A triple helix stabilizes the 3' ends of long noncoding RNAs that lack poly(A) tails

The cellular paraspeckle component SFPQ associates with the viral processivity factor ORF59 during lytic replication of Kaposi's Sarcoma-associated herpesvirus (KSHV)

Kaposi's sarcoma-associated herpesvirus (KSHV) relies on many cellular proteins to complete replication and generate new virions. Paraspeckle nuclear bodies consisting of core ribonucleoproteins splicing factor proline/glutamine-rich (SFPQ), Non-POU domain-containing octamer-binding protein (NONO), and paraspeckle protein component 1 (PSPC1) along with the long non-coding RNA NEAT1, form a complex that has been speculated to play an important role in viral replication. Paraspeckle bodies are multifunctional and involved in various processes including gene expression, mRNA splicing, and anti-viral defenses. To better understand the role of SFPQ during KSHV replication, we performed SFPQ immunoprecipitation followed by mass spectrometry from KSHV-infected cells. Proteomic analysis showed that during lytic reactivation, SFPQ associates with viral proteins, including ORF10, ORF59, and ORF61. These results are consistent with a previously reported ORF59 proteomics assay identifying SFPQ. To test if the association between ORF59 and SFPQ is important for replication, we first identified the region of ORF59 that associates with SFPQ using a series of 50 amino acid deletion mutants of ORF59 in the KSHV BACmid system. By performing co-immunoprecipitations, we identified the region spanning amino acids 101-150 of ORF59 as the association domain with SFPQ. Using this information, we generated a dominant negative polypeptide of ORF59 encompassing amino acids 101-150, that disrupted the association between SFPQ and full-length ORF59, and decreased virus production. Interestingly, when we tested other human herpesvirus processivity factors (EBV BMRF1, HSV-1 UL42, and HCMV UL44) by transfection of each expression plasmid followed by co-immunoprecipitation, we found a conserved association with SFPQ. These are limited studies that remain to be done in the context of infection but suggest a potential association of SFPQ with processivity factors across multiple herpesviruses.

Optimizing a CRISPR-Cas13d Gene Circuit for Tunable Target RNA Downregulation with Minimal Collateral RNA Cutting

The invention of RNA-guided DNA cutting systems has revolutionized biotechnology. More recently, RNA-guided RNA cutting by Cas13d entered the scene as a highly promising alternative to RNA interference to engineer cellular transcriptomes for biotechnological and therapeutic purposes. Unfortunately, "collateral damage" by indiscriminate off-target cutting tampered enthusiasm for these systems. Yet, how collateral activity, or even RNA target reduction depends on Cas13d and guide RNA abundance has remained unclear due to the lack of expression-tuning studies to address this question. Here we use precise expression-tuning gene circuits to show that both nonspecific and specific, on-target RNA reduction depend on Cas13d and guide RNA levels, and that nonspecific RNA cutting from trans cleavage might contribute to on-target RNA reduction. Using RNA-level control techniques, we develop new Multi-Level Optimized Negative-Autoregulated Cas13d and crRNA Hybrid (MONARCH) gene circuits that achieve a high dynamic range with low basal on-target RNA reduction while minimizing collateral activity in human kidney cells and green monkey cells most frequently used in human virology. MONARCH should bring RNA-guided RNA cutting systems to the forefront, as easily applicable, programmable tools for transcriptome engineering in biotechnological and medical applications.

Metastasis-Associated Lung Adenocarcinoma Transcript 1 (MALAT1) lncRNA Conformational Dynamics in Complex with RNA-Binding Protein with Serine-Rich Domain 1 (RNPS1) in the Pan-cancer Splicing and Gene Expression

Alternative splicing events increase the transcriptomic and proteomic complexity in cancers. Overexpression of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), a highly conserved lncRNA, is widely known to promote cancer development, one mechanism for which may be through the regulation of alternative splicing and, thereby, gene expression. Its regulatory interactions with proteins have been a subject of much interest, yet little research has been carried out on the mechanisms adopted. It has been observed that MALAT1 binds to RNA-binding protein with serine-rich domain 1 (RNPS1), being colocalized in the nuclear speckles, and together, these two binding partners may regulate alternative splicing. Upregulated RNPS1 is predicted to play a key role in the pan-cancer development. Experimental tertiary structure of full-length MALAT1 is currently lacking despite the availability of the 3D structure of 3' expression and nuclear retention element. We hypothesize that the computationally modeled tertiary structures of the specific binding motifs in the M-region, E-region, and full-length structures of MALAT1 may adopt a modular structure and bind to the RNPS1 loop region of RS/P domain involved in exon skipping, interacting in a manner fully consistent with the biochemical experiments. Extensive observations using the powerful molecular dynamics (MD) simulations of MALAT1 regions bound to RNPS1 suggested that all three regions form interactive, yet stable complexes. The ranking of the MM-GBSA- and MM-PBSA-derived binding free energies between these complexes corroborated well in the MD simulations and experiments. Energy decomposition analyses suggested that arginines in the RNPS1 protein are among the major contributors toward the binding free energies as calculated by MM-GBSA present in the Amber package; while among the nucleotides, the major contributors were nucleotides with G and A nucleobases, with more contributory effect in comparison to arginines, across the bound M-region, E-region, and full-length MALAT1. This suggests that specific purines play a greater role in the complex formation, in a loop-specific manner, and the more proactive approach in complexation tilts toward MALAT1. To the best of our knowledge, our studies are the first studies taking a unique approach, utilizing the binding motifs to deduce a tertiary structure of MALAT1, toward our understanding of the lncRNA-protein interactions, stability, and binding on a structural basis. The therapeutic implications of targeting this complex formation to regulate splicing and hence, oncogenesis, is further envisaged.

Reconstructing signaling history of single cells with imaging-based molecular recording

The intensity and duration of biological signals encode information that allows a few pathways to regulate a wide array of cellular behaviors. Despite the central importance of signaling in biomedical research, our ability to quantify it in individual cells over time remains limited. Here, we introduce INSCRIBE, an approach for reconstructing signaling history in single cells using endpoint fluorescence images. By regulating a CRISPR base editor, INSCRIBE generates mutations in genomic target sequences, at a rate proportional to signaling activity. The number of edits is then recovered through a novel ratiometric readout strategy, from images of two fluorescence channels. We engineered human cell lines for recording WNT and BMP pathway activity, and demonstrated that INSCRIBE faithfully recovers both the intensity and duration of signaling. Further, we used INSCRIBE to study the variability of cellular response to WNT and BMP stimulation, and test whether the magnitude of response is a stable, heritable trait. We found a persistent memory in the BMP pathway. Progeny of cells with higher BMP response levels are likely to respond more strongly to a second BMP stimulation, up to 3 weeks later. Together, our results establish a scalable platform for genetic recording and in situ readout of signaling history in single cells, advancing quantitative analysis of cell-cell communication during development and disease.

PAM-relaxed and temperature-tolerant CRISPR-Mb3Cas12a single transcript unit systems for efficient singular and multiplexed genome editing in rice, maize, and tomato

Class 2 Type V-A CRISPR-Cas (Cas12a) nucleases are powerful genome editing tools, particularly effective in A/T-rich genomic regions, complementing the widely used CRISPR-Cas9 in plants. To enhance the utility of Cas12a, we investigate three Cas12a orthologs-Mb3Cas12a, PrCas12a, and HkCas12a-in plants. Protospacer adjacent motif (PAM) requirements, editing efficiencies, and editing profiles are compared in rice. Among these orthologs, Mb3Cas12a exhibits high editing efficiency at target sites with a simpler, relaxed TTV PAM which is less restrictive than the canonical TTTV PAM of LbCas12a and AsCas12a. To optimize Mb3Cas12a, we develop an efficient single transcription unit (STU) system by refining the linker between Mb3Cas12a and CRISPR RNA (crRNA), nuclear localization signal (NLS), and direct repeat (DR). This optimized system enables precise genome editing in rice, particularly for fine-tuning target gene expression by editing promoter regions. Further, we introduced Arginine (R) substitutions at Aspartic acid (D) 172, Asparagine (N) 573, and Lysine (K) 579 of Mb3Cas12a, creating two temperature-tolerant variants: Mb3Cas12a-R (D172R) and Mb3Cas12a-RRR (D172R/N573R/K579R). These variants demonstrate significantly improved editing efficiency at lower temperatures (22 °C and 28 °C) in rice cells, with Mb3Cas12a-RRR showing the best performance. We extend this approach by developing efficient Mb3Cas12a-RRR STU systems in maize and tomato, achieving biallelic mutants targeting single or multiple genes in T0 lines cultivated at 28 °C and 25 °C, respectively. This study significantly expands Cas12a's targeting capabilities in plant genome editing, providing valuable tools for future research and practical applications.

Identification of Human Pathways Acting on Nuclear Non-Coding RNAs Using the Mirror Forward Genetic Approach

Despite critical roles in diseases, human pathways acting on strictly nuclear non-coding RNAs have been refractory to forward genetics. To enable their forward genetic discovery, we developed a single-cell approach that "Mirrors" activities of nuclear pathways with cytoplasmic fluorescence. Application of Mirror to two nuclear pathways targeting MALAT1's 3' end, the pathway of its maturation and the other, the degradation pathway blocked by the triple-helical Element for Nuclear Expression (ENE), identified nearly all components of three complexes: Ribonuclease P and the RNA Exosome, including nuclear DIS3, EXOSC10, and C1D, as well as the Nuclear Exosome Targeting (NEXT) complex. Additionally, Mirror identified DEAD-box helicase DDX59 associated with the genetic disorder Oral-Facial-Digital syndrome (OFD), yet lacking known substrates or roles in nuclear RNA degradation. Knockout of DDX59 exhibits stabilization of the full-length MALAT1 with a stability-compromised ENE and increases levels of such long non-coding RNAs as NEAT1_1 and NIPBL-DT, as well as 3'-extended forms of small nuclear RNAs. It also exhibits extensive retention of minor introns, including in OFD-associated genes, suggesting a mechanism for DDX59 association with OFD. Mirror efficiently identifies pathways acting on strictly nuclear non-coding RNAs, including essential and indirectly-acting components, and, as a result, uncovers unexpected links to human disease.

A Newly Identified Peripheral Duplex Anchors and Stabilizes the MALAT1 Triplex

The accumulation of the 8-kb oncogenic long noncoding MALAT1 RNA in cells is dependent on the presence of a protective triple helix structure at the 3' terminus. While recent studies have examined the functional importance of numerous base triples within the triplex and its immediately adjacent base pairs, the functional importance of peripheral duplex elements has not been thoroughly investigated. To investigate the functional importance of a peripheral linker region that was previously described as unstructured, we employed a variety of assays including thermal melting, protection from exonucleolytic degradation by RNase R, small-angle X-ray scattering, biochemical ligation and binding assays, and computational modeling. Our results demonstrate the presence of a duplex within this linker that enhances the functional stability of the triplex in vitro, despite its location more than 40 Å from the 3' terminus. We present a full-length model of the MALAT1 triple helix-containing RNA having an extended rod-like structure and comprising 33 layers of coaxial stacking interactions. Taken together with recent research on a homologous triplex, our results demonstrate that peripheral elements anchor and stabilize triplexes in vitro. Such peripheral elements may also contribute to the formation and stability of some triple helices in vivo.

CRISPR-array-mediated imaging of non-repetitive and multiplex genomic loci in living cells

Dynamic imaging of genomic loci is key for understanding gene regulation, but methods for imaging genomes, in particular non-repetitive DNAs, are limited. We developed CRISPRdelight, a DNA-labeling system based on endonuclease-deficient CRISPR-Cas12a (dCas12a), with an engineered CRISPR array to track DNA location and motion. CRISPRdelight enables robust imaging of all examined 12 non-repetitive genomic loci in different cell lines. We revealed the confined movement of the CCAT1 locus (chr8q24) at the nuclear periphery for repressed expression and active motion in the interior nucleus for transcription. We uncovered the selective repositioning of HSP gene loci to nuclear speckles, including a remarkable relocation of HSPH1 (chr13q12) for elevated transcription during stresses. Combining CRISPR-dCas12a and RNA aptamers allowed multiplex imaging of four types of satellite DNA loci with a single array, revealing their spatial proximity to the nucleolus-associated domain. CRISPRdelight is a user-friendly and robust system for imaging and tracking genomic dynamics and regulation.

Isoform balance of the long noncoding RNA NEAT1 is regulated by the RNA-binding protein QKI, governs the glioma transcriptome, and impacts cell migration

The long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) is involved in a variety of human cancers. Two overlapping NEAT1 isoforms, NEAT1_1 and NEAT1_2, are produced through mutually exclusive alternative 3' end formation. Previous studies extensively investigated NEAT1 dysregulation in tumors, but often failed to achieve distinct quantification of the two NEAT1 isoforms. Moreover, molecular mechanisms governing the biogenesis of NEAT1 isoforms and the functional impacts of their dysregulation in tumorigenesis remain poorly understood. In this study, we employed an isoform-specific quantification assay and found differential dysregulation of NEAT1 isoforms in patient-derived glioblastoma multiforme cells. We further showed usage of the NEAT1 proximal polyadenylation site (PAS) is a critical mechanism that controls glioma NEAT1 isoform production. CRISPR-Cas9-mediated PAS deletion reduced NEAT1_1 and reciprocally increased NEAT1_2, which enhanced nuclear paraspeckle formation in human glioma cells. Moreover, the utilization of the NEAT1 PAS is facilitated by the RNA-binding protein quaking (QKI), which binds to the proximal QKI recognition elements. Functionally, we identified transcriptomic changes and altered biological pathways caused by NEAT1 isoform imbalance in glioma cells, including the pathway for the regulation of cell migration. Finally, we demonstrated the forced increase of NEAT1_2 upon NEAT1 PAS deletion is responsible for driving glioma cell migration and promoting the expression of genes implicated in the regulation of cell migration. Together, our studies uncovered a novel mechanism that regulates NEAT1 isoforms and their functional impacts on the glioma transcriptome, which affects pathological pathways of glioma, represented by migration.

Structural basis of tRNA recognition by the widespread OB fold

The widespread oligonucleotide/oligosaccharide-binding (OB)-fold recognizes diverse substrates from sugars to nucleic acids and proteins, and plays key roles in genome maintenance, transcription, translation, and tRNA metabolism. OB-containing bacterial Trbp and yeast Arc1p proteins are thought to recognize the tRNA elbow or anticodon regions. Here we report a 2.6 Å co-crystal structure of Aquifex aeolicus Trbp111 bound to tRNAIle, which reveals that Trbp recognizes tRNAs solely by capturing their 3' ends. Structural, mutational, and biophysical analyses show that the Trbp/EMAPII-like OB fold precisely recognizes the single-stranded structure, 3' terminal location, and specific sequence of the 3' CA dinucleotide - a universal feature of mature tRNAs. Arc1p supplements its OB - tRNA 3' end interaction with additional contacts that involve an adjacent basic region and the tRNA body. This study uncovers a previously unrecognized mode of tRNA recognition by an ancient protein fold, and provides insights into protein-mediated tRNA aminoacylation, folding, localization, trafficking, and piracy.

A nuclear RNA degradation code for eukaryotic transcriptome surveillance

The RNA exosome plays critical roles in eukaryotic RNA degradation, but it remains unclear how the exosome specifically recognizes its targets. The PAXT connection is an adaptor that recruits the exosome to polyadenylated RNAs in the nucleus, especially transcripts polyadenylated at intronic poly(A) sites. Here we show that PAXT-mediated RNA degradation is induced by the combination of a 5' splice site and a poly(A) junction, but not by either sequence alone. These sequences are bound by U1 snRNP and cleavage/polyadenylation factors, which in turn cooperatively recruit PAXT. As the 5' splice site-poly(A) junction combination is typically not found on correctly processed full-length RNAs, we propose that it functions as a "nuclear RNA degradation code" (NRDC). Importantly, disease-associated single nucleotide polymorphisms that create novel 5' splice sites in 3' untranslated regions can induce aberrant mRNA degradation via the NRDC mechanism. Together our study identified the first NRDC, revealed its recognition mechanism, and characterized its role in human diseases.

MUC1-C regulates NEAT1 lncRNA expression and paraspeckle formation in cancer progression

The MUC1 gene evolved in mammals for adaptation of barrier tissues in response to infections and damage. Paraspeckles are nuclear bodies formed on the NEAT1 lncRNA in response to loss of homeostasis. There is no known intersection of MUC1 with NEAT1 or paraspeckles. Here, we demonstrate that the MUC1-C subunit plays an essential role in regulating NEAT1 expression. MUC1-C activates the NEAT1 gene with induction of the NEAT1_1 and NEAT1_2 isoforms by NF-κB- and MYC-mediated mechanisms. MUC1-C/MYC signaling also induces expression of the SFPQ, NONO and FUS RNA binding proteins (RBPs) that associate with NEAT1_2 and are necessary for paraspeckle formation. MUC1-C integrates activation of NEAT1 and RBP-encoding genes by recruiting the PBAF chromatin remodeling complex and increasing chromatin accessibility of their respective regulatory regions. We further demonstrate that MUC1-C and NEAT1 form an auto-inductive pathway that drives common sets of genes conferring responses to inflammation and loss of homeostasis. Of functional significance, we find that the MUC1-C/NEAT1 pathway is of importance for the cancer stem cell (CSC) state and anti-cancer drug resistance. These findings identify a previously unrecognized role for MUC1-C in the regulation of NEAT1, RBPs, and paraspeckles that has been co-opted in promoting cancer progression.

Hippocampal astrocytes induce sex-dimorphic effects on memory

Astrocytic receptors influence cognitive function and can promote behavioral deficits in disease. These effects may vary based on variables such as biological sex, but it is not known if the effects of astrocytic receptors are dependent on sex. We leveraged in vivo gene editing and chemogenetics to examine the roles of astrocytic receptors in spatial memory and other processes. We show that reductions in metabotropic glutamate receptor 3 (mGluR3), the main astrocytic glutamate receptor in adults, impair memory in females but enhance memory in males. Similarly, increases in astrocytic mGluR3 levels have sex-dependent effects and enhance memory in females. mGluR3 manipulations also alter spatial search strategies during recall in a sex-specific manner. In addition, acute chemogenetic stimulation of Gi/o-coupled or Gs-coupled receptors in hippocampal astrocytes induces bidirectional and sex-dimorphic effects on memory. Thus, astrocytes are sex-dependent modulators of cognitive function and may promote sex differences in aging and disease.

Overexpression of Malat1 drives metastasis through inflammatory reprogramming of the tumor microenvironment

Expression of the long noncoding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) correlates with tumor progression and metastasis in many tumor types. However, the impact and mechanism of action by which MALAT1 promotes metastatic disease remain elusive. Here, we used CRISPR activation (CRISPRa) to overexpress MALAT1/Malat1 in patient-derived lung adenocarcinoma (LUAD) cell lines and in the autochthonous K-ras/p53 LUAD mouse model. Malat1 overexpression was sufficient to promote the progression of LUAD to metastatic disease in mice. Overexpression of MALAT1/Malat1 enhanced cell mobility and promoted the recruitment of protumorigenic macrophages to the tumor microenvironment through paracrine secretion of CCL2/Ccl2. Ccl2 up-regulation was the result of increased global chromatin accessibility upon Malat1 overexpression. Macrophage depletion and Ccl2 blockade counteracted the effects of Malat1 overexpression. These data demonstrate that a single lncRNA can drive LUAD metastasis through reprogramming of the tumor microenvironment.

Breed and timepoint-based analysis of chicken harderian gland transcriptome during Newcastle disease virus challenge

Introduction: Newcastle disease is a highly infectious disease caused by the Newcastle Disease Virus (NDV) and has a devastating financial impact on the global chicken industry. It was previously established that Leghorn and Fayoumi breeds of chicken exhibit variable resistance against NDV infection. The harderian gland is the less studied tissue of the chicken, known to play an essential role in the immune response. Methods: Our previous study, we reported differential gene expression and long noncoding RNAs (lncRNAs) between challenged and non-challenged chickens in the Harderian gland transcriptomic data. Now, we report the analysis of the same data studying the differential expression patterns between Leghorn and Fayoumi and between different timepoints during disease. First, the pipeline FHSpipe was used for identification of lncRNAs, followed by differential expression analysis by edgeR (GLM), functional annotation by OmicsBox, co-expression analysis using WGCNA and finally validation of selected lncRNAs and co-expressing genes using qRT-PCR. Results: Here, we observed that Leghorn showed a higher number of upregulated immune-related genes than Fayoumi in timepoint-based analysis, especially during the initial stages. Surprisingly, Fayoumi, being comparatively resistant, showed little difference between challenged and non-challenged conditions and different time points of the challenge. The breed-based analysis, which compared Leghorn with Fayoumi in both challenged and non-challenged conditions separately, identified several immune-related genes and positive co-expressing cis lncRNAs to be upregulated in Fayoumi when compared to Leghorn in both challenged and non-challenged conditions. Discussion: The current study shows that Leghorn, being comparatively more susceptible to NDV than Fayoumi, showed several immune-related genes and positive co-expressing cis lncRNAs upregulated in challenged Leghorn when compared to non-challenged Leghorn and also in different timepoints during challenge. While, breed-based analysis showed that there were more upregulated immune genes and positive cis-lncRNAs in Fayoumi than Leghorn. This result clearly shows that the differences in the expression of genes annotated with immune-related GO terms and pathways, i.e., immune-related genes and the co-expressing cis-lncRNAs between Leghorn and Fayoumi, and their role in the presence of differences in the resistance of Leghorn and Fayoumi chicken against NDV. Conclusion: These immune-genes and cis-lncRNAs could play a role in Fayoumi being comparatively more resistant to NDV than Leghorn. Our study elucidated the importance of lncRNAs during the host defense against NDV infection, paving the way for future research on the mechanisms governing the genetic improvement of chicken breeds.

MIAT LncRNA: A multifunctional key player in non-oncological pathological conditions

The discovery of non-coding RNAs (ncRNAs) has unveiled a wide range of transcripts that do not encode proteins but play key roles in several cellular and molecular processes. Long noncoding RNAs (lncRNAs) are specific class of ncRNAs that are longer than 200 nucleotides and have gained significant attention due to their diverse mechanisms of action and potential involvement in various pathological conditions. In the current review, the authors focus on the role of lncRNAs, specifically highlighting the Myocardial Infarction Associated Transcript (MIAT), in non-oncological context. MIAT is a nuclear lncRNA that has been directly linked to myocardial infarction and is reported to control post-transcriptional processes as a competitive endogenous RNA (ceRNA) molecule. It interacts with microRNAs (miRNAs), thereby limiting the translation and expression of their respective target messenger RNA (mRNA) and regulating protein expression. Yet, MIAT has been implicated in other numerous pathological conditions such as other cardiovascular diseases, autoimmune disease, neurodegenerative diseases, metabolic diseases, and many others. In this review, the authors emphasize that MIAT exhibits distinct expression patterns and functions across different pathological conditions and is emerging as potential diagnostic, prognostic, and therapeutic agent. Additionally, the authors highlight the regulatory role of MIAT and shed light on the involvement of lncRNAs and specifically MIAT in various non-oncological pathological conditions.

Beyond the Genome: Deciphering the Role of MALAT1 in Breast Cancer Progression

The MALAT1, a huge non-coding RNA, recently came to light as a multifaceted regulator in the intricate landscape of breast cancer (BC) progression. This review explores the multifaceted functions and molecular interactions of MALAT1, shedding light on its profound implications for understanding BC pathogenesis and advancing therapeutic strategies. The article commences by acknowledging the global impact of BC and the pressing need for insights into its molecular underpinnings. It is stated that the core lncRNA MALAT1 has a range of roles in both healthy and diseased cell functions. The core of this review unravels MALAT1's multifaceted role in BC progression, elucidating its participation in critical processes like resistance, invasion, relocation, and proliferating cells to therapy. It explores the intricate mechanisms through which MALAT1 modulates gene expression, interacts with other molecules, and influences signalling pathways. Furthermore, the paper emphasizes MALAT1's clinical significance as a possible prognostic and diagnostic biomarker. Concluding on a forward-looking note, the review highlights the broader implications of MALAT1 in BC biology, such as its connections to therapy resistance and metastasis. It underscores the significance of deeper investigations into these intricate molecular interactions to pave the way for precision medicine approaches. This review highlights the pivotal role of MALAT1 in BC progression by deciphering its multifaceted functions beyond the genome, offering profound insights into its implications for disease understanding and the potential for targeted therapeutic interventions.

An unexpected path for Malat1 in neurons: trafficking out of the nucleus for translation

The Malat1 (metastasis-associated lung adenocarcinoma transcript 1) long noncoding RNA is highly and broadly expressed in mammalian tissues, accumulating in the nucleus where it modulates expression and pre-mRNA processing of many protein-coding genes. In this issue of Genes & Development, Xiao and colleagues (doi:10.1101/gad.351557.124) report that a significant fraction of Malat1 transcripts in cultured mouse neurons are surprisingly exported from the nucleus. These transcripts are packaged with Staufen proteins in RNA granules and traffic down the lengths of neurites. They then can be released in a stimulus-dependent manner to be locally translated into a microprotein that alters neuronal gene expression patterns.

The lncRNA Malat1 is trafficked to the cytoplasm as a localized mRNA encoding a small peptide in neurons

Synaptic function in neurons is modulated by local translation of mRNAs that are transported to distal portions of axons and dendrites. The metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is broadly expressed across cell types, almost exclusively as a nuclear long noncoding RNA. We found that in differentiating neurons, a portion of Malat1 RNA redistributes to the cytoplasm. Depletion of Malat1 using antisense oligonucleotides (ASOs) stimulates the expression of particular pre- and postsynaptic proteins, implicating Malat1 in their regulation. Neuronal Malat1 is localized in puncta of both axons and dendrites that costain with Staufen1 protein, similar to neuronal RNA granules formed by locally translated mRNAs. Ribosome profiling of cultured mouse cortical neurons identified ribosome footprints within a 5' region of Malat1 containing short open reading frames. The upstream-most reading frame (M1) of the Malat1 locus was linked to the GFP-coding sequence in mouse embryonic stem cells. When these gene-edited cells were differentiated into glutamatergic neurons, the M1-GFP fusion protein was expressed. Antibody staining for the M1 peptide confirmed its presence in wild-type neurons and showed that M1 expression was enhanced by synaptic stimulation with KCl. Our results indicate that Malat1 serves as a cytoplasmic coding RNA in the brain that is both modulated by and modulates synaptic function.

The Long Non-Coding RNA MALAT1 Modulates NR4A1 Expression through a Downstream Regulatory Element in Specific Cancer Cell Types

Long non-coding RNAs (lncRNAs) have been shown to modulate gene expression and are involved in the initiation and progression of various cancer types. Despite the wealth of studies describing transcriptome changes upon lncRNA knockdown, there is limited information describing lncRNA-mediated effects on regulatory elements (REs) modulating gene expression. In this study, we investigated how the metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) lncRNA regulates primary target genes using time-resolved MALAT1 knockdown followed by parallel RNA-seq and ATAC-seq assays. The results revealed that MALAT1 primarily regulates specific protein-coding genes and a substantial decrease in the accessibility downstream of the NR4A1 gene that was associated with a decreased NR4A1 expression. Moreover, the presence of an NR4A1-downstream RE was demonstrated by CRISPR-i assays to define a functional MALAT1/NR4A1 axis. By analyzing TCGA data, we identified a positive correlation between NR4A1 expression and NR4A1-downstream RE accessibility in breast cancer but not in pancreatic cancer. Accordingly, this regulatory mechanism was experimentally validated in breast cancer cells (MCF7) but not in pancreatic duct epithelial carcinoma (PANC1) cells. Therefore, our results demonstrated that MALAT1 is involved in a molecular mechanism that fine-tunes NR4A1 expression by modulating the accessibility of a downstream RE in a cell type-specific manner.

Noncoding RNAs in atherosclerosis: regulation and therapeutic potential

Atherosclerosis, a chronic disease of arteries, results in high mortality worldwide as the leading cause of cardiovascular disease. The development of clinically relevant atherosclerosis involves the dysfunction of endothelial cells and vascular smooth muscle cells. A large amount of evidence indicates that noncoding RNAs, such as microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), are involved in various physiological and pathological processes. Recently, noncoding RNAs were identified as key regulators in the development of atherosclerosis, including the dysfunction of endothelial cells, and vascular smooth muscle cells and it is pertinent to understand the potential function of noncoding RNAs in atherosclerosis development. In this review, the latest available research relates to the regulatory role of noncoding RNAs in the progression of atherosclerosis and the therapeutic potential for atherosclerosis is summarized. This review aims to provide a comprehensive overview of the regulatory and interventional roles of ncRNAs in atherosclerosis and to inspire new insights for the prevention and treatment of this disease.

MALAT1 as a potential salivary biomarker in oral squamous cell carcinoma through targeting miRNA-124

OBJECTIVES

To determine the diagnostic accuracy of the long non-coding RNA "MALAT1" measured in the saliva of patients with oral squamous cell carcinoma (OSCC) and assess the salivary expression of microRNA-124, which MALAT1 targets.

SUBJECTS AND METHODS

Forty subjects were collected in a consecutive pattern and allocated into two groups. Group A included 20 patients with OSCC, while Group B included 20 healthy subjects. Salivary expression of MALAT1 and microRNA (miRNA)-124 was evaluated in the two study groups using quantitative real-time polymerase chain reaction and correlated with histopathological examination of OSCC subjects.

RESULTS

OSCC yielded a statistically significant higher expression of MALAT1 than healthy controls and a lower expression of miRNA-124 in OSCC than controls. There is a statistically significant inverse relationship between salivary MALAT1 and miRNA-124. Moreover, there is a statistically significant difference in the MALAT1 expression in saliva samples from metastatic cases compared with non-metastatic cases, as well as in patients with lymph node involvement compared with those without involvement. At a cut-off value of 2.24, salivary MALAT1 exhibited 95% sensitivity and 90% specificity in differentiating OSCC from healthy subjects.

CONCLUSION

Salivary MALAT1 acts as a sponge for miRNA-124 and could be a potential salivary biomarker for OSCC.

RNA: The Unsuspected Conductor in the Orchestra of Macromolecular Crowding

This comprehensive Review delves into the chemical principles governing RNA-mediated crowding events, commonly referred to as granules or biological condensates. We explore the pivotal role played by RNA sequence, structure, and chemical modifications in these processes, uncovering their correlation with crowding phenomena under physiological conditions. Additionally, we investigate instances where crowding deviates from its intended function, leading to pathological consequences. By deepening our understanding of the delicate balance that governs molecular crowding driven by RNA and its implications for cellular homeostasis, we aim to shed light on this intriguing area of research. Our exploration extends to the methodologies employed to decipher the composition and structural intricacies of RNA granules, offering a comprehensive overview of the techniques used to characterize them, including relevant computational approaches. Through two detailed examples highlighting the significance of noncoding RNAs, NEAT1 and XIST, in the formation of phase-separated assemblies and their influence on the cellular landscape, we emphasize their crucial role in cellular organization and function. By elucidating the chemical underpinnings of RNA-mediated molecular crowding, investigating the role of modifications, structures, and composition of RNA granules, and exploring both physiological and aberrant phase separation phenomena, this Review provides a multifaceted understanding of the intriguing world of RNA-mediated biological condensates.

Comparative analysis of 10X Chromium vs. BD Rhapsody whole transcriptome single-cell sequencing technologies in complex human tissues

The development of single-cell omics tools has enabled scientists to study the tumor microenvironment (TME) in unprecedented detail. However, each of the different techniques may have its unique strengths and limitations. Here we directly compared two commercially available high-throughput single-cell RNA sequencing (scRNA-seq) technologies - droplet-based 10X Chromium vs. microwell-based BD Rhapsody - using paired samples from patients with localized prostate cancer (PCa) undergoing a radical prostatectomy. Although high technical consistency was observed in unraveling the whole transcriptome, the relative abundance of cell populations differed. Cells with low mRNA content such as T cells were underrepresented in the droplet-based system, at least partly due to lower RNA capture rates. In contrast, microwell-based scRNA-seq recovered less cells of epithelial origin. Moreover, we discovered platform-dependent variabilities in mRNA quantification and cell-type marker annotation. Overall, our study provides important information for selection of the appropriate scRNA-seq platform and for the interpretation of published results.

Beyond the genome: MALAT1's role in advancing urologic cancer care

Urologic cancers (UCs), which include bladder, kidney, and prostate tumors, account for almost a quarter of all malignancies. Long non-coding RNAs (lncRNAs) are tissue-specific RNAs that influence cell growth, death, and division. LncRNAs are dysregulated in UCs, and their abnormal expression may allow them to be used in cancer detection, outlook, and therapy. With the identification of several novel lncRNAs and significant exploration of their functions in various illnesses, particularly cancer, the study of lncRNAs has evolved into a new obsession. MALAT1 is a flexible tumor regulator implicated in an array of biological activities and disorders, resulting in an important research issue. MALAT1 appears as a hotspot, having been linked to the dysregulation of cell communication, and is intimately linked to cancer genesis, advancement, and response to treatment. MALAT1 additionally operates as a competitive endogenous RNA, binding to microRNAs and resuming downstream mRNA transcription and operation. This regulatory system influences cell growth, apoptosis, motility, penetration, and cell cycle pausing. MALAT1's evaluation and prognosis significance are highlighted, with a thorough review of its manifestation levels in several UC situations and its association with clinicopathological markers. The investigation highlights MALAT1's adaptability as a possible treatment target, providing fresh ways for therapy in UCs as we integrate existing information The article not only gathers current knowledge on MALAT1's activities but also lays the groundwork for revolutionary advances in the treatment of UCs.

RNA-Small-Molecule Interaction: Challenging the "Undruggable" Tag

RNA targeting, specifically with small molecules, is a relatively new and rapidly emerging avenue with the promise to expand the target space in the drug discovery field. From being "disregarded" as an "undruggable" messenger molecule to FDA approval of an RNA-targeting small-molecule drug Risdiplam, a radical change in perspective toward RNA has been observed in the past decade. RNAs serve important regulatory functions beyond canonical protein synthesis, and their dysregulation has been reported in many diseases. A deeper understanding of RNA biology reveals that RNA molecules can adopt a variety of structures, carrying defined binding pockets that can accommodate small-molecule drugs. Due to its functional diversity and structural complexity, RNA can be perceived as a prospective target for therapeutic intervention. This perspective highlights the proof of concept of RNA-small-molecule interactions, exemplified by targeting of various transcripts with functional modulators. The advent of RNA-oriented knowledge would help expedite drug discovery.

Poly(A) tale: From A to A; RNA polyadenylation in prokaryotes and eukaryotes

Most eukaryotic mRNAs and different non-coding RNAs undergo a form of 3' end processing known as polyadenylation. Polyadenylation machinery is present in almost all organisms except few species. In bacteria, the machinery has evolved from PNPase, which adds heteropolymeric tails, to a poly(A)-specific polymerase. Differently, a complex machinery for accurate polyadenylation and several non-canonical poly(A) polymerases are developed in eukaryotes. The role of poly(A) tail has also evolved from serving as a degradative signal to a stabilizing modification that also regulates translation. In this review, we discuss poly(A) tail emergence in prokaryotes and its development into a stable, yet dynamic feature at the 3' end of mRNAs in eukaryotes. We also describe how appearance of novel poly(A) polymerases gives cells flexibility to shape poly(A) tail. We explain how poly(A) tail dynamics help regulate cognate RNA metabolism in a context-dependent manner, such as during oocyte maturation. Finally, we describe specific mRNAs in metazoans that bear stem-loops instead of poly(A) tails. We conclude with how recent discoveries about poly(A) tail can be applied to mRNA technology. This article is categorized under: RNA Evolution and Genomics > RNA and Ribonucleoprotein Evolution RNA Processing > 3' End Processing RNA Turnover and Surveillance > Regulation of RNA Stability.

Decryption of sequence, structure, and functional features of SINE repeat elements in SINEUP non-coding RNA-mediated post-transcriptional gene regulation

RNA structure folding largely influences RNA regulation by providing flexibility and functional diversity. In silico and in vitro analyses are limited in their ability to capture the intricate relationships between dynamic RNA structure and RNA functional diversity present in the cell. Here, we investigate sequence, structure and functional features of mouse and human SINE-transcribed retrotransposons embedded in SINEUPs long non-coding RNAs, which positively regulate target gene expression post-transcriptionally. In-cell secondary structure probing reveals that functional SINEs-derived RNAs contain conserved short structure motifs essential for SINEUP-induced translation enhancement. We show that SINE RNA structure dynamically changes between the nucleus and cytoplasm and is associated with compartment-specific binding to RBP and related functions. Moreover, RNA-RNA interaction analysis shows that the SINE-derived RNAs interact directly with ribosomal RNAs, suggesting a mechanism of translation regulation. We further predict the architecture of 18 SINE RNAs in three dimensions guided by experimental secondary structure data. Overall, we demonstrate that the conservation of short key features involved in interactions with RBPs and ribosomal RNA drives the convergent function of evolutionarily distant SINE-transcribed RNAs.

Mechanistic actions of long non-coding RNA MALAT1 within the ovary and at the feto-maternal interface

Long non-coding RNAs (LncRNAs) are being unveiled as crucial regulators of several biological processes and pathways. Among the lncRNAs is metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), which is also known as nuclear enriched abundant transcript 2 (NEAT2). MALAT1 is highly conserved in mammals, and controls cellular processes such as proliferation, migration, invasion, angiogenesis, and apoptosis in both physiological and pathological conditions. Roles of MALAT1 in the female reproductive system are gradually getting explored. Within the ovarian micro-environment, the physiological expression of MALAT1 potentially modulates folliculogenesis while its upregulation promotes the metastasis of epithelial ovarian cancers. Interestingly, women with polycystic ovary syndrome have been shown to exhibit aberrant ovarian expression of MALAT1 and this is believed to contribute to the development of the disease. At the feto-maternal interface, MALAT1 potentially promotes trophoblast development. While its placental downregulation is linked to the pathogenesis of preeclampsia, its placental upregulation is associated with placenta increta and placenta percreta. Hence, abnormal expression of MALAT1 is a candidate molecular biomarker and therapeutic target for the treatment of these obstetric and gynecologic anomalies. To enhance a quick uncovering and detailed characterization of the mechanistic actions of MALAT1 in the female reproductive system, we have highlighted some knowledge deficits and have recommended ideal experimental models to be employed in prospective investigations.

Stability-Based Proteomics for Investigation of Structured RNA-Protein Interactions

RNA-protein interactions are essential to RNA function throughout biology. Identifying the protein interactions associated with a specific RNA, however, is currently hindered by the need for RNA labeling or costly tiling-based approaches. Conventional strategies, which commonly rely on affinity pull-down approaches, are also skewed to the detection of high affinity interactions and frequently miss weaker interactions that may be biologically important. Reported here is the first adaptation of stability-based mass spectrometry methods for the global analysis of RNA-protein interactions. The stability of proteins from rates of oxidation (SPROX) and thermal protein profiling (TPP) methods are used to identify the protein targets of three RNA ligands, the MALAT1 triple helix (TH), a viral stem loop (SL), and an unstructured RNA (PolyU), in LNCaP nuclear lysate. The 315 protein hits with RNA-induced conformational and stability changes detected by TPP and/or SPROX were enriched in previously annotated RNA-binding proteins and included new proteins for hypothesis generation. Also demonstrated are the orthogonality of the SPROX and TPP approaches and the utility of the domain-specific information available with SPROX. This work establishes a novel platform for the global discovery and interrogation of RNA-protein interactions that is generalizable to numerous biological contexts and RNA targets.

Translational control by long non-coding RNAs

Long non-coding (lnc) RNAs, once considered as junk and useless, are now broadly recognized to have major functions in the cell. LncRNAs are defined as non-coding RNAs of more than 200 nucleotides, regulate all steps of gene expression. Their origin is diverse, they can arise from intronic, intergenic or overlapping region, in sense or antisense direction. LncRNAs are mainly described for their action on transcription, while their action at the translational level is more rarely cited. However, the bibliography in the field is more and more abundant. The present synopsis of lncRNAs involved in the control of translation reveals a wide field of regulation of gene expression, with at least nine distinct molecular mechanisms. Furthermore, it appears that all these lncRNAs are involved in various pathologies including cancer, cardiovascular and neurodegenerative diseases.

The lncRNA Malat1 is trafficked to the cytoplasm as a localized mRNA encoding a small peptide in neurons

Synaptic function is modulated by local translation of mRNAs that are transported to distal portions of axons and dendrites. The Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is broadly expressed across cell types, almost exclusively as a nuclear non-coding RNA. We found that in differentiating neurons, a portion of Malat1 RNA redistributes to the cytoplasm. Depletion of Malat1 from neurons stimulated expression of particular pre- and post- synaptic proteins, implicating Malat1 in their regulation. Neuronal Malat1 is localized to both axons and dendrites in puncta that co-stain with Staufen1 protein, similar to neuronal granules formed by locally translated mRNAs. Ribosome profiling of mouse cortical neurons identified ribosome footprints within a region of Malat1 containing short open reading frames. The upstream-most reading frame (M1) of the Malat1 locus was linked to the GFP coding sequence in mouse ES cells. When these gene-edited cells were differentiated into glutamatergic neurons, the M1-GFP fusion protein was expressed. Antibody staining for the M1 peptide confirmed its presence in wildtype neurons, and showed enhancement of M1 expression after synaptic stimulation with KCL. Our results indicate that Malat1 serves as a cytoplasmic coding RNA in the brain that is both modulated by and modulates synaptic function.

Locked Nucleic Acid Oligonucleotides Facilitate RNA•LNA-RNA Triple-Helix Formation and Reduce MALAT1 Levels

Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and multiple endocrine neoplasia-β (MENβ) are two long noncoding RNAs upregulated in multiple cancers, marking these RNAs as therapeutic targets. While traditional small-molecule and antisense-based approaches are effective, we report a locked nucleic acid (LNA)-based approach that targets the MALAT1 and MENβ triple helices, structures comprised of a U-rich internal stem-loop and an A-rich tract. Two LNA oligonucleotides resembling the A-rich tract (i.e., A9GCA4) were examined: an LNA (L15) and a phosphorothioate LNA (PS-L15). L15 binds tighter than PS-L15 to the MALAT1 and MENβ stem loops, although both L15 and PS-L15 enable RNA•LNA-RNA triple-helix formation. Based on UV thermal denaturation assays, both LNAs selectively stabilize the Hoogsteen interface by 5-13 °C more than the Watson-Crick interface. Furthermore, we show that L15 and PS-L15 displace the A-rich tract from the MALAT1 and MENβ stem loop and methyltransferase-like protein 16 (METTL16) from the METTL16-MALAT1 triple-helix complex. Human colorectal carcinoma (HCT116) cells transfected with LNAs have 2-fold less MALAT1 and MENβ. This LNA-based approach represents a potential therapeutic strategy for the dual targeting of MALAT1 and MENβ.

Global RNA modifications to the MALAT1 triple helix differentially affect thermostability and weaken binding to METTL16

Therapeutic mRNAs are generated using modified nucleotides, namely N1-methylpseudouridine (m1Ψ) triphosphate, so that the mRNA evades detection by the immune system. RNA modifications, even at a single-nucleotide position, perturb RNA structure, although it is not well understood how structure and function is impacted by globally modified RNAs. Therefore, we examined the metastasis-associated lung adenocarcinoma transcript 1 triple helix, a highly structured stability element that includes single-, double-, and triple-stranded RNA, globally modified with N6-methyladenosine (m6A), pseudouridine (Ψ), or m1Ψ. UV thermal denaturation assays showed that m6A destabilizes both the Hoogsteen and Watson-Crick faces of the RNA by ∼20 °C, Ψ stabilizes the Hoogsteen and Watson-Crick faces of the RNA by ∼12 °C, and m1Ψ has minimal effect on the stability of the Hoogsteen face of the RNA but increases the stability of the Watson-Crick face by ∼9 °C. Native gel-shift assays revealed that binding of the methyltransferase-like protein 16 to the metastasis-associated lung adenocarcinoma transcript 1 triple helix was weakened by at least 8-, 99-, and 23-fold, respectively, when RNA is globally modified with m6A, Ψ, or m1Ψ. These results demonstrate that a more thermostable RNA structure does not lead to tighter RNA-protein interactions, thereby highlighting the regulatory power of RNA modifications by multiple means.

Synonymous codon usage regulates translation initiation

Nonoptimal synonymous codons repress gene expression, but the underlying mechanisms are poorly understood. We and others have previously shown that nonoptimal codons slow translation elongation speeds and thereby trigger messenger RNA (mRNA) degradation. Nevertheless, transcript levels are often insufficient to explain protein levels, suggesting additional mechanisms by which codon usage regulates gene expression. Using reporters in human and Drosophila cells, we find that transcript levels account for less than half of the variation in protein abundance due to codon usage. This discrepancy is explained by translational differences whereby nonoptimal codons repress translation initiation. Nonoptimal transcripts are also less bound by the translation initiation factors eIF4E and eIF4G1, providing a mechanistic explanation for their reduced initiation rates. Importantly, translational repression can occur without mRNA decay and deadenylation, and it does not depend on the known nonoptimality sensor, CNOT3. Our results reveal a potent mechanism of regulation by codon usage where nonoptimal codons repress further rounds of translation.

Comprehensive landscape and future perspective of long noncoding RNAs in non-small cell lung cancer: it takes a village

Long noncoding RNAs (lncRNAs) are a distinct subtype of RNA that lack protein-coding capacity but exert significant influence on various cellular processes. In non-small cell lung cancer (NSCLC), dysregulated lncRNAs act as either oncogenes or tumor suppressors, contributing to tumorigenesis and tumor progression. LncRNAs directly modulate gene expression, act as competitive endogenous RNAs by interacting with microRNAs or proteins, and associate with RNA binding proteins. Moreover, lncRNAs can reshape the tumor immune microenvironment and influence cellular metabolism, cancer cell stemness, and angiogenesis by engaging various signaling pathways. Notably, lncRNAs have shown great potential as diagnostic or prognostic biomarkers in liquid biopsies and therapeutic strategies for NSCLC. This comprehensive review elucidates the significant roles and diverse mechanisms of lncRNAs in NSCLC. Furthermore, we provide insights into the clinical relevance, current research progress, limitations, innovative research approaches, and future perspectives for targeting lncRNAs in NSCLC. By summarizing the existing knowledge and advancements, we aim to enhance the understanding of the pivotal roles played by lncRNAs in NSCLC and stimulate further research in this field. Ultimately, unraveling the complex network of lncRNA-mediated regulatory mechanisms in NSCLC could potentially lead to the development of novel diagnostic tools and therapeutic strategies.

Functional domains of nuclear long noncoding RNAs: Insights into gene regulation and intracellular architecture

Recent functional research on long noncoding RNAs (lncRNAs) has revealed their significant regulatory roles in gene expression and intracellular architecture. Well-characterized examples of such lncRNAs include Xist and NEAT1_2, which play critical roles in heterochromatin formation of inactive X-chromosomes and paraspeckle assembly, in mammalian cells. Both lncRNAs possess modular domain structures with multiple functionally distinct domains that serve as platforms for specific RNA-binding proteins (RBPs), which dictate the function of each lncRNA. Some of these RBPs bind characteristic RNA structures, which can be targeted by small chemical compounds that modulate lncRNA function by perturbing the interaction of RBPs with the RNA structures. Therefore, RNA structures hidden in lncRNAs represent a novel and potent type of therapeutic target.

Non-B DNA structures as a booster of genome instability

Non-canonical secondary structures (NCSs) are alternative nucleic acid structures that differ from the canonical B-DNA conformation. NCSs often occur in repetitive DNA sequences and can adopt different conformations depending on the sequence. The majority of these structures form in the context of physiological processes, such as transcription-associated R-loops, G4s, as well as hairpins and slipped-strand DNA, whose formation can be dependent on DNA replication. It is therefore not surprising that NCSs play important roles in the regulation of key biological processes. In the last years, increasing published data have supported their biological role thanks to genome-wide studies and the development of bioinformatic prediction tools. Data have also highlighted the pathological role of these secondary structures. Indeed, the alteration or stabilization of NCSs can cause the impairment of transcription and DNA replication, modification in chromatin structure and DNA damage. These events lead to a wide range of recombination events, deletions, mutations and chromosomal aberrations, well-known hallmarks of genome instability which are strongly associated with human diseases. In this review, we summarize molecular processes through which NCSs trigger genome instability, with a focus on G-quadruplex, i-motif, R-loop, Z-DNA, hairpin, cruciform and multi-stranded structures known as triplexes.

Shell protein composition specified by the lncRNA NEAT1 domains dictates the formation of paraspeckles as distinct membraneless organelles

Many membraneless organelles (MLOs) formed through phase separation play crucial roles in various cellular processes. Although these MLOs co-exist in cells, how they maintain their independence without coalescence or engulfment remains largely unknown. Here, we investigated the molecular mechanism by which paraspeckles with core-shell architecture scaffolded by NEAT1_2 long noncoding RNAs exist as distinct MLOs. We identified NEAT1 deletion mutants that assemble paraspeckles that are incorporated into nuclear speckles. Several paraspeckle proteins, including SFPQ, HNRNPF and BRG1, prevent this incorporation and thus contribute to the segregation of paraspeckles from nuclear speckles. Shell localization of these proteins in the paraspeckles, which is determined by NEAT1_2 long noncoding RNA domains, is required for this segregation process. Conversely, U2-related spliceosomal proteins are involved in internalizing the paraspeckles into nuclear speckles. This study shows that the paraspeckle shell composition dictates the independence of MLOs in the nucleus, providing insights into the importance of the shell in defining features and functions of MLOs.

The chromatin - triple helix connection

Mammalian genomes are extensively transcribed, producing a large number of coding and non-coding transcripts. A large fraction of the nuclear RNAs is physically associated with chromatin, functioning in gene activation and silencing, shaping higher-order genome organisation, such as involvement in long-range enhancer-promoter interactions, transcription hubs, heterochromatin, nuclear bodies and phase transitions. Different mechanisms allow the tethering of these chromatin-associated RNAs (caRNA) to chromosomes, including RNA binding proteins, the RNA polymerases and R-loops. In this review, we focus on the sequence-specific targeting of RNA to DNA by forming triple helical structures and describe its interplay with chromatin. It turns out that nucleosome positioning at triple helix target sites and the nucleosome itself are essential factors in determining the formation and stability of triple helices. The histone H3-tail plays a critical role in triple helix stabilisation, and the role of its epigenetic modifications in this process is discussed.

Identification of G-quadruplex structures in MALAT1 lncRNA that interact with nucleolin and nucleophosmin

Nuclear-retained long non-coding RNAs (lncRNAs) including MALAT1 have emerged as critical regulators of many molecular processes including transcription, alternative splicing and chromatin organization. Here, we report the presence of three conserved and thermodynamically stable RNA G-quadruplexes (rG4s) located in the 3' region of MALAT1. Using rG4 domain-specific RNA pull-down followed by mass spectrometry and RNA immunoprecipitation, we demonstrated that the MALAT1 rG4 structures are specifically bound by two nucleolar proteins, Nucleolin (NCL) and Nucleophosmin (NPM). Using imaging, we found that the MALAT1 rG4s facilitate the localization of both NCL and NPM to nuclear speckles, and specific G-to-A mutations that disrupt the rG4 structures compromised the localization of both NCL and NPM in speckles. In vitro biophysical studies established that a truncated version of NCL (ΔNCL) binds tightly to all three rG4s. Overall, our study revealed new rG4s within MALAT1, established that they are specifically recognized by NCL and NPM, and showed that disrupting the rG4s abolished localization of these proteins to nuclear speckles.

Noncoding RNAs and their roles in regulating the agronomic traits of crops

Molecular breeding is one of the most effective methods for improving the performance of crops. Understanding the genome features of crops, especially the physiological functions of individual genes, is of great importance to molecular breeding. Evidence has shown that genomes of both animals and plants transcribe numerous non-coding RNAs, which are involved in almost every aspect of development. In crops, an increasing number of studies have proven that non-coding RNAs are new genetic resources for regulating crop traits. In this review, we summarize the current knowledge of non-coding RNAs, which are potential crop trait regulators, and focus on the functions of long non-coding RNAs (lncRNAs) in determining crop grain yield, phased small-interfering RNAs (phasiRNAs) in regulating fertility, small interfering RNAs (siRNAs) and microRNAs (miRNAs) in facilitating plant immune response and disease resistance, and miRNAs mediating nutrient and metal stress. Finally, we also discuss the next-generation method for ncRNA application in crop domestication and breeding.

Nondomain biopolymers: Flexible molecular strategies to acquire biological functions

A long-standing assumption in molecular biology posits that the conservation of protein and nucleic acid sequences emphasizes the functional significance of biomolecules. These conserved sequences fold into distinct secondary and tertiary structures, enable highly specific molecular interactions, and regulate complex yet organized molecular processes within living cells. However, recent evidence suggests that biomolecules can also function through primary sequence regions that lack conservation across species or gene families. These regions typically do not form rigid structures, and their inherent flexibility is critical for their functional roles. This review examines the emerging roles and molecular mechanisms of "nondomain biomolecules," whose functions are not easily predicted due to the absence of conserved functional domains. We propose the hypothesis that both domain- and nondomain-type molecules work together to enable flexible and efficient molecular processes within the highly crowded intracellular environment.

TFOFinder: Python program for identifying purine-only double-stranded stretches in the predicted secondary structure(s) of RNA targets

Nucleic acid probes are valuable tools in biology and chemistry and are indispensable for PCR amplification of DNA, RNA quantification and visualization, and downregulation of gene expression. Recently, triplex-forming oligonucleotides (TFO) have received increased attention due to their improved selectivity and sensitivity in recognizing purine-rich double-stranded RNA regions at physiological pH by incorporating backbone and base modifications. For example, triplex-forming peptide nucleic acid (PNA) oligomers have been used for imaging a structured RNA in cells and inhibiting influenza A replication. Although a handful of programs are available to identify triplex target sites (TTS) in DNA, none are available that find such regions in structured RNAs. Here, we describe TFOFinder, a Python program that facilitates the identification of intramolecular purine-only RNA duplexes that are amenable to forming parallel triple helices (pyrimidine/purine/pyrimidine) and the design of the corresponding TFO(s). We performed genome- and transcriptome-wide analyses of TTS in Drosophila melanogaster and found that only 0.3% (123) of total unique transcripts (35,642) show the potential of forming 12-purine long triplex forming sites that contain at least one guanine. Using minimization algorithms, we predicted the secondary structure(s) of these transcripts, and using TFOFinder, we found that 97 (79%) of the identified 123 transcripts are predicted to fold to form at least one TTS for parallel triple helix formation. The number of transcripts with potential purine TTS increases when the strict search conditions are relaxed by decreasing the length of the probe or by allowing up to two pyrimidine inversions or 1-nucleotide bulge in the target site. These results are encouraging for the use of modified triplex forming probes for live imaging of endogenous structured RNA targets, such as pre-miRNAs, and inhibition of target-specific translation and viral replication.

Efficient and versatile multiplex prime editing in hexaploid wheat

Prime editing is limited by low efficiency in plants. Here, we develop an upgraded engineered plant prime editor in hexaploid wheat, ePPEplus, by introducing a V223A substitution into reverse transcriptase in the ePPEmax* architecture. ePPEplus enhances the efficiency by an average 33.0-fold and 6.4-fold compared to the original PPE and ePPE, respectively. Importantly, a robust multiplex prime editing platform is established for simultaneous editing of four to ten genes in protoplasts and up to eight genes in regenerated wheat plants at frequencies up to 74.5%, thus expanding the applicability of prime editors for stacking of multiple agronomic traits.

Translation and mRNA Stability Control

Messenger RNA (mRNA) stability and translational efficiency are two crucial aspects of the post-transcriptional process that profoundly impact protein production in a cell. While it is widely known that ribosomes produce proteins, studies during the past decade have surprisingly revealed that ribosomes also control mRNA stability in a codon-dependent manner, a process referred to as codon optimality. Therefore, codons, the three-nucleotide words read by the ribosome, have a potent effect on mRNA stability and provide cis-regulatory information that extends beyond the amino acids they encode. While the codon optimality molecular mechanism is still unclear, the translation elongation rate appears to trigger mRNA decay. Thus, transfer RNAs emerge as potential master gene regulators affecting mRNA stability. Furthermore, while few factors related to codon optimality have been identified in yeast, the orthologous genes in vertebrates do not necessary share the same functions. Here, we discuss codon optimality findings and gene regulation layers related to codon composition in different eukaryotic species.

Roles of lncRNAs in brain development and pathogenesis: Emerging therapeutic opportunities

The human genome is pervasively transcribed, producing a majority of short and long noncoding RNAs (lncRNAs) that can influence cellular programs through a variety of transcriptional and post-transcriptional regulatory mechanisms. The brain houses the richest repertoire of long noncoding transcripts, which function at every stage during central nervous system development and homeostasis. An example of functionally relevant lncRNAs is species involved in spatiotemporal organization of gene expression in different brain regions, which play roles at the nuclear level and in transport, translation, and decay of other transcripts in specific neuronal sites. Research in the field has enabled identification of the contributions of specific lncRNAs to certain brain diseases, including Alzheimer's disease, Parkinson's disease, cancer, and neurodevelopmental disorders, resulting in notions of potential therapeutic strategies that target these RNAs to recover the normal phenotype. Here, we summarize the latest mechanistic findings associated with lncRNAs in the brain, focusing on their dysregulation in neurodevelopmental or neurodegenerative disorders, their use as biomarkers for central nervous system (CNS) diseases in vitro and in vivo, and their potential utility for therapeutic strategies.

Long non-coding RNAs: definitions, functions, challenges and recommendations

Genes specifying long non-coding RNAs (lncRNAs) occupy a large fraction of the genomes of complex organisms. The term 'lncRNAs' encompasses RNA polymerase I (Pol I), Pol II and Pol III transcribed RNAs, and RNAs from processed introns. The various functions of lncRNAs and their many isoforms and interleaved relationships with other genes make lncRNA classification and annotation difficult. Most lncRNAs evolve more rapidly than protein-coding sequences, are cell type specific and regulate many aspects of cell differentiation and development and other physiological processes. Many lncRNAs associate with chromatin-modifying complexes, are transcribed from enhancers and nucleate phase separation of nuclear condensates and domains, indicating an intimate link between lncRNA expression and the spatial control of gene expression during development. lncRNAs also have important roles in the cytoplasm and beyond, including in the regulation of translation, metabolism and signalling. lncRNAs often have a modular structure and are rich in repeats, which are increasingly being shown to be relevant to their function. In this Consensus Statement, we address the definition and nomenclature of lncRNAs and their conservation, expression, phenotypic visibility, structure and functions. We also discuss research challenges and provide recommendations to advance the understanding of the roles of lncRNAs in development, cell biology and disease.

Multiplexed Gene Engineering Based on dCas9 and gRNA-tRNA Array Encoded on Single Transcript

Simultaneously, multiplexed genome engineering and targeting multiple genomic loci are valuable to elucidating gene interactions and characterizing genetic networks that affect phenotypes. Here, we developed a general CRISPR-based platform to perform four functions and target multiple genome loci encoded in a single transcript. To establish multiple functions for multiple loci targets, we fused four RNA hairpins, MS2, PP7, com and boxB, to stem-loops of gRNA (guide RNA) scaffolds, separately. The RNA-hairpin-binding domains MCP, PCP, Com and λN22 were fused with different functional effectors. These paired combinations of cognate-RNA hairpins and RNA-binding proteins generated the simultaneous, independent regulation of multiple target genes. To ensure that all proteins and RNAs are expressed in one transcript, multiple gRNAs were constructed in a tandemly arrayed tRNA (transfer RNA)-gRNA architecture, and the triplex sequence was cloned between the protein-coding sequences and the tRNA-gRNA array. By leveraging this system, we illustrate the transcriptional activation, transcriptional repression, DNA methylation and DNA demethylation of endogenous targets using up to 16 individual CRISPR gRNAs delivered on a single transcript. This system provides a powerful platform to investigate synthetic biology questions and engineer complex-phenotype medical applications.