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PubMed2026

Suppression of AAV-Delivered Transgene Expression Using Artificial MicroRNAs Delivered by an Alternative AAV Serotype.

Adeno-associated virus (AAV) gene transfer vectors mediate long-term expression in nondividing cells, an advantage for treating chronic disorders. However, current platforms lack a way to selectively shut down transgene expression if adverse effects arise. To create an "off switch," we hypothesized that incorporating unique artificial microRNA (amiRNA) target sequences into an AAV expression cassette would allow subsequent suppression of transgene expression using a second AAV vector encoding the cognate amiRNA. We introduced 22-nt sequences absent from human and mouse transcriptomes into the 3' untranslated region (UTR) of a therapeutic AAV cassette. To identify optimal amiRNAs, two tandem copies of each amiRNA were cloned into the 3'UTR of an mCherry reporter gene. In vitro assessment of six amiRNA/target pairs using a dual luciferase assay identified four amiRNAs that efficiently suppressed reporter expression. Cells cotransfected with target site 3 (TS3) and amiRNA-T3B showed the greatest reduction in luciferase activity (80%, p < 0.0001) and were selected for further study. The "off-switch" system was then evaluated using an AAV5 therapeutic vector expressing a recombinant humanized anti-IgE monoclonal antibody (AAV5-TBG-anti-IgE-TS3), designed for long-term suppression of allergen-induced reactions. Co-transfection of HEK293T cells with anti-IgE-TS3 and amiRNA-T3B significantly reduced anti-IgE mRNA and protein levels relative to a control amiRNA (p < 0.0001). In vivo testing in Balb/c mice (n = 5) involved intravenous administration of AAV5-anti-IgE-TS3 (3.2 × 1010 gc), followed 4 weeks later by an AAVrh.10 amiRNA vector (AAVrh.10-TBG-amiRNA-T3B; 1 × 1011 gc). Control mice receiving only the therapeutic vector expressed 18.4 ± 13.8 µg/mL serum anti-IgE at 10 weeks. In contrast, mice receiving the amiRNA "off" vector showed marked suppression of anti-IgE (0.3 ± 0.15 µg/mL, p < 0.0001). These findings provide proof-of-concept that AAV-delivered amiRNAs can selectively switch off transgene expression, offering a strategy to improve the safety of AAV-mediated gene therapies.

Dependovirus↗

PubMed2024

ALDH1A1 promotes immune escape of tumor cells through ZBTB7B-glycolysis pathway.

The primary impediment to the success of immunotherapy lies in the immune evasion orchestrated by tumors, contributing to the suboptimal overall response rates observed. Despite this recognition, the intricacies of the underlying mechanisms remain incompletely understood. Through preliminary detection of clinical patient tissues, we have found that ALDH1A1 was a key gene for the prognosis of cancer patients and tumor glycolysis. In vitro experiments and tumor formation in nude mice suggested that targeting ALDH1A1 could inhibit tumor growth. Through further analysis of xenograft tumor models in immune-normal mice and flow cytometry, we found that deficiency in ALDH1A1 could promote immune system suppression of tumors in vivo. Specifically, RNA-seq analysis, combined with qPCR and western blot, identified the transcription factor ZBTB7B as downstream of ALDH1A1. The binding sites of the transcription factor ZBTB7B on the LDHA promoter region, which is responsible for regulating the rate-limiting enzyme gene LDHA in glycolysis, were determined using luciferase reporter gene detection and Chip-qPCR, respectively. In addition, the increased SUMOylation of ZBTB7B stabilized its transcriptional activity. Further in vivo and in vitro experiments confirmed that the combination of targeting ALDH1A1 and ZBTB7B with immune checkpoint inhibitors could synergistically inhibit tumors in vivo. Finally, after conducting additional verification of patient tissue and clinical data, we have confirmed the potential translational value of targeting ALDH1A1 and ZBTB7B for tumor immunotherapy. These results emphasize the potential translational significance of targeting ALDH1A1 and ZBTB7B in the realm of tumor immunotherapy. The convergence of ALDH1A1 inhibition and immune checkpoint blockade, particularly with PD-L1/PD-1 mAb, presents a compelling avenue for curtailing tumor immune escape.

Animals↗

PubMed2025

Validation of caprine H11 and the Rosa26 platform for transgene integration via CRISPR-based system: investigations on stable transgene expression and genetic biosafety.

CRISPR/Cas9 technology is an efficient tool for site-specific livestock gene editing. However, to minimize potential disruption of host genome function, exogenous genes should be integrated into well-characterized genomic loci, such as H11 or Rosa26, which have been empirically validated for stable transgene expression. This study established a multi-dimensional assessment system to evaluate the biological applicability of the H11 locus and the widely used Rosa26 targeting platform as sites for targeted integration of exogenous genes in goats. Donor cells carrying the enhanced green fluorescent protein (EGFP) reporter gene at the H11 and Rosa26 loci were generated via CRISPR/Cas9-mediated homology-directed repair; this was followed by somatic cell nuclear transfer to produce transgenic cloned embryos and healthy offspring. Multi-dimensional analyses revealed the following. At the cellular level, there was stable and efficient EGFP expression at integration sites, with donor cells maintaining normal cell cycle progression, proliferation capacity, and apoptosis levels, and with no alterations in the transcriptional integrity of adjacent genes. At the embryonic level, there was sustained EGFP expression across pre-implantation embryonic stages, with developmental metrics statistically indistinguishable from wild-type embryos. Finally, at the individual level, cloned offspring exhibited growth phenotypes consistent with wild-type counterparts, and EGFP showed broad-spectrum expression in eight tissues. This study establishes the first CRISPR/Cas9-based crossscale (cellular-embryonic-individual) validation in goats, demonstrating that the H11 and Rosa26 loci support efficient and stable transgene integration in goats. These results provide a precise and predictable technical framework for livestock genetic improvement.

Animals↗

PubMed2026

Pathogen Species-Specific Differences in Induction of the Maize Polyubiquitin Gene Promoter in Transgenic Wheat.

The maize polyubiquitin promoter (ZmUbi) is a mainstay in molecular biology for transgene expression and is used for constitutive expression of defense-related gene products. Transgenic wheat lines were produced expressing a ZmUbi-RUBY reporter gene that produces the red pigment betalain. Some lines showed transgene silencing with reduced RUBY transcript accumulation and chimeric sectors of betalain. Infection of these plants with Blumeria graminis, Puccinia graminis f. sp. tritici (Pgt), or P. triticina (Pt) each resulted in localized betalain accumulation at infection sites and increased RUBY transcript accumulation. In contrast, two isolates of P. striiformis f. sp. tritici (Pst) caused no detectable RUBY transcript accumulation and no visible betalain accumulation at infection sites, although a modest betalain increase was detected in infected tissue extracts. Compared with Pst, Pgt more strongly induced host genes involved in transcriptional and post-transcriptional regulatory processes, although no obvious pathogen-induced changes in ZmUbi promoter methylation were observed. ZmUbi-GUS transgenic wheat plants were also pathogen challenged, and, unlike Pst, both Pgt and Pt induced localized GUS staining at infection sites. Database mining showed that the endogenous maize polyubiquitin gene from which ZmUbi is derived was pathogen inducible, albeit in a species-specific fashion. These pathogen differences in ZmUbi induction have implications when using this regulatory element to express defense-related transgenes in wheat. Comparing the resistance efficacy of transgenes against different pathogens using this promoter is potentially influenced by significant, localized expression differences occurring at infection sites of different pathogen species. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Promoter Regions, Genetic↗

PubMed2009

A myocardium tropic adeno-associated virus (AAV) evolved by DNA shuffling and in vivo selection.

To engineer gene vectors that target striated muscles after systemic delivery, we constructed a random library of adeno-associated virus (AAV) by shuffling the capsid genes of AAV serotypes 1 to 9, and screened for muscle-targeting capsids by direct in vivo panning after tail vein injection in mice. After 2 rounds of in vivo selection, a capsid gene named M41 was retrieved mainly based on its high frequency in the muscle and low frequency in the liver. Structural analyses revealed that the AAVM41 capsid is a recombinant of AAV1, 6, 7, and 8 with a mosaic capsid surface and a conserved capsid interior. AAVM41 was then subjected to a side-by-side comparison to AAV9, the most robust AAV for systemic heart and muscle gene delivery; to AAV6, a parental AAV with strong muscle tropism. After i.v. delivery of reporter genes, AAVM41 was found more efficient than AAV6 in the heart and muscle, and was similar to AAV9 in the heart but weaker in the muscle. In fact, the myocardium showed the highest gene expression among all tissues tested in mice and hamsters after systemic AAVM41 delivery. However, gene transfer in non-muscle tissues, mainly the liver, was dramatically reduced. AAVM41 was further tested in a genetic cardiomyopathy hamster model and achieved efficient long-term delta-sarcoglycan gene expression and rescue of cardiac functions. Thus, direct in vivo panning of capsid libraries is a simple tool for the de-targeting and retargeting of viral vector tissue tropisms facilitated by acquisition of desirable sequences and properties.

Animals↗

PubMed2026

An XRE-type regulator in Streptococcus mutans plays an important role in brpA expression and oxidative stress tolerance response.

This study used a functional genomics approach to explore the role of a xenobiotic response element (XRE)-type regulator (SMU.405c) in Streptococcus mutans physiology, including the expression of biofilm regulatory protein BrpA. Results showed that deletional mutation of xre significantly reduced the ability of the deficient mutant to grow in the presence of methyl viologen, a commonly used oxidative stressor (P < 0.001). When challenged in a hydrogen peroxide killing assay, the survival rate of the ∆xre mutant was >2-log less than the parent strain after 60 min (P < 0.001). Luciferase reporter fusion assays showed that xre deficiency had no significant effect on luciferase expression when it was under the control of the intact brpA promoter, but the reporter activity increased by >6-fold (P < 0.001) when the reporter gene was fused to a brpA promoter derivative with deletion of a putative XRE-binding box. Electrophoretic mobility shift assay (EMSA) showed that recombinant XRE interacted with the brpA promoter, resulting in an electrophoretic shift of the promoter probes. In vitro transcription assay also showed that inclusion of XRE caused transcription to fall off, significantly reducing full-length brpA transcripts. RNA-seq analysis revealed that deficiency of XRE led to altered expression of >102 genes by >2-fold (P < 0.05), including 28 with increased expression, and 74 with decreased expression. Among the down-regulated were genes for DNA repair and oxidative stress tolerance response. These results suggest that XRE (SMU.405c) in S. mutans plays an important role in brpA expression and oxidative stress tolerance response.IMPORTANCEStreptococcus mutans, a keystone pathogen in human dental caries, primarily lives in the highly diverse microbiota on tooth surfaces, where the conditions are often harsh and fluctuate frequently. Locus SMU.405c was annotated to encode a xenobiotic response element (XRE)-like transcriptional regulator, but no information is available concerning the role of this protein in S. mutans pathophysiology. This study used a functional genomics approach along with molecular and transcriptomic analysis to characterize a deletional xre mutant, and the results showed that xre deficiency in S. mutans resulted in weakened oxidative stress tolerance response and alterations in transcription of >102 genes, including those known to play an important role in cell envelope biogenesis and stress tolerance response. Reporter fusion assay, electrophoretic mobility shift assay (EMSA), and in vitro transcription further demonstrated that the XRE-like regulator encoded by SMU.405c is a repressor of brpA expression and plays an important role in oxidative stress tolerance response.

Streptococcus mutans↗

PubMed2013

Long-term robust myocardial transduction of the dog heart from a peripheral vein by adeno-associated virus serotype-8.

Molecular intervention using noninvasive myocardial gene transfer holds great promise for treating heart diseases. Robust cardiac transduction from peripheral vein injection has been achieved in rodents using adeno-associated virus (AAV) serotype-9 (AAV-9). However, a similar approach has failed to transduce the heart in dogs, a commonly used large animal model for heart diseases. To develop an effective noninvasive method to deliver exogenous genes to the dog heart, we employed an AAV-8 vector that expresses human placental alkaline phosphatase reporter gene under the transcriptional regulation of the Rous sarcoma virus promoter. Vectors were delivered to three neonatal dogs at the doses of 1.35×10(14), 7.14×10(14), and 9.06×10(14) viral genome particles/kg body weight via the jugular vein. Transduction efficiency and overall safety were evaluated at 1.5, 2.5, and 12 months postinjection. AAV delivery was well tolerated and dog growth was normal. Blood chemistry and internal organ histology were unremarkable. Widespread skeletal muscle transduction was observed in all dogs without T-cell infiltration. Encouragingly, whole heart myocardial transduction was achieved in two dogs that received higher doses and cardiac expression lasted for at least 1 year. In summary, peripheral vein AAV-8 injection may represent a simple heart gene transfer method in large mammals. Further optimization of this gene delivery strategy may open the door for a readily applicable gene therapy method to treat many heart diseases.

Animals↗

PubMed2014

Genome-wide computational analysis reveals cardiomyocyte-specific transcriptional Cis-regulatory motifs that enable efficient cardiac gene therapy.

Gene therapy is a promising emerging therapeutic modality for the treatment of cardiovascular diseases and hereditary diseases that afflict the heart. Hence, there is a need to develop robust cardiac-specific expression modules that allow for stable expression of the gene of interest in cardiomyocytes. We therefore explored a new approach based on a genome-wide bioinformatics strategy that revealed novel cardiac-specific cis-acting regulatory modules (CS-CRMs). These transcriptional modules contained evolutionary-conserved clusters of putative transcription factor binding sites that correspond to a "molecular signature" associated with robust gene expression in the heart. We then validated these CS-CRMs in vivo using an adeno-associated viral vector serotype 9 that drives a reporter gene from a quintessential cardiac-specific α-myosin heavy chain promoter. Most de novo designed CS-CRMs resulted in a >10-fold increase in cardiac gene expression. The most robust CRMs enhanced cardiac-specific transcription 70- to 100-fold. Expression was sustained and restricted to cardiomyocytes. We then combined the most potent CS-CRM4 with a synthetic heart and muscle-specific promoter (SPc5-12) and obtained a significant 20-fold increase in cardiac gene expression compared to the cytomegalovirus promoter. This study underscores the potential of rational vector design to improve the robustness of cardiac gene therapy.

Animals↗

PubMed2026

An inducer-independent, single-plasmid CRISPR-Cas9 system for genome editing in Bacillus species.

Advances in molecular biology tools are essential for streamlining and accelerating genetic engineering of cells across industrial and academic applications. While CRISPR-Cas improves genome editing efficiency, current systems have limitations and are often host specific, which restricts their versatility. This study describes a versatile CRISPR-Cas9 system for genome editing in industrially relevant Bacillus species. By adapting the well-established pJOE8999 vector-based CRISPR-Cas9 genome editing system, we constructed an inducer-independent, broad-host-range genome editing system. It maintains the benefits of low toxicity to the target cell and the cloning host as well as the ease to use of a single-plasmid CRISPR-Cas9 system. We utilized the constitutive Sigma70-type promoter from the conserved veg gene of Bacillus, to develop and test the suitability of promoter variants of different strengths for Cas9 expression. Successful gene deletions in three different Bacillus species demonstrated the versatility of the modified system for this industrially important genus. This was further confirmed by the integration of a reporter gene fusion and the introduction of a single point mutation in the genome of Bacillus licheniformis. This one-step CRISPR-based transformation protocol developed in this study enables fast genome editing workflows with minimal hands-on time. KEY POINTS: • Editing and screening of promoter variants for balanced Cas9 expression in Bacillus. • Development of a versatile inducer-independent, single-plasmid CRISPR-Cas-based system. • Verification of the modified CRISPR-based system for genome editing in different Bacilli.

CRISPR-Cas Systems↗

PubMed2025

Combinatorial genome engineering of pseudorabies virus Bartha by developing a reverse genetic system based on three overlapping genomic segments.

INTRODUCTION: The 138-kilobase genome of pseudorabies virus vaccine strain Bartha K61 harbors many nonessential genes for replication and exhibits remarkable capacity for incorporating foreign genes for therapeutic applications. However, the large size of the Bartha genome complicates its efficient engineering. OBJECTIVES: Development of a reverse genetic system for pseudorabies virus Bartha based on three overlapping genomic segments to facilitate multiplex genome engineering. METHODS: The 138-kb genome of Bartha was split into three overlapping segments (42 kb, 43 kb, and 53 kb), each cloned in a bacterial artificial chromosome (BAC) to facilitate genome engineering. The infectious virus was reconstituted by transfecting the 3 genomic fragments released from the BACs into Vero cells in which a complete virus genome was assembled using 2-kb overlaps between adjacent pieces. RESULTS: Employing the reverse genetic system, we individually deleted 15 candidate nonessential genes and confirmed that 10 were dispensable for viral growth in cell culture. Deletion of 7 nonessential genes had no impact on viral growth, whereas UL47 deletion reduced viral growth rate and deletions of UL44, UL47, or US3 resulted in smaller viral plaques. A total of 45 viral genomes with double deletions of nonessential genes were constructed, among which 22 were successfully rescued into infectious virions. Fifteen double-deletion mutant viruses had a viral titer comparable with the wild-type Bartha, while the remaining 7 showed a lower titer. Additionally, expressions of the mNeonGreen reporter gene at nonessential gene loci were evaluated. Cells infected with recombinant viruses carrying mNeonGreen at 8 loci showed strong green fluorescence, whereas those with mNeonGreen at 2 loci exhibited very weak fluorescence. CONCLUSION: The reverse genetic system developed in this study enables rapid and combinatorial engineering of viruses with the large DNA genome, and will accelerate development of large DNA virus-based therapeutics including live-attenuated vaccines, vector vaccines, and oncolytic herpesviruses.

Herpesvirus 1, Suid↗

PubMed2025

A functional assay to classify RB1 variants of uncertain significance.

PURPOSE: The RB1 gene encodes the retinoblastoma protein (pRB) playing a major role in cell cycle control, particularly by its interaction with E2F transcription factors. Familial forms of retinoblastoma are caused by germline pathogenic variants in the RB1 gene predisposing to retinoblastoma and other tumors. By analyzing the RB1 gene in patients with retinoblastoma, we found that missense variants often remain variants of uncertain significance (VUS). METHODS: To classify RB1 VUS, we developed a functional assay evaluating their impact on the ability of pRB to inhibit the activity of the E2F1 promoter, with a luciferase reporter gene. A set of 14 pathogenic/likely pathogenic and benign/likely benign RB1 variants was used for validation. RESULTS: We tested 16 VUS detected in patients with retinoblastoma and found that 9 VUS reduced the ability of pRB to inhibit E2F1 promoter. Among them, the (RB1) c.2263T>G p.(Phe755Val) variant showed a reduced level of pRB on Western blot, suggesting a defect in pRB stability. By applying the criterion PS3_moderate of the American College of Medical Genetics and Genomics/Association for Molecular Pathology classification to this functional assay, 5 of the 9 VUS with functional impact could be classified as likely pathogenic. CONCLUSION: This functional assay can improve the molecular diagnosis of retinoblastoma predisposition by a better determination of pathogenic/likely pathogenic RB1 variants.

Humans↗

PubMed2024

A mammalian tripartite enhancer cluster controls hypothalamic Pomc expression, food intake, and body weight.

Food intake and energy balance are tightly regulated by a group of hypothalamic arcuate neurons expressing the proopiomelanocortin (POMC) gene. In mammals, arcuate-specific POMC expression is driven by two cis-acting transcriptional enhancers known as nPE1 and nPE2. Because mutant mice lacking these two enhancers still showed hypothalamic Pomc mRNA, we searched for additional elements contributing to arcuate Pomc expression. By combining molecular evolution with reporter gene expression in transgenic zebrafish and mice, here, we identified a mammalian arcuate-specific Pomc enhancer that we named nPE3, carrying several binding sites also present in nPE1 and nPE2 for transcription factors known to activate neuronal Pomc expression, such as ISL1, NKX2.1, and ERα. We found that nPE3 originated in the lineage leading to placental mammals and remained under purifying selection in all mammalian orders, although it was lost in Simiiformes (monkeys, apes, and humans) following a unique segmental deletion event. Interestingly, ablation of nPE3 from the mouse genome led to a drastic reduction (>70%) in hypothalamic Pomc mRNA during development and only moderate (<33%) in adult mice. Comparison between double (nPE1 and nPE2) and triple (nPE1, nPE2, and nPE3) enhancer mutants revealed the relative contribution of nPE3 to hypothalamic Pomc expression and its importance in the control of food intake and adiposity in male and female mice. Altogether, these results demonstrate that nPE3 integrates a tripartite cluster of partially redundant enhancers that originated upon a triple convergent evolutionary process in mammals and that is critical for hypothalamic Pomc expression and body weight homeostasis.

Animals↗

PubMed2025

Spatial and longitudinal tracking of enhancer-AAV vectors that target transgene expression to injured mouse myocardium.

Tissue regeneration enhancer elements (TREEs) direct expression of target genes in injured and regenerating tissues. Additionally, TREEs of zebrafish origin were shown to direct expression of transgenes in border zone regions after cardiac injury when packaged into recombinant adeno-associated viral (AAV) vectors and introduced into mice. Future implementation of TREEs into AAV-based vectors as research tools and potential gene therapy modalities requires a deeper understanding of expression dynamics and potential off-target effects. Here, we applied in vivo bioluminescent imaging to mice systemically injected with AAV vectors containing different combinations of capsids, enhancers, and timing of delivery. Longitudinal tracking of expression directed by different TREEs revealed distinct amplitudes and durations of reporter gene expression in the injured heart. The liver-de-targeted AAV capsid, AAV.cc84, could deliver TREEs either pre- or post-cardiac injury to negate off-target expression in the liver while maintaining transduction in the heart. By screening AAV9-based capsid libraries dosed systemically in mice post-cardiac injury, we discovered a new capsid variant, AAV.IR41, with enhanced transduction in cardiac injuries and with elevated transduction of TREE-driven transgenes versus conventional AAV9 vectors. In vivo bioluminescence imaging offers insights into how enhancers and engineered capsids can be implemented to modulate spatiotemporal transgene expression for targeted therapies.

Animals↗

PubMed2025

Large-scale screening of genes responsible for silique length and seed size in Brassica Napus via pooled CRISPR library.

BACKGROUND: Enhancing rapeseed (Brassica napus, B. napus) yield is critical for ensuring global vegetable oil security. However, yield is heavily influenced by silique development and seed size, the enhancement of which is limited by scarce genetic resources. The CRISPR/Cas9 system has emerged as a powerful tool for constructing genome-wide mutant libraries, even in polyploid crops with complex genomes. RESULTS: The transcriptome-wide association study (TWAS) data, tissue-specific expression profiles data and reported genes were integrated to identify candidate genes regulating silique development and seed size. We constructed a sgRNA library targeting these genes and generated a CRISPR/Cas9 editing mutant library through genetic transformation. Specifically, 6124 sgRNAs were designed for 1739 candidate genes with ≦ 4 orthologues. 681 T0 plants were obtained through genetic transformation, which harbor 453 sgRNAs. Of 408 T0 plants analyzed, 151 (37.00%) exhibited successful gene editing events, targeting 84 candidate genes. Ten homozygous mutant plants were isolated and preliminary phenotypic analysis was performed in mutants targeting the BnaHRDs. The results suggest that mutations in BnaHRD.A03 and BnaHRD.C03 may modulate plant height (PH), main inflorescence length (MIL), silique length (SL), effective silique number per plant (ENS), seed number per silique (SNPS), and thousand-seed weight (TSW). CONCLUSIONS: This study harnessed the CRISPR/Cas9 technology to establish a preliminary library of gene-edited mutants in B. napus, thereby laying a robust foundation for the future screening of candidate genes pertaining to silique development and seed size. Furthermore, this study provides a methodological framework for rapid functional gene discovery in B. napus through CRISPR-based approaches.

Brassica napus↗

PubMed2004

The proneural proteins Atonal and Scute regulate neural target genes through different E-box binding sites.

For a particular functional family of basic helix-loop-helix (bHLH) transcription factors, there is ample evidence that different factors regulate different target genes but little idea of how these different target genes are distinguished. We investigated the contribution of DNA binding site differences to the specificities of two functionally related proneural bHLH transcription factors required for the genesis of Drosophila sense organ precursors (Atonal and Scute). We show that the proneural target gene, Bearded, is regulated by both Scute and Atonal via distinct E-box consensus binding sites. By comparing with other Ato-dependent enhancer sequences, we define an Ato-specific binding consensus that differs from the previously defined Scute-specific E-box consensus, thereby defining distinct E(Ato) and E(Sc) sites. These E-box variants are crucial for function. First, tandem repeats of 20-bp sequences containing E(Ato) and E(Sc) sites are sufficient to confer Atonal- and Scute-specific expression patterns, respectively, on a reporter gene in vivo. Second, interchanging E(Ato) and E(Sc) sites within enhancers almost abolishes enhancer activity. While the latter finding shows that enhancer context is also important in defining how proneural proteins interact with these sites, it is clear that differential utilization of DNA binding sites underlies proneural protein specificity.

3' Flanking Region↗

PubMed2024

In vitro one-pot construction of influenza viral genomes for virus particle synthesis based on reverse genetics system.

The reverse genetics system, which allows the generation of influenza viruses from plasmids encoding viral genome, is a powerful tool for basic research on viral infection mechanisms and application research such as vaccine development. However, conventional plasmid construction using Escherichia coli (E.coli) cloning is time-consuming and has difficulties handling DNA encoding genes toxic for E.coli or highly repeated sequences. These limitations hamper rapid virus synthesis. In this study, we establish a very rapid in vitro one-pot plasmid construction (IVOC) based virus synthesis. This method dramatically reduced the time for genome plasmid construction, which was used for virus synthesis, from several days or more to about 8 hours. Moreover, infectious viruses could be synthesized with a similar yield to the conventional E.coli cloning-based method with high accuracy. The applicability of this method was also demonstrated by the generation of recombinant viruses carrying reporter genes from the IVOC products. This method enables the pathogenicity analysis and vaccine development using genetically modified viruses, and it is expected to allow for faster analysis of newly emerging variants than ever before. Furthermore, its application to other RNA viruses is also expected.

Genome, Viral↗

PubMed2025

Heterochromatin-based silencing of a foreign tandem repeat in Drosophila melanogaster shows unusual biochemistry and temperature sensitivity.

Eukaryotic genomes are packaged into chromatin, a regulatory nucleoprotein assembly. Establishment, maintenance, and interconversion of chromatin states is required for correct patterns of gene expression, genome integrity, and survival. Transcriptionally repressive heterochromatin minimizes mobilization of transposable elements and limits expansion of other repetitive DNA, but mechanisms for recognition of the latter sequences are not well established. We previously demonstrated in Drosophila melanogaster that transcripts derived from 1360 and Invader4 transposon insertions can trigger local conversion of transcriptionally permissive euchromatin to heterochromatin through the piRNA system, but only in a subset of genomic locations near existing blocks of heterochromatin. Here we show that a ~9 kb tandem array of the 36-nucleotide lac operator (lacO) sequence of Escherichia coli can form ectopic heterochromatin at a similar subset of sites, resulting in variegating expression of an adjacent reporter gene. Heterochromatin Protein 1a (HP1a) and histone deacetylation are required for lacO repeat-induced silencing, but, contrasting with previously described Position Effect Variegation (PEV), we do not observe increased histone H3 lysine 9 methylation. Silencing is effective at 25°C and suppressed at 18°C (in contrast to canonical PEV, which is enhanced at 18°C), indicating involvement of a temperature-sensitive component. Temperature switching experiments show that lacO repeat-induced heterochromatin formation is reversible throughout larval development following an HP1a-dependent initiation step in the early embryo. We conclude that the Drosophila nucleus can recognize a completely foreign tandem repeat as a target for heterochromatin formation, and that the heterochromatin structure established is distinct from that of endogenous tandem arrays.

HP1a↗

PubMed2026

Field-isolate recombinant tick-borne encephalitis viruses define reporter-stability guidelines for antiviral testing in flaviviruses.

As arthropod-borne viruses continue to threaten populations globally, there is a pressing need for experimental systems that enable rapid antiviral discovery. Reverse-genetics platforms producing recombinant reporter orthoflaviviruses have been developed to address this gap. Here, we present two new recombinant tick-borne encephalitis viruses (TBEVrec) generated on a European-subtype Haselmühl Tiho1 isolate backbone. A reporter gene, either eGFP or Nluc, was inserted in the capsid-coding region of the genome downstream of the capsid RNA regulatory signal and separated from the complete viral polyprotein by a 2A self-cleaving peptide. TBEVrec was better rescued using the circular polymerase extension reaction (CPER) than with the infectious subgenomic amplicon (ISA) method. TBEVrec replicated efficiently in relevant human cell lines, with comparable replication to wild-type TBEV in a neuronal cell line and moderately reduced titers and RNA levels in immune-derived cell lines. Using either eGFP or Nluc, we illustrate how TBEVrec enabled high-content RNAi screening, highlighting Nucleolin and PRKD1 as potential TBEV host factors, and drug testing on a benchtop plate reader. Nanopore sequencing of the eGFP insert revealed that the reporter is excised without affecting flanking regions. Comparative analysis of eGFP and Nluc further shows that this instability is time- and cell type-dependent, and that Nluc is comparatively more stable. From these observations, we outline safeguards and design principles that are broadly applicable both to the rescue of existing constructs and to the design of future recombinant reporter virus platforms.

CPER↗