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At least 271 records · Page 15Linked to original sources

RNA editing in Drosophila 4f-rnp gene nuclear transcripts by multiple A-to-G conversions.

Pre-mRNA editing results in production of transcripts having nucleotide sequences differing from that of the DNA template. We describe the first example of RNA editing in the fruitfly Drosophila melanogaster. This editing occurs in an alternatively spliced adult head transcript arising from the single-copy nuclear 4f-rnp gene via numerous A to G conversions. Editing sites were identified from comparisons of the genomic DNA sequence with that of corresponding cDNAs prepared from various developmental stages. We show that only the non-edited sequence is present in wild-type fly chromosomes, and have conducted a genetic rescue experiment that suggests that the edited cDNA is expressed in a protein that partially complements a lethal 4f-rnp mutation. The extensive editing observed is predicted to significantly alter the amino acid sequence of the encoded protein, and thus could provide a novel mechanism for the modulation of gene expression in Drosophila. The true significance of our discovery is that it was made in Drosophila, and the advantages of using Drosophila as a genetic model to further study RNA editing in the 4f-rnp gene are discussed.

Adenine↗

Gene-protein database of Escherichia coli K-12: edition 3.

The first two editions of the E. coli Gene-Protein Index were published to provide identifications of protein spots resolved by two-dimensional gel electrophoresis as the products of known genes. This third edition has been expanded to include information about genes and proteins gained directly from two-dimensional gel analysis--including information about protein spots not yet characterized genetically or biochemically--and is therefore more properly called a cellular protein database. An alpha-numeric designation has been uniquely assigned to each of the 616 polypeptide spots in the current database. To this, information is linked about the polypeptide's identification (protein name, gene name, Enzyme Commission--EC number), location on reference gels (x-y coordinates), genetics (Genbank code, DNA sequence reference), biochemistry (molecular weight, isoelectric point), and physiology (steady state level of the protein as a function of media and temperature, membership in various regulons and stimulons).

Bacterial Proteins↗

RNA editing-like phenomenon in paramyxovirus V gene mRNA observed in insect cells infected with a recombinant baculovirus.

The V gene of the paramyxovirus human parainfluenza virus type 2 (hPIV2) is transcribed into both V and P mRNA. The V mRNA is a faithful transcript of the V gene; however, the P mRNA is transcribed by an RNA-editing mechanism in hPIV2-infected mammalian cells. Recombinant baculoviruses (rBV) were constructed containing the wild-type V gene, which has seven G residues at its editing site, and a manipulated V gene with ten G residues at its editing site. A small amount of the P protein was synthesized, in addition to the V protein, when the wild-type V gene was expressed in rBV-infected insect cells. Furthermore, synthesis of the P protein increased when rBV containing the manipulated V gene was used to infect insect cells. Both the P and V proteins were detected after in vitro translation of mRNA from rBV-infected cells. Moreover, G-residue insertions and a deletion were detected in mRNA. Since the P protein was not detected after in vitro translation of V RNA that had been transcribed in vitro by T7 RNA polymerase, these results suggest that the non-encoded G residues were inserted and deleted during transcription in insect cells. This RNA editing-like phenomenon and the implications of the length of the G cluster are discussed.

Animals↗

Directing fratricide within T cell products using an anti-uPAR chimeric antigen receptor to drive the production of potent therapeutic cells.

Cell therapy manufacturing of primary T cells often results in heterogeneous cell populations in the final product, with many cells lacking desired receptor expression or exhausted and other dysfunctional phenotypes. Here, we design a novel cell-intrinsic strategy to genetically reprogram primary human T cells to autonomously detect and eliminate dysfunctional cells. This integrated detection and elimination process, known as directed fratricide, is programmed via non-viral CRISPR genome editing to eliminate the T cell receptor (TCR) alpha chain (TRAC gene knockout) and integrate a chimeric antigen receptor (CAR) against the urokinase-type plasminogen activator receptor (uPAR), also known as CD87. In these cell products, strong T cell stimulation or activation during manufacturing causes a small subset of cells to express uPAR, which triggers CAR-mediated killing within the product. This fratricide induces proliferation in the desired cells and destroys undesired cells, a process that could be modeled computationally and controlled robustly via supplements to the culture media. The strategy enabled enrichment of anti-uPAR and anti-disialoganglioside (GD2) CAR-T cell products up to ≥99% CAR+/TCR-, favoring a memory-like phenotype. Understanding growth dynamics among T cell subsets and reprogramming them via CRISPR could accelerate the biomanufacturing of potent cell products without extensive selection methods.

Humans↗

dCas-Based Tools to Visualize Chromatin or Modify Epigenetic Marks at Specific Plant Genomic Loci.

Development of locus-specific approaches targeting precise regions on chromatin, for locus/transcription visualization or transcription/epigenetic marks editing, is a critical challenge in functional genetics and epigenetics. Systems engineered from the clustered regularly interspaced short palindromic repeats (CRISPR) and its associated endonuclease (Cas) operate through DNA sequence-specific recognition by so-called guide RNAs, which provides high flexibility and modularity for precise chromatin visualization or edition. Here, we provide an overview of the CRISPR/Cas-derived tools developed for visualization of chromatin loci in live imaging or for effective modification of gene expression. These tools make use of effector modules that combine activators, repressors, and epigenetic modifiers with a deactivated Cas protein (dCas). We present how their use in plants brought advances in visualizing or manipulating the expression of loci involved in agronomically interesting traits such as flowering time and response to drought or heat. We also discuss the limitations and future improvements of the dCas-related technologies, such as more compact and combinatorial systems, spatiotemporal targeting for fine-tuning of gene expression, and live visualization of chromatin dynamics.

Chromatin↗

Using Prime Editing Guide Generator (PEGG) for high-throughput generation of prime editing sensor libraries.

Prime editing enables the generation of nearly any small genetic variant. However, the process of prime editing guide RNA (pegRNA) design is challenging and requires automated computational design tools. We developed Prime Editing Guide Generator (PEGG), a fast, flexible, and user-friendly Python package that enables the rapid generation of pegRNA and pegRNA-sensor libraries. Here, we describe the installation and use of PEGG (https://pegg.readthedocs.io) to rapidly generate custom pegRNA-sensor libraries for use in high-throughput prime editing screens.

Gene Editing↗

Analog epigenetic memory revealed by targeted chromatin editing.

Cells store information by means of chromatin modifications that persist through cell divisions and can hold gene expression silenced over generations. However, how these modifications may maintain other gene expression states has remained unclear. This study shows that chromatin modifications can maintain a wide range of gene expression levels over time, thus uncovering analog epigenetic memory. By engineering a genomic reporter and epigenetic effectors, we tracked the gene expression dynamics following targeted perturbations to the chromatin state. We found that distinct grades of DNA methylation led to corresponding, persistent gene expression levels. Altering the DNA methylation grade, in turn, resulted in permanent loss of gene expression memory. Consistent with experiments, our chromatin modification model indicates that analog memory arises when the positive feedback between DNA methylation and repressive histone modifications is lacking. This discovery will lead to a deeper understanding of epigenetic memory and to new tools for synthetic biology.

Epigenesis, Genetic↗

Genetic analysis of cytochrome b5 from arachidonic acid-producing fungus, Mortierella alpina 1S-4: cloning, RNA editing and expression of the gene in Escherichia coli, and purification and characterization of the gene product.

Information on the amino acid sequences of the internal peptide fragments of cytochrome b5 from Mortierella hygrophila was used to prepare synthetic oligonucleotides as primers for the polymerase chain reaction. A 100-base DNA fragment was thus amplified, by using a genomic gene from Mortierella alpina 1S-4 as a template, which produced polyunsaturated fatty acids such as arachidonic acid. The amplified DNA fragment was used as the probe to clone both a 523-base cDNA fragment and a 2.1-kilobase SalI-NruI genomic fragment coding for the whole M. alpina 1S-4 cytochrome b5. On the basis of nucleotide sequences of both cytochrome b5 genomic gene and cDNA, the genomic cytochrome b5 gene was found to consist of four exons and three introns. A novel type of RNA editing, in which the cDNA included either guanine insertion or adenine-->guanine substitution at one base upstream of poly(A), was interestingly observed. The deduced amino acid sequence of M. alpina 1S-4 cytochrome b5 showed significant similarities with those of cytochrome b5s from other organisms such as rat, chicken, and yeast. The soluble form of the cytochrome b5 gene was expressed to 16% of the total soluble protein in Escherichia coli. The holo-cytochrome b5 accounted for 8% of the total cytochrome b5 in the transformants. The purified cytochrome b5 showed the oxidized and reduced absorbance spectra characteristic of fungal microsomal cytochrome b5.

Amino Acid Sequence↗

Transgene-free genome editing in citrus and poplar trees using positive and negative selection markers.

Transgene-free genome editing of the gene of interest in citrus and poplar has been achieved by co-editing the ALS gene via transient transgene expression of an efficient cytosine base editor. CRISPR-Cas genome editing systems have been widely used in plants. However, such genome-edited plants are nearly always transgenic in the first generation when Agrobacterium-mediated transformation is used. Transgene-free genome-edited plants are valuable for genetic analysis and breeding as well as simplifying regulatory approval. It can be challenging to generate transgene-free genome-edited plants in vegetatively propagated or perennial plants. To advance transgene-free genome editing in citrus and poplar, we investigated a co-editing strategy using an efficient cytosine base editor (CBE) to edit the ALS gene to confer herbicide resistance combined with transient transgene expression and potential mobile RNA-based movement of CBE transcripts to neighboring, non-transgenic cells. An FCY-UPP based cytotoxin system was used to select non-transgenic plants that survive after culturing on 5-FC containing medium. While the editing efficiency is higher in poplar than in citrus, our results show that the CBE-based co-editing strategy works in both citrus and poplar, albeit with low efficiency for biallelic edits. Unexpectedly, the addition of the TLS mobile RNA sequence reduced genome editing efficiency in both transgenic and non-transgenic plants. Although a small fraction of escaping plants is detected in both positive and negative selection processes, our data demonstrate a promising approach for generating transgene-free base-edited plants.

Populus↗

The evolution of cellular computing: nature's solution to a computational problem.

How do cells and nature 'compute'? They read and 'rewrite' DNA all the time, by processes that modify sequences at the DNA or RNA level. In 1994, Adleman's elegant solution to a seven-city directed Hamiltonian path problem using DNA launched the new field of DNA computing, which in a few years has grown to international scope. However, unknown to this field, two ciliated protozoans of the genus Oxytricha had solved a potentially harder problem using DNA several million years earlier. The solution to this problem, which occurs during the process of gene unscrambling, represents one of nature's ingenious solutions to the problem of the creation of genes. RNA editing, which can also be viewed as a computational process, offers a second algorithm for the construction of functional genes from encrypted pieces of the genome.

Animals↗

ADAR1 interacts with NF90 through double-stranded RNA and regulates NF90-mediated gene expression independently of RNA editing.

The RNA-editing enzyme ADAR1 modifies adenosines by deamination and produces A-to-I mutations in mRNA. ADAR1 was recently demonstrated to function in host defense and in embryonic erythropoiesis during fetal liver development. The mechanisms for these phenotypic effects are not yet known. Here we report a novel function of ADAR1 in the regulation of gene expression by interacting with the nuclear factor 90 (NF90) proteins, known regulators that bind the antigen response recognition element (ARRE-2) and have been demonstrated to stimulate transcription and translation. ADAR1 upregulates NF90-mediated gene expression by interacting with the NF90 proteins, including NF110, NF90, and NF45. A knockdown of NF90 with small interfering RNA suppresses this function of ADAR1. Coimmunoprecipitation and double-stranded RNA (dsRNA) digestion demonstrate that ADAR1 is associated with NF110, NF90, and NF45 through the bridge of cellular dsRNA. Studies with ADAR1 deletions demonstrate that the dsRNA binding domain and a region covering the Z-DNA binding domain and the nuclear export signal comprise the complete function of ADAR1 in upregulating NF90-mediated gene expression. These data suggest that ADAR1 has the potential both to change information content through editing of mRNA and to regulate gene expression through interacting with the NF90 family proteins.

Adenosine Deaminase↗

Circulating human B cells that express surrogate light chains and edited receptors.

Immunoglobulin gene recombination can result in the assembly of self-reactive antibodies. Deletion, anergy or receptor editing normally silence B cells that produce these autoantibodies. Receptor editing is highly efficient in mouse B cells that carry pre-recombined autoantibody transgenes or gene "knock-ins". However, it has been difficult to identify cells that have edited receptors in unmanipulated mice and humans. To try to identify such cells we isolated and characterized B cells that coexpress surrogate and conventional light chains (V-preB+L+) from the blood of normal human donors. V-preB+L+ B cells express RAG mRNA, display an unusual heavy and light chain antibody repertoire consistent with antiself reactivity, and show evidence of receptor editing. These cells accumulate in the joints of patients with rheumatoid arthritis, consistent with a role for V-preB+L+ B cells and receptor editing in autoimmune disease.

Agammaglobulinemia↗

Developmental regulation of apolipoprotein B mRNA editing is an autonomous function of small intestine involving homeobox gene Cdx1.

Apolipoprotein B mRNA editing is developmentally regulated in the human and rodent small intestine, changing from <1% at day 14 to approximately 90% by day 20 in the rat fetus. This regulation is coincident with the developmental formation of the crypt-to-villus axis functional unit, a continuous and rapidly renewing system involving cell generation, migration, and differentiation. Utilizing small intestine isografts implanted into the subcutaneous tissue of adult recipients, apolipoprotein B mRNA editing was developmentally up-regulated, parallel to that seen with an intact control. In contrast, apoB mRNA expression remains nearly constant in the isograft, unlike the normal intact small intestine. Immunohistochemical analyses demonstrated that apoB-48 protein existed predominantly in well differentiated enterocytes along the villus surface whereas apoB-100 was in the lamina propria and crypts. ApoB mRNA editing levels were very low in the crypt-like rat intestinal cell line, IEC-6 ( approximately 0.3%), but very high in well differentiated enterocytes ( approximately 91.5%). The expression of homeobox gene Cdx1 increased 18-fold in small intestine in vivo during the same time course when apoB mRNA editing increased from approximately 2 to approximately 90%. The overexpression of Cdx1 in IEC-6 cells increased apoB mRNA editing over 10-fold compared with the vector control. This increase was associated with a significant increase of activating factor ACF, a component of the apoB mRNA editing complex. Taken together, these data suggest that the developmental regulation of apoB mRNA editing is an autonomous cytodifferentiation function of small intestine for which homeobox gene Cdx1 may play an important role.

Age Factors↗

Mammalian growth factors enhance regeneration in transgenic tomato lines.

Genome editing technologies are now available for many crop species, greatly enhancing our ability to investigate gene function and transforming the field of plant transgenesis. However, the capacity to regenerate whole plants from cell culture remains a major limiting factor in many crops. Even in species with regeneration potential, certain genotypes remain recalcitrant. The physiological state of plant cells plays a central role in growth and development and is closely associated with kinase-mediated signaling networks. Notably, several defense-related genes activated during cellular repair processes following transgenesis share significant homology with mammalian defense genes. In this study, we evaluated whether supplementation with three mammalian growth factors could enhance regeneration efficiency in tomato. We selected two cytokines and a pro-inflamatory factor showing homology with plant kinase genes. We compared the percentage of transgenic plants generated through CRISPR-Cas9-mediated mutagenesis of four genes involved in sugar and organic acid metabolism across six tomato lines exhibiting varying regeneration capacities. Over three years of transformation experiments, we demonstrated that the addition of mammalian growth factors during transgenesis significantly improved regeneration frequency, particularly in recalcitrant tomato genotypes. Furthermore, growth factor supplementation not only enhanced transformation efficiency in difficult-to-transform lines but also increased the production of stable secondary lines.

Solanum lycopersicum↗

Powering Genome Editing in Rice by Harnessing Promising Gene Resources: A Comprehensive Roadmap.

The imprecise breeding methods including recombination breeding, physical/chemical mutagenesis, and marker-assisted breeding have been extensively utilized for trait improvement of rice crop. Despite tremendous progress made through these breeding methods, the critical issues, such as linkage drag, unintended phenotype, and longer duration of time required to breed a cultivar, have been the major limitations. Among the new breeding technologies, genome editing (GE) has become the most promising approach because of its specificity, precision, and speed. Despite its transformative potential, genome editing continues to face several limitations in crop improvement. These include well-recognized policy challenges, such as biosafety regulations and intellectual property constraints, alongside technical barriers like inefficient tissue culture and transformation systems. Additionally, researchers remain constrained by the limited availability of precise gene information necessary for accurate targeted editing and effective trait enhancement. This review presents an analysis of genes that regulate abiotic and biotic stresses, yield, grain quality and nutrition, plant architecture, nutrient absorption and use efficiency, and other agronomically important traits of rice. The trait-wise probable target genes for genome editing have been discussed in detail. This review will serve as a ready reckoner for rice researchers and funding agencies.

Oryza↗

Activation of the imprinted Prader-Willi syndrome locus by CRISPR-based epigenome editing.

Epigenome editing with DNA-targeting technologies such as CRISPR-dCas9 can be used to dissect gene regulatory mechanisms and potentially treat associated disorders. For example, Prader-Willi syndrome (PWS) results from loss of paternally expressed imprinted genes on chromosome 15q11.2-q13.3, although the maternal allele is intact but epigenetically silenced. Using CRISPR repression and activation screens in human induced pluripotent stem cells (iPSCs), we identified genomic elements that control the expression of the PWS gene SNRPN from the paternal and maternal chromosomes. We showed that either targeted transcriptional activation or DNA demethylation can activate the silenced maternal SNRPN and downstream PWS transcripts. However, these two approaches function at unique regions, preferentially activating different transcript variants and involving distinct epigenetic reprogramming mechanisms. Remarkably, transient expression of the targeted demethylase leads to stable, long-term maternal SNRPN expression in PWS iPSCs. This work uncovers targeted epigenetic manipulations to reprogram a disease-associated imprinted locus and suggests possible therapeutic interventions.

Prader-Willi Syndrome↗

A base editor for the long-term restoration of auditory function in mice with recessive profound deafness.

A prevalent recessive mutation (c.2485C>T, p.Q829X) within the OTOF gene leads to profound prelingual hearing loss. Here we show that in Otof mice harbouring a mutation (c.2482C>T, p.Q828X) homozygous to human OTOF that faithfully mimics the hearing-loss phenotype, a base editor (consisting of the deaminase ABE7.10max and the Cas9 variant SpCas9-NG) packaged in adeno-associated viruses and injected into the inner ear of the mice via the round-window membrane effectively corrected the pathogenic mutation, with no apparent off-target effects. The treatment restored the levels of the otoferlin protein in 88% of the inner hair cells and stably rescued the auditory function of the mice to near-wild-type levels for over 1.5&#x2009;years while improving synaptic exocytosis in the inner hair cells. We also show that an adenine base editor that targets the prevalent human OTOF mutation restored hearing in humanized mice to levels comparable to those of the wild-type counterparts. Base editors may be effective for the treatment of hereditary deafness.

Animals↗

From scissors to editors: how the evolution of precision is redefining therapeutic genome editing.

Since its introduction as a genome-editing tool, CRISPR-based technology has undergone rapid refinement, with precision emerging as a central focus of development. Early CRISPR-Cas9 systems demonstrated unprecedented ease and efficiency in targeting specific DNA sequences, but concerns over off-target effects and variable editing outcomes limited their broader application. This review outlines the progression of CRISPR from its discovery in prokaryotes to its application as a versatile tool in precision medicine, where it supports targeted therapies for genetic disorders in various ways. Although technical challenges, including off-target editing and delivery inefficiencies, persist alongside ethical considerations of accessibility and long-term consequences, CRISPR's ongoing refinements and innovations reflect a clear trajectory toward greater specificity, safety, and predictability, positioning CRISPR as an increasingly precise platform for both fundamental research and therapeutic use.

Gene Editing↗