Integrator mediates the biogenesis of enhancer RNAs

Structural basis of Integrator-dependent RNA polymerase II termination

The Integrator complex can terminate RNA polymerase II (Pol II) in the promoter-proximal region of genes. Previous work has shed light on how Integrator binds to the paused elongation complex consisting of Pol II, the DRB sensitivity-inducing factor (DSIF) and the negative elongation factor (NELF) and how it cleaves the nascent RNA transcript1, but has not explained how Integrator removes Pol II from the DNA template. Here we present three cryo-electron microscopy structures of the complete Integrator-PP2A complex in different functional states. The structure of the pre-termination complex reveals a previously unresolved, scorpion-tail-shaped INTS10-INTS13-INTS14-INTS15 module that may use its 'sting' to open the DSIF DNA clamp and facilitate termination. The structure of the post-termination complex shows that the previously unresolved subunit INTS3 and associated sensor of single-stranded DNA complex (SOSS) factors prevent Pol II rebinding to Integrator after termination. The structure of the free Integrator-PP2A complex in an inactive closed conformation2 reveals that INTS6 blocks the PP2A phosphatase active site. These results lead to a model for how Integrator terminates Pol II transcription in three steps that involve major rearrangements.

Transcription directionality is licensed by Integrator at active human promoters

A universal characteristic of eukaryotic transcription is that the promoter recruits RNA polymerase II (RNAPII) to produce both precursor mRNAs (pre-mRNAs) and short unstable promoter upstream transcripts (PROMPTs) toward the opposite direction. However, how the transcription machinery selects the correct direction to produce pre-mRNAs is largely unknown. Here, through multiple acute auxin-inducible degradation systems, we show that rapid depletion of an RNAPII-binding protein complex, Integrator, results in robust PROMPT accumulation throughout the genome. Interestingly, the accumulation of PROMPTs is compensated by the reduction of pre-mRNA transcripts in actively transcribed genes. Consistently, Integrator depletion alters the distribution of polymerase between the sense and antisense directions, which is marked by increased RNAPII-carboxy-terminal domain Tyr1 phosphorylation at PROMPT regions and a reduced Ser2 phosphorylation level at transcription start sites. Mechanistically, the endonuclease activity of Integrator is critical to suppress PROMPT production. Furthermore, our data indicate that the presence of U1 binding sites on nascent transcripts could counteract the cleavage activity of Integrator. In this process, the absence of robust U1 signal at most PROMPTs allows Integrator to suppress the antisense transcription and shift the transcriptional balance in favor of the sense direction.

Widespread impact of nucleosome remodelers on transcription at cis-regulatory elements

Nucleosome remodeling complexes and other regulatory factors work in concert to build a chromatin environment that directs the expression of a distinct set of genes in each cell using cis-regulatory elements (CREs), such as promoters and enhancers, that drive transcription of both mRNAs and CRE-associated non-coding RNAs (ncRNAs). Two classes of CRE-associated ncRNAs include upstream antisense RNAs (uaRNAs), which are transcribed divergently from a shared mRNA promoter, and enhancer RNAs (eRNAs), which are transcribed bidirectionally from active enhancers. The complicated network of CRE regulation by nucleosome remodelers remains only partially explored, with a focus on a select, limited number of remodelers. We endeavored to elucidate a remodeler-based regulatory network governing CRE-associated transcription (mRNA, eRNA, and uaRNA) in murine embryonic stem (ES) cells to test the hypothesis that many SNF2-family nucleosome remodelers collaborate to regulate the coding and non-coding transcriptome via alteration of underlying nucleosome architecture. Using depletion followed by transient transcriptome sequencing (TT-seq), we identified thousands of misregulated mRNAs and CRE-associated ncRNAs across the remodelers examined, identifying novel contributions by understudied remodelers in the regulation of coding and noncoding transcription. Our findings suggest that mRNA and eRNA transcription are coordinately co-regulated, while mRNA and uaRNAs sharing a common promoter are independently regulated. Subsequent mechanistic studies suggest that while remodelers SRCAP and CHD8 modulate transcription through classical mechanisms such as transcription factors and histone variants, a broad set of remodelers including SMARCAL1 indirectly contribute to transcriptional regulation through maintenance of genomic stability and proper Integrator complex localization. This study systematically examines the contribution of SNF2-remodelers to the CRE-associated transcriptome, identifying at least two classes for remodeler action.

Global control of RNA polymerase II

RNA polymerase II (Pol II) is the multi-protein complex responsible for transcribing all protein-coding messenger RNA (mRNA). Most research on gene regulation is focused on the mechanisms controlling which genes are transcribed when, or on the mechanics of transcription. How global Pol II activity is determined receives comparatively less attention. Here, we follow the life of a Pol II molecule from 'assembly of the complex' to nuclear import, enzymatic activity, and degradation. We focus on how Pol II spends its time in the nucleus, and on the two-way relationship between Pol II abundance and activity in the context of homeostasis and global transcriptional changes.

A homozygous variant in INTS11 links mitosis and neurogenesis defects to a severe neurodevelopmental disorder

The INTS11 endonuclease is crucial in modulating gene expression and has only recently been linked to human neurodevelopmental disorders (NDDs). However, how INTS11 participates in human development and disease remains unclear. Here, we identify a homozygous INTS11 variant in two siblings with a severe NDD. The variant impairs INTS11 catalytic activity, supported by its substrate's accumulation, and causes G2/M arrest in patient cells with length-dependent dysregulation of genes involved in mitosis and neural development, including the NDD gene CDKL5. The mutant knockin (KI) in induced pluripotent stem cells (iPSCs) disturbs their mitotic spindle organization and thus leads to slow proliferation and increased apoptosis, possibly through the decreased neurally functional CDKL5-induced extracellular signal-regulated kinase (ERK) pathway inhibition. The generation of neural progenitor cells (NPCs) from the mutant iPSCs is also delayed, with long transcript loss concerning neurogenesis. Our work reveals a mechanism underlying INTS11 dysfunction-caused human NDD and provides an iPSC model for this disease.

IntS6 and the Integrator phosphatase module tune the efficiency of select premature transcription termination events

The metazoan-specific Integrator complex catalyzes 3' end processing of small nuclear RNAs (snRNAs) and premature termination that attenuates the transcription of many protein-coding genes. Integrator has RNA endonuclease and protein phosphatase activities, but it remains unclear if both are required for complex function. Here, we show IntS6 (Integrator subunit 6) over-expression blocks Integrator function at a subset of Drosophila protein-coding genes, although having no effect on snRNAs or attenuation of other loci. Over-expressed IntS6 titrates protein phosphatase 2A (PP2A) subunits, thereby only affecting gene loci where phosphatase activity is necessary for Integrator function. IntS6 functions analogous to a PP2A regulatory B subunit as over-expression of canonical B subunits, which do not bind Integrator, is also sufficient to inhibit Integrator activity. These results show that the phosphatase module is critical at only a subset of Integrator-regulated genes and point to PP2A recruitment as a tunable step that modulates transcription termination efficiency.

Identification of a Novel Long Non-Coding RNA G8110 That Modulates Porcine Adipogenic Differentiation and Inflammatory Responses

Long non-coding RNAs (lncRNAs) have been extensively studied, and their crucial roles in adipogenesis, lipid metabolism, and gene expression have been revealed. However, the exact regulatory or other mechanisms by which lncRNAs influence the functioning of mesenteric adipose tissue (MAT) remain largely unknown. In this paper, we report the identification of a new lncRNA, named G8110, from the MAT of Bama pigs. The coordinated expression levels of lncRNA G8110 and NFE2L1 were significantly decreased in the MAT of obese Bama pigs compared with those in the MAT of lean pigs. Using a bone mesenchymal stem cell adipogenic differentiation model, we found that lncRNA G8110 played a role in adipocyte differentiation by positively regulating NFE2L1. We also found that lncRNA G8110 inhibited the formation of intracellular lipid synthesis, promoted lipid metabolism, and inhibited the expression of inflammatory cytokines. Our findings regarding lipid synthesis may further promote the role of lncRNAs in driving adipose tissue remodeling and maintaining metabolic health.

Transcriptional elongation control in developmental gene expression, aging, and disease

The elongation stage of transcription by RNA polymerase II (RNA Pol II) is central to the regulation of gene expression in response to developmental and environmental cues in metazoan. Dysregulated transcriptional elongation has been associated with developmental defects as well as disease and aging processes. Decades of genetic and biochemical studies have painstakingly identified and characterized an ensemble of factors that regulate RNA Pol II elongation. This review summarizes recent findings taking advantage of genetic engineering techniques that probe functions of elongation factors in vivo. We propose a revised model of elongation control in this accelerating field by reconciling contradictory results from the earlier biochemical evidence and the recent in vivo studies. We discuss how elongation factors regulate promoter-proximal RNA Pol II pause release, transcriptional elongation rate and processivity, RNA Pol II stability and RNA processing, and how perturbation of these processes is associated with developmental disorders, neurodegenerative disease, cancer, and aging.

Emerging insights into enhancer biology and function

Cell type-specific gene expression is coordinated by DNA-encoded enhancers and the transcription factors (TFs) that bind to them in a sequence-specific manner. As such, these enhancers and TFs are critical mediators of normal development and altered enhancer or TF function is associated with the development of diseases such as cancer. While initially defined by their ability to activate gene transcription in reporter assays, putative enhancer elements are now frequently defined by their unique chromatin features including DNase hypersensitivity and transposase accessibility, bidirectional enhancer RNA (eRNA) transcription, CpG hypomethylation, high H3K27ac and H3K4me1, sequence-specific transcription factor binding, and co-factor recruitment. Identification of these chromatin features through sequencing-based assays has revolutionized our ability to identify enhancer elements on a genome-wide scale, and genome-wide functional assays are now capitalizing on this information to greatly expand our understanding of how enhancers function to provide spatiotemporal coordination of gene expression programs. Here, we highlight recent technological advances that are providing new insights into the molecular mechanisms by which these critical cis-regulatory elements function in gene control. We pay particular attention to advances in our understanding of enhancer transcription, enhancer-promoter syntax, 3D organization and biomolecular condensates, transcription factor and co-factor dependencies, and the development of genome-wide functional enhancer screens.

Temporal analyses reveal a pivotal role for sense and antisense enhancer RNAs in coordinate immunoglobulin lambda locus activation

Transcription enhancers are essential activators of V(D)J recombination that orchestrate non-coding transcription through complementary, unrearranged gene segments. How transcription is coordinately increased at spatially distinct promoters, however, remains poorly understood. Using the murine immunoglobulin lambda (Igλ) locus as model, we find that three enhancer-like elements in the 3' Igλ domain, Eλ3-1, HSCλ1 and HSE-1, show strikingly similar transcription factor binding dynamics and close spatial proximity, suggesting that they form an active enhancer hub. Temporal analyses show coordinate recruitment of complementary V and J gene segments to this hub, with comparable transcription factor binding dynamics to that at enhancers. We find further that E2A, p300, Mediator and Integrator bind to enhancers as early events, whereas YY1 recruitment and eRNA synthesis occur later, corresponding to transcription activation. Remarkably, the interplay between sense and antisense enhancer RNA is central to both active enhancer hub formation and coordinate Igλ transcription: Antisense Eλ3-1 eRNA represses Igλ activation whereas temporal analyses demonstrate that accumulating levels of sense eRNA boost YY1 recruitment to stabilise enhancer hub/promoter interactions and lead to coordinate transcription activation. These studies therefore demonstrate for the first time a critical role for threshold levels of sense versus antisense eRNA in locus activation.

Genome-wide measurement of RNA dissociation from chromatin classifies transcripts by their dynamics and reveals rapid dissociation of enhancer lncRNAs

Long non-coding RNAs (lncRNAs) are involved in gene expression regulation in cis. Although enriched in the cell chromatin fraction, to what degree this defines their regulatory potential remains unclear. Furthermore, the factors underlying lncRNA chromatin tethering, as well as the molecular basis of efficient lncRNA chromatin dissociation and its impact on enhancer activity and target gene expression, remain to be resolved. Here, we developed chrTT-seq, which combines the pulse-chase metabolic labeling of nascent RNA with chromatin fractionation and transient transcriptome sequencing to follow nascent RNA transcripts from their transcription on chromatin to release and allows the quantification of dissociation dynamics. By incorporating genomic, transcriptomic, and epigenetic metrics, as well as RNA-binding protein propensities, in machine learning models, we identify features that define transcript groups of different chromatin dissociation dynamics. Notably, lncRNAs transcribed from enhancers display reduced chromatin retention, suggesting that, in addition to splicing, their chromatin dissociation may shape enhancer activity.

Understanding blood development and leukemia using sequencing-based technologies and human cell systems

Our current understanding of human hematopoiesis has undergone significant transformation throughout the years, challenging conventional views. The evolution of high-throughput technologies has enabled the accumulation of diverse data types, offering new avenues for investigating key regulatory processes in blood cell production and disease. In this review, we will explore the opportunities presented by these advancements for unraveling the molecular mechanisms underlying normal and abnormal hematopoiesis. Specifically, we will focus on the importance of enhancer-associated regulatory networks and highlight the crucial role of enhancer-derived transcription regulation. Additionally, we will discuss the unprecedented power of single-cell methods and the progression in using in vitro human blood differentiation system, in particular induced pluripotent stem cell models, in dissecting hematopoietic processes. Furthermore, we will explore the potential of ever more nuanced patient profiling to allow precision medicine approaches. Ultimately, we advocate for a multiparameter, regulatory network-based approach for providing a more holistic understanding of normal hematopoiesis and blood disorders.

Merging short and stranded long reads improves transcript assembly

Long-read RNA sequencing has arisen as a counterpart to short-read sequencing, with the potential to capture full-length isoforms, albeit at the cost of lower depth. Yet this potential is not fully realized due to inherent limitations of current long-read assembly methods and underdeveloped approaches to integrate short-read data. Here, we critically compare the existing methods and develop a new integrative approach to characterize a particularly challenging pool of low-abundance long noncoding RNA (lncRNA) transcripts from short- and long-read sequencing in two distinct cell lines. Our analysis reveals severe limitations in each of the sequencing platforms. For short-read assemblies, coverage declines at transcript termini resulting in ambiguous ends, and uneven low coverage results in segmentation of a single transcript into multiple transcripts. Conversely, long-read sequencing libraries lack depth and strand-of-origin information in cDNA-based methods, culminating in erroneous assembly and quantitation of transcripts. We also discover a cDNA synthesis artifact in long-read datasets that markedly impacts the identity and quantitation of assembled transcripts. Towards remediating these problems, we develop a computational pipeline to "strand" long-read cDNA libraries that rectifies inaccurate mapping and assembly of long-read transcripts. Leveraging the strengths of each platform and our computational stranding, we also present and benchmark a hybrid assembly approach that drastically increases the sensitivity and accuracy of full-length transcript assembly on the correct strand and improves detection of biological features of the transcriptome. When applied to a challenging set of under-annotated and cell-type variable lncRNA, our method resolves the segmentation problem of short-read sequencing and the depth problem of long-read sequencing, resulting in the assembly of coherent transcripts with precise 5' and 3' ends. Our workflow can be applied to existing datasets for superior demarcation of transcript ends and refined isoform structure, which can enable better differential gene expression analyses and molecular manipulations of transcripts.

Flipons and small RNAs accentuate the asymmetries of pervasive transcription by the reset and sequence-specific microcoding of promoter conformation

The role of alternate DNA conformations such as Z-DNA in the regulation of transcription is currently underappreciated. These structures are encoded by sequences called flipons, many of which are enriched in promoter and enhancer regions. Through a change in their conformation, flipons provide a tunable mechanism to mechanically reset promoters for the next round of transcription. They act as actuators that capture and release energy to ensure that the turnover of the proteins at promoters is optimized to cell state. Likewise, the single-stranded DNA formed as flipons cycle facilitates the docking of RNAs that are able to microcode promoter conformations and canalize the pervasive transcription commonly observed in metazoan genomes. The strand-specific nature of the interaction between RNA and DNA likely accounts for the known asymmetry of epigenetic marks present on the histone tetramers that pair to form nucleosomes. The role of these supercoil-dependent processes in promoter choice and transcriptional interference is reviewed. The evolutionary implications are examined: the resilience and canalization of flipon-dependent gene regulation is contrasted with the rapid adaptation enabled by the spread of flipon repeats throughout the genome. Overall, the current findings underscore the important role of flipons in modulating the readout of genetic information and how little we know about their biology.

R-loop-dependent promoter-proximal termination ensures genome stability

The proper regulation of transcription is essential for maintaining genome integrity and executing other downstream cellular functions1,2. Here we identify a stable association between the genome-stability regulator sensor of single-stranded DNA (SOSS)3 and the transcription regulator Integrator-PP2A (INTAC)4-6. Through SSB1-mediated recognition of single-stranded DNA, SOSS-INTAC stimulates promoter-proximal termination of transcription and attenuates R-loops associated with paused RNA polymerase II to prevent R-loop-induced genome instability. SOSS-INTAC-dependent attenuation of R-loops is enhanced by the ability of SSB1 to form liquid-like condensates. Deletion of NABP2 (encoding SSB1) or introduction of cancer-associated mutations into its intrinsically disordered region leads to a pervasive accumulation of R-loops, highlighting a genome surveillance function of SOSS-INTAC that enables timely termination of transcription at promoters to constrain R-loop accumulation and ensure genome stability.

BRAT1 associates with INTS11/INTS9 heterodimer to regulate key neurodevelopmental genes

Integrator is a multi-subunits protein complex involved in regulation of gene expression. Several Integrator subunits have been found to be mutated in human neurodevelopmental disorders, suggesting a key role for the complex in the development of nervous system. BRAT1 is similarly linked with neurodegenerative diseases and neurodevelopmental disorders such as rigidity and multifocal-seizure syndrome. Here, we show that INTS11 and INTS9 subunits of Integrator complex interact with BRAT1 and form a trimeric complex in human HEK293T cells as well as in pluripotent human embryonal carcinoma cell line (NT2). We find that BRAT1 depletion disrupts the differentiation of NT2 cells into astrocytes and neural cells. Loss of BRAT1 results in inability to activate many neuronal genes that are targets of REST, a neuronal silencer. We identified BRAT1 and INTS11 co-occupying the promoter region of these genes and pinpoint a role for BRAT1 in recruiting INTS11 to their promoters. Disease-causing mutations in BRAT1 diminish its association with INTS11/INTS9, linking the manifestation of disease phenotypes with a defect in transcriptional activation of key neuronal genes by BRAT1/INTS11/INTS9 complex.

Highlights

Integrator subunits INTS9 and INTS11 tightly interact with BRAT1 Depletion of BRAT1 causes a dramatic delay in human neural differentiation BRAT1 and INTS11 module targets the promoters of neural marker genes and co-regulates their expression. The recruitment of INTS11 to these sites is BRAT1-dependent. Pathogenic E522K mutation in BRAT1 disrupts its interaction with INTS11/INTS9 heterodimer.

Sensitized piRNA reporter identifies multiple RNA processing factors involved in piRNA-mediated gene silencing

Metazoans guard their germlines against transposons and other foreign transcripts with PIWI-interacting RNAs (piRNAs). Due to the robust heritability of the silencing initiated by piRNAs in Caenorhabditis elegans (C. elegans), previous screens using C. elegans were strongly biased to uncover members of this pathway in the maintenance process but not in the initiation process. To identify novel piRNA pathway members, we have utilized a sensitized reporter strain which detects defects in initiation, amplification, or regulation of piRNA silencing. Using our reporter, we have identified Integrator complex subunits, nuclear pore components, protein import components, and pre-mRNA splicing factors as essential for piRNA-mediated gene silencing. We found the small nuclear processing cellular machine termed the Integrator complex is required for both type I and type II piRNA production. Notably, we identified a role for nuclear pore and nucleolar components NPP-1/Nup54, NPP-6/Nup160, NPP-7/Nup153, and FIB-1 in promoting the perinuclear localization of anti-silencing CSR-1 Argonaute, as well as a role for Importin factor IMA-3 in nuclear localization of silencing Argonaute HRDE-1. Together, we have shown that piRNA silencing in C. elegans is dependent on evolutionarily ancient RNA processing machinery that has been co-opted to function in the piRNA-mediated genome surveillance pathway.

Enhancer RNAs: mechanisms in transcriptional regulation and functions in diseases

In recent years, increasingly more non-coding RNAs have been detected with the development of high-throughput sequencing technology, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), small nucleolar RNAs (snoRNAs), and piwi-interacting RNA (piRNAs). The discovery of enhancer RNAs (eRNAs) in 2010 has further broadened the range of non-coding RNAs revealed. eRNAs are non-coding RNA molecules produced by the transcription of DNA cis-acting elements, enhancer fragments. Recent studies revealed that the transcription of eRNAs may be a biological marker responding to enhancer activity that can participate in the regulation of coding gene transcription. In this review, we discussed the biological characteristics of eRNAs, their functions in transcriptional regulation, the regulation factors of eRNAs production, and the research progress of eRNAs in different diseases. Video Abstract.

Complementary Alu sequences mediate enhancer-promoter selectivity

Enhancers determine spatiotemporal gene expression programs by engaging with long-range promoters^1-4. However, it remains unknown how enhancers find their cognate promoters. We recently developed a RNA in situ conformation sequencing technology to identify enhancer-promoter connectivity using pairwise interacting enhancer RNAs and promoter-derived noncoding RNAs^5,6. Here we apply this technology to generate high-confidence enhancer-promoter RNA interaction maps in six additional cell lines. Using these maps, we discover that 37.9% of the enhancer-promoter RNA interaction sites are overlapped with Alu sequences. These pairwise interacting Alu and non-Alu RNA sequences tend to be complementary and potentially form duplexes. Knockout of Alu elements compromises enhancer-promoter looping, whereas Alu insertion or CRISPR-dCasRx-mediated Alu tethering to unregulated promoter RNAs can create new loops to homologous enhancers. Mapping 535,404 noncoding risk variants back to the enhancer-promoter RNA interaction maps enabled us to construct variant-to-function maps for interpreting their molecular functions, including 15,318 deletions or insertions in 11,677 Alu elements that affect 6,497 protein-coding genes. We further demonstrate that polymorphic Alu insertion at the PTK2 enhancer can promote tumorigenesis. Our study uncovers a principle for determining enhancer-promoter pairing specificity and provides a framework to link noncoding risk variants to their molecular functions.

Identification and characterization of transcribed enhancers during cerebellar development through enhancer RNA analysis

BACKGROUND

The development of the brain requires precise coordination of molecular processes across many cell-types. Underpinning these events are gene expression programs which require intricate regulation by non-coding regulatory sequences known as enhancers. In the context of the developing brain, transcribed enhancers (TEs) regulate temporally-specific expression of genes critical for cell identity and differentiation. Transcription of non-coding RNAs at active enhancer sequences, known as enhancer RNAs (eRNAs), is tightly associated with enhancer activity and has been correlated with target gene expression. TEs have been characterized in a multitude of developing tissues, however their regulatory role has yet to be described in the context of embryonic and early postnatal brain development. In this study, eRNA transcription was analyzed to identify TEs active during cerebellar development, as a proxy for the developing brain. Cap Analysis of Gene Expression followed by sequencing (CAGE-seq) was conducted at 12 stages throughout embryonic and early postnatal cerebellar development.

RESULTS

Temporal analysis of eRNA transcription identified clusters of TEs that peak in activity during either embryonic or postnatal times, highlighting their importance for temporally specific developmental events. Functional analysis of putative target genes identified molecular mechanisms under TE regulation revealing that TEs regulate genes involved in biological processes specific to neurons. We validate enhancer activity using in situ hybridization of eRNA expression from TEs predicted to regulate Nfib, a gene critical for cerebellar granule cell differentiation.

CONCLUSIONS

The results of this analysis provide a valuable dataset for the identification of cerebellar enhancers and provide insight into the molecular mechanisms critical for brain development under TE regulation. This dataset is shared with the community through an online resource ( https://goldowitzlab.shinyapps.io/trans-enh-app/ ).

A restrictor complex of ZC3H4, WDR82, and ARS2 integrates with PNUTS to control unproductive transcription

The transcriptional termination of unstable non-coding RNAs (ncRNAs) is poorly understood compared to coding transcripts. We recently identified ZC3H4-WDR82 ("restrictor") as restricting human ncRNA transcription, but how it does this is unknown. Here, we show that ZC3H4 additionally associates with ARS2 and the nuclear exosome targeting complex. The domains of ZC3H4 that contact ARS2 and WDR82 are required for ncRNA restriction, suggesting their presence in a functional complex. Consistently, ZC3H4, WDR82, and ARS2 co-transcriptionally control an overlapping population of ncRNAs. ZC3H4 is proximal to the negative elongation factor, PNUTS, which we show enables restrictor function and is required to terminate the transcription of all major RNA polymerase II transcript classes. In contrast to short ncRNAs, longer protein-coding transcription is supported by U1 snRNA, which shields transcripts from restrictor and PNUTS at hundreds of genes. These data provide important insights into the mechanism and control of transcription by restrictor and PNUTS.

Bi-allelic variants in INTS11 are associated with a complex neurological disorder

The Integrator complex is a multi-subunit protein complex that regulates the processing of nascent RNAs transcribed by RNA polymerase II (RNAPII), including small nuclear RNAs, enhancer RNAs, telomeric RNAs, viral RNAs, and protein-coding mRNAs. Integrator subunit 11 (INTS11) is the catalytic subunit that cleaves nascent RNAs, but, to date, mutations in this subunit have not been linked to human disease. Here, we describe 15 individuals from 10 unrelated families with bi-allelic variants in INTS11 who present with global developmental and language delay, intellectual disability, impaired motor development, and brain atrophy. Consistent with human observations, we find that the fly ortholog of INTS11, dIntS11, is essential and expressed in the central nervous systems in a subset of neurons and most glia in larval and adult stages. Using Drosophila as a model, we investigated the effect of seven variants. We found that two (p.Arg17Leu and p.His414Tyr) fail to rescue the lethality of null mutants, indicating that they are strong loss-of-function variants. Furthermore, we found that five variants (p.Gly55Ser, p.Leu138Phe, p.Lys396Glu, p.Val517Met, and p.Ile553Glu) rescue lethality but cause a shortened lifespan and bang sensitivity and affect locomotor activity, indicating that they are partial loss-of-function variants. Altogether, our results provide compelling evidence that integrity of the Integrator RNA endonuclease is critical for brain development.

Super-enhancer landscape rewiring in cancer: The epigenetic control at distal sites

Super-enhancers evolve as elements at the top of the hierarchical control of gene expression. They are important end-gatherers of signaling pathways that control stemness, differentiation or adaptive responses. Many epigenetic regulations focus on these regions, and not surprisingly, during the process of tumorigenesis, various alterations can account for their dysfunction. Super-enhancers are emerging as key drivers of the aberrant gene expression landscape that sustain the aggressiveness of cancer cells. In this review, we will describe and discuss about the structure of super-enhancers, their epigenetic regulation, and the major changes affecting their functionality in cancer.

INTAC endonuclease and phosphatase modules differentially regulate transcription by RNA polymerase II

Gene expression in metazoans is controlled by promoter-proximal pausing of RNA polymerase II, which can undergo productive elongation or promoter-proximal termination. Integrator-PP2A (INTAC) plays a crucial role in determining the fate of paused polymerases, but the underlying mechanisms remain unclear. Here, we establish a rapid degradation system to dissect the functions of INTAC RNA endonuclease and phosphatase modules. We find that both catalytic modules function at most if not all active promoters and enhancers, yet differentially affect polymerase fate. The endonuclease module induces promoter-proximal termination, with its disruption leading to accumulation of elongation-incompetent polymerases and downregulation of highly expressed genes, while elongation-competent polymerases accumulate at lowly expressed genes and non-coding elements, leading to their upregulation. The phosphatase module primarily prevents the release of paused polymerases and limits transcriptional activation, especially for highly paused genes. Thus, both INTAC catalytic modules have unexpectedly general yet distinct roles in dynamic transcriptional control.

Insights into Enhancer RNAs: Biogenesis and Emerging Role in Brain Diseases

Enhancers are cis-acting elements that control the transcription of target genes and are transcribed into a class of noncoding RNAs (ncRNAs) termed enhancer RNAs (eRNAs). eRNAs have shorter half-lives than mRNAs and long noncoding RNAs; however, the frequency of transcription of eRNAs is close to that of mRNAs. eRNA expression is associated with a high level of histone mark H3K27ac and a low level of H3K27me3. Although eRNAs only account for a small proportion of ncRNAs, their functions are important. eRNAs can not only increase enhancer activity by promoting the formation of enhancer-promoter loops but also regulate transcriptional activation. Increasing numbers of studies have found that eRNAs play an important role in the occurrence and development of brain diseases; however, further research into eRNAs is required. This review discusses the concept, characteristics, classification, function, and potential roles of eRNAs in brain diseases.

A combinatorial approach to uncover an additional Integrator subunit

RNA polymerase II (RNAPII) controls expression of all protein-coding genes and most noncoding loci in higher eukaryotes. Calibrating RNAPII activity requires an assortment of polymerase-associated factors that are recruited at sites of active transcription. The Integrator complex is one of the most elusive transcriptional regulators in metazoans, deemed to be recruited after initiation to help establish and modulate paused RNAPII. Integrator is known to be composed of 14 subunits that assemble and operate in a modular fashion. We employed proteomics and machine-learning structure prediction (AlphaFold2) to identify an additional Integrator subunit, INTS15. We report that INTS15 assembles primarily with the INTS13/14/10 module and interfaces with the Int-PP2A module. Functional genomics analysis further reveals a role for INTS15 in modulating RNAPII pausing at a subset of genes. Our study shows that omics approaches combined with AlphaFold2-based predictions provide additional insights into the molecular architecture of large and dynamic multiprotein complexes.

Genomic regulation of transcription and RNA processing by the multitasking Integrator complex

In higher eukaryotes, fine-tuned activation of protein-coding genes and many non-coding RNAs pivots around the regulated activity of RNA polymerase II (Pol II). The Integrator complex is the only Pol II-associated large multiprotein complex that is metazoan specific, and has therefore been understudied for years. Integrator comprises at least 14 subunits, which are grouped into distinct functional modules. The phosphodiesterase activity of the core catalytic module is co-transcriptionally directed against several RNA species, including long non-coding RNAs (lncRNAs), U small nuclear RNAs (U snRNAs), PIWI-interacting RNAs (piRNAs), enhancer RNAs and nascent pre-mRNAs. Processing of non-coding RNAs by Integrator is essential for their biogenesis, and at protein-coding genes, Integrator is a key modulator of Pol II promoter-proximal pausing and transcript elongation. Recent studies have identified an Integrator-specific serine/threonine-protein phosphatase 2A (PP2A) module, which targets Pol II and other components of the basal transcription machinery. In this Review, we discuss how the activity of Integrator regulates transcription, RNA processing, chromatin landscape and DNA repair. We also discuss the diverse roles of Integrator in development and tumorigenesis.

The Integrator complex regulates microRNA abundance through RISC loading

MicroRNA (miRNA) homeostasis is crucial for the posttranscriptional regulation of their target genes during development and in disease states. miRNAs are derived from primary transcripts and are processed from a hairpin precursor intermediary to a mature 22-nucleotide duplex RNA. Loading of the duplex into the Argonaute (AGO) protein family is pivotal to miRNA abundance and its posttranscriptional function. The Integrator complex plays a key role in protein coding and noncoding RNA maturation, RNA polymerase II pause-release, and premature transcriptional termination. Here, we report that loss of Integrator results in global destabilization of mature miRNAs. Enhanced ultraviolet cross-linking and immunoprecipitation of Integrator uncovered an association with duplex miRNAs before their loading onto AGOs. Tracing miRNA fate from biogenesis to stabilization by incorporating 4-thiouridine in nascent transcripts pinpointed a critical role for Integrator in miRNA assembly into AGOs.

Integrator is a global promoter-proximal termination complex

Integrator is a metazoan-specific protein complex capable of inducing termination at all RNAPII-transcribed loci. Integrator recognizes paused, promoter-proximal RNAPII and drives premature termination using dual enzymatic activities: an endonuclease that cleaves nascent RNA and a protein phosphatase that removes stimulatory phosphorylation associated with RNAPII pause release and productive elongation. Recent breakthroughs in structural biology have revealed the overall architecture of Integrator and provided insights into how multiple Integrator modules are coordinated to elicit termination effectively. Furthermore, functional genomics and biochemical studies have unraveled how Integrator-mediated termination impacts protein-coding and noncoding loci. Here, we review the current knowledge about the assembly and activity of Integrator and describe the role of Integrator in gene regulation, highlighting the importance of this complex for human health.

The Integrator complex desensitizes cellular response to TGF-β/BMP signaling

Maintenance of stem cells requires the concerted actions of niche-derived signals and stem cell-intrinsic factors. Although Decapentaplegic (Dpp), a Drosophila bone morphogenetic protein (BMP) molecule, can act as a long-range morphogen, its function is spatially limited to the germline stem cell niche in the germarium. We show here that Integrator, a complex known to be involved in RNA polymerase II (RNAPII)-mediated transcriptional regulation in the nucleus, promotes germline differentiation by restricting niche-derived Dpp/BMP activity in the cytoplasm. Further results show that Integrator works in various developmental contexts to desensitize the cellular response to Dpp/BMP signaling during Drosophila development. Mechanistically, our results show that Integrator forms a multi-subunit complex with the type I receptor Thickveins (Tkv) and other Dpp/BMP signaling components and acts in a negative feedback loop to promote Tkv turnover independent of its transcriptional activity. Similarly, human Integrator subunits bind transforming growth factor β (TGF-β)/BMP signaling components and antagonize their activity, suggesting a conserved role of Integrator across metazoans.

iEnhancer-SKNN: a stacking ensemble learning-based method for enhancer identification and classification using sequence information

Enhancers, a class of distal cis-regulatory elements located in the non-coding region of DNA, play a key role in gene regulation. It is difficult to identify enhancers from DNA sequence data because enhancers are freely distributed in the non-coding region, with no specific sequence features, and having a long distance with the targeted promoters. Therefore, this study presents a stacking ensemble learning method to accurately identify enhancers and classify enhancers into strong and weak enhancers. Firstly, we obtain the fusion feature matrix by fusing the four features of Kmer, PseDNC, PCPseDNC and Z-Curve9. Secondly, five K-Nearest Neighbor (KNN) models with different parameters are trained as the base model, and the Logistic Regression algorithm is utilized as the meta-model. Thirdly, the stacking ensemble learning strategy is utilized to construct a two-layer model based on the base model and meta-model to train the preprocessed feature sets. The proposed method, named iEnhancer-SKNN, is a two-layer prediction model, in which the function of the first layer is to predict whether the given DNA sequences are enhancers or non-enhancers, and the function of the second layer is to distinguish whether the predicted enhancers are strong enhancers or weak enhancers. The performance of iEnhancer-SKNN is evaluated on the independent testing dataset and the results show that the proposed method has better performance in predicting enhancers and their strength. In enhancer identification, iEnhancer-SKNN achieves an accuracy of 81.75%, an improvement of 1.35% to 8.75% compared with other predictors, and in enhancer classification, iEnhancer-SKNN achieves an accuracy of 80.50%, an improvement of 5.5% to 25.5% compared with other predictors. Moreover, we identify key transcription factor binding site motifs in the enhancer regions and further explore the biological functions of the enhancers and these key motifs. Source code and data can be downloaded from https://github.com/HaoWuLab-Bioinformatics/iEnhancer-SKNN.

Sensitized piRNA reporter identifies multiple RNA processing factors involved in piRNA-mediated gene silencing

Metazoans guard their germlines against transposons and other foreign transcripts with PIWI-interacting RNAs (piRNAs). Due to the robust heritability of the silencing initiated by piRNAs in C.elegans , previous screens using Caenorhabditis elegans were strongly biased to uncover members of this pathway in the maintenance process but not in the initiation process. To identify novel piRNA pathway members, we have utilized a sensitized reporter strain which detects defects in initiation, amplification, or regulation of piRNA silencing. Using our reporter, we have identified Integrator complex subunits, nuclear pore components, protein import components, and pre-mRNA splicing factors as essential for piRNA-mediated gene silencing. We found the snRNA processing cellular machine termed the Integrator complex is required for both type I and type II piRNA production. Notably, we identified a role for nuclear pore and nucleolar components in promoting the perinuclear localization of anti-silencing CSR-1 Argonaute, as well as a role for Importin factor IMA-3 in nuclear localization of silencing Argonaute HRDE-1. Together, we have shown that piRNA silencing is dependent on evolutionarily ancient RNA processing machinery that has been co-opted to function in the piRNA mediated genome surveillance pathway.

Control of RNA degradation in cell fate decision

Cell fate is shaped by a unique gene expression program, which reflects the concerted action of multilayered precise regulation. Substantial research attention has been paid to the contribution of RNA biogenesis to cell fate decisions. However, increasing evidence shows that RNA degradation, well known for its function in RNA processing and the surveillance of aberrant transcripts, is broadly engaged in cell fate decisions, such as maternal-to-zygotic transition (MZT), stem cell differentiation, or somatic cell reprogramming. In this review, we first look at the diverse RNA degradation pathways in the cytoplasm and nucleus. Then, we summarize how selective transcript clearance is regulated and integrated into the gene expression regulation network for the establishment, maintenance, and exit from a special cellular state.

Mechanisms of eukaryotic transcription termination at a glance

Transcription termination is the final step of a transcription cycle, which induces the release of the transcript at the termination site and allows the recycling of the polymerase for the next round of transcription. Timely transcription termination is critical for avoiding interferences between neighbouring transcription units as well as conflicts between transcribing RNA polymerases (RNAPs) and other DNA-associated processes, such as replication or DNA repair. Understanding the mechanisms by which the very stable transcription elongation complex is dismantled is essential for appreciating how physiological gene expression is maintained and also how concurrent processes that occur synchronously on the DNA are coordinated. Although the strategies employed by the different classes of eukaryotic RNAPs are traditionally considered to be different, novel findings point to interesting commonalities. In this Cell Science at a Glance and the accompanying poster, we review the current understanding about the mechanisms of transcription termination by the three eukaryotic RNAPs.

Mutations in the non-coding RNU4ATAC gene affect the homeostasis and function of the Integrator complex

Various genetic diseases associated with microcephaly and developmental defects are due to pathogenic variants in the U4atac small nuclear RNA (snRNA), a component of the minor spliceosome essential for the removal of U12-type introns from eukaryotic mRNAs. While it has been shown that a few RNU4ATAC mutations result in impaired binding of essential protein components, the molecular defects of the vast majority of variants are still unknown. Here, we used lymphoblastoid cells derived from RNU4ATAC compound heterozygous (g.108_126del;g.111G>A) twin patients with MOPD1 phenotypes to analyze the molecular consequences of the mutations on small nuclear ribonucleoproteins (snRNPs) formation and on splicing. We found that the U4atac108_126del mutant is unstable and that the U4atac111G>A mutant as well as the minor di- and tri-snRNPs are present at reduced levels. Our results also reveal the existence of 3'-extended snRNA transcripts in patients' cells. Moreover, we show that the mutant cells have alterations in splicing of INTS7 and INTS10 minor introns, contain lower levels of the INTS7 and INTS10 proteins and display changes in the assembly of Integrator subunits. Altogether, our results show that compound heterozygous g.108_126del;g.111G>A mutations induce splicing defects and affect the homeostasis and function of the Integrator complex.

Take a break: Transcription regulation and RNA processing by the Integrator complex

The metazoan-specific Integrator complex is a >1.5 MDa machinery that interacts with RNA polymerase II (RNAP2) to attenuate coding gene transcription by early termination close to transcription start sites. Using a highly related mechanism, Integrator also performs the initial 3'-end processing step for many non-coding RNAs. Its transcription regulation functions are essential for cell differentiation and response to external stimuli. Recent studies revealed that the complex incorporates phosphatase PP2A to counteract phosphorylation reactions that are required for transcription elongation. Structures of Integrator bound to RNAP2 explain the basis for its recruitment to promoter proximal RNAP2 by recognition of its paused state. Furthermore, several studies indicate that Integrator's cleavage activity is regulated at multiple levels through activators, modifications, and small molecules.

SUMO conjugation regulates the activity of the Integrator complex

RNA polymerase II (RNAPII) transcribes small nuclear RNA (snRNA) genes in close proximity to Cajal bodies, subnuclear compartments that depend on the SUMO isopeptidase USPL1 for their assembly. We show here that overexpression of USPL1 as well as of another nuclear SUMO isopeptidase, SENP6, alters snRNA 3'-end cleavage, a process carried out by the Integrator complex. Beyond its role in snRNA biogenesis, this complex is responsible for regulating the expression of different RNAPII transcripts. While several subunits of the complex are SUMO conjugation substrates, we found that the SUMOylation of the INTS11 subunit is regulated by USPL1 and SENP6. We defined Lys381, Lys462 and Lys475 as bona fide SUMO attachment sites on INTS11 and observed that SUMOylation of this protein modulates its subcellular localization and is required for Integrator activity. Moreover, while an INTS11 SUMOylation-deficient mutant is still capable of interacting with INTS4 and INTS9, its interaction with other subunits of the complex is affected. These findings point to a regulatory role for SUMO conjugation on Integrator activity and suggest the involvement of INTS11 SUMOylation in the assembly of the complex. Furthermore, this work adds Integrator-dependent RNA processing to the growing list of cellular processes regulated by SUMO conjugation.

XLID syndrome gene Med12 promotes Ig isotype switching through chromatin modification and enhancer RNA regulation

The transcriptional coactivator Med12 regulates gene expression through its kinase module. Here, we show a kinase module-independent function of Med12 in CSR. Med12 is essential for super-enhancer activation by collaborating with p300-Jmjd6/Carm1 coactivator complexes. Med12 loss decreases H3K27 acetylation and eRNA transcription with concomitant impairment of AID-induced DNA breaks, S-S synapse formation, and 3'RR-Eμ interaction. CRISPR-dCas9-mediated enhancer activation reestablishes the epigenomic and transcriptional hallmarks of the super-enhancer and fully restores the Med12 depletion defects. Moreover, 3'RR-derived eRNAs are critical for promoting S region epigenetic regulation, synapse formation, and recruitment of Med12 and AID to the IgH locus. We find that XLID syndrome-associated Med12 mutations are defective in both 3'RR eRNA transcription and CSR, suggesting that B and neuronal cells may have cell-specific super-enhancer dysfunctions. We conclude that Med12 is essential for IgH 3'RR activation/eRNA transcription and plays a central role in AID-induced antibody gene diversification and genomic instability in B cells.

Integrator endonuclease drives promoter-proximal termination at all RNA polymerase II-transcribed loci

RNA polymerase II (RNAPII) pausing in early elongation is critical for gene regulation. Paused RNAPII can be released into productive elongation by the kinase P-TEFb or targeted for premature termination by the Integrator complex. Integrator comprises endonuclease and phosphatase activities, driving termination by cleavage of nascent RNA and removal of stimulatory phosphorylation. We generated a degron system for rapid Integrator endonuclease (INTS11) depletion to probe the direct consequences of Integrator-mediated RNA cleavage. Degradation of INTS11 elicits nearly universal increases in active early elongation complexes. However, these RNAPII complexes fail to achieve optimal elongation rates and exhibit persistent Integrator phosphatase activity. Thus, only short transcripts are significantly upregulated following INTS11 loss, including transcription factors, signaling regulators, and non-coding RNAs. We propose a uniform molecular function for INTS11 across all RNAPII-transcribed loci, with differential effects on particular genes, pathways, or RNA biotypes reflective of transcript lengths rather than specificity of Integrator activity.

iEnhancer-DCLA: using the original sequence to identify enhancers and their strength based on a deep learning framework

Enhancers are small regions of DNA that bind to proteins, which enhance the transcription of genes. The enhancer may be located upstream or downstream of the gene. It is not necessarily close to the gene to be acted on, because the entanglement structure of chromatin allows the positions far apart in the sequence to have the opportunity to contact each other. Therefore, identifying enhancers and their strength is a complex and challenging task. In this article, a new prediction method based on deep learning is proposed to identify enhancers and enhancer strength, called iEnhancer-DCLA. Firstly, we use word2vec to convert k-mers into number vectors to construct an input matrix. Secondly, we use convolutional neural network and bidirectional long short-term memory network to extract sequence features, and finally use the attention mechanism to extract relatively important features. In the task of predicting enhancers and their strengths, this method has improved to a certain extent in most evaluation indexes. In summary, we believe that this method provides new ideas in the analysis of enhancers.

Epigenetics of neural differentiation: Spotlight on enhancers

Neural induction, both in vivo and in vitro, includes cellular and molecular changes that result in phenotypic specialization related to specific transcriptional patterns. These changes are achieved through the implementation of complex gene regulatory networks. Furthermore, these regulatory networks are influenced by epigenetic mechanisms that drive cell heterogeneity and cell-type specificity, in a controlled and complex manner. Epigenetic marks, such as DNA methylation and histone residue modifications, are highly dynamic and stage-specific during neurogenesis. Genome-wide assessment of these modifications has allowed the identification of distinct non-coding regulatory regions involved in neural cell differentiation, maturation, and plasticity. Enhancers are short DNA regulatory regions that bind transcription factors (TFs) and interact with gene promoters to increase transcriptional activity. They are of special interest in neuroscience because they are enriched in neurons and underlie the cell-type-specificity and dynamic gene expression profiles. Classification of the full epigenomic landscape of neural subtypes is important to better understand gene regulation in brain health and during diseases. Advances in novel next-generation high-throughput sequencing technologies, genome editing, Genome-wide association studies (GWAS), stem cell differentiation, and brain organoids are allowing researchers to study brain development and neurodegenerative diseases with an unprecedented resolution. Herein, we describe important epigenetic mechanisms related to neurogenesis in mammals. We focus on the potential roles of neural enhancers in neurogenesis, cell-fate commitment, and neuronal plasticity. We review recent findings on epigenetic regulatory mechanisms involved in neurogenesis and discuss how sequence variations within enhancers may be associated with genetic risk for neurological and psychiatric disorders.

INTS13 variants causing a recessive developmental ciliopathy disrupt assembly of the Integrator complex

Oral-facial-digital (OFD) syndromes are a heterogeneous group of congenital disorders characterized by malformations of the face and oral cavity, and digit anomalies. Mutations within 12 cilia-related genes have been identified that cause several types of OFD, suggesting that OFDs constitute a subgroup of developmental ciliopathies. Through homozygosity mapping and exome sequencing of two families with variable OFD type 2, we identified distinct germline variants in INTS13, a subunit of the Integrator complex. This multiprotein complex associates with RNA Polymerase II and cleaves nascent RNA to modulate gene expression. We determined that INTS13 utilizes its C-terminus to bind the Integrator cleavage module, which is disrupted by the identified germline variants p.S652L and p.K668Nfs*9. Depletion of INTS13 disrupts ciliogenesis in human cultured cells and causes dysregulation of a broad collection of ciliary genes. Accordingly, its knockdown in Xenopus embryos leads to motile cilia anomalies. Altogether, we show that mutations in INTS13 cause an autosomal recessive ciliopathy, which reveals key interactions between components of the Integrator complex.

Transcriptional enhancers at 40: evolution of a viral DNA element to nuclear architectural structures

Gene regulation by transcriptional enhancers is the dominant mechanism driving cell type- and signal-specific transcriptional diversity in metazoans. However, over four decades since the original discovery, how enhancers operate in the nuclear space remains largely enigmatic. Recent multidisciplinary efforts combining real-time imaging, genome sequencing, and biophysical strategies provide insightful but conflicting models of enhancer-mediated gene control. Here, we review the discovery and progress in enhancer biology, emphasizing the recent findings that acutely activated enhancers assemble regulatory machinery as mesoscale architectural structures with distinct physical properties. These findings help formulate novel models that explain several mysterious features of the assembly of transcriptional enhancers and the mechanisms of spatial control of gene expression.

Enhancer RNA (eRNA) in Human Diseases

Enhancer RNAs (eRNAs), a class of non-coding RNAs (ncRNAs) transcribed from enhancer regions, serve as a type of critical regulatory element in gene expression. There is increasing evidence demonstrating that the aberrant expression of eRNAs can be broadly detected in various human diseases. Some studies also revealed the potential clinical utility of eRNAs in these diseases. In this review, we summarized the recent studies regarding the pathological mechanisms of eRNAs as well as their potential utility across human diseases, including cancers, neurodegenerative disorders, cardiovascular diseases and metabolic diseases. It could help us to understand how eRNAs are engaged in the processes of diseases and to obtain better insight of eRNAs in diagnosis, prognosis or therapy. The studies we reviewed here indicate the enormous therapeutic potency of eRNAs across human diseases.

BRAT1 links Integrator and defective RNA processing with neurodegeneration

Mutations in BRAT1, encoding BRCA1-associated ATM activator 1, have been associated with neurodevelopmental and neurodegenerative disorders characterized by heterogeneous phenotypes with varying levels of clinical severity. However, the underlying molecular mechanisms of disease pathology remain poorly understood. Here, we show that BRAT1 tightly interacts with INTS9/INTS11 subunits of the Integrator complex that processes 3' ends of various noncoding RNAs and pre-mRNAs. We find that Integrator functions are disrupted by BRAT1 deletion. In particular, defects in BRAT1 impede proper 3' end processing of UsnRNAs and snoRNAs, replication-dependent histone pre-mRNA processing, and alter the expression of protein-coding genes. Importantly, impairments in Integrator function are also evident in patient-derived cells from BRAT1 related neurological disease. Collectively, our data suggest that defects in BRAT1 interfere with proper Integrator functions, leading to incorrect expression of RNAs and proteins, resulting in neurodegeneration.

Enhancer RNAs step forward: new insights into enhancer function

Enhancers confer precise spatiotemporal patterns of gene expression in response to developmental and environmental stimuli. Over the last decade, the transcription of enhancer RNAs (eRNAs) – nascent RNAs transcribed from active enhancers – has emerged as a key factor regulating enhancer activity. eRNAs are relatively short-lived RNA species that are transcribed at very high rates but also quickly degraded. Nevertheless, eRNAs are deeply intertwined within enhancer regulatory networks and are implicated in a number of transcriptional control mechanisms. Enhancers show changes in function and sequence over evolutionary time, raising questions about the relationship between enhancer sequences and eRNA function. Moreover, the vast majority of single nucleotide polymorphisms associated with human complex diseases map to the non-coding genome, with causal disease variants enriched within enhancers. In this Primer, we survey the diverse roles played by eRNAs in enhancer-dependent gene expression, evaluating different models for eRNA function. We also explore questions surrounding the genetic conservation of enhancers and how this relates to eRNA function and dysfunction.

Summary: This Primer evaluates the ideas that underpin developing models for eRNA function, exploring cases in which perturbed eRNA function contributes to disease.

The pleiotropic roles of SPT5 in transcription

Initially discovered by genetic screens in budding yeast, SPT5 and its partner SPT4 form a stable complex known as DSIF in metazoa, which plays pleiotropic roles in multiple steps of transcription. SPT5 is the most conserved transcription elongation factor, being found in all three domains of life; however, its structure has evolved to include new domains and associated posttranslational modifications. These gained features have expanded transcriptional functions of SPT5, likely to meet the demand for increasingly complex regulation of transcription in higher organisms. This review discusses the pleiotropic roles of SPT5 in transcription, including RNA polymerase II (Pol II) stabilization, enhancer activation, Pol II pausing and its release, elongation, and termination, with a focus on the most recent progress of SPT5 functions in regulating metazoan transcription.

Prognostic Ability of Enhancer RNAs in Metastasis of Non-Small Cell Lung Cancer

(1) Background: Non-small cell lung cancer (NSCLC) is the most common lung cancer. Enhancer RNA (eRNA) has potential utility in the diagnosis, prognosis and treatment of cancer, but the role of eRNAs in NSCLC metastasis is not clear; (2) Methods: Differentially expressed transcription factors (DETFs), enhancer RNAs (DEEs), and target genes (DETGs) between primary NSCLC and metastatic NSCLC were identified. Prognostic DEEs (PDEEs) were screened by Cox regression analyses and a predicting model for metastatic NSCLC was constructed. We identified DEE interactions with DETFs, DETGs, reverse phase protein arrays (RPPA) protein chips, immunocytes, and pathways to construct a regulation network using Pearson correlation. Finally, the mechanisms and clinical significance were explained using multi-dimensional validation unambiguously; (3) Results: A total of 255 DEEs were identified, and 24 PDEEs were selected into the multivariate Cox regression model (AUC = 0.699). Additionally, the NSCLC metastasis-specific regulation network was constructed, and six key PDEEs were defined (ANXA8L1, CASTOR2, CYP4B1, GTF2H2C, PSMF1 and TNS4); (4) Conclusions: This study focused on the exploration of the prognostic value of eRNAs in the metastasis of NSCLC. Finally, six eRNAs were identified as potential markers for the prediction of metastasis of NSCLC.

Coming full circle: on the origin and evolution of the looping model for enhancer-promoter communication

In mammalian organisms, enhancers can regulate transcription from great genomic distances. How enhancers affect distal gene expression has been a major question in the field of gene regulation. One model to explain how enhancers communicate with their target promoters, the chromatin looping model, posits that enhancers and promoters come in close spatial proximity to mediate communication. Chromatin looping has been broadly accepted as a means for enhancer–promoter communication, driven by accumulating in vitro and in vivo evidence. The genome is now known to be folded into a complex 3D arrangement, created and maintained in part by the interplay of the Cohesin complex and the DNA-binding protein CTCF. In the last few years, however, doubt over the relationship between looping and transcriptional activation has emerged, driven by studies finding that only a modest number of genes are perturbed with acute degradation of looping machinery components. In parallel, newer models describing distal enhancer action have also come to prominence. In this article, we explore the emergence and development of the looping model as a means for enhancer–promoter communication and review the contrasting evidence between historical gene-specific and current global data for the role of chromatin looping in transcriptional regulation. We also discuss evidence for alternative models to chromatin looping and their support in the literature. We suggest that, while there is abundant evidence for chromatin looping as a major mechanism for enhancer function, enhancer–promoter communication is likely mediated by more than one mechanism in an enhancer- and context-dependent manner.

Pervasive transcription: a controlled risk

Transcriptome-wide interrogation of eukaryotic genomes has unveiled the pervasive nature of RNA polymerase II transcription. Virtually, any DNA region with an accessible chromatin structure can be transcribed, resulting in a mass production of noncoding RNAs (ncRNAs) with the potential of interfering with gene expression programs. Budding yeast has proved to be a powerful model organism to understand the mechanisms at play to control pervasive transcription and overcome the risks of hazardous disruption of cellular functions. In this review, we focus on the actors and strategies yeasts employ to govern ncRNA production, and we discuss recent findings highlighting the dangers of losing control over pervasive transcription.