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MYC-bound enhancer RNAs in cis regulate gene transcription and tumorigenesis.

Emerging evidence suggests that MYC binds RNAs, but its functional consequences remain unclear. Here, we integrate multiomics data and reveal that MYC broadly binds enhancer RNAs (eRNAs), which exhibit high cancer- and tissue-specific expression in cancer cell lines and patient tumors. Moreover, we developed a computational pipeline to identify potential cis-regulatory MYC-eRNA target genes, with most predicted eRNA-target pairs supported by RNA polymerase II-mediated chromatin interaction data. Among these, we functionally characterized MERG1 as an oncogenic eRNA that promotes breast cancer tumorigenesis. Mechanistically, MERG1 interacts with MYC to enhance its occupancy at the GREB1 promoter, driving chromatin remodeling and epigenetic activation. This process specifically amplifies GREB1 expression and promotes tumor progression. Last, nanoparticle-mediated delivery of antisense oligonucleotides targeting MERG1 suppresses MYC-mediated breast cancer growth. These results advance our understanding of the enhancer-driven regulation of gene expression and tumorigenesis and provide insights into the regulatory landscape of MYC in cancer.

Humans

Discovering the interactome, functions, and clinical relevance of enhancer RNAs in kidney renal clear cell carcinoma.

Enhancer RNA (eRNA) has emerged as a key player in cancer biology, influencing various aspects of tumor development and progression. In this study, we investigated the role of eRNAs in kidney renal clear cell carcinoma (KIRC), the most common subtype of renal cell carcinoma. Leveraging high-throughput sequencing data and bioinformatics analysis, we identified differentially expressed eRNAs in KIRC and constructed eRNA-centric regulatory networks. Our findings revealed that up-regulated eRNAs in KIRC potentially regulate immune response and hypoxia pathways, while down-regulated eRNAs may impact ion transport, cell cycle, and metabolism. Furthermore, we developed a diagnostic prediction model based on eRNA expression profiles, demonstrating its effectiveness in KIRC diagnosis. Finally, we elucidated the regulatory mechanism of an eRNA (ENSR00000305834) on the expression of SLC15A2, a potential prognostic biomarker in KIRC, through bioinformatics analysis and in vitro validation experiments. In summary, Our study highlights the clinical significance of eRNAs in KIRC and underscores their potential as therapeutic targets.

Carcinoma, Renal Cell

hnRNPK condensates facilitate enhancer-promoter looping and RNA polymerase II recruitment.

Enhancer RNAs interact with promoter-derived RNAs to dictate enhancer-promoter looping, but the RNA-binding protein that mediates this process has remained unidentified. Here we identify hnRNPK as a general structural regulator that preferentially binds to nascent RNAs transcribed from enhancer and promoter regions, promoting enhancer-promoter looping and transcriptional activation. We further show that hnRNPK forms phase-separated, cavity-containing condensates that encapsulate RNA polymerase II (Pol II) via its RPB3 subunit, facilitating chromatin looping and potentially enabling recruitment of Pol II from enhancers to promoters through protein dimerization. Notably, a mutation associated with Au-Kline syndrome in hnRNPK (c.953+1dupG) alters its condensates from a liquid-like to a gel-like state, leading to developmental defects in knock-in mice. Fibroblasts derived from these mutants display reduced enhancer-promoter looping and decreased Pol II recruitment at promoters of key developmental genes. These findings suggest that hnRNPK is a structural regulator of enhancer-promoter communication and highlight the importance of RNA-RNA interactions mediated by RNA-binding proteins in transcriptional regulation.

RNA Polymerase II

Transposable element-driven expansion of enhancer RNA repertoires underlies regulatory innovation and polyploid adaptation in cereal crops.

Cereal genomes have undergone repeated polyploidization and transposable element (TE) proliferation, collectively generating complex regulatory landscapes. However, the evolutionary trajectories and functional implications of these landscapes remain largely unexplored. Using chromatin-bound RNA sequencing across seven cereal species, we systematically mapped 45,952 regulatory element transcripts (RETs), including 32,867 distal RETs corresponding to enhancer RNAs (eRNAs). Our analysis revealed that 56% of lineage-specific eRNAs originated from TE expansions, indicating that TEs serve as major reservoirs of species-specific regulatory innovation in cereals. Notably, we identified remarkable conservation in defense-related functions, root-specific expression, and TE-derived origins of eRNAs across both ancient and recent evolutionary layers of Triticeae, suggesting recurrent recruitment of TE-derived, root-associated regulatory elements throughout Triticeae evolution. Furthermore, we found that young eRNA pairs in hexaploid wheat with high sequence similarity, many originating from RLG_famc8.3 and DTC_famc4.3, exhibited pronounced root specificity and coordinated expression, suggesting targeted amplification and refinement of successful ancestral regulatory strategies established after Triticeae divergence. To facilitate community access, we developed Cereal-eRNAdb (http://bioinfo.cemps.ac.cn/Cereal-eRNAdb/), a comprehensive database integrating 69,426 eRNAs with functional annotations across 296 samples. Our findings suggest that TE-mediated innovation of root-specific eRNAs may contribute to Triticeae adaptation and provide a foundational resource for exploiting regulatory variation in cereal crop breeding.

Enhancer RNAs

N6-methyladenosine modification of the subgroup J avian leukosis viral RNAs attenuates host innate immunity via MDA5 signaling.

Subgroup J avian leukosis virus (ALV-J), a retrovirus, elicits immunosuppression and persistent infections in chickens. Although it is widely acknowledged that ALV-J can evade the host's innate immune defenses, the mechanisms behind this immune evasion remain elusive. N6-methyladenosine (m6A), the most prevalent internal RNA modification, plays a role in innate immune evasion. Our research identified ALV-J as an inefficient stimulator of innate immunity in vitro and in vivo, with its genomic RNA featuring m6A modifications predominantly in the envelope protein (Env) region and 3' untranslated region (3'UTR). To elucidate the functional consequences of m6A modification, we subsequently generated m6A-deficient ALV-J through its culturing in the DF-1 overexpressing fat mass and obesity-associated protein (FTO) cells. The m6A-deficient ALV-J virus, or its RNAs significantly enhanced IFN-β production compared to the wild-type (wt) ALV-J, suggesting a pivotal regulatory function of m6A modifications in modulating innate immune response. Mechanistically, the m6A modification of the ALV-J genomic RNA directly impacted its recognition by MDA5, weakening its binding and ubiquitination and attenuating IFN-β activation. Moreover, m6A-deficient ALV-J, created by inducing mutations in m6A sites within Env and 3'UTR, exhibited reduced replication capacity and elevated IFN-β expression in host cells. Importantly, this phenomenon was abolished in MDA5-knockout DF-1 cells, further demonstrating the core role of MDA5. These data demonstrate that m6A modification of ALV-J genomic RNA dampens the host's innate immune response through MDA5 signaling pathway.

Animals

Nuclear exosome targeting complexes modulate cohesin binding and enhancer-promoter interactions in 3D.

Three-dimensional long-range contacts between enhancers and promoters are thought to be largely determined by loop extrusion driven by the cohesin complex and insulator factors. However, recent evidence also suggests a role for noncoding RNAs, such as enhancer-associated RNAs and promoter upstream transcripts, in shaping enhancer-promoter connectivity. While the nuclear RNA exosome, together with targeting complexes, poly(A) tail exosome targeting connection and nuclear exosome targeting complex, controls the decay of noncoding RNAs, it remains unclear whether these complexes regulate three-dimensional chromatin contacts. Chromatin recruitment maps of the nuclear exosome targeting complex subunit ZCCHC8, the poly(A) tail exosome targeting connection subunit ZFC3H1, and the RNA helicase MTR4 in human cells reveal that these factors associate with sites of enhancer-promoter interactions. Depletion of these factors leads to the accumulation of ncRNAs, notably enhancer-associated RNAs and promoter upstream transcripts, and increases cohesin occupancy at these sites. Chromatin conformation capture analysis reveals that MTR4 modulates long-range enhancer-promoter contacts. Upon loss of MTR4, enhancer-promoter contacts increase while intraloop contacts decrease, suggesting that MTR4 facilitates loop extrusion. These data highlight a key interplay between cohesin-mediated enhancer-promoter interactions and the regulation of noncoding RNAs by nuclear RNA exosome targeting complexes that is consistent with a role for RNA in genome folding.

Cohesins

Evolution of intestinal apolipoprotein B mRNA editing. Chicken apolipoprotein B mRNA is not edited, but chicken enterocytes contain in vitro editing enhancement factor(s).

Mammalian intestinal apolipoprotein B (apoB) messenger RNA (mRNA) undergoes posttranscriptional editing, changing codon 2153 from CAA in apoB100 mRNA to an in-frame translational stop codon (UAA) in apoB48 mRNA. By contrast, chicken intestinal apoB cDNA contains a CAA codon at the corresponding site and apoB mRNA from chicken enterocytes, kidney, and liver is unedited. The cDNA sequence of chicken apoB spanning the edited base is divergent from mammalian apoB cDNA sequence, with 70% homology over the conserved 29-nucleotide sequence (6662-6690) flanking codon 2153. Efficient in vitro editing of both human and rat, but not chicken, synthetic apoB RNA was achieved using rat enterocyte S-100 extracts. By contrast, chicken enterocyte S-100 extracts failed to edit chicken, rat, or human synthetic apoB RNA. Mixing experiments, however, revealed that chicken enterocyte S-100 extracts enhance the in vitro editing activity of rat, pig, and human enterocyte S-100 extracts upon homologous RNAs. The editing enhancement activity of chicken enterocyte S-100 extracts is tissue-specific, heat-sensitive, substrate-saturable, and sensitive to proteinase K, but resistant to micrococcal nuclease. The activity was partially purified by Q-Sepharose chromatography and has an average molecular mass of 49 kDa when analyzed by gel filtration chromatography. We conclude that the evolutionary adaptation of intestinal apoB mRNA editing requires both a requisite RNA motif and tissue-specific factors which mediate the site-specific modification.

Animals

Enhanced CRISPR-Cas3-mediated genome editing using circularized crRNAs.

Type I-E CRISPR-Cas3 represents a genome-editing technology in which large deletions averaging several kilobases are introduced in target regions. However, its genome-editing efficiency varies considerably across targets and cell types, making it difficult to achieve consistent results. Here, we investigated the efficacy and stability of circularized CRISPR RNAs (ccrRNAs) to enhance CRISPR-Cas3-mediated genome editing in human cells. Using in vitro single-strand DNA cleavage assays, we demonstrated that ccrRNA induces Cascade complex formation. Significant genome-editing activity targeting the EMX1 and B2M genes was observed in cellular assays using K562 cells. Long-read sequencing identified large-scale deletion mutations at the target loci and no detectable off-target effects using ccrRNA. Furthermore, ccrRNAs exhibited extended intracellular stability compared with that for linear crRNAs, resulting in an enhanced editing efficiency. These results demonstrate that ccrRNAs enable stable, efficient, and highly specific genome editing and support the broader application of the long-range deletion system.

CRISPR-Cas3

Expression of hematopoietic growth factor RNAs in human mesenchymal cells from various organs.

Experiments were undertaken to study expression of hematopoietic growth factor RNAs in mesenchymal cells from a variety of organs including bone marrow, foreskin, gingiva, and lung. Cells from each organ had negligible expression of RNAs coding for granulocyte (G), macrophage (M), and granulocyte-macrophage (GM) colony stimulating factor (CSF), interleukin 1 beta (IL-1 beta), and IL-6. Fibroblasts from each tissue had a comparable ability to express the same cytokine RNAs. Surprisingly, the stimuli for expression of G-CSF RNA was disparate from the stimuli for expression of the other cytokine RNAs. While IL-1 beta enhanced accumulation of G-CSF RNA, tumor necrosis factor alpha (TNF) and 12-O-tetradecanoylphorbol-13-acetate (TPA) did not. In contrast, IL-1 beta, TNF, and TPA equally stimulated increased levels of M-CSF, GM-CSF, IL-1 beta and IL-6 RNAs.

Bone Marrow

Prediction of rho-independent Escherichia coli transcription terminators. A statistical analysis of their RNA stem-loop structures.

Escherichia coli rho-independent transcription terminators are characterized by an RNA structure having a G+C-rich stem-loop followed by a series of uridine residues, but they can be only partially predicted by the stability of this structure or by its primary sequence. A large number of such terminators have been identified or proposed in the literature, and we have constituted a list of them (148 found in 1021 x 10(3) base-pairs of E. coli DNA sequences) in order to analyze statistically the corresponding RNA hairpins. We show that the size of the loops presents a narrow distribution, that their sequences are not random, and that most loops are closed by a C.G base-pair. In particular, 55% of the loops are tetranucleotides and the most abundant loop sequences are UUCG and GAAA. These loops are abundant in prokaryotic and eukaryotic RNAs, and are known to enhance the stability of RNA hairpins. We propose that these tetraloops play an important role in the nucleation of the nascent RNA structures, as does also the presence of a C.G base-pair closing a hairpin loop. This analysis allows us to propose a model of formation of an RNA hairpin during the termination process and to construct an algorithm of prediction of the terminators in a given DNA sequence. For the E. coli sequences, it clearly distinguishes inter- from intracistronic terminator-like structures, and selects 141 of the 148 rho-independent terminators given in the literature, with a very low background. It also predicts with reasonable accuracy the in vitro termination efficiency of known rho-independent terminators, as well as predicting the existence of 35 as yet uncharacterized terminators.

Algorithms

Interaction of two cis sites with the RNA replicase of the yeast L-A virus.

L-A is a 4.6-kilobase double-stranded RNA virus of Saccharomyces cerevisiae. The in vitro L-A replication reaction ((-)-strand synthesis) requires an internal site 400 bases from the 3' end in addition to the 3'-terminal 30 nucleotides of the L-A (+)-single-stranded RNA. Elimination of the internal site reduces the template activity 5-10-fold. Here we investigate how the internal site can stimulate the replication reaction which starts at the 3' end of the template. When these two sites are split into two distinct RNA molecules, the internal site can no longer stimulate replication (no trans-activation). However, establishment of an intermolecular hydrogen bonding between these RNAs restored the replication-enhancing activity of the internal site. This result is consistent with a model wherein L-A's RNA polymerase interacts first with the internal site and then with the 3' end site by either looping or by a local dissociation-reassociation mechanism. These results, however, clearly eliminate anchored tracking and sliding models which require continuity of the RNA molecule between these two cis sites.

Autoradiography

A Dual-Selection System for Enhanced Efficiency and Fidelity of Circular RNA Overexpression.

Circular RNAs (circRNAs) are essential regulators of cellular processes, but are challenging to study using traditional methods. Overexpression approaches, such as the use of linearized plasmids and viral vectors, often result in high rates of false-positive clones, where cells retain selection markers without expressing the target circRNA. This study addresses this limitation by developing a dual-selection circRNA system designed to enhance the accuracy and reliability of circRNA overexpression. Our system integrates a fluorescent reporter gene upstream of the circRNA expression cassette, under a shared promoter, and a downstream antibiotic resistance marker, allowing for both antibiotic selection and flow cytometric cell-sorting to identify and enrich cells with genuine circRNA expression. We successfully incorporated this system into an inducible lentiviral vector for controlled overexpression in various cell types. The dual-selection circRNA system offers a significant advance for circRNA research and studies of other RNA species where accurate and reliable overexpression is essential.

RNA, Circular

Exploring the transcriptional cooperation between RUNX2 and its associated elncRNA RAIN.

Recent insights into the mechanisms controlling gene expression identified enhancer-associated long non-coding RNAs (elncRNAs) as master players of transcription in cancers. RUNX2, a mammalian RUNT-related transcription factor, is increasingly recognized in cancer biology for its role in supporting survival and progression also in thyroid cancer (TC). We recently identified, within the RUNX2 locus, a novel elncRNA that we named RAIN (RUNX2 associated intergenic lncRNA). We showed that RAIN and RUNX2 expression correlate in TC, both in vitro and in vivo, and that RAIN promotes RUNX2 expression by interacting with and affecting the activity of the RUNX2 P2 promoter through two distinct mechanisms. Here, we took forward these observations to explore the genome-wide transcriptional function of RAIN and its contribution to the RUNX2-dependent gene expression program in TC. By combining multiple omics data, we demonstrated that RAIN functionally cooperates with RUNX2 to the regulation of a subset of functionally related genes involved in promoting matrix remodeling, migration, and loss of differentiation. We showed that RAIN interacts with RUNX2 and its expression is required for the efficient recruitment of this TF to its target regulatory regions. In addition, our data revealed that besides RUNX2, RAIN governs a hierarchically organized complex transcriptional program by controlling a core of cancer-associated TFs that, in turn, orchestrate the expression of downstream genes. This evidence indicates that the functional cooperation observed between RAIN and RUNX2 can be a diffuse work mechanism for this elncRNA.

Core Binding Factor Alpha 1 Subunit

Mallory stain may indicate differential rates of RNA synthesis: I. A seasonal cycle in the harderian gland of the green frog (Rana esculenta).

When Mallory's trichrome stain is used, acinar nuclei of the Harderian gland of Rana esculenta display different affinities for the dye. Some of the orangiophilic nuclei show affinity for aniline blue (blue nuclei). In the Harderian gland of Rana esculenta their number and the intensity of staining with aniline blue may vary during the year. The affinity for aniline blue disappears following digestion of paraffin sections with RNAase, but not with DNAase or trypsin. Furthermore, in vitro incubation with [5, 6-3H]-Uridine shows a selective incorporation by the majority of blue nuclei. Therefore, the affinity for aniline blue is likely due to increased RNA synthesis. The increment of nuclear RNA shown by these methods is supported by the quantitative determination of total RNAs during the resumption (October) and enhancement (May) of secretory activity, when the percentage of blue nuclei of the acinar cells is at its highest levels of the year. The affinity of RNA-rich nuclei for aniline blue, while others are strictly orangiophil, is discussed on the basis of molecular structure of the dyes used in the staining mixture. Mallory's trichrome stain appears to be an useful tool for detecting changes in cell nuclear status.

Animals

Association of AUUUA-binding protein with A+U-rich mRNA during nucleo-cytoplasmic transport.

Resealed nuclear envelope (NE) vesicles from rat liver containing entrapped exogenous RNA were used to study the effect of adenosine+uridine binding factor (AUBF), present in cytosolic cell extracts, on ATP-dependent transport of A+U-rich RNA (AU+RNA) and A+U-free RNA (AU-RNA) across the NE. This factor specifically binds to A+U-rich sequences present in the 3' untranslated regions of lymphokine and cytokine mRNAs, containing overlapping AUUUA boxes (granulocyte-macrophage colony stimulating factor, interleukin-3). Addition of AUBF to the extravesicular compartment markedly increased the efflux of the in vitro transcribed, capped and polyadenylated AU+ RNAs. Export of entrapped AU- control RNA, such as beta-globin RNA, was not affected by AUBF, in contrast to chimeric AU+ beta-globin RNA containing the A+U-rich sequence of human interferon-alpha mRNA (6 reiterated AUUUA motifs). Competition experiments revealed that AUBF enhances the affinity of poly(A)-containing AU+ RNAs to the NE poly(A)-binding component (poly(A)-recognizing mRNA carrier p106), and thereby accelerates nuclear export of these RNAs. We could demonstrate that AUBF added to the extravesicular space forms stable complexes with polyadenylated AU+ RNA with relative molecular masses of about 45,000, 62,000 and 70,000 inside the vesicles or during ATP-dependent export. In addition we determined that AUBF may affect mRNA stability by protecting A+U-rich RNA against degradation by trans-acting, nuclear matrix-associated and A+U-specific endoribonuclease V.

Adenosine

[A change in the relative concentration of individual fractions of low molecular weight nuclear RNA in tumor tissues].

Low molecular weight nuclear RNAs (LMWN RNAs) of normal and neoplastic tissues: the rat liver and Zajdela hepatoma, mouse spleen and NK/Ly ascites tumor, as well as the cultures of normal chick embryo fibroblasts and of those transformed with Rous sarcoma virus were studied by electrophoresis in 8% and 15% polyacrylamide gels. As a result of the study no qualitative differences, i.e. differences in the number of LMWN RNA main fractions and their electrophoretic mobility were found. But there were revealed quantitative variations in the relative amount of definite fractions of these RNAs. An increase of the U3 RNA content in ascites tumors may be connected with an enhancement of the ribosomal RNA synthesis. Variations in the content of low molecular weight RNAs in oncogenic virus transformed cells may reflect an excessive synthesis of low molecular weight viral RNAs during the process of virus reproduction. The quantitative alterations observed seem to be of special value since LMWN RNAs are likely to perform regulatory functions.

Animals