediction of new parasite targets: Entamoeba histolytica as a working model

Protein-protein interactions (PPI) play a key role in predicting the function of a target protein and drug ability to affect an entire biological system. Prediction of PPI networks greatly contributes to determine a target protein and signal pathways related to its function. Polyadenylation of mRNA 3'-end is essential for gene expression regulation and several polyadenylation factors have been shown as valuable targets for controlling protozoan parasites that affect human health. Here, by using a computational strategy based on sequence-based prediction approaches, phylogenetic analyses, and computational prediction of PPI networks, we compared interactomes of polyadenylation factors in relevant protozoan parasites and the human host, to identify key proteins and define potential targets for pathogen control. Then, we used Entamoeba histolytica as a working model to validate our computational results. RT-qPCR assays confirmed the coordinated modulation of connected proteins in the PPI network and evidenced that silencing of the bottleneck protein EhCFIm25 affects the expression of interacting proteins. In addition, molecular dynamics simulations and docking approaches allowed to characterize the relationships between EhCFIm25 and Ehnopp34, two connected bottleneck proteins. Interestingly, the experimental identification of EhCFIm25 interactome confirmed the close relationships among proteins involved in gene expression regulation and evidenced new links with moonlight proteins in E. histolytica, suggesting a connection between RNA biology and metabolism as described in other organisms. Altogether, our results strengthened the relevance of comparative genomics and interactomics of polyadenylation factors for the prediction of new targets for the control of these human pathogens.

Transcript shortening via alternative polyadenylation promotes gene expression during fracture healing

Maturation of the 3' end of almost all eukaryotic messenger RNAs (mRNAs) requires cleavage and polyadenylation. Most mammalian mRNAs are polyadenylated at different sites within the last exon, generating alternative polyadenylation (APA) isoforms that have the same coding region but distinct 3' untranslated regions (UTRs). The 3'UTR contains motifs that regulate mRNA metabolism; thus, changing the 3'UTR length via APA can significantly affect gene expression. Endochondral ossification is a central process in bone healing, but the impact of APA on gene expression during this process is unknown. Here, we report the widespread occurrence of APA, which impacts multiple pathways that are known to participate in bone healing. Importantly, the progression of endochondral ossification involves global 3'UTR shortening, which is coupled with an increased abundance of shortened transcripts relative to other transcripts; these results highlight the role of APA in promoting gene expression during endochondral bone formation. Our mechanistic studies of transcripts that undergo APA in the fracture callus revealed an intricate regulatory network in which APA enhances the expression of the collagen, type I, alpha 1 (Col1a1) and Col1a2 genes, which encode the 2 subunits of the abundantly expressed protein collagen 1. APA exerts this effect by shortening the 3'UTRs of the Col1a1 and Col1a2 mRNAs, thus removing the binding sites of miR-29a-3p, which would otherwise strongly promote the degradation of both transcripts. Taken together, our study is the first to characterize the crucial roles of APA in regulating the 3'UTR landscape and modulating gene expression during fracture healing.

UBE3D Regulates mRNA 3'-End Processing and Maintains Adipogenic Potential in 3T3-L1 Cells

We have previously described the role of an essential Saccharomyces cerevisiae gene, important for cleavage and polyadenylation 1 (IPA1), in the regulation of gene expression through its interaction with Ysh1, the endonuclease subunit of the mRNA 3'-end processing complex. Through a similar mechanism, the mammalian homolog ubiquitin protein ligase E3D (UBE3D) promotes the migratory and invasive potential of breast cancer cells, but its role in the regulation of gene expression during normal cellular differentiation has not previously been described. In this study, we show that CRISPR/Cas9-mediated knockout of Ube3d in 3T3-L1 cells blocks their ability to differentiate into mature adipocytes. Consistent with previous studies in other cell types, Ube3d knockout leads to decreased levels of CPSF73 and global changes in cellular mRNAs indicative of a loss of 3'-end processing capacity. Ube3d knockout cells also display decreased expression of known preadipogenic markers. Overexpression of either UBE3D or CPSF73 rescues the differentiation defect and partially restores protein levels of these markers. These results support a model in which UBE3D is necessary for the maintenance of the adipocyte-committed state via its regulation of the mRNA 3'-end processing machinery.

Genomic organization, intragenic tandem duplication, and expression analysis of chicken TGFBR2 gene

Transforming growth factor beta receptor Ⅱ (TGFBR2), a core member of the transforming growth factor-β (TGF-β) signaling pathway. To date, chicken TGFBR2 (cTGFBR2) genomic structure has not been fully explored. Here, the complete sequences of cTGFBR2 transcript isoforms were determined by 5′ and 3′ rapid amplification of cDNA ends (5′ & 3′ RACE) and reverse transcription polymerase chain reaction (RT-PCR); the tissue expression profiling of cTGFBR2 transcript isoforms was performed using quantitative real-time polymerase chain reaction (qRT-PCR). The results showed that cTGFBR2 gene produced 3 transcript isoforms though alternative transcription initiation, splicing, and polyadenylation, which were designated as cTGFBR2-1, cTGFBR2-2, and cTGFBR2-3, respectively. These 3 cTGFBR2 transcript isoforms encoded 3 protein isoforms: cTGFBR2-1, cTGFBR2-2, and cTGFBR2-3. Duplication analysis revealed that, unlike other animal species, cTGFBR2 gene harbored a 5.5-kb intragenic tandem duplication. Tissue expression profiling in the 4-wk-old Arbor Acres (AA) broiler chickens showed that cTGFBR2-1 was ubiquitously expressed, with high expression in abdominal fat, subcutaneous fat, lung, gizzard, and muscle; cTGFBR2-2 was highly expressed in heart, kidney, gizzard, and muscle; cTGFBR2-3 was weakly expressed in all the tested chicken tissues. Tissue expression profiling in the 7-wk-old broiler chickens of the fat and lean lines of Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF) showed that cTGFBR2-1 was significantly differentially expressed in all the tested tissues except heart, cTGFBR2-2 was significantly differentially expressed in all the tested tissues except subcutaneous fat and liver, and cTGFBR2-3 was significantly differentially expressed in all the tested tissues between the lean and fat lines. Intriguingly, in the fat line, the 3 cTGFBR2 transcript isoforms were expressed to varying degrees in all the 3 tested fat tissues, while in the lean line, only cTGFBR2-1 was expressed in all the 3 tested fat tissues. This is the first report of intragenic tandem duplication within TGFBR2 gene. Our findings pave the way for further studies on the functions and regulation of cTGFBR2 gene.

Pathophysiological Role and Diagnostic Potential of R-Loops in Cancer and Beyond

R-loops are DNA-RNA hybrids that play multifunctional roles in gene regulation, including replication, transcription, transcription-replication collision, epigenetics, and preserving the integrity of the genome. The aberrant formation and accumulation of unscheduled R-loops can disrupt gene expression and damage DNA, thereby causing genome instability. Recent links between unscheduled R-loop accumulation and the abundance of proteins that modulate R-loop biogenesis have been associated with numerous human diseases, including various cancers. Although R-loops are not necessarily causative for all disease entities described to date, they can perpetuate and even exacerbate the initially disease-eliciting pathophysiology, making them structures of interest for molecular diagnostics. In this review, we discuss the (patho) physiological role of R-loops in health and disease, their surprising diagnostic potential, and state-of-the-art techniques for their detection.

NUDT21 limits CD19 levels through alternative mRNA polyadenylation in B cell acute lymphoblastic leukemia

B cell progenitor acute lymphoblastic leukemia (B-ALL) treatment has been revolutionized by T cell-based immunotherapies-including chimeric antigen receptor T cell therapy (CAR-T) and the bispecific T cell engager therapeutic, blinatumomab-targeting surface glycoprotein CD19. Unfortunately, many patients with B-ALL will fail immunotherapy due to 'antigen escape'-the loss or absence of leukemic CD19 targeted by anti-leukemic T cells. In the present study, we utilized a genome-wide CRISPR-Cas9 screening approach to identify modulators of CD19 abundance on human B-ALL blasts. These studies identified a critical role for the transcriptional activator ZNF143 in CD19 promoter activation. Conversely, the RNA-binding protein, NUDT21, limited expression of CD19 by regulating CD19 messenger RNA polyadenylation and stability. NUDT21 deletion in B-ALL cells increased the expression of CD19 and the sensitivity to CD19-specific CAR-T and blinatumomab. In human B-ALL patients treated with CAR-T and blinatumomab, upregulation of NUDT21 mRNA coincided with CD19 loss at disease relapse. Together, these studies identify new CD19 modulators in human B-ALL.

Identification of aberrant transcription termination at specific gene loci with DNA hypomethylated transcription termination sites caused by DNA methyltransferase deficiency

CpG methylation of genomic DNA is a well-known repressive epigenetic marker in eukaryotic transcription, and DNA methylation of promoter regions is correlated with gene silencing. In contrast to the promoter regions, the function of DNA methylation during transcription termination remains to be elucidated. A recent study revealed that mouse DNA methyltransferase 3a (Dnmt3a) mainly functions in de novo methylation in the promoter and gene body regions, including transcription termination sites (TTSs), during development. To investigate the relationship between DNA methylation overlapping the TTSs and transcription termination, we performed bioinformatics analysis using six pre-existing Dnmt^-/- mouse cell datasets: four types of neurons (three Dnmt3a^-/- and one Dnmt1^-/- mutants) and two types of embryonic fibroblasts (MEFs) (Dnmt3a^-/- and Dnmt3b^-/- mutants). Combined analyses using methylome and transcriptome data revealed that read counts downstream of hypomethylated TTSs were increased in three types of neurons (two Dnmt3a^-/- and one Dnmt1^-/- mutants). Among these, an increase in chimeric transcripts downstream of the TTSs was observed in Dnmt3a^-/- mature olfactory sensory neurons and Dnmt3a^-/- agouti-related peptide (protein)-producing neurons, thereby indicating that read-through occurs in hypomethylated TTSs at specific gene loci in these two mutants. Conversely, in Dnmt3a^-/- MEFs, we detected reductions in read counts downstream of hypomethylated TTSs. These results indicate that the hypomethylation of TTSs can both positively and negatively regulate transcription termination, dependent on Dnmt and cell types. This study is the first to identify the aberrant termination of transcription at specific gene loci with DNA hypomethylated TTSs attributable to Dnmt deficiency.

PCF11, a Novel CD44-Downstream Transcriptional Target, Linking Its 3'-End Polyadenylation Function to Tumor Cell Metastasis

Breast Cancer (BC) is the most common and the major health issue in women worldwide. Metastasis, a multistep process, is the worst aspect of cancer and tumor cell invasion is the defining step. Tumor cell invasion requires cell adhesion molecules (CAMs), and alterations in CAMs is considered as an initiating event in metastasis. Among CAMs, CD44 is a large family of more than 100 isoform, and its precise function was initially controversial in BC. Therefore, we have previously established a (Tet)-off inducible expression system of CD44 in MCF-7 primary BC cell line, and showed that CD44 promoted BC invasion/metastasis both in vitro and in vivo. A microarray gene expression profiling revealed more than 200 CD44-downstream potential transcriptional target genes, mediating its role in BC cell invasion and metastasis. Among these CD44-target genes, the Pre-mRNA cleavage complex 2 protein (PCF11) was upregulated upon the activation of CD44 by its major ligand hyaluronan (HA); This prompted us to hypothesize PCF11 as a potential novel transcriptional target of CD44-promoted BC cell invasion and metastasis. A large body of evidence from the literature supports our hypothesis that CD44 might regulate PCF11 via MAPK/ERK pathway. This review aims to discuss these findings from the literature that support our hypothesis, and further provide possible mechanisms linking CD44-promoted cell invasion through regulation of its potential target PCF11.

At the crossroads of RNA biology, genome integrity and cancer

This article is the synthesis of the scientific presentations that took place during two international courses at Institute Curie, one on post-transcriptional gene regulation and the other on genome instability and human disease, that were joined together in their 2021 edition. This joined course brought together the knowledge on RNA metabolism and the maintenance of genome stability.

Precise gene models using long-read sequencing reveal a unique poly(A) signal in Giardia lamblia

During pre-mRNA processing, the poly(A) signal is recognized by a protein complex that ensures precise cleavage and polyadenylation of the nascent transcript. The location of this cleavage event establishes the length and sequence of the 3' UTR of an mRNA, thus determining much of its post-transcriptional fate. Using long-read sequencing, we characterize the polyadenylation signal and related sequences surrounding Giardia lamblia cleavage sites for over 2600 genes. We find that G. lamblia uses an AGURAA poly(A) signal, which differs from the mammalian AAUAAA. We also describe how G. lamblia lacks common auxiliary elements found in other eukaryotes, along with the proteins that recognize them. Further, we identify 133 genes with evidence of alternative polyadenylation. These results suggest that despite pared-down cleavage and polyadenylation machinery, 3' end formation still appears to be an important regulatory step for gene expression in G. lamblia.

The Bidirectional Link Between RNA Cleavage and Polyadenylation and Genome Stability: Recent Insights From a Systematic Screen

The integrity of the genome is governed by multiple processes to ensure optimal survival and to prevent the inheritance of deleterious traits. While significant progress has been made to characterize components involved in the DNA Damage Response (DDR), little is known about the interplay between RNA processing and the maintenance of genome stability. Here, we describe the emerging picture of an intricate bidirectional coupling between RNA processing and genome integrity in an integrative manner. By employing insights from a recent large-scale RNAi screening involving the depletion of more than 170 components that direct (alternative) polyadenylation, we provide evidence of bidirectional crosstalk between co-transcriptional RNA 3′end processing and the DDR in a manner that optimizes genomic integrity. We provide instructive examples illustrating the wiring between the two processes and show how perturbations at one end are either compensated by buffering mechanisms at the other end, or even propel the initial insult and thereby become disease-eliciting as evidenced by various disorders.

RNA polyadenylation patterns in the human transcriptome

The eukaryotic transcriptome undergoes various post-transcriptional modifications which assists gene expression. Polyadenylation is a molecular process occurring at the 3'-end of the RNA molecule which involves the poly(A) polymerase attaching adenine monophosphate molecules in a chain-like fashion to assemble a poly(A) tail. Multiple RNA isoforms are produced with differing 3'-UTR and exonic compositions through alternative polyadenylation (APA) which enhances the diversification of alternatively spliced mRNA transcripts. To study polyadenylation patterns, novel methods have been developed using short-read and long-read sequencing technologies to analyse the 3'-ends of the transcript. Recent studies have identified unique polyadenylation patterns in different cellular functions, including oncogenic activity, which could prove valuable in the understanding of medical genetics, particularly in the discovery of biomarkers in diseased states. We present a review of current literature reporting on polyadenylation and the biological relevance in the mammalian transcriptome, with a focus on the human transcriptome. Additionally, we have explored the various methods available to detect polyadenylation patterns using second and third generation sequencing technologies.

Implications of Poly(A) Tail Processing in Repeat Expansion Diseases

Repeat expansion diseases are a group of more than 40 disorders that affect mainly the nervous and/or muscular system and include myotonic dystrophies, Huntington’s disease, and fragile X syndrome. The mutation-driven expanded repeat tract occurs in specific genes and is composed of tri- to dodeca-nucleotide-long units. Mutant mRNA is a pathogenic factor or important contributor to the disease and has great potential as a therapeutic target. Although repeat expansion diseases are quite well known, there are limited studies concerning polyadenylation events for implicated transcripts that could have profound effects on transcript stability, localization, and translation efficiency. In this review, we briefly present polyadenylation and alternative polyadenylation (APA) mechanisms and discuss their role in the pathogenesis of selected diseases. We also discuss several methods for poly(A) tail measurement (both transcript-specific and transcriptome-wide analyses) and APA site identification—the further development and use of which may contribute to a better understanding of the correlation between APA events and repeat expansion diseases. Finally, we point out some future perspectives on the research into repeat expansion diseases, as well as APA studies.

mRNA - A game changer in regenerative medicine, cell-based therapy and reprogramming strategies

After thirty years of intensive research shaping and optimizing the technology, the approval of the first mRNA-based formulation by the EMA and FDA in order to stop the COVID-19 pandemic was a breakthrough in mRNA research. The astonishing success of these vaccines have brought the mRNA platform into the spotlight of the scientific community. The remarkable persistence of the groundwork is mainly attributed to the exceptional benefits of mRNA application, including the biological origin, immediate but transitory mechanism of action, non-integrative properties, safe and relatively simple manufacturing as well as the flexibility to produce any desired protein. Based on these advantages, a practical implementation of in vitro transcribed mRNA has been considered in most areas of medicine. In this review, we discuss the key preconditions for the rise of the mRNA in the medical field, including the unique structural and functional features of the mRNA molecule and its vehicles, which are crucial aspects for a production of potent mRNA-based therapeutics. Further, we focus on the utility of mRNA tools particularly in the scope of regenerative medicine, i.e. cell reprogramming approaches or manipulation strategies for targeted tissue restoration. Finally, we highlight the strong clinical potential but also the remaining hurdles to overcome for the mRNA-based regenerative therapy, which is only a few steps away from becoming a reality.

Comprehensive characterization of somatic variants associated with intronic polyadenylation in human cancers

Somatic single nucleotide variants (SNVs) in cancer genome affect gene expression through various mechanisms depending on their genomic location. While somatic SNVs near canonical splice sites have been reported to cause abnormal splicing of cancer-related genes, whether these SNVs can affect gene expression through other mechanisms remains an open question. Here, we analyzed RNA sequencing and exome data from 4,998 cancer patients covering ten cancer types and identified 152 somatic SNVs near splice sites that were associated with abnormal intronic polyadenylation (IPA). IPA-associated somatic variants favored the localization near the donor splice sites compared to the acceptor splice sites. A proportion of SNV-associated IPA events overlapped with premature cleavage and polyadenylation events triggered by U1 small nuclear ribonucleoproteins (snRNP) inhibition. GC content, intron length and polyadenylation signal were three genomic features that differentiated between SNV-associated IPA and intron retention. Notably, IPA-associated SNVs were enriched in tumor suppressor genes (TSGs), including the well-known TSGs such as PTEN and CDH1 with recurrent SNV-associated IPA events. Minigene assay confirmed that SNVs from PTEN, CDH1, VEGFA, GRHL2, CUL3 and WWC2 could lead to IPA. This work reveals that IPA acts as a novel mechanism explaining the functional consequence of somatic SNVs in human cancer.

Alternative polyadenylation: An enigma of transcript length variation in health and disease

Alternative polyadenylation (APA) is a molecular mechanism during a pre-mRNA processing that involves usage of more than one polyadenylation site (PA-site) generating transcripts of varying length from a single gene. The location of a PA-site affects transcript length and coding potential of an mRNA contributing to both mRNA and protein diversification. This variation in the transcript length affects mRNA stability and translation, mRNA subcellular and tissue localization, and protein function. APA is now considered as an important regulatory mechanism in the pathophysiology of human diseases. An important consequence of the changes in the length of 3'-untranslated region (UTR) from disease-induced APA is altered protein expression. Yet, the relationship between 3'-UTR length and protein expression remains a paradox in a majority of diseases. Here, we review occurrence of APA, mechanism of PA-site selection, and consequences of transcript length variation in different diseases. Emerging evidence reveals coordinated involvement of core RNA processing factors including poly(A) polymerases in the PA-site selection in diseases-associated APAs. Targeting such APA regulators will be therapeutically significant in combating drug resistance in cancer and other complex diseases. This article is categorized under: RNA Processing > 3' End Processing RNA in Disease and Development > RNA in Disease Translation > Regulation.

Regulation of closely juxtaposed proto-oncogene c-fms and HMGXB3 gene expression by mRNA 3' end polymorphism in breast cancer cells

Sense-antisense mRNA pairs generated by convergent transcription is a way of gene regulation. c-fms gene is closely juxtaposed to the HMGXB3 gene in the opposite orientation, in chromosome 5. The intergenic region (IR) between c-fms and HMGXB3 genes is 162 bp. We found that a small portion (∼4.18%) of HMGXB3 mRNA is transcribed further downstream, including the end of the c-fms gene generating antisense mRNA against c-fms mRNA. Similarly, a small portion (∼1.1%) of c-fms mRNA is transcribed further downstream, including the end of the HMGXB3 gene generating antisense mRNA against the HMGXB3 mRNA. Insertion of the strong poly(A) signal sequence in the IR results in decreased c-fms and HMGXB3 antisense mRNAs, resulting in up-regulation of both c-fms and HMGXB3 mRNA expression. miR-324-5p targets HMGXB3 mRNA 3' UTR, and as a result, regulates c-fms mRNA expression. HuR stabilizes c-fms mRNA, and as a result, down-regulates HMGXB3 mRNA expression. UALCAN analysis indicates that the expression pattern between c-fms and HMGXB3 proteins are opposite in vivo in breast cancer tissues. Together, our results indicate that the mRNA encoded by the HMGXB3 gene can influence the expression of adjacent c-fms mRNA, or vice versa.

Emerging roles of alternative cleavage and polyadenylation (APA) in human disease

In the messenger RNA (mRNA) maturation process, the 3'-end of pre-mRNA is cleaved and a poly(A) sequence is added, this is an important determinant of mRNA stability and its cellular functions. More than 60%-70% of human genes have three or more polyadenylation (APA) sites and can be cleaved at different sites, generating mRNA transcripts of varying lengths. This phenomenon is termed as alternative cleavage and polyadenylation (APA) and it plays role in key biological processes like gene regulation, cell proliferation, senescence, and also in various human diseases. Loss of regulatory microRNA binding sites and interactions with RNA-binding proteins leading to APA are largely investigated in human diseases. However, the functions of the core APA machinery and related factors during disease conditions remain largely unknown. In this review, we discuss the roles of polyadenylation machinery in relation to brain disease, cardiac failure, pulmonary fibrosis, cancer, infectious conditions, and other human diseases. Collectively, we believe this review will be a useful avenue for understanding the emerging role of APA in the pathobiology of various human diseases.

MAAPER: model-based analysis of alternative polyadenylation using 3' end-linked reads

Most eukaryotic genes express alternative polyadenylation (APA) isoforms. A growing number of RNA sequencing methods, especially those used for single-cell transcriptome analysis, generate reads close to the polyadenylation site (PAS), termed nearSite reads, hence inherently containing information about APA isoform abundance. Here, we present a probabilistic model-based method named MAAPER to utilize nearSite reads for APA analysis. MAAPER predicts PASs with high accuracy and sensitivity and examines different types of APA events with robust statistics. We show MAAPER's performance with both bulk and single-cell data and its applicability in unpaired or paired experimental designs.

m6A RNA methylation facilitates pre-mRNA 3'-end formation and is essential for viability of Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular parasite that can cause serious opportunistic disease in the immunocompromised or through congenital infection. To progress through its life cycle, Toxoplasma relies on multiple layers of gene regulation that includes an array of transcription and epigenetic factors. Over the last decade, the modification of mRNA has emerged as another important layer of gene regulation called epitranscriptomics. Here, we report that epitranscriptomics machinery exists in Toxoplasma, namely the methylation of adenosines (m6A) in mRNA transcripts. We identified novel components of the m6A methyltransferase complex and determined the distribution of m6A marks within the parasite transcriptome. m6A mapping revealed the modification to be preferentially located near the 3’-boundary of mRNAs. Knockdown of the m6A writer components METTL3 and WTAP resulted in diminished m6A marks and a complete arrest of parasite replication. Furthermore, we examined the two proteins in Toxoplasma that possess YTH domains, which bind m6A marks, and showed them to be integral members of the cleavage and polyadenylation machinery that catalyzes the 3’-end processing of pre-mRNAs. Loss of METTL3, WTAP, or YTH1 led to a defect in transcript 3’-end formation. Together, these findings establish that the m6A epitranscriptome is essential for parasite viability by contributing to the processing of mRNA 3’-ends.

Toxoplasma gondii is a parasite of medical importance that causes disease upon immuno-suppression. Uncovering essential pathways that the parasite uses for its basic biological processes may reveal opportunities for new anti-parasitic drug therapies. Here, we describe the machinery that Toxoplasma uses to modify specific adenosine residues within its messenger RNAs (mRNA) by N6-adenosine methylation (m6A). We discovered that m6A mRNA methylation is prevalent in multiple stages of the parasite life cycle and is required for parasite replication. We also establish that m6A plays a major role in the proper maturation of mRNA. Two proteins that bind m6A modifications on mRNA associate with factors responsible for the cleavage and final processing steps of mRNA maturation. Since all of the machinery is conserved from plants to Toxoplasma and other related parasites, we propose that this system operates similarly in these organisms.

CRISPRpas: programmable regulation of alternative polyadenylation by dCas9

Most human protein-coding genes produce alternative polyadenylation (APA) isoforms that differ in 3' UTR size or, when coupled with splicing, have variable coding sequences. APA is an important layer of gene expression program critical for defining cell identity. Here, by using a catalytically dead Cas9 and coupling its target site with polyadenylation site (PAS), we develop a method, named CRISPRpas, to alter APA isoform abundance. CRISPRpas functions by enhancing proximal PAS usage, whose efficiency is influenced by several factors, including targeting strand of DNA, distance between PAS and target sequence and strength of the PAS. For intronic polyadenylation (IPA), splicing features, such as strengths of 5' splice site and 3' splice site, also affect CRISPRpas efficiency. We show modulation of APA of multiple endogenous genes, including IPA of PCF11, a master regulator of APA and gene expression. In sum, CRISPRpas offers a programmable tool for APA regulation that impacts gene expression.

TRENDseq-A highly multiplexed high throughput RNA 3' end sequencing for mapping alternative polyadenylation

Alternative polyadenylation (APA) is a widespread and highly dynamic mechanism of gene regulation. It affects more than 70% of all genes, resulting in transcript isoforms with distinct 3' end termini. APA thereby considerably expands the diversity of the transcriptome 3' end (TREND). This leads to mRNA isoforms with profoundly different physiological effects, by affecting protein output, production of distinct protein isoforms, or modulating protein localization. APA is globally regulated in various conditions, including developmental and adaptive programs. Since perturbations of APA can disrupt biological processes, ultimately resulting in most devastating disorders, querying the APA landscape is crucial to decipher underlying mechanisms, resulting consequences and potential diagnostic and therapeutic implications. Here we provide a detailed step-by-step protocol for TRENDseq, a method for transcriptome-wide high-throughput sequencing of polyadenylated RNA 3' ends in a highly multiplexed fashion. TRENDseq exploits linear amplification of the starting material to improve sensitivity while significantly reducing the amount of input material. It thereby represents a powerful tool to study APA in numerous experimental set-ups and/or limited human samples in a highly multiplexed and reproducible manner.

Establishment and analysis of the lncRNA-miRNA-mRNA network based on competitive endogenous RNA identifies functional genes in heart failure

Heart failure (HF), a common disease in adults, accounts for significantly global morbidity and mortality. Due to population aging, therapeutic progression in acute cardiovascular events, the prevalence of HF is increasing, in spite of the efficacy of multiple therapies for HF patients with decreased ejection fraction. Despite great progress in the underlying molecular mechanisms, it remains incompletely clear of the function of competing endogenous RNA (ceRNA) network in HF pathogenesis. Herein, we established an HF-related ceRNA network on the basis of differentially expressed long noncoding RNAs (lncRNAs), microRNAs (miRNAs) as well as mRNAs from GSE136547 and GSE124401 datasets. In brief, the ceRNA network composed of 58 mRNA nodes, 5 miRNA nodes, 82 lncRNA nodes as well as 252 edges. In addition, three lncRNAs (KCNQ1OT1, XIST and AC010336) with higher node degrees than other lncRNAs were chosen as hub nodes. At the same time, we have established five subnetwork of miR-17-5p, miR-20b-5p, miR-107, miR-125a-5p and miR-140-5p centered ceRNA. Pathway analysis revealed the enrichment of ceRNA network in cell cycle pathways. Collectively, our research sheds new lights on the essential functions of ceRNA network in HF development, which also suggests possible application of these hub nodes as diagnostic biomarkers as well as therapeutic targets.

Mutations in cis that affect mRNA synthesis, processing and translation

Genetic mutations that cause hereditary diseases usually affect the composition of the transcribed mRNA and its encoded protein, leading to instability of the mRNA and/or the protein. Sometimes, however, such mutations affect the synthesis, the processing or the translation of the mRNA, with similar disastrous effects. We here present an overview of mRNA synthesis, its posttranscriptional modification and its translation into protein. We then indicate which elements in these processes are known to be affected by pathogenic mutations, but we restrict our review to mutations in cis, in the DNA of the gene that encodes the affected protein. These mutations can be in enhancer or promoter regions of the gene, which act as binding sites for transcription factors involved in pre-mRNA synthesis. We also describe mutations in polyadenylation sequences and in splice site regions, exonic and intronic, involved in intron removal. Finally, we include mutations in the Kozak sequence in mRNA, which is involved in protein synthesis. We provide examples of genetic diseases caused by mutations in these DNA regions and refer to databases to help identify these regions. The over-all knowledge of mRNA synthesis, processing and translation is essential for improvement of the diagnosis of patients with genetic diseases.

PAPOLA contributes to cyclin D1 mRNA alternative polyadenylation and promotes breast cancer cell proliferation

Poly(A) polymerases add the poly(A) tail at the 3' end of nearly all eukaryotic mRNA, and are associated with proliferation and cancer. To elucidate the role of the most-studied mammalian poly(A) polymerase, poly(A) polymerase α (PAPOLA), in cancer, we assessed its expression in 221 breast cancer samples and found it to correlate strongly with the aggressive triple-negative subtype. Silencing PAPOLA in MCF-7 and MDA-MB-231 breast cancer cells reduced proliferation and anchorage-independent growth by decreasing steady-state cyclin D1 (CCND1) mRNA and protein levels. Whereas the length of the CCND1 mRNA poly(A) tail was not affected, its 3' untranslated region (3'UTR) lengthened. Overexpressing PAPOLA caused CCND1 mRNA 3'UTR shortening with a concomitant increase in the amount of corresponding transcript and protein, resulting in growth arrest in MCF-7 cells and DNA damage in HEK-293 cells. Such overexpression of PAPOLA promoted proliferation in the p53 mutant MDA-MB-231 cells. Our data suggest that PAPOLA is a possible candidate target for the control of tumor growth that is mostly relevant to triple-negative tumors, a group characterized by PAPOLA overexpression and lack of alternative targeted therapies.

On the function and relevance of alternative 3'-UTRs in gene expression regulation

Messanger RNA (mRNA) isoforms with alternative 3'-untranslated regions (3'-UTRs) are produced by alternative polyadenylation (APA), which occurs during transcription in most eukaryotic genes. APA fine-tunes gene expression in a cell-type- and cellular state-dependent manner. Selection of an APA site entails the binding of core cleavage and polyadenylation factors to a particular polyadenylation site localized in the pre-mRNA and is controlled by multiple regulatory determinants, including transcription, pre-mRNA cis-regulatory sequences, and protein factors. Alternative 3'-UTRs serve as platforms for specific RNA binding proteins and microRNAs, which regulate gene expression in a coordinated manner by controlling mRNA fate and function in the cell. Genome-wide studies illustrated the full extent of APA prevalence and revealed that specific 3'-UTR profiles are associated with particular cellular states and diseases. Generally, short 3'-UTRs are associated with proliferative and cancer cells, and long 3'-UTRs are mostly found in polarized and differentiated cells. Fundamental new insights on the physiological consequences of this widespread event and the molecular mechanisms involved have been revealed through single-cell studies. Publicly available comprehensive databases that cover all APA mRNA isoforms identified in many cellular states and diseases reveal specific APA signatures. Therapies tackling APA mRNA isoforms or APA regulators may be regarded as innovative and attractive tools for diagnostics or treatment of several pathologies. We highlight the function of APA and alternative 3'-UTRs in gene expression regulation, the control of these mechanisms, their physiological consequences, and their potential use as new biomarkers and therapeutic tools. This article is categorized under: RNA Processing > 3' End Processing RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA in Disease and Development > RNA in Disease.

Nuclear Envelope and Nuclear Pore Complexes in Neurodegenerative Diseases-New Perspectives for Therapeutic Interventions

Transport of proteins, transcription factors, and other signaling molecules between the nucleus and cytoplasm is necessary for signal transduction. The study of these transport phenomena is particularly challenging in neurons because of their highly polarized structure. The bidirectional exchange of molecular cargoes across the nuclear envelope (NE) occurs through nuclear pore complexes (NPCs), which are aqueous channels embedded in the nuclear envelope. The NE and NPCs regulate nuclear transport but are also emerging as relevant regulators of chromatin organization and gene expression. The alterations in nuclear transport are regularly identified in affected neurons associated with human neurodegenerative diseases. This review presents insights into the roles played by nuclear transport defects in neurodegenerative disease, focusing primarily on NE proteins and NPCs. The subcellular mislocalization of proteins might be a very desirable means of therapeutic intervention in neurodegenerative disorders.

Reciprocal Links between Pre-messenger RNA 3'-End Processing and Genome Stability

The 3'-end processing of most pre-messenger RNAs (pre-mRNAs) involves RNA cleavage and polyadenylation and is coupled to transcription termination. In both yeast and human cells, pre-mRNA 3'-end cleavage is globally inhibited by DNA damage. Recently, further links between pre-mRNA 3'-end processing and the control of genome stability have been uncovered, as reviewed here. Upon DNA damage, various genes related to the DNA damage response (DDR) escape 3'-end processing inhibition or are regulated through alternative polyadenylation (APA). Conversely, various pre-mRNA 3'-end processing factors prevent genome instability and are found at sites of DNA damage. Finally, the reciprocal link between pre-mRNA 3'-end processing and genome stability control seems important because it is conserved in evolution and involved in disease development.

TREND-DB-a transcriptome-wide atlas of the dynamic landscape of alternative polyadenylation

Alternative polyadenylation (APA) profoundly expands the transcriptome complexity. Perturbations of APA can disrupt biological processes, ultimately resulting in devastating disorders. A major challenge in identifying mechanisms and consequences of APA (and its perturbations) lies in the complexity of RNA 3′ end processing, involving poorly conserved RNA motifs and multi-component complexes consisting of far more than 50 proteins. This is further complicated in that RNA 3′ end maturation is closely linked to transcription, RNA processing and even epigenetic (histone/DNA/RNA) modifications. Here, we present TREND-DB (http://shiny.imbei.uni-mainz.de:3838/trend-db), a resource cataloging the dynamic landscape of APA after depletion of >170 proteins involved in various facets of transcriptional, co- and post-transcriptional gene regulation, epigenetic modifications and further processes. TREND-DB visualizes the dynamics of transcriptome 3′ end diversification (TREND) in a highly interactive manner; it provides a global APA network map and allows interrogating genes affected by specific APA-regulators and vice versa. It also permits condition-specific functional enrichment analyses of APA-affected genes, which suggest wide biological and clinical relevance across all RNAi conditions. The implementation of the UCSC Genome Browser provides additional customizable layers of gene regulation accounting for individual transcript isoforms (e.g. epigenetics, miRNA-binding sites and RNA-binding proteins). TREND-DB thereby fosters disentangling the role of APA for various biological programs, including potential disease mechanisms, and helps identify their diagnostic and therapeutic potential.