Core promoters in transcription: old problem, new insights

Exploring the Use of Alternative Promoters for Enhanced Transgene and sgRNA Expression in Atlantic Salmon Cells

This study facilitates design of expression vectors and lentivirus tools for gene editing of Atlantic salmon. We have characterized widely used heterologous promoters and novel endogenous promoters in Atlantic salmon cells. We used qPCR to evaluate the activity of several U6 promoters for sgRNA expression, including human U6 (hU6), tilapia U6 (tU6), mouse U6 (mU6), zebrafish U6 (zU6), Atlantic salmon U6 (sU6), medaka U6 (medU6), and fugu U6 (fU6) promoters. We also evaluated several polymerase type II (pol II) promoters by luciferase assay. Our results showed that hU6 and tU6 promoters were the most active among all the tested U6 promoters, and heterologous promoters (CMV, hEF1α core) had higher activity compared to endogenous Atlantic salmon promoters sHSP8, sNUC3L, sEF1α. Among endogenous pol II promoters, sEF1α and sHSP8 displayed higher activity than sNUC3L, sHSP703, sHSP7C, sXRCC1L, and sETF. We observed that extending the promoter sequence to include the region up to the start codon (ATG) resulted in a significant increase in expression efficiency for sNUC3L and sEF1α. We also show that mutating the PRDM1 motif will significantly decrease the activity of the sEF1α promoter. The presence of the PRDM1 motif in sHSP8 promoter was also associated with relatively high expression compared to the promoters that naturally lacked this motif, such as sNUC3L. We speculate that this short sequence might be included in other promoters to further enhance the promoter activity, but further experiments are needed to confirm this. Our findings provide valuable insights into the activity of different promoters in Atlantic salmon cells and can be used to facilitate further transgenic studies and improve the efficiency of transgene expression in Atlantic salmon.

The general transcription factors (GTFs) of RNA polymerase II and their roles in plant development and stress responses

In eukaryotes, general transcription factors (GTFs) enable recruitment of RNA polymerase II (RNA Pol II) to core promoters to facilitate initiation of transcription. Extensive research in mammals and yeast has unveiled their significance in basal transcription as well as in diverse biological processes. Unlike mammals and yeast, plant GTFs exhibit remarkable degree of variability and flexibility. This is because plant GTFs and GTF subunits are often encoded by multigene families, introducing complexity to transcriptional regulation at both cellular and biological levels. This review provides insights into the general transcription mechanism, GTF composition, and their cellular functions. It further highlights the involvement of RNA Pol II-related GTFs in plant development and stress responses. Studies reveal that GTFs act as important regulators of gene expression in specific developmental processes and help equip plants with resilience against adverse environmental conditions. Their functions may be direct or mediated through their cofactor nature. The versatility of GTFs in controlling gene expression, and thereby influencing specific traits, adds to the intricate complexity inherent in the plant system.

FOXO3/Rab7-Mediated Lipophagy and Its Role in Zn-Induced Lipid Metabolism in Yellow Catfish (Pelteobagrus fulvidraco)

Lipophagy is a selective autophagy that regulates lipid metabolism and reduces hepatic lipid deposition. However, the underlying mechanism has not been understood in fish. In this study, we used micronutrient zinc (Zn) as a regulator of autophagy and lipid metabolism and found that Ras-related protein 7 (rab7) was involved in Zn-induced lipophagy in hepatocytes of yellow catfish Pelteobagrus pelteobagrus. We then characterized the rab7 promoter and identified binding sites for a series of transcription factors, including Forkhead box O3 (FOXO3). Site mutation experiments showed that the -1358/-1369 bp FOXO3 binding site was responsible for Zn-induced transcriptional activation of rab7. Further studies showed that inhibition of rab7 significantly inhibited Zn-induced lipid degradation by lipophagy. Moreover, rab7 inhibitor also mitigated the Zn-induced increase of cpt1α and acadm expression. Our results suggested that Zn exerts its lipid-lowering effect partly through rab7-mediated lipophagy and FA β-oxidation in hepatocytes. Overall, our findings provide novel insights into the FOXO3/rab7 axis in lipophagy regulation and enhance the understanding of lipid metabolism by micronutrient Zn, which may help to reduce excessive lipid accumulation in fish.

New insights into molecular features of the genome-wide AOX family and their responses to various stresses in common wheat (Triticum aestivum L.)

Alternative oxidase (AOX) is an important terminal oxidase involved in the alternative oxidation pathway in plants, which is closely related to various biotic and abiotic stress responses. However, a comprehensive research on AOX gene family of wheat is still lacking. In this study, the members of wheat AOX (TaAOX) family were identified, and their molecular characteristics and gene expression patterns were systematically investigated. Seventeen TaAOX genes were identified from Chinese Spring (CS) genome, which were mapped on 7 chromosomes and mainly clustered on the long arm's distal end of the second homologous groups. Phylogenetic analysis showed that TaAOX genes were classified into four subgroups (Ia, Ib, Ic, and Id), and the Ia subgroup possessed the most members. Tandem duplication and segmental duplication events were found during the evolution of TaAOX genes and they were affected by purifying selection demonstrated by Ka/Ks analysis. The exon numbers of this family gene varied greatly from 1 to 9. Except for Ta3BSAOX14, all the proteins encoded by the other 16 TaAOX genes contained the amino acid residues of the key active sites in the AOX domain (cd01053). The expression patterns of TaAOX genes in various tissues and under abiotic and biotic stresses were analyzed using public transcriptome data, furthermore, qRT-PCR analysis was performed for some selected TaAOX genes, and the results suggested that most members of this gene family play an important role in response to different stresses in common wheat. Our results provide basic information and valuable reference for further exploring the gene function of TaAOX family by using gene editing, RNAi, VIGS, and other technologies.

Mechanisms regulating heterogeneity of hemostatic gene expression in endothelial cells

The hemostatic system involves an array of circulating coagulation factors that work in concert with platelets and the vascular endothelium to promote clotting in a space- and time-defined manner. Despite equal systemic exposure to circulating factors, bleeding and thrombotic diseases tend to prefer specific sites, suggesting an important role for local factors. This may be provided by endothelial heterogeneity. Endothelial cells differ not only between arteries, veins, and capillaries but also between microvascular beds from different organs, which present unique organotypic morphology and functional and molecular profiles. Accordingly, regulators of hemostasis are not uniformly distributed in the vasculature. The establishment and maintenance of endothelial diversity are orchestrated at the transcriptional level. Recent transcriptomic and epigenomic studies have provided a global picture of endothelial cell heterogeneity. In this review, we discuss the organotypic differences in the hemostatic profile of endothelial cells; we focus on 2 major endothelial regulators of hemostasis, namely von Willebrand factor and thrombomodulin, to provide examples of transcriptional mechanisms that control heterogeneity; finally, we consider some of the methodological challenges and opportunities for future studies.

Using Synthetic DNA Libraries to Investigate Chromatin and Gene Regulation

Despite the recent explosion in genome-wide studies in chromatin and gene regulation, we are still far from extracting a set of genetic rules that can predict the function of the regulatory genome. One major reason for this deficiency is that gene regulation is a multi-layered process that involves an enormous variable space, which cannot be fully explored using native genomes. This problem can be partially solved by introducing synthetic DNA libraries into cells, a method that can test the regulatory roles of thousands to millions of sequences with limited variables. Here, we review recent applications of this method to study transcription factor (TF) binding, nucleosome positioning, and transcriptional activity. We discuss the design principles, experimental procedures, and major findings from these studies and compare the pros and cons of different approaches.

Promoter editing for the genetic improvement of crops

Gene expression plays a fundamental role in the regulation of agronomically important traits in crop plants. The genetic manipulation of plant promoters through genome editing has emerged as an effective strategy to create favorable traits in crops by altering the expression pattern of the pertinent genes. Promoter editing can be applied in a directed manner, where nucleotide sequences associated with favorable traits are precisely generated. Alternatively, promoter editing can also be exploited as a random mutagenic approach to generate novel genetic variations within a designated promoter, from which elite alleles are selected based on their phenotypic effects. Pioneering studies have demonstrated the potential of promoter editing in engineering agronomically important traits as well as in mining novel promoter alleles valuable for plant breeding. In this review, we provide an update on the application of promoter editing in crops for increased yield, enhanced tolerance to biotic and abiotic stresses, and improved quality. We also discuss several remaining technical bottlenecks and how this strategy may be better employed for the genetic improvement of crops in the future.

The minimal intrinsic stochasticity of constitutively expressed eukaryotic genes is sub-Poissonian

Gene expression inherently gives rise to stochastic variation ("noise") in the production of gene products. Minimizing noise is crucial for ensuring reliable cellular functions. However, noise cannot be suppressed below a certain intrinsic limit. For constitutively expressed genes, this limit is typically assumed to be Poissonian noise, wherein the variance in mRNA numbers is equal to their mean. Here, we demonstrate that several cell division genes in fission yeast exhibit mRNA variances significantly below this limit. The reduced variance can be explained by a gene expression model incorporating multiple transcription and mRNA degradation steps. Notably, in this sub-Poissonian regime, distinct from Poissonian or super-Poissonian regimes, cytoplasmic noise is effectively suppressed through a higher mRNA export rate. Our findings redefine the lower limit of eukaryotic gene expression noise and uncover molecular requirements for achieving ultralow noise, which is expected to be important for vital cellular functions.

Genome-Wide Analysis of Proline-Rich Extensin-Like Receptor Kinases (PERKs) Gene Family Reveals Their Roles in Plant Development and Stress Conditions in Oryza sativa L

Proline-rich extensin-like receptor kinases (PERKs) play a crucial role in a wide range of biological processes in plants. In model plants like Arabidopsis, the PERK gene family has been well investigated. Conversely, no information available on the PERK gene family and their biological functions largely remained unknown in rice. This study analyzed the basic physicochemical properties, phylogeny, gene structure, cis-acting elements, Gene ontology (GO) annotation and protein-protein interaction of OsPERK gene family members using various bioinformatics tools based on the whole-genome data of O. sativa. Thus, in this work, 8 PERK genes in rice were identified, and their roles in plant development, growth, and response to various stresses were studied. A phylogenetic study revealed that OsPERKs are grouped into seven classes. Chromosomal mapping also displayed that 8 PERK genes were unevenly distributed on 12 chromosomes. Further, the prediction of subcellular localization indicated that OsPERKs were mainly located at the endomembrane system. Gene structure analysis of OsPERKs has shown a distinctive evolutionary path. In addition, synteny analysis exhibited the 40 orthologous gene pairs in Arabidopsis thaliana, Triticum aestivum, Hordeum vulgare and Medicago truncatula. Furthermore, Ka to Ks proportion shows that most OsPERK genes experienced resilient purifying selection during evolutionary processes. The OsPERK promoters contained several cis-acting regulatory, which are crucial for plant development processes, phytohormone signaling, stress, and defense response. Moreover, the expression pattern of OsPERK family members showed differential expression patterns in different tissues and various stress conditions. Taken together, these results provide clear messages for a better understanding the roles of OsPERK genes in various development stages, tissues, and multifactorial stress as well as enriched the related research of OsPERK family members in rice.

On the Role of TATA Boxes and TATA-Binding Protein in Arabidopsis thaliana

For transcription initiation by RNA polymerase II (Pol II), all eukaryotes require assembly of basal transcription machinery on the core promoter, a region located approximately in the locus spanning a transcription start site (-50; +50 bp). Although Pol II is a complex multi-subunit enzyme conserved among all eukaryotes, it cannot initiate transcription without the participation of many other proteins. Transcription initiation on TATA-containing promoters requires the assembly of the preinitiation complex; this process is triggered by an interaction of TATA-binding protein (TBP, a component of the general transcription factor TFIID (transcription factor II D)) with a TATA box. The interaction of TBP with various TATA boxes in plants, in particular Arabidopsis thaliana, has hardly been investigated, except for a few early studies that addressed the role of a TATA box and substitutions in it in plant transcription systems. This is despite the fact that the interaction of TBP with TATA boxes and their variants can be used to regulate transcription. In this review, we examine the roles of some general transcription factors in the assembly of the basal transcription complex, as well as functions of TATA boxes of the model plant A. thaliana. We review examples showing not only the involvement of TATA boxes in the initiation of transcription machinery assembly but also their indirect participation in plant adaptation to environmental conditions in responses to light and other phenomena. Examples of an influence of the expression levels of A. thaliana TBP1 and TBP2 on morphological traits of the plants are also examined. We summarize available functional data on these two early players that trigger the assembly of transcription machinery. This information will deepen the understanding of the mechanisms underlying transcription by Pol II in plants and will help to utilize the functions of the interaction of TBP with TATA boxes in practice.

Transcriptome-based Mining of the Constitutive Promoters for Tuning Gene Expression in Aspergillus oryzae

Transcriptional regulation has been adopted for developing metabolic engineering tools. The regulatory promoter is a crucial genetic element for strain optimization. In this study, a gene set of Aspergillus oryzae with highly constitutive expression across different growth stages was identified through transcriptome data analysis. The candidate promoters were functionally characterized in A. oryzae by transcriptional control of β-glucuronidase (GUS) as a reporter. The results showed that the glyceraldehyde triphosphate dehydrogenase promoter (PgpdA1) of A. oryzae with a unique structure displayed the most robust strength in constitutively controlling the expression compared to the PgpdA2 and other putative promoters tested. In addition, the ubiquitin promoter (Pubi) of A. oryzae exhibited a moderate expression strength. The deletion analysis revealed that the 5' untranslated regions of gpdA1 and ubi with the length of 1028 and 811 nucleotides, counted from the putative translation start site (ATG), respectively, could efficiently drive the GUS expression. Interestingly, both promoters could function on various carbon sources for cell growth. Glucose was the best fermentable carbon source for allocating high constitutive expressions during cell growth, and the high concentrations (6-8% glucose, w/v) did not repress their functions. It was also demonstrated that the secondary metabolite gene coding for indigoidine could express under the control of PgpdA1 or Pubi promoter. These strong and moderate promoters of A. oryzae provided beneficial options in tuning the transcriptional expression for leveraging the metabolic control towards the targeted products.

DeePromClass: Delineator for Eukaryotic Core Promoters Employing Deep Neural Networks

Computational promoter identification in eukaryotes is a classical biological problem that should be refurbished with the availability of an avalanche of experimental data and emerging deep learning technologies. The current knowledge indicates that eukaryotic core promoters display multifarious signals such as TATA-Box, Inr element, TCT, and Pause-button, etc., and structural motifs such as G-quadruplexes. In the present study, we combined the power of deep learning with a plethora of promoter motifs to delineate promoter and non-promoters gleaned from the statistical properties of DNA sequence arrangement. To this end, we implemented convolutional neural network (CNN) and long short-term memory (LSTM) recurrent neural network architecture for five model systems with [-100 to +50] segments relative to the transcription start site being the core promoter. Unlike previous state-of-the-art tools, which furnish a binary decision of promoter or non-promoter, we classify a chunk of 151mer sequence into a promoter along with the consensus signal type or a non-promoter. The combined CNN-LSTM model; we call "DeePromClass", achieved testing accuracy of 90.6%, 93.6%, 91.8%, 86.5%, and 84.0% for S. cerevisiae, C. elegans, D. melanogaster, Mus musculus, and Homo sapiens respectively. In total, our tool provides an insightful update on next-generation promoter prediction tools for promoter biologists.

Genome-Wide Identification and Expression Profiling of Aconitase Gene Family Members Reveals Their Roles in Plant Development and Adaptation to Diverse Stress in Triticum aestivum L

Global warming is a serious threat to food security and severely affects plant growth, developmental processes, and, eventually, crop productivity. Respiratory metabolism plays a critical role in the adaptation of diverse stress in plants. Aconitase (ACO) is the main enzyme, which catalyzes the revocable isomerization of citrate to isocitrate in the Krebs cycle. The function of ACO gene family members has been extensively studied in model plants, for instance Arabidopsis. However, their role in plant developmental processes and various stress conditions largely remained unknown in other plant species. Thus, we identified 15 ACO genes in wheat to elucidate their function in plant developmental processes and different stress environments. The phylogenetic tree revealed that TaACO genes were classified into six groups. Further, gene structure analysis of TaACOs has shown a distinctive evolutionary path. Synteny analysis showed the 84 orthologous gene pairs in Brachypodium distachyon, Aegilops tauschii, Triticum dicoccoides, Oryza sativa, and Arabidopsis thaliana. Furthermore, Ka/Ks ratio revealed that most TaACO genes experienced strong purifying selection during evolution. Numerous cis-acting regulatory elements were detected in the TaACO promoters, which play a crucial role in plant development processes, phytohormone signaling, and are related to defense and stress. To understand the function of TaACO genes, the expression profiling of TaACO genes were investigated in different tissues, developmental stages, and stress conditions. The transcript per million values of TaACOs genes were retrieved from the Wheat Expression Browser Database. We noticed the differential expression of the TaACO genes in different tissues and various stress conditions. Moreover, gene ontology analysis has shown enrichment in the tricarboxylic acid metabolic process (GO:0072350), citrate metabolic process (GO:0006101), isocitrate metabolic process GO:0006102, carbohydrate metabolic (GO:0005975), and glyoxylate metabolic process (GO:0046487). Therefore, this study provided valuable insight into the ACO gene family in wheat and contributed to the further functional characterization of TaACO during different plant development processes and various stress conditions.

Molecular characterization of the genome-wide BOR transporter family and their responses to boron conditions in common wheat (Triticum aestivum L.)

Boron (B) deficiency is an agricultural problem that causes significant yield losses in many countries. B transporters (BORs) are responsible for B uptake and distribution and play important roles in yield formation. A comprehensive analysis of the BOR family members in common wheat is still lacking. In the present study, to clarify the molecular characterization and response to B status, genome-wide TaBOR genes and expression patterns were investigated. Fourteen TaBOR genes were identified in common wheat by a homology search. The corresponding phylogenetic tree indicated that 14 TaBOR genes were separately classified into subfamilies of TaBOR1, TaBOR3, and TaBOR4. All TaBOR genes had 12-14 extrons and 11-13 introns. Most TaBOR proteins contained 10 conserved motifs, and motifs 1, 2, 3, 4, and 6 constituted the conserved bicarbonate (HCO₃ ^-) domain. Fourteen TaBOR genes were mapped on 13 chromosomes mainly distributed in the first, third, fifth, and seventh homologous groups. The promoters of TaBOR genes consisted of phytohormones, light responses, and stress-related cis-elements. GO analysis indicated that TaBOR genes were enriched in terms of transmembrane transport and ion homeostasis. TaBOR genes showed diverse expression profiles in different tissues. The members of the TaBOR1 subfamily showed high expression in grains, leaves, roots, stems, and spikes, but members of the TaBOR4 subfamily were highly expressed only in spikes and grains. RT-qPCR indicated that TaBOR1-5A, TaBOR1-5B, and TaBOR1-5D were induced by low B concentrations and had much higher expression in roots than in shoots. TaBOR3-3A, TaBOR3-3B, TaBOR3-3D, TaBOR4-1A, TaBOR4-1B, TaBOR4-1D, and TaBOR3-4B were induced by low and high B concentrations and had high expression in roots and shoots. TaBOR3-4D and TaBOR3-7B were upregulated by low and high B concentrations, respectively, but had expression only in roots. Our results provide basic information on the TaBOR family, which is beneficial for elucidating the functions of TaBOR genes to overcome the problem of B deficiency.

Structural and Functional Analysis of SHP Promoter and Its Transcriptional Response to FXR in Zn-Induced Changes to Lipid Metabolism

Zinc alleviates hepatic lipid deposition, but the transcriptional regulatory mechanisms are still unclear. In this study, we characterized the promoter of an SHP (short heterodimer partner) in a teleost Pelteobagrus fulvidraco. The binding sites of an FXR (farnesoid X receptor) were predicted by the SHP promoter, indicating that the FXR mediated its transcriptional activity. The site mutagenesis and the EMSA (electrophoretic mobility shift assay) found that the -375/-384 bp FXR site on the SHP promoter was the functional binding locus responsible for the Zn-induced transcriptional activation. A further study of yellow catfish hepatocytes suggested that the activation of the FXR/SHP is responsible for the effect of Zn on the decreasing lipid content. Thus, this study provides direct evidence of the interaction between the FXR and SHP promoter in fish, and accordingly elucidates the potential transcriptional mechanism by which Zn reduces hepatic lipid accumulation.

Robust and tunable signal processing in mammalian cells via engineered covalent modification cycles

Engineered signaling networks can impart cells with new functionalities useful for directing differentiation and actuating cellular therapies. For such applications, the engineered networks must be tunable, precisely regulate target gene expression, and be robust to perturbations within the complex context of mammalian cells. Here, we use bacterial two-component signaling proteins to develop synthetic phosphoregulation devices that exhibit these properties in mammalian cells. First, we engineer a synthetic covalent modification cycle based on kinase and phosphatase proteins derived from the bifunctional histidine kinase EnvZ, enabling analog tuning of gene expression via its response regulator OmpR. By regulating phosphatase expression with endogenous miRNAs, we demonstrate cell-type specific signaling responses and a new strategy for accurate cell type classification. Finally, we implement a tunable negative feedback controller via a small molecule-stabilized phosphatase, reducing output expression variance and mitigating the context-dependent effects of off-target regulation and resource competition. Our work lays the foundation for establishing tunable, precise, and robust control over cell behavior with synthetic signaling networks.

Delineation of the DNA Structural Features of Eukaryotic Core Promoter Classes

The eukaryotic transcription is orchestrated from a chunk of the DNA region stated as the core promoter. Multifarious and punctilious core promoter signals, viz., TATA-box, Inr, BREs, and Pause Button, are associated with a subset of genes and regulate their spatiotemporal expression. However, the core promoter architecture linked with these signals has not been investigated exhaustively for several species. In this study, we attempted to envisage the adaptive binding landscape of the transcription initiation machinery as a function of DNA structure. To this end, we deployed a set of k-mer based DNA structural estimates and regular expression models derived from experiments, molecular dynamic simulations, and theoretical frameworks, and high-throughout promoter data sets retrieved from the eukaryotic promoter database. We categorized protein-coding gene core promoters based on characteristic motifs at precise locations and analyzed the B-DNA structural properties and non-B-DNA structural motifs for 15 different eukaryotic genomes. We observed that Inr, BREd, and no-motif classes display common patterns of DNA sequence and structural environment. TATA-containing, BREu, and Pause Button classes show a deviant behavior with the TATA class displaying varied axial and twisting flexibility while BREu and Pause Button leaned toward G-quadruplex motif enrichment. Intriguingly, DNA meltability and shape signals are conserved irrespective of the presence or absence of distinct core promoter motifs in the majority of species. Altogether, here we delineated the conserved DNA structural signals associated with several promoter classes that may contribute to the chromatin configuration, orchestration of transcription machinery, and DNA duplex melting during the transcription process.

Genome-Wide Analysis and Characterization of the Proline-Rich Extensin-like Receptor Kinases (PERKs) Gene Family Reveals Their Role in Different Developmental Stages and Stress Conditions in Wheat (Triticum aestivum L.)

Proline-rich extensin-like receptor kinases (PERKs) are a class of receptor kinases implicated in multiple cellular processes in plants. However, there is a lack of information on the PERK gene family in wheat. Therefore, we identified 37 PERK genes in wheat to understand their role in various developmental processes and stress conditions. Phylogenetic analysis of PERK genes from Arabidopsis thaliana, Oryza sativa, Glycine max, and T. aestivum grouped them into eight well-defined classes. Furthermore, synteny analysis revealed 275 orthologous gene pairs in B. distachyon, Ae. tauschii, T. dicoccoides, O. sativa and A. thaliana. Ka/Ks values showed that most TaPERK genes, except TaPERK1, TaPERK2, TaPERK17, and TaPERK26, underwent strong purifying selection during evolutionary processes. Several cis-acting regulatory elements, essential for plant growth and development and the response to light, phytohormones, and diverse biotic and abiotic stresses, were predicted in the promoter regions of TaPERK genes. In addition, the expression profile of the TaPERK gene family revealed differential expression of TaPERK genes in various tissues and developmental stages. Furthermore, TaPERK gene expression was induced by various biotic and abiotic stresses. The RT-qPCR analysis also revealed similar results with slight variation. Therefore, this study's outcome provides valuable information for elucidating the precise functions of TaPERK in developmental processes and diverse stress conditions in wheat.

Genome-Wide Prediction of Transcription Start Sites in Conifers

The identification of promoters is an essential step in the genome annotation process, providing a framework for gene regulatory networks and their role in transcription regulation. Despite considerable advances in the high-throughput determination of transcription start sites (TSSs) and transcription factor binding sites (TFBSs), experimental methods are still time-consuming and expensive. Instead, several computational approaches have been developed to provide fast and reliable means for predicting the location of TSSs and regulatory motifs on a genome-wide scale. Numerous studies have been carried out on the regulatory elements of mammalian genomes, but plant promoters, especially in gymnosperms, have been left out of the limelight and, therefore, have been poorly investigated. The aim of this study was to enhance and expand the existing genome annotations using computational approaches for genome-wide prediction of TSSs in the four conifer species: loblolly pine, white spruce, Norway spruce, and Siberian larch. Our pipeline will be useful for TSS predictions in other genomes, especially for draft assemblies, where reliable TSS predictions are not usually available. We also explored some of the features of the nucleotide composition of the predicted promoters and compared the GC properties of conifer genes with model monocot and dicot plants. Here, we demonstrate that even incomplete genome assemblies and partial annotations can be a reliable starting point for TSS annotation. The results of the TSS prediction in four conifer species have been deposited in the Persephone genome browser, which allows smooth visualization and is optimized for large data sets. This work provides the initial basis for future experimental validation and the study of the regulatory regions to understand gene regulation in gymnosperms.

Genomic environments scale the activities of diverse core promoters

A classical model of gene regulation is that enhancers provide specificity whereas core promoters provide a modular site for the assembly of the basal transcriptional machinery. However, examples of core promoter specificity have led to an alternate hypothesis in which specificity is achieved by core promoters with different sequence motifs that respond differently to genomic environments containing different enhancers and chromatin landscapes. To distinguish between these models, we measured the activities of hundreds of diverse core promoters in four different genomic locations and, in a complementary experiment, six different core promoters at thousands of locations across the genome. Although genomic locations had large effects on expression, the intrinsic activities of different classes of promoters were preserved across genomic locations, suggesting that core promoters are modular regulatory elements whose activities are independently scaled up or down by different genomic locations. This scaling of promoter activities is nonlinear and depends on the genomic location and the strength of the core promoter. Our results support the classical model of regulation in which diverse core promoter motifs set the intrinsic strengths of core promoters, which are then amplified or dampened by the activities of their genomic environments.

TSSFinder-fast and accurate ab initio prediction of the core promoter in eukaryotic genomes

Promoter annotation is an important task in the analysis of a genome. One of the main challenges for this task is locating the border between the promoter region and the transcribing region of the gene, the transcription start site (TSS). The TSS is the reference point to delimit the DNA sequence responsible for the assembly of the transcribing complex. As the same gene can have more than one TSS, so to delimit the promoter region, it is important to locate the closest TSS to the site of the beginning of the translation. This paper presents TSSFinder, a new software for the prediction of the TSS signal of eukaryotic genes that is significantly more accurate than other available software. We currently are the only application to offer pre-trained models for six different eukaryotic organisms: Arabidopsis thaliana, Drosophila melanogaster, Gallus gallus, Homo sapiens, Oryza sativa and Saccharomyces cerevisiae. Additionally, our software can be easily customized for specific organisms using only 125 DNA sequences with a validated TSS signal and corresponding genomic locations as a training set. TSSFinder is a valuable new tool for the annotation of genomes. TSSFinder source code and docker container can be downloaded from http://tssfinder.github.io. Alternatively, TSSFinder is also available as a web service at http://sucest-fun.org/wsapp/tssfinder/.

Expression of Two Rye CENH3 Variants and Their Loading into Centromeres

Gene duplication and the preservation of both copies during evolution is an intriguing evolutionary phenomenon. Their preservation is related to the function they perform. The central component of centromere specification and function is the centromere-specific histone H3 (CENH3). Some cereal species (maize, rice) have one copy of the gene encoding this protein, while some (wheat, barley, rye) have two. Therefore, they represent a good model for a comparative study of the functional activity of the duplicated CENH3 genes and their protein products. We determined the organization of the CENH3 locus in rye (Secale cereale L.) and identified the functional motifs in the vicinity of the CENH3 genes. We compared the expression of these genes at different stages of plant development and the loading of their products, the CENH3 proteins, into nucleosomes during mitosis and meiosis. Using extended chromatin fibers, we revealed patterns of loading CENH3 proteinsinto polynucleosomal domains in centromeric chromatin. Our results indicate no sign of neofunctionalization, subfunctionalization or specialization in the gene copies. The influence of negative selection on the coding part of the genes led them to preserve their conserved function. The advantage of having two functional genes appears as the gene-dosage effect.

The Core Promoter Is a Regulatory Hub for Developmental Gene Expression

The development of multicellular organisms and the uniqueness of each cell are achieved by distinct transcriptional programs. Multiple processes that regulate gene expression converge at the core promoter region, an 80 bp region that directs accurate transcription initiation by RNA polymerase II (Pol II). In recent years, it has become apparent that the core promoter region is not a passive DNA component, but rather an active regulatory module of transcriptional programs. Distinct core promoter compositions were demonstrated to result in different transcriptional outputs. In this mini-review, we focus on the role of the core promoter, particularly its downstream region, as the regulatory hub for developmental genes. The downstream core promoter element (DPE) was implicated in the control of evolutionarily conserved developmental gene regulatory networks (GRNs) governing body plan in both the anterior-posterior and dorsal-ventral axes. Notably, the composition of the basal transcription machinery is not universal, but rather promoter-dependent, highlighting the importance of specialized transcription complexes and their core promoter target sequences as key hubs that drive embryonic development, differentiation and morphogenesis across metazoan species. The extent of transcriptional activation by a specific enhancer is dependent on its compatibility with the relevant core promoter. The core promoter content also regulates transcription burst size. Overall, while for many years it was thought that the specificity of gene expression is primarily determined by enhancers, it is now clear that the core promoter region comprises an important regulatory module in the intricate networks of developmental gene expression.

ReFeaFi: Genome-wide prediction of regulatory elements driving transcription initiation

Regulatory elements control gene expression through transcription initiation (promoters) and by enhancing transcription at distant regions (enhancers). Accurate identification of regulatory elements is fundamental for annotating genomes and understanding gene expression patterns. While there are many attempts to develop computational promoter and enhancer identification methods, reliable tools to analyze long genomic sequences are still lacking. Prediction methods often perform poorly on the genome-wide scale because the number of negatives is much higher than that in the training sets. To address this issue, we propose a dynamic negative set updating scheme with a two-model approach, using one model for scanning the genome and the other one for testing candidate positions. The developed method achieves good genome-level performance and maintains robust performance when applied to other vertebrate species, without re-training. Moreover, the unannotated predicted regulatory regions made on the human genome are enriched for disease-associated variants, suggesting them to be potentially true regulatory elements rather than false positives. We validated high scoring "false positive" predictions using reporter assay and all tested candidates were successfully validated, demonstrating the ability of our method to discover novel human regulatory regions.

Genome-Wide Identification and Characterization of the Brassinazole-resistant (BZR) Gene Family and Its Expression in the Various Developmental Stage and Stress Conditions in Wheat (Triticum aestivum L.)

Brassinosteroids (BRs) play crucial roles in various biological processes, including plant developmental processes and response to diverse biotic and abiotic stresses. However, no information is currently available about this gene family in wheat (Triticum aestivum L.). In the present investigation, we identified the BZR gene family in wheat to understand the evolution and their role in diverse developmental processes and under different stress conditions. In this study, we performed the genome-wide analysis of the BZR gene family in the bread wheat and identified 20 TaBZR genes through a homology search and further characterized them to understand their structure, function, and distribution across various tissues. Phylogenetic analyses lead to the classification of TaBZR genes into five different groups or subfamilies, providing evidence of evolutionary relationship with Arabidopsis thaliana, Zea mays, Glycine max, and Oryza sativa. A gene exon/intron structure analysis showed a distinct evolutionary path and predicted the possible gene duplication events. Further, the physical and biochemical properties, conserved motifs, chromosomal, subcellular localization, and cis-acting regulatory elements were also examined using various computational approaches. In addition, an analysis of public RNA-seq data also shows that TaBZR genes may be involved in diverse developmental processes and stress tolerance mechanisms. Moreover, qRT-PCR results also showed similar expression with slight variation. Collectively, these results suggest that TaBZR genes might play an important role in plant developmental processes and various stress conditions. Therefore, this work provides valuable information for further elucidate the precise role of BZR family members in wheat.

Genome-Wide Identification and Characterization of PIN-FORMED (PIN) Gene Family Reveals Role in Developmental and Various Stress Conditions in Triticum aestivum L

PIN-FORMED (PIN) genes play a crucial role in regulating polar auxin distribution in diverse developmental processes, including tropic responses, embryogenesis, tissue differentiation, and organogenesis. However, the role of PIN-mediated auxin transport in various plant species is poorly understood. Currently, no information is available about this gene family in wheat (Triticum aestivum L.). In the present investigation, we identified the PIN gene family in wheat to understand the evolution of PIN-mediated auxin transport and its role in various developmental processes and under different biotic and abiotic stress conditions. In this study, we performed genome-wide analysis of the PIN gene family in common wheat and identified 44 TaPIN genes through a homology search, further characterizing them to understand their structure, function, and distribution across various tissues. Phylogenetic analyses led to the classification of TaPIN genes into seven different groups, providing evidence of an evolutionary relationship with Arabidopsis thaliana and Oryza sativa. A gene exon/intron structure analysis showed a distinct evolutionary path and predicted the possible gene duplication events. Further, the physical and biochemical properties, conserved motifs, chromosomal, subcellular localization, transmembrane domains, and three-dimensional (3D) structure were also examined using various computational approaches. Cis-elements analysis of TaPIN genes showed that TaPIN promoters consist of phytohormone, plant growth and development, and stress-related cis-elements. In addition, expression profile analysis also revealed that the expression patterns of the TaPIN genes were different in different tissues and developmental stages. Several members of the TaPIN family were induced during biotic and abiotic stress. Moreover, the expression patterns of TaPIN genes were verified by qRT-PCR. The qRT-PCR results also show a similar expression with slight variation. Therefore, the outcome of this study provides basic genomic information on the expression of the TaPIN gene family and will pave the way for dissecting the precise role of TaPINs in plant developmental processes and different stress conditions.

Functional Diversification, Redundancy, and Epistasis among Paralogs of the Drosophila melanogaster Obp50a-d Gene Cluster

Large multigene families, such as the insect odorant-binding proteins (OBPs), are thought to arise through functional diversification after repeated gene duplications. Whereas many OBPs function in chemoreception, members of this family are also expressed in tissues outside chemosensory organs. Paralogs of the Obp50 gene cluster are expressed in metabolic and male reproductive tissues, but their functions and interrelationships remain unknown. Here, we report the genetic dissection of four members of the Obp50 cluster, which are in close physical proximity without intervening genes. We used CRISPR technology to excise the entire cluster while introducing a PhiC31 reintegration site to reinsert constructs in which different combinations of the constituent Obp genes were either intact or rendered inactive. We performed whole transcriptome sequencing and assessed sexually dimorphic changes in transcript abundances (transcriptional niches) associated with each gene-edited genotype. Using this approach, we were able to estimate redundancy, additivity, diversification, and epistasis among Obp50 paralogs. We analyzed the effects of gene editing of this cluster on organismal phenotypes and found a significant skewing of sex ratios attributable to Obp50a, and sex-specific effects on starvation stress resistance attributable to Obp50d. Thus, there is functional diversification within the Obp50 cluster with Obp50a contributing to development and Obp50d to stress resistance. The deletion-reinsertion approach we applied to the Obp50 cluster provides a general paradigm for the genetic dissection of paralogs of multigene families.

Evolution of Diverse Strategies for Promoter Regulation

DNA is fundamentally important for all cellular organisms due to its role as a store of hereditary genetic information. The precise and accurate regulation of gene transcription depends primarily on promoters, which vary significantly within and between genomes. Some promoters are rich in specific types of bases, while others have more varied, complex sequence characteristics. However, it is not only base sequence but also epigenetic modifications and altered DNA structure that regulate promoter activity. Significantly, many promoters across all organisms contain sequences that can form intrastrand hairpins (cruciforms) or four-stranded structures (G-quadruplex or i-motif). In this review we integrate recent studies on promoter regulation that highlight the importance of DNA structure in the evolutionary adaptation of promoter sequences.

Investigation of the Wilson gene ATP7B transcriptional start site and the effect of core promoter alterations

Pathogenic genetic variants in the ATP7B gene cause Wilson disease, a recessive disorder of copper metabolism showing a significant variability in clinical phenotype. Promoter mutations have been rarely reported, and controversial data exist on the site of transcription initiation (the core promoter). We quantitatively investigated transcription initiation and found it to be located in immediate proximity of the translational start. The effects human single-nucleotide alterations of conserved bases in the core promoter on transcriptional activity were moderate, explaining why clearly pathogenic mutations within the core promoter have not been reported. Furthermore, the core promoter contains two frequent polymorphisms (rs148013251 and rs2277448) that could contribute to phenotypical variability in Wilson disease patients with incompletely inactivating mutations. However, neither polymorphism significantly modulated ATP7B expression in vitro, nor were copper household parameters in healthy probands affected. In summary, the investigations allowed to determine the biologically relevant site of ATP7B transcription initiation and demonstrated that genetic variations in this site, although being the focus of transcriptional activity, do not contribute significantly to Wilson disease pathogenesis.

Molecular and computational approaches to map regulatory elements in 3D chromatin structure

Epigenetic marks do not change the sequence of DNA but affect gene expression in a cell-type specific manner by altering the activities of regulatory elements. Development of new molecular biology assays, sequencing technologies, and computational approaches enables us to profile the human epigenome in three-dimensional structure genome-wide. Here we describe various molecular biology techniques and bioinformatic tools that have been developed to measure the activities of regulatory elements and their chromatin interactions. Moreover, we list currently available three-dimensional epigenomic data sets that are generated in various human cell types and tissues to assist in the design and analysis of research projects.

Transposable elements: a jump toward the future of expression vectors

Expression vectors (EVs) are artificial nucleic acid molecules with a modular structure that allows for the transcription of DNA sequences of interest in either cellular or cell-free environments. These vectors have emerged as cross-disciplinary tools with multiple applications in an expanding Life Sciences market. The cis-regulatory sequences (CRSs) that control the transcription in EVs are typically sourced from either viruses or from characterized genes. However, the recent advancement in transposable elements (TEs) technology provides attractive alternatives that may enable a significant improvement in the design of EVs. Commonly known as "jumping genes," due to their ability to move between genetic loci, TEs are constitutive components of both eukaryotic and prokaryotic genomes. TEs harbor native CRSs that allow the regulated transcription of transposition-related genes. However, some TE-related CRSs display striking characteristics, which provides the opportunity to reconsider TEs as lead actors in the design of EVs. In this article, we provide a synopsis of the transcriptional control elements commonly found in EVs together with an extensive discussion of their advantages and limitations. We also highlight the latest findings that may allow for the implementation of TE-derived sequences in the EVs feasible, possibly improving existing vectors. By introducing this new concept of TEs as a source of regulatory sequences, we aim to stimulate a profitable discussion of the potential advantages and benefits of developing a new generation of EVs based on the use of TE-derived control sequences.

Involvement of TFAP2A in the activation of GSDMD gene promoter in hyperoxia-induced ALI

Oxygen therapy is a common treatment in neonatal intensive care units, but long-term continuous hyperoxia ventilation may induce acute lung injury (ALI). Gasdermin D (GSDMD)-mediated pyroptosis participates in various diseases including ALI, but the role of GSDMD in hyperoxia-induced ALI is yet understood. Here, we showed a significant increase in GSDMD after exposure to high oxygen. To elucidate the molecular mechanisms involved in GSDMD regulation, we identified the core promoter of GSDMD, -98 ~ -12 bp relative to the transcriptional start site (TSS). The results of mutational analysis, overexpression or siRNA interference, EMSA and ChIP demonstrated that E2F4 and TFAP2A positively regulate the transcriptional activity of the GSDMD by binding to its promoter. However, only TFAP2A showed a regulatory effect on the expression of GSDMD. Moreover, TFAP2A was increased in the lung tissues of rats exposed to hyperoxia and showed a strong linear correlation with GSDMD. Our results indicated that TFAP2A positively regulates the GSDMD expression via binding to the promoter region of GSDMD.

Highly diversified core promoters in the human genome and their effects on gene expression and disease predisposition

Background

Core promoter controls transcription initiation. However, little is known for core promoter diversity in the human genome and its relationship with diseases. We hypothesized that as a functional important component in the genome, the core promoter in the human genome could be under evolutionary selection, as reflected by its highly diversification in order to adjust gene expression for better adaptation to the different environment.

Results

Applying the “Exome-based Variant Detection in Core-promoters” method, we analyzed human core-promoter diversity by using the 2682 exome data sets of 25 worldwide human populations sequenced by the 1000 Genome Project. Collectively, we identified 31,996 variants in the core promoter region (− 100 to + 100) of 12,509 human genes (https://dbhcpd.fhs.um.edu.mo). Analyzing the rich variation data identified highly ethnic-specific patterns of core promoter variation between different ethnic populations, the genes with highly variable core promoters, the motifs affected by the variants, and their involved functional pathways. eQTL test revealed that 12% of core promoter variants can significantly alter gene expression level. Comparison with GWAS data we located 163 variants as the GWAS identified traits associated with multiple diseases, half of these variants can alter gene expression.

Conclusion

Data from our study reals the highly diversified nature of core promoter in the human genome, and highlights that core promoter variation could play important roles not only in gene expression regulation but also in disease predisposition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-020-07222-5.

The PWWP2A Histone Deacetylase Complex Represses Intragenic Spurious Transcription Initiation in mESCs

Transcriptional fidelity depends on accurate promoter selection and initiation from the correct sites. In yeast, H3K36me3-mediated recruitment of the Rpd3S HDAC complex to gene bodies suppresses spurious transcription initiation. Here we describe an equivalent pathway in metazoans. PWWP2A/B is an H3K36me3 reader that forms a stable complex with HDAC1/2. We used CAGE-seq to profile all transcription initiation sites in wild-type mESCs and cells lacking PWWP2A/B. Loss of PWWP2A/B enhances spurious initiation from intragenic sites present in wild-type mESCs, and this effect is associated with increased levels of initiating Pol-II and histone acetylation. Spurious initiation events in Pwwp2a/b DKO mESCs do not overlap in genomic location or chromatin features with spurious sites that arise in Dnmt3b KO mESCs, previously reported to function in the suppression of intragenic transcriptional initiation, suggesting these pathways function cooperatively in maintaining the fidelity of transcription initiation in metazoans.

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Loss of PWWP2A/B leads to increased levels of spurious transcription initiation

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Spurious TSS sites are predominantly in the gene bodies of highly expressed genes

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Spurious sites are marked with increased histone acetylation and initiating Pol II

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PWWP2-spurious TSSs are distinct from those caused by DNMT3B loss

A unified view of the sequence and functional organization of the human RNA polymerase II promoter

To better understand human RNA polymerase II (Pol II) promoters in the context of promoter-proximal pausing and local chromatin organization, 5′ and 3′ ends of nascent capped transcripts and the locations of nearby nucleosomes were accurately identified through sequencing at exceptional depth. High-quality visualization tools revealed a preferred sequence that defines over 177 000 core promoters with strengths varying by >10 000-fold. This sequence signature encompasses and better defines the binding site for TFIID and is surprisingly invariant over a wide range of promoter strength. We identified a sequence motif associated with promoter-proximal pausing and demonstrated that cap methylation only begins once transcripts are about 30 nt long. Mapping also revealed a ∼150 bp periodic downstream sequence element (PDE) following the typical pause location, strongly suggestive of a +1 nucleosome positioning element. A nuclear run-off assay utilizing the unique properties of the DNA fragmentation factor (DFF) coupled with sequencing of DFF protected fragments demonstrated that a +1 nucleosome is present downstream of paused Pol II. Our data more clearly define the human Pol II promoter: a TFIID binding site with built-in downstream information directing ubiquitous promoter-proximal pausing and downstream nucleosome location.

Functional Analysis of Two Zinc (Zn) Transporters (ZIP3 and ZIP8) Promoters and Their Distinct Response to MTF1 and RREB1 in the Regulation of Zn Metabolism

ZIP (zinc-regulated transporters, iron-regulated transporter-like protein) family plays an important role in organism Zn balance. This research identified the promoter regions of ZIP3 and ZIP8, two members of ZIP family, from a freshwater teleost yellow catfish Pelteobagrus fulvidraco, characterized the binding sequences of the metal-responsive transcription factor-1 (MTF-1) and Ras responsive element binding protein 1 (RREB1) on their promoter regions. The present study cloned and obtained the 2027 bp of ZIP3 promoter and 1664 bp of ZIP8 promoter, and predicted several key elements on their promoters, such as the binding sites of CREB (cAMP-response element binding protein), KLF4 (Kruppel like factor 4), MTF-1 and RREB1. The sequence deletion from −361 bp to −895 bp down-regulated the luciferase activity of ZIP3 promoter, and the deletion from −897 bp to −1664 bp down-regulated the luciferase activity of ZIP8 promoter. Within different deletion plasmids, the relative luciferase activities of ZIP3 and ZIP8 promoters changes to Zn incubation in a Zn concentration-dependent manner. The site mutagenesis and EMSA (electrophoretic mobility shift assay) found that the −1327 bp/−1343 bp MTF-1 binding site and the −248 bp/−267 bp RREB1 binding site on the ZIP3 promoter, and the −1543 bp/−1557 bp MTF-1 binding site on the ZIP8 promoter are functional sites. Low Zn increased the binding capability between MTF-1 and its responsive site on the ZIP3 promoter, and high Zn increased the transcriptional activation ZIP3 by RREB1; Zn also promoted the binding ability between MTF-1 and its responsive element on the ZIP8 promoter. This study provides the first direct evidence for the response elements of MTF-1 and RREB1 on ZIP3 and MTF-1 on ZIP8 to Zn, which are very important for the evaluation of Zn nutrition and toxicity in vertebrates.

Universal promoter scanning by Pol II during transcription initiation in Saccharomyces cerevisiae

BACKGROUND

The majority of eukaryotic promoters utilize multiple transcription start sites (TSSs). How multiple TSSs are specified at individual promoters across eukaryotes is not understood for most species. In Saccharomyces cerevisiae, a pre-initiation complex (PIC) comprised of Pol II and conserved general transcription factors (GTFs) assembles and opens DNA upstream of TSSs. Evidence from model promoters indicates that the PIC scans from upstream to downstream to identify TSSs. Prior results suggest that TSS distributions at promoters where scanning occurs shift in a polar fashion upon alteration in Pol II catalytic activity or GTF function.

RESULTS

To determine the extent of promoter scanning across promoter classes in S. cerevisiae, we perturb Pol II catalytic activity and GTF function and analyze their effects on TSS usage genome-wide. We find that alterations to Pol II, TFIIB, or TFIIF function widely alter the initiation landscape consistent with promoter scanning operating at all yeast promoters, regardless of promoter class. Promoter architecture, however, can determine the extent of promoter sensitivity to altered Pol II activity in ways that are predicted by a scanning model.

CONCLUSIONS

Our observations coupled with previous data validate key predictions of the scanning model for Pol II initiation in yeast, which we term the shooting gallery. In this model, Pol II catalytic activity and the rate and processivity of Pol II scanning together with promoter sequence determine the distribution of TSSs and their usage.

Characterization of histone modification patterns and prediction of novel promoters using functional principal component analysis

Characterization of distinct histone methylation and acetylation binding patterns in promoters and prediction of novel regulatory regions remains an important area of genomic research, as it is hypothesized that distinct chromatin signatures may specify unique genomic functions. However, methods that have been proposed in the literature are either descriptive in nature or are fully parametric and hence more restrictive in pattern discovery. In this article, we propose a two-step non-parametric statistical inference procedure to characterize unique histone modification patterns and apply it to analyzing the binding patterns of four histone marks, H3K4me2, H3K4me3, H3K9ac, and H4K20me1, in human B-lymphoblastoid cells. In the first step, we used a functional principal component analysis method to represent the concatenated binding patterns of these four histone marks around the transcription start sites as smooth curves. In the second step, we clustered these curves to reveal several unique classes of binding patterns. These uncovered patterns were used in turn to scan the whole-genome to predict novel and alternative promoters. Our analyses show that there are three distinct promoter binding patterns of active genes. Further, 19654 regions not within known gene promoters were found to overlap with human ESTs, CpG islands, or common SNPs, indicative of their potential role in gene regulation, including being potential novel promoter regions.

TERT-rs33963617 and CLPTM1L-rs77518573 reduce the risk of non-small cell lung cancer in Chinese population

BACKGROUND

Genome-wide association studies (GWAS) have identified 5p15.33 as a susceptible locus for lung cancer. However, for non-small cell lung cancer (NSCLC), low-frequency risk variants in this region have not been systematically studied. We intended to explore the associations between low-frequency variants on 5p15.33 and NSCLC using a next-generation sequencing based approach in this study.

METHODS

We have acquisited the variation spectrum of 400 NSCLC patients on 5p15.33 by sequencing the targeted region before. Candidate variants were primarily selected by restricting the minor allele frequency (MAF 1-5%) and then by comparing their frequency in 400 NSCLC patients with 1008 East Asians from The genome Aggregation Database (gnomAD). The associations between candidate variants and NSCLC were discovered and replicated in two case-control sets: discovery stage with 960 cases and 916 controls, and replication stage with 1596 cases and 1614 controls in total.

RESULTS

Five low-frequency variants were selected as our candidates and subsequent association analyses showed that 2 polymorphisms were significantly associated with risk of NSCLC, including rs33963617 (OR = 0.63, 95% CI: 0.53-0.76, P = 3.80 × 10^-7) in TERT and rs77518573 (OR = 0.73, 95% CI: 0.63-0.84, P = 2.00 × 10^-5) in upstream of CLPTM1L. When stratified by histologic subtype, a significant association was only investigated in adenocarcinoma for rs77518573. We also observed an obvious cumulative effect of the two significant variants.

CONCLUSIONS

We newly identified two NSCLC related variants on chromosome 5p15.33. Both TERT-rs33963617 and CLPTM1L-rs77518573 conferred reduced risk for NSCLC in Chinese Han population.

RNA at DNA Double-Strand Breaks: The Challenge of Dealing with DNA:RNA Hybrids

RNA polymerase II is recruited to DNA double-strand breaks (DSBs), transcribes the sequences that flank the break and produces a novel RNA type that has been termed damage-induced long non-coding RNA (dilncRNA). DilncRNAs can be processed into short, miRNA-like molecules or degraded by different ribonucleases. They can also form double-stranded RNAs or DNA:RNA hybrids. The DNA:RNA hybrids formed at DSBs contribute to the recruitment of repair factors during the early steps of homologous recombination (HR) and, in this way, contribute to the accuracy of the DNA repair. However, if not resolved, the DNA:RNA hybrids are highly mutagenic and prevent the recruitment of later HR factors. Here recent discoveries about the synthesis, processing, and degradation of dilncRNAs are revised. The focus is on RNA clearance, a necessary step for the successful repair of DSBs and the aim is to reconcile contradictory findings on the effects of dilncRNAs and DNA:RNA hybrids in HR.

Control of human testis-specific gene expression

Background

As a result of decades of effort by many investigators we now have an advanced level of understanding about several molecular systems involved in the control of gene expression. Examples include CpG islands, promoters, mRNA splicing and epigenetic signals. It is less clear, however, how such systems work together to integrate the functions of a living organism. Here I describe the results of a study to test the idea that a contribution might be made by focusing on genes specifically expressed in a particular tissue, the human testis.

Experimental design

A database of 239 testis-specific genes was accumulated and each was examined for the presence of features relevant to control of gene expression. These include: (1) the presence of a promoter, (2) the presence of a CpG island (CGI) within the promoter, (3) the presence in the promoter of a transcription factor binding site near the transcription start site, (4) the level of gene expression, and (5) the above features in genes of testis-specific cell types such as spermatocyte and spermatid that differ in their extent of differentiation.

Results

Of the 107 database genes with an annotated promoter, 56 were found to have one or more transcription factor binding sites near the transcription start site. Three of the binding sites observed, Pax-5, AP-2αA and GRα, stand out in abundance suggesting they may be involved in testis-specific gene expression. Compared to less differentiated testis-specific cells, genes of more differentiated cells were found to be (1) more likely to lack a CGI, (2) more likely to lack introns and (3) higher in expression level. The results suggest genes of more differentiated cells have a reduced need for CGI-based regulatory repression, reduced usage of gene splicing and a smaller set of expressed proteins.

A Muscle Hybrid Promoter as a Novel Tool for Gene Therapy

Gene therapy is a promising strategy to cure rare diseases. The lack of regulatory sequences ensuring specific and robust expression in skeletal and cardiac muscle is a substantial limitation of gene therapy efficiency targeting the muscle tissue. Here we describe a novel muscle hybrid (MH) promoter that is highly active in both skeletal and cardiac muscle cells. It has an easily exchangeable modular structure, including an intronic module that highly enhances the expression of the gene driven by it. In cultured myoblasts, myotubes, and cardiomyocytes, the MH promoter gives relatively stable expression as well as higher activity and protein levels than the standard CMV and desmin gene promoters or the previously developed synthetic or CKM-based promoters. Combined with AAV2/9, the MH promoter also provides a high in vivo expression level in skeletal muscle and the heart after both intramuscular and systemic delivery. It is much more efficient than the desmin-encoding gene promoter, and it maintains the same specificity. This novel promoter has potential for gene therapy in muscle cells. It can provide stable transgene expression, ensuring high levels of therapeutic protein, and limited side effects because of its specificity. This constitutes an improvement in the efficiency of genetic disease therapy.

The RNA Polymerase II Core Promoter in Drosophila

Transcription by RNA polymerase II initiates at the core promoter, which is sometimes referred to as the "gateway to transcription." Here, we describe the properties of the RNA polymerase II core promoter in Drosophila The core promoter is at a strategic position in the expression of genes, as it is the site of convergence of the signals that lead to transcriptional activation. Importantly, core promoters are diverse in terms of their structure and function. They are composed of various combinations of sequence motifs such as the TATA box, initiator (Inr), and downstream core promoter element (DPE). Different types of core promoters are transcribed via distinct mechanisms. Moreover, some transcriptional enhancers exhibit specificity for particular types of core promoters. These findings indicate that the core promoter is a central component of the transcriptional apparatus that regulates gene expression.

NF-Y controls fidelity of transcription initiation at gene promoters through maintenance of the nucleosome-depleted region

Faithful transcription initiation is critical for accurate gene expression, yet the mechanisms underlying specific transcription start site (TSS) selection in mammals remain unclear. Here, we show that the histone-fold domain protein NF-Y, a ubiquitously expressed transcription factor, controls the fidelity of transcription initiation at gene promoters in mouse embryonic stem cells. We report that NF-Y maintains the region upstream of TSSs in a nucleosome-depleted state while simultaneously protecting this accessible region against aberrant and/or ectopic transcription initiation. We find that loss of NF-Y binding in mammalian cells disrupts the promoter chromatin landscape, leading to nucleosomal encroachment over the canonical TSS. Importantly, this chromatin rearrangement is accompanied by upstream relocation of the transcription pre-initiation complex and ectopic transcription initiation. Further, this phenomenon generates aberrant extended transcripts that undergo translation, disrupting gene expression profiles. These results suggest NF-Y is a central player in TSS selection in metazoans and highlight the deleterious consequences of inaccurate transcription initiation.

The mechanisms underlying specific TSS selection in mammals remain unclear. Here the authors show that the ubiquitously expressed transcription factor NF-Y regulate fidelity of transcription initiation at gene promoters, maintaining the region upstream of TSSs in a nucleosome-depleted state, while protecting this region from ectopic transcription initiation.

Characterization of an iron-inducible Haemaphysalis longicornis tick-derived promoter in an Ixodes scapularis-derived tick cell line (ISE6)

Background

Ticks are important vectors of disease-causing pathogens. With the rise of resistance to chemical acaricides, alternative methods in tick control are warranted. Gene manipulation has been successful in controlling mosquitoes and mosquito-borne diseases and is now looked upon as a candidate method to control ticks and tick-borne pathogens. Our previous study has identified the actin and ferritin promoter regions in the Haemaphysalis longicornis tick.

Results

Here, the ferritin-derived promoter from the H. longicornis tick was characterized in silico, and the core promoter sequences and some of its important components were identified. Several truncations of the promoter region were created and inserted to a reporter plasmid to determine the important components for its activity. The activities of the truncated promoters on the Ixodes scapularis tick cell line (ISE6) were measured via a dual luciferase assay using experimental and control reporter genes. To induce the promoter’s activity, transfected ISE6 cells were exposed to ferrous sulfate. The 639 nucleotides truncated promoter showed the highest activity on ISE6 cells when exposed to 1 mM ferrous sulfate.

Conclusion

In this study, we characterized an iron-inducible tick promoter that could be a valuable tool in the development of a gene-manipulation system to control ticks and tick-borne pathogens.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3574-9) contains supplementary material, which is available to authorized users.

Feed-forward regulation adaptively evolves via dynamics rather than topology when there is intrinsic noise

In transcriptional regulatory networks (TRNs), a canonical 3-node feed-forward loop (FFL) is hypothesized to evolve to filter out short spurious signals. We test this adaptive hypothesis against a novel null evolutionary model. Our mutational model captures the intrinsically high prevalence of weak affinity transcription factor binding sites. We also capture stochasticity and delays in gene expression that distort external signals and intrinsically generate noise. Functional FFLs evolve readily under selection for the hypothesized function but not in negative controls. Interestingly, a 4-node “diamond” motif also emerges as a short spurious signal filter. The diamond uses expression dynamics rather than path length to provide fast and slow pathways. When there is no idealized external spurious signal to filter out, but only internally generated noise, only the diamond and not the FFL evolves. While our results support the adaptive hypothesis, we also show that non-adaptive factors, including the intrinsic expression dynamics, matter.

Feed‐forward loops (FFLs) can filter out noise, but whether their overrepresentation in GRNs reflects adaptive evolution for this function is debated. Here, the authors develop a null model of regulatory evolution and find that FFLs evolve readily under selection for the noise filtering function.

The CtBP1-p300-FOXO3a transcriptional complex represses the expression of the apoptotic regulators Bax and Bim in human osteosarcoma cells

C-terminal binding protein 1 (CtBP1), a well-known transcriptional corepressor, functions as an oncogene in multiple cancer types, including osteosarcoma, by modulating the transcription of many tumor suppressors, such as cadherin 1 (CDH1), phosphatase and tensin homolog (PTEN), Bcl2-associated X (Bax), Bcl-2-interacting mediator (Bim), and cyclin-dependent kinase inhibitor 1A (CDKN1A). However, it is still unclear how CtBP1 regulates the expression of these downstream targets. Here, we identified that CtBP1 is overexpressed in osteosarcoma cells and found that CtBP1 directly interacts with the transcription factor forkhead box O3 (FOXO3a) and the histone acetyltransferase p300 in vivo and in vitro. Through microarray analysis, we found that CtBP1 negatively regulates FOXO3a levels. In contrast to the CtBP1 level, the FOXO3a expression level was found to be significantly reduced in osteosarcoma cells. Knockdown of CtBP1 or overexpression of FOXO3a in U2OS cells resulted in different gene expression patterns, and the former caused upregulation of CtBP1 downstream target genes such as CDH1, PTEN, Bax, Bim, and CDKN1A, whereas the latter caused upregulation of Bax and Bim, but not CDH1, PTEN, and CDKN1A. Further analysis indicated that the CtBP1-p300-FOXO3a transcriptional complex specifically binds to the promoters of Bax and Bim. Inhibition of CtBP1 by the constitutive expression of Pep1-E1A^WT peptide in U2OS and OSA cells reversed oncogenic phenotypes, including colony formation, cellular proliferation, and migration, and limited tumor growth in vivo. Together our results demonstrated that the CtBP1-p300-FOXO3a transcriptional complex represses the expression of the apoptotic regulators Bax and Bim in human osteosarcoma cells and that targeting CtBP1-mediated transcriptional events might be a potential therapeutic strategy for the osteosarcoma treatment.