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Advances in Experimental Medicine and... 2024Posttranscriptional regulation comprises those mechanisms occurring after the initial copy of the DNA sequence is transcribed into an intermediate RNA molecule (i.e.,...
Posttranscriptional regulation comprises those mechanisms occurring after the initial copy of the DNA sequence is transcribed into an intermediate RNA molecule (i.e., messenger RNA) until such a molecule is used as a template to generate a protein. A subset of these posttranscriptional regulatory mechanisms essentially are destined to process the immature mRNA toward its mature form, conferring the adequate mRNA stability, providing the means for pertinent introns excision, and controlling mRNA turnover rate and quality control check. An additional layer of complexity is added in certain cases, since discrete nucleotide modifications in the mature RNA molecule are added by RNA editing, a process that provides large mature mRNA diversity. Moreover, a number of posttranscriptional regulatory mechanisms occur in a cell- and tissue-specific manner, such as alternative splicing and noncoding RNA-mediated regulation. In this chapter, we will briefly summarize current state-of-the-art knowledge of general posttranscriptional mechanisms, while major emphases will be devoted to those tissue-specific posttranscriptional modifications that impact on cardiac development and congenital heart disease.
Topics: Animals; Humans; Alternative Splicing; Gene Expression Regulation; RNA Editing; RNA Processing, Post-Transcriptional; RNA Stability; RNA, Messenger; RNA, Untranslated
PubMed: 38884719
DOI: 10.1007/978-3-031-44087-8_17 -
Nucleic Acids Research Jun 2024The poly(A) tail plays an important role in maintaining mRNA stability and influences translation efficiency via binding with PABP. However, the impact of poly(A) tail...
The poly(A) tail plays an important role in maintaining mRNA stability and influences translation efficiency via binding with PABP. However, the impact of poly(A) tail length on mRNA translation remains incompletely understood. This study explores the effects of poly(A) tail length on human translation. We determined the translation rates in cell lysates using mRNAs with different poly(A) tails. Cap-dependent translation was stimulated by the poly(A) tail, however, it was largely independent of poly(A) tail length, with an exception observed in the case of the 75 nt poly(A) tail. Conversely, cap-independent translation displayed a positive correlation with poly(A) tail length. Examination of translation stages uncovered the dependence of initiation and termination on the presence of the poly(A) tail, but the efficiency of initiation remained unaffected by poly(A) tail extension. Further study unveiled that increased binding of eRFs to the ribosome with the poly(A) tail extension induced more efficient hydrolysis of peptidyl-tRNA. Building upon these findings, we propose a crucial role for the 75 nt poly(A) tail in orchestrating the formation of a double closed-loop mRNA structure within human cells which couples the initiation and termination phases of translation.
PubMed: 38874498
DOI: 10.1093/nar/gkae510 -
Experimental & Molecular Medicine Jun 2024Circular RNAs (circRNAs) are covalently closed single-stranded RNAs without a 5' cap structure and a 3' poly(A) tail typically present in linear mRNAs of eukaryotic... (Review)
Review
Circular RNAs (circRNAs) are covalently closed single-stranded RNAs without a 5' cap structure and a 3' poly(A) tail typically present in linear mRNAs of eukaryotic cells. CircRNAs are predominantly generated through a back-splicing process within the nucleus. CircRNAs have long been considered non-coding RNAs seemingly devoid of protein-coding potential. However, many recent studies have challenged this idea and have provided substantial evidence that a subset of circRNAs can associate with polysomes and indeed be translated. Therefore, in this review, we primarily highlight the 5' cap-independent internal initiation of translation that occurs on circular RNAs. Several molecular features of circRNAs, including the internal ribosome entry site, N-methyladenosine modification, and the exon junction complex deposited around the back-splicing junction after back-splicing event, play pivotal roles in their efficient internal translation. We also propose a possible relationship between the translatability of circRNAs and their stability, with a focus on nonsense-mediated mRNA decay and nonstop decay, both of which are well-characterized mRNA surveillance mechanisms. An in-depth understanding of circRNA translation will reshape and expand our current knowledge of proteomics.
PubMed: 38871818
DOI: 10.1038/s12276-024-01220-3 -
Concerted action of ataxin-2 and PABPC1-bound mRNA poly(A) tail in the formation of stress granules.Nucleic Acids Research Jun 2024Stress induces global stabilization of the mRNA poly(A) tail (PAT) and the assembly of untranslated poly(A)-tailed mRNA into mRNPs that accumulate in stress granules...
Stress induces global stabilization of the mRNA poly(A) tail (PAT) and the assembly of untranslated poly(A)-tailed mRNA into mRNPs that accumulate in stress granules (SGs). While the mechanism behind stress-induced global PAT stabilization has recently emerged, the biological significance of PAT stabilization under stress remains elusive. Here, we demonstrate that stress-induced PAT stabilization is a prerequisite for SG formation. Perturbations in PAT length impact SG formation; PAT shortening, achieved by overexpressing mRNA deadenylases, inhibits SG formation, whereas PAT lengthening, achieved by overexpressing their dominant negative mutants or downregulating deadenylases, promotes it. PABPC1, which specifically binds to the PAT, is crucial for SG formation. Complementation analyses reveal that the PABC/MLLE domain of PABPC1, responsible for binding PAM2 motif-containing proteins, plays a key role. Among them, ataxin-2 is a known SG component. A dominant-negative approach reveals that the PAM2 motif of ataxin-2 is essential for SG formation. Notably, ataxin-2 increases stress sensitivity, lowering the threshold for SG formation, probably by promoting the aggregation of PABPC1-bound mRNA. The C-terminal region is responsible for the self-aggregation of ataxin-2. These findings underscore the critical roles of mRNA PAT, PABPC1 and ataxin-2 in SG formation and provide mechanistic insights into this process.
PubMed: 38869059
DOI: 10.1093/nar/gkae497 -
Nucleic Acids Research Jun 2024Alu elements are non-autonomous Short INterspersed Elements (SINEs) derived from the 7SL RNA gene that are present at over one million copies in human genomic DNA. Alu...
Alu elements are non-autonomous Short INterspersed Elements (SINEs) derived from the 7SL RNA gene that are present at over one million copies in human genomic DNA. Alu mobilizes by a mechanism known as retrotransposition, which requires the Long INterspersed Element-1 (LINE-1) ORF2-encoded protein (ORF2p). Here, we demonstrate that HeLa strains differ in their capacity to support Alu retrotransposition. Human Alu elements retrotranspose efficiently in HeLa-HA and HeLa-CCL2 (Alu-permissive) strains, but not in HeLa-JVM or HeLa-H1 (Alu-nonpermissive) strains. A similar pattern of retrotransposition was observed for other 7SL RNA-derived SINEs and tRNA-derived SINEs. In contrast, mammalian LINE-1s, a zebrafish LINE, a human SINE-VNTR-Alu (SVA) element, and an L1 ORF1-containing mRNA can retrotranspose in all four HeLa strains. Using an in vitro reverse transcriptase-based assay, we show that Alu RNAs associate with ORF2p and are converted into cDNAs in both Alu-permissive and Alu-nonpermissive HeLa strains, suggesting that 7SL- and tRNA-derived SINEs use strategies to 'hijack' L1 ORF2p that are distinct from those used by SVA elements and ORF1-containing mRNAs. These data further suggest ORF2p associates with the Alu RNA poly(A) tract in both Alu-permissive and Alu-nonpermissive HeLa strains, but that Alu retrotransposition is blocked after this critical step in Alu-nonpermissive HeLa strains.
PubMed: 38850156
DOI: 10.1093/nar/gkae448 -
Molecular Cell Jun 2024Protein synthesis is metabolically costly and must be tightly coordinated with changing cellular needs and nutrient availability. The cap-binding protein eIF4E makes the...
Protein synthesis is metabolically costly and must be tightly coordinated with changing cellular needs and nutrient availability. The cap-binding protein eIF4E makes the earliest contact between mRNAs and the translation machinery, offering a key regulatory nexus. We acutely depleted this essential protein and found surprisingly modest effects on cell growth and recovery of protein synthesis. Paradoxically, impaired protein biosynthesis upregulated genes involved in the catabolism of aromatic amino acids simultaneously with the induction of the amino acid biosynthetic regulon driven by the integrated stress response factor GCN4. We further identified the translational control of Pho85 cyclin 5 (PCL5), a negative regulator of Gcn4, that provides a consistent protein-to-mRNA ratio under varied translation environments. This regulation depended in part on a uniquely long poly(A) tract in the PCL5 5' UTR and poly(A) binding protein. Collectively, these results highlight how eIF4E connects protein synthesis to metabolic gene regulation, uncovering mechanisms controlling translation during environmental challenges.
Topics: Eukaryotic Initiation Factor-4E; Saccharomyces cerevisiae Proteins; Protein Biosynthesis; Amino Acids; Saccharomyces cerevisiae; Gene Expression Regulation, Fungal; RNA, Messenger; 5' Untranslated Regions; Basic-Leucine Zipper Transcription Factors; Cyclins; Poly(A)-Binding Proteins
PubMed: 38848691
DOI: 10.1016/j.molcel.2024.05.008 -
Molecular Cell Jun 2024Circular RNAs (circRNAs) are upregulated during neurogenesis. Where and how circRNAs are localized and what roles they play during this process have remained elusive....
Circular RNAs (circRNAs) are upregulated during neurogenesis. Where and how circRNAs are localized and what roles they play during this process have remained elusive. Comparing the nuclear and cytoplasmic circRNAs between H9 cells and H9-derived forebrain (FB) neurons, we identify that a subset of adenosine (A)-rich circRNAs are restricted in H9 nuclei but exported to cytosols upon differentiation. Such a subcellular relocation of circRNAs is modulated by the poly(A)-binding protein PABPC1. In the H9 nucleus, newly produced (A)-rich circRNAs are bound by PABPC1 and trapped by the nuclear basket protein TPR to prevent their export. Modulating (A)-rich motifs in circRNAs alters their subcellular localization, and introducing (A)-rich circRNAs in H9 cytosols results in mRNA translation suppression. Moreover, decreased nuclear PABPC1 upon neuronal differentiation enables the export of (A)-rich circRNAs, including circRTN4(2,3), which is required for neurite outgrowth. These findings uncover subcellular localization features of circRNAs, linking their processing and function during neurogenesis.
Topics: RNA, Circular; Neurons; Active Transport, Cell Nucleus; Adenosine; Cell Nucleus; Neurogenesis; Humans; Poly(A)-Binding Protein I; Animals; RNA; Cell Line; Cell Differentiation; Cytoplasm; Prosencephalon
PubMed: 38838666
DOI: 10.1016/j.molcel.2024.05.011 -
RNA Biology Jan 2024Production and storage of synthetic mRNA can introduce a variety of byproducts which reduce the overall integrity and functionality of mRNA vaccines and therapeutics....
Production and storage of synthetic mRNA can introduce a variety of byproducts which reduce the overall integrity and functionality of mRNA vaccines and therapeutics. mRNA integrity is therefore designated as a critical quality attribute which must be evaluated with state-of-the-art analytical methods before clinical use. The current study first demonstrates the effect of heat degradation on transcript translatability and then describes a novel enzymatic approach to assess the integrity of conventional mRNA and long self-amplifying mRNA. By first hybridizing oligo-T to the poly(A) tail of intact mRNA and subsequently digesting the unhybridized RNA fragments with a 3'-5' exoribonuclease, individual nucleotides can be selectively released from RNA fragments. The adenosine-based fraction of these nucleotides can then be converted into ATP and detected by luminescence as a sensitive indicator of mRNA byproducts. We developed a polynucleotide phosphorylase (PNPase)-based assay that offers fast and sensitive evaluation of mRNA integrity, regardless of its length, thus presenting a novel and fully scalable alternative to chromatographic-, electrophoresis-, or sequencing-based techniques.
Topics: RNA, Messenger; Polyribonucleotide Nucleotidyltransferase; Humans; Oligonucleotides; RNA Stability
PubMed: 38836544
DOI: 10.1080/15476286.2024.2363029 -
Frontiers in Microbiology 2024Lymphatic filariasis is caused by parasitic nematodes and is a leading cause of disability worldwide. Many filarial worms contain the bacterium as an obligate...
Lymphatic filariasis is caused by parasitic nematodes and is a leading cause of disability worldwide. Many filarial worms contain the bacterium as an obligate endosymbiont. RNA sequencing is a common technique used to study their molecular relationships and to identify potential drug targets against the nematode and bacteria. Ribosomal RNA (rRNA) is the most abundant RNA species, accounting for 80-90% of the RNA in a sample. To reduce sequencing costs, it is necessary to remove ribosomal reads through poly-A enrichment or ribosomal depletion. Bacterial RNA does not contain a poly-A tail, making it difficult to sequence both the nematode and from the same library preparation using standard poly-A selection. Ribosomal depletion can utilize species-specific oligonucleotide probes to remove rRNA through pull-down or degradation methods. While species-specific probes are commercially available for many commonly studied model organisms, there are currently limited depletion options for filarial parasites. Here, we performed total RNA sequencing from containing the symbiont (Bm) and designed ssDNA depletion probes against their rRNA sequences. We compared the total RNA library to poly-A enriched, Terminator 5'-Phosphate-Dependent Exonuclease treated, NEBNext Human/Bacteria rRNA depleted and our custom nematode probe depleted libraries. The custom nematode depletion library had the lowest percentage of ribosomal reads across all methods, with a 300-fold decrease in rRNA when compared to the total RNA library. The nematode depletion libraries also contained the highest percentage of mRNA reads, resulting in a 16-1,000-fold increase in bacterial reads compared to the other enrichment and depletion methods. Finally, we found that the depletion probes can remove rRNA from the filarial worm and the majority of rRNA from the more distantly related free living nematode . These custom filarial probes will allow for future dual RNA-seq experiments between nematodes and their bacterial symbionts from a single sequencing library.
PubMed: 38832111
DOI: 10.3389/fmicb.2024.1418032 -
Bioelectrochemistry (Amsterdam,... Oct 2024Carcinoembryonic antigen (CEA), a key colon biomarker, demands a precise detection method for cancer diagnosis and prognosis. This study introduces a novel...
Triblock polyadenine-based electrochemical aptasensor for ultra-sensitive detection of carcinoembryonic antigen via exonuclease III-assisted target recycling and hybridization chain reaction.
Carcinoembryonic antigen (CEA), a key colon biomarker, demands a precise detection method for cancer diagnosis and prognosis. This study introduces a novel electrochemical aptasensor using a triblock polyadenine probe for ultra-sensitive detection of CEA. The method leverages Exonuclease III (Exo III)-assisted target recycling and hybridization chain reaction. The triblock polyadenine probe self-assembles on the bare gold electrode through the strong affinity between adenine and gold electrode, blocking CEA diffusion and providing a large immobilization surface. CEA binding to hairpin probe 1 (HP1), followed by the hybridization between HP1 and hairpin probe 2 (HP2), triggers DNA cleavage by Exo III, amplifying the signal via a hybridization chain reaction and producing numerous dsDNA walkers that generates a dramatic electrochemical impedance signal. Under optimized conditions, the aptasensor achieved two ultra-low detection limits: 0.39 ag∙mL within the concentration range of 5 ag∙mL to 5 × 10 ag∙mL, and 1.5 ag∙mL within the concentration range of 5 × 10 ag∙mL to 1 × 10 ag∙mL. Its performance in human serum samples meets the practical standards, offering a promising new tool for ultrasensitive tumor marker detection, potentially revolutionizing early cancer diagnosis.
Topics: Exodeoxyribonucleases; Carcinoembryonic Antigen; Humans; Nucleic Acid Hybridization; Biosensing Techniques; Electrochemical Techniques; Aptamers, Nucleotide; Limit of Detection; Poly A; Gold; Electrodes
PubMed: 38823375
DOI: 10.1016/j.bioelechem.2024.108749