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Stacked mutations in multi-copy AHAS genes enhance sulfonylurea herbicide resistance in soybean.

Weeds are a major factor that negatively impact crop yields. Developing herbicide-resistant germlines is crucial for efficient weed control. Sulfonylurea- and pyrimidinyl benzoate-based herbicides inhibit the function of acetohydroxyacid synthase (AHAS), a key enzyme in the biosynthesis of branched-chain amino acids in plants. To create soybean plants resistant to these classes of herbicides, we performed base editing of AHAS genes in Glycine max. A guide RNA was designed to target the codon for proline-182 in GmAHAS2, with the prediction that off-target base editing might also occur in the GmAHAS3 and GmAHAS4 genes. We selected six genome-edited soybean lines, each carrying distinct mutations in GmAHAS2, GmAHAS3, or GmAHAS4. These lines were treated with three different AHAS-targeting herbicides to evaluate resistance. The results show that the number of mutated GmAHAS genes and the mutation patterns significantly influence herbicide resistance.

Herbicide Resistance↗

[ATPase subunit 6 gene of Leptomonas seymouri (Trypanosomatidae) is transcribed and edited as a polycistronic transcript].

The maturation of mitochondrial RNA transcripts proceeds through several steps. Here we use insects trypanosomatid Leptomonas seymouri as a model organism for analysis of transcription and posttranscriptional processing of mitochondria encoded gene for the subunit 6 of ATPase (A6). It was shown that Cyt b (cytochrome b) and A6 genes were transcribed and edited as a polycistronic template. Analysis of twelve RT-PCR products of both genes led to identification of four types of differently and/or partially edited cDNA molecules. Based on the analysis of two fully edited A6 transcripts we propose the existence of two alternatively edited products.

Adenosine Triphosphatases↗

Efficient and versatile rapeseed transformation for new breeding technologies.

Many gene functions are widely studied and understood in Arabidopsis; however, the lack of efficient transformation systems often limits the application and verification of this knowledge in crop plants. Brassica napus L., a member of the Brassicaceae family, is usually transformed by Agrobacterium-mediated hypocotyl transformation, but not all growth types are equally amenable to transformation. In particular, winter rapeseed, which requires vernalization to initiate flowering, is recalcitrant to in vitro regeneration and transformation. The analysis of gene functions in rapeseed is further complicated by the allotetraploid nature of its genome and the genome triplication within the Brassica genus, which has led to the presence of a large number of gene homologs for each Arabidopsis ortholog. We have established a transformation method that facilitates the regeneration of winter rapeseed by using the WUSCHEL gene from Beta vulgaris. This allowed us to efficiently transform a winter and spring rapeseed genotype in small-scale experiments. As proof of principle, we targeted BnCLV3 and BnSPL9/15 with CRISPR/Cas9 and showed that entire gene families are effectively edited using this transformation protocol. This allowed us to simultaneously study many redundantly acting homologous genes in rapeseed. We observed mutant phenotypes for BnCLV3 and BnSPL9/15 in primary transformants, indicating that biallelic knockouts were obtained for up to eight genes. This allowed an initial phenotypic characterization to be performed already a few months after starting the experiment.

Brassica napus↗

Gene regulation technologies for gene and cell therapy.

Gene therapy stands at the forefront of medical innovation, offering unique potential to treat the underlying causes of genetic disorders and broadly enable regenerative medicine. However, unregulated production of therapeutic genes can lead to decreased clinical utility due to various complications. Thus, many technologies for controlled gene expression are under development, including regulated transgenes, modulation of endogenous genes to leverage native biological regulation, mapping and repurposing of transcriptional regulatory networks, and engineered systems that dynamically react to cell state changes. Transformative therapies enabled by advances in tissue-specific promoters, inducible systems, and targeted delivery have already entered clinical testing and demonstrated significantly improved specificity and efficacy. This review highlights next-generation technologies under development to expand the reach of gene therapies by enabling precise modulation of gene expression. These technologies, including epigenome editing, antisense oligonucleotides, RNA editing, transcription factor-mediated reprogramming, and synthetic genetic circuits, have the potential to provide powerful control over cellular functions. Despite these remarkable achievements, challenges remain in optimizing delivery, minimizing off-target effects, and addressing regulatory hurdles. However, the ongoing integration of biological insights with engineering innovations promises to expand the potential for gene therapy, offering hope for treating not only rare genetic disorders but also complex multifactorial diseases.

Humans↗

Is yeast on its way to evolving tRNA editing?

In human mitochondria, genes for tRNA(Tyr) and tRNA(Cys) overlap by a single nucleotide. From polycistronic precursors, a 3'-truncated upstream tRNA(Tyr) is released, missing the overlapping position. A subsequent editing reaction restores this position. Similar mitochondrial tRNA gene overlaps exist in all metazoans, but not in organisms such as yeast or Escherichia coli. Therefore, we asked whether tRNA overlaps are processed in these organisms. Corresponding constructs were introduced and transcripts tested for processing and editing in E. coli and yeast. E. coli produces only one functional tRNA from these precursors, indicating that tRNA overlaps are incompatible with its processing pathway. In contrast, yeast processes overlapping tRNAs similar to human mitochondria, releasing a 3'-truncated upstream tRNA. This tRNA is restored in an editing-like event, although yeast does not carry a corresponding endogenous editing substrate. These findings support the hypothesis of the evolution of editing by recruitment of a pre-existing and promiscuous editing enzyme.

Base Sequence↗

Characterization of the mitochondrial orfB gene and its derivative, orf224, a chimeric open reading frame specific to one mitochondrial genome of the "Polima" male-sterile cytoplasm in rapeseed (Brassica napus L.).

orf224 is a novel reading frame present upstream of the atp6 gene in the mitochondria of "Polima" cms cytoplasm of rapeseed. In order to determine the origin of orf224, the sequences homologous to orf224 were isolated and characterized. Sequence analysis indicated that orf224 originated by recombination events involving the 5'-flanking region and the amino-terminal segment of the coding region of orf158 (well-known as orfB in other plants), part of exon 1 of the ribosomal protein S3 (rps3) gene, and an unidentified sequence. Transcripts of the orf158 gene were found to be edited at three positions, one of which induces an amino-acid change, while orf224 transcripts have only one RNA editing site within the region homologous to the rps3 gene. This editing site is also present in the proper rps3 transcripts. This result indicates that editing of orf224 occurred because of the sequence homology to rps3. Polyclonal antibodies prepared against a rapeseed ORF158 fusion protein specifically recognize a 18-kDa protein in the membrane fractions of mitochondria from both normal and cms rapeseed.

Amino Acid Sequence↗

In Vivo Genome Editing Approach to Disrupt Hydroxyacid Oxidase 1 for the Treatment of Primary Hyperoxaluria Type 1.

Primary hyperoxaluria type 1 (PH1) is a rare autosomal recessive disorder that leads to kidney and liver failure. PH1 is caused by a mutation in the alanine glyoxylate aminotransferase (AGXT) gene, which encodes a key metabolic enzyme that converts glyoxylate to glycine in the liver. Inability to metabolize glyoxylate leads to oxalate overproduction, yielding insoluble calcium oxalate crystals; accumulation of these crystals leads to progressive organ failure. Here, we used a novel, minimally disruptive genome-editing approach to disrupt the mechanism of action of hydroxyacid oxidase 1 (HAO1), an upstream enzyme in the glyoxylate metabolic pathway. Successful gene editing and disruption of the HAO1 gene is expected to increase levels of glycolate, a harmless intermediate of the glycine metabolic pathway, thereby preventing the formation of calcium oxalate crystals. We intravenously administered an adeno-associated virus (AAV) vector expressing the M1HAO1 meganuclease to both wild-type and Agxt-/- mice, a mouse model of PH1. We observed >30% editing of HAO1 in Agxt-/- mice, correlating with a dose-dependent increase in serum glycolate levels. At the highest dose tested, urine glycolate levels increased by 79%, with a concomitant 75% decrease in urine oxalate levels. We also evaluated in vivo targeting in rhesus macaques injected with AAV expressing two different versions of the HAO1 meganuclease. Dose-dependent editing of hepatic DNA and RNA was achieved, and serum glycolate levels changed in a manner consistent with successful liver editing; additionally, the treatment was well tolerated. Our results indicate that AAV-delivered meganucleases can effectively target HAO1 in mice and nonhuman primates to achieve high levels of HAO1 gene editing. Moreover, increased glycolate levels in serum indicate that this intervention significantly impacts the HAO1-mediated glycolate-to-glyoxylate pathway. These data suggest that this approach may represent an effective treatment for PH1.

Hyperoxaluria, Primary↗

An extensively edited mitochondrial transcript in kinetoplastids encodes a protein homologous to ATPase subunit 6.

The mitochondrial MURF4 gene of T. brucei has pronounced G versus C strand bias and heterogeneously sized transcripts, characteristic of genes encoding extensively edited transcripts. We find that MURF4 transcripts of T. brucei are extensively edited throughout by the addition and deletion of numerous uridines, creating potential initiation and termination codons and a continuous open reading frame. A potential guide RNA sequence occurs in a minicircle between inverted repeats. The 5' region of L. tarentolae MURF4 transcripts is also extensively edited, with a created initiation codon. The predicted MURF4 amino acid sequences have homology to those of mitochondrial ATP-ase subunit 6 genes from a variety of organisms. In addition, their hydropathic profiles are quite similar to those of other species. We therefore conclude that MURF4 encodes ATPase subunit 6 genes.

Adenosine Triphosphatases↗

Discovery and Engineering of a Rat Endogenous Retrovirus Reverse Transcriptase for Efficient Prime Editing.

CRISPR-based prime editors (PEs) install precise edits into genomic DNA without generating double-strand breaks. Their editing efficiency is highly dependent on reverse transcriptases (RTs), but efficient RT candidates remain limited. Here, we identified 19 novel active RTs by screening 558 candidates. Among them, RERV-RT, derived from Rattus norvegicus, exhibited the highest activity. Through structure-guided engineering and deep mutational scanning, we developed an optimized variant, enRERV-RT, which outperforms conventional M-MLV-RT-based PE systems by 1.20-fold in mammalian and plant cells, and by 1.88-fold at hard-to-edit loci, while enabling precise multiplex editing of functionally relevant genes. Additionally, we developed a high-throughput platform, TRAP-seq-PE, to systematically evaluate prime editor performance. Across diverse mutation types, we found that PE systems based on enRERV-RT exhibited higher editing efficiencies than those based on M-MLV-RT. Collectively, our work establishes a versatile, high-efficiency PE system, thereby facilitating advances in clinical gene therapy and precise crop breeding.

Animals↗

Development of pathogenic anti-DNA antibodies in patients with systemic lupus erythematosus.

The anti-DNA response is a hallmark of systemic lupus erythematosus (SLE). The precise mechanisms leading to anti-DNA antibody (Ab) production remain to be studied. Nonetheless, it is becoming clear that anti-DNA Abs cause inflammatory lesions not only via deposition of circulating immune complexes (IC) consisting of anti-DNA Ab and antigens (Ags), but also via in situ IC formation by cationic anti-DNA Abs. It is intriguing that cationic anti-DNA Abs are encoded by a unique germline Vkappa gene, A30, which encodes an extraordinary cationic light chain, whereas somatic mutations did not induce a cationic shift of electrical charge in human lupus nephritis, suggesting that the usage of a specific germline gene may confer the cationic charge (or pathogenicity) on anti-DNA Abs and that somatic mutations induce the affinity maturation of Abs. Whether cationic anti-DNA Abs will develop depends at least partly on the presence or absence of the germline A30 gene, since patients who lack this gene in the germline Vkappa repertoire did not develop severe lupus nephritis. Receptor editing, a mechanism for changing the affinity of the B cell Ag receptor [surface immunoglobulin (Ig) receptor] to avoid self-reactivity actually seems defective in patients with SLE because normal B cells edited the A30 gene, whereas SLE B cells express A30 mRNA. Thus, along with the importance of somatic mutations, polymorphisms of Ig Vkappa locus, and genetic predisposition, the failure of receptor editing may contribute to the development of pathogenic anti-DNA responses in humans.

Antibodies, Antinuclear↗

Control of gene expression by base deamination: the case of RNA editing in wheat mitochondria.

The term 'RNA editing' was used for the first time in 1986 to describe the process of uridylate insertion into trypanosomal mitochondrial transcripts. Since then, the term has been used more generally to describe a large variety of processes involving base insertions, deletions and conversions that generate RNAs with a primary sequence different to those encoded by the gene. RNA editing has been observed in the mitochondrial fraction of trypanosomes, plants and other organisms, in the animal nuclear fraction in the case of the apolipoprotein B and glutamate brain receptors mRNAs as well as in viruses like paramyxovirus, hepatitis delta and probably HIV. The role of cytidine and adenine deamination leading to C to U and A to I transitions has became pivotal to explain this process by base conversion. In this review we will focus mainly on the work performed in our group on plant mitochondria and more specifically on the mechanism and the functional significance of RNA editing in wheat organelles. The original contributions of our laboratory in this field are: i) showing that RNA editing is reflected at the protein level; ii) settling three in vitro systems to assay C to U conversion using a wheat mitochondrial lysate as source of enzymes and factors, and unedited mRNA from the same source, as substrate; iii) determination by double labelling of the unedited substrate that RNA editing in wheat mitochondria occurs via a deamination step; and iv) that introducing unedited proteins in the mitochondria of transgenic plants leads to the emergence of cytoplasmic male sterility supporting the idea that the role of this process is to produce functional proteins. Using the antisense approach in transgenic plants we were able to obtain a significant male fertility restoration.

Cytosine Deaminase↗

The molecular biology of the porcine paramyxovirus LPMV.

Protein and genomic studies of a previously uncharacterized porcine paramyxovirus (designated LPMV) confirmed that it was a member of the paramyxovirus genus. The nucleotide sequences and deduced amino acids of the complete P-gene, M-gene, F-gene and HN-gene as well as the intergenic sequences have been determined. Comparative sequence analysis of the M-gene of LPMV revealed the closest relationship of LPMV was to human mumps virus with a homology of 46% and 55% at the amino acid and nucleotide levels respectively. The P-gene of LPMV is transcribed to V protein mRNA and by editing of the gene to the P protein mRNA. The LPMV P-gene has the coding capacity for an additional protein of 126 amino acids, a C protein.

Amino Acid Sequence↗

Newcastle disease virus V protein is associated with viral pathogenesis and functions as an alpha interferon antagonist.

Newcastle disease virus (NDV) edits its P gene by inserting one or two G residues at the conserved editing site (UUUUUCCC, genome sense) and transcribes the P mRNA (unedited), the V mRNA (with a +1 frameshift), and the W mRNA (with a +2 frameshift). All three proteins are amino coterminal but vary at their carboxyl terminus in length and amino acid composition. Little is known about the role of the V and W proteins in NDV replication and pathogenesis. We have constructed and recovered two recombinant viruses in which the expression of the V or both the V and W proteins has been abolished. Compared to the parental virus, the mutant viruses showed impaired growth in cell cultures, except in Vero cells. However, transient expression of the carboxyl-terminal portion of the V protein enhanced the growth of the mutant viruses. In embryonated chicken eggs, the parental virus grew to high titers in embryos of different gestational ages, whereas the mutant viruses showed an age-dependent phenomenon, growing to lower titer in more-developed embryos. An interferon (IFN) sensitivity assay showed that the parental virus was more resistant to the antiviral effect of IFN than the mutant viruses. Moreover, infection with the parental virus resulted in STAT1 protein degradation, but not with the mutant viruses. These findings indicate that the V protein of NDV possesses the ability to inhibit alpha IFN and that the IFN inhibitory function lies in the carboxyl-terminal domain. Pathogenicity studies showed that the V protein of NDV significantly contributes to the virus virulence.

Animals↗

PREP-Mt: predictive RNA editor for plant mitochondrial genes.

BACKGROUND: In plants, RNA editing is a process that converts specific cytidines to uridines and uridines to cytidines in transcripts from virtually all mitochondrial protein-coding genes. There are thousands of plant mitochondrial genes in the sequence databases, but sites of RNA editing have not been determined for most. Accurate methods of RNA editing site prediction will be important in filling in this information gap and could reduce or even eliminate the need for experimental determination of editing sites for many sequences. Because RNA editing tends to increase protein conservation across species by "correcting" codons that specify unconserved amino acids, this principle can be used to predict editing sites by identifying positions where an RNA editing event would increase the conservation of a protein to homologues from other plants. PREP-Mt takes this approach to predict editing sites for any protein-coding gene in plant mitochondria. RESULTS: To test the general applicability of the PREP-Mt methodology, RNA editing sites were predicted for 370 full-length or nearly full-length DNA sequences and then compared to the known sites of RNA editing for these sequences. Of 60,263 cytidines in this test set, PREP-Mt correctly classified 58,994 as either an edited or unedited site (accuracy = 97.9%). PREP-Mt properly identified 3,038 of the 3,698 known sites of RNA editing (sensitivity = 82.2%) and 55,956 of the 56,565 known unedited sites (specificity = 98.9%). Accuracy and sensitivity increased to 98.7% and 94.7%, respectively, after excluding the 489 silent editing sites (which have no effect on protein sequence or function) from the test set. CONCLUSION: These results indicate that PREP-Mt is effective at identifying C to U RNA editing sites in plant mitochondrial protein-coding genes. Thus, PREP-Mt should be useful in predicting protein sequences for use in molecular, biochemical, and phylogenetic analyses. In addition, PREP-Mt could be used to determine functionality of a mitochondrial gene or to identify particular sequences with unusual editing properties. The PREP-Mt methodology should be applicable to any system where RNA editing increases protein conservation across species.

Amino Acid Sequence↗

Systematic discovery of CRISPR-boosted CAR T cell immunotherapies.

Chimeric antigen receptor (CAR) T cell therapy has shown remarkable success in treating blood cancers, but CAR T cell dysfunction remains a common cause of treatment failure1. Here we present CELLFIE, a CRISPR screening platform for enhancing CAR T cells across multiple clinical objectives. We performed genome-wide screens in human primary CAR T cells, with readouts capturing key aspects of T cell biology, including proliferation, target cell recognition, activation, apoptosis and fratricide, and exhaustion. Screening hits were prioritized using a new in vivo CROP-seq2 method in a xenograft model of human leukaemia, establishing several gene knockouts that boost CAR T cell efficacy. Most notably, we discovered that RHOG knockout is a potent and unexpected CAR T cell enhancer, both individually and together with FAS knockout, which was validated across multiple in vivo models, CAR designs and sample donors, and in patient-derived cells. Demonstrating the versatility of the CELLFIE platform, we also conducted combinatorial CRISPR screens to identify synergistic gene pairs and saturation base-editing screens to characterize RHOG variants. In summary, we discovered, validated and biologically characterized CRISPR-boosted CAR T cells that outperform standard CAR T cells in widely used benchmarks, establishing a foundational resource for optimizing cell-based immunotherapies.

Humans↗

Targeted Forward Genetics: Saturating Mutational Analyses of Specific Target Loci Within the Genome.

Precise allele replacement by homologous recombination (also known as "gene targeting" or "genome editing") allows scientists to engineer altered DNA sequences, insertions, or deletions at specific locations in the genome. Such reverse genetics provides powerful tools to elucidate the structure and function of regulatory DNA elements, genes, RNAs, and proteins within their natural, endogenous context. Here, we describe in detail the methodology for Targeted Forward Genetics (TFG), which supports population-scale, saturating screens of allele replacements spanning thousands of base pairs at a specific target locus in the genome. The overall approach and detailed protocols, developed for the fission yeast Schizosaccharomyces pombe, are extensible to other organisms in which gene targeting is feasible.

Schizosaccharomyces↗

Sequences directing C to U editing of the plastid psbL mRNA are located within a 22 nucleotide segment spanning the editing site.

In plastids, editing of an ACG codon to an AUG codon creates the translation initiation codon for the psbL and ndhD transcripts in tobacco. To identify the RNA segment required for psbL editing, chimeric kanamycin resistance genes were constructed containing psbL deletion derivatives, and tested in vivo for editing in transgenic plants. We report here that a 22 nucleotide segment is sufficient to direct efficient psbL editing, including 16 nucleotides upstream and five nucleotides downstream of the editing site. Mutation of the A nucleotide to a C upstream of the editing site completely abolished editing, while mutation of the downstream G to a C only reduced the editing efficiency. Out of the 22 nucleotide editing target sequence, the 16 upstream nucleotides were found to compete with the endogenous psbL transcript for a depletable trans-factor. To test whether editing of initiation codons involves a common trans-factor, a chimeric gene containing the ndhD editing site was expressed in tobacco plastids. As for psbL, editing of the ndhD site requires a depletable trans-factor. However, the ndhD trans-factor is distinct from that required for psbL editing. Distinct cissequences and trans-factor requirements for the psbL and ndhD editing sites indicate an individual recognition mechanism for the editing of plastid initiation codons.

Amino Acid Sequence↗

Hydrolytic nucleoside and nucleotide deamination, and genetic instability: a possible link between RNA-editing enzymes and cancer?

Post-transcriptional RNA editing generates novel gene products by changing the coding sequence of the transcript from that in the genome. Two classes of RNA editing exist in mammals, each of which involves an enzymatic deamination. These reactions have stringent sequence and structural requirements for their target RNAs, and each requires distinctive enzymatic machinery. Alterations in the expression or abundance of RNA-editing factors produce unanticipated alterations in the processing or expression of RNAs, in some cases outside their physiological targets. Recent findings suggest that unregulated expression of the cytidine-deaminase gene family might lead to deamination of deoxycytidine nucleotides in DNA. Aberrant or dysregulated RNA editing, or altered expression of editing factors, might contribute to genomic instability in cancer.

Animals↗