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Assessment of mRNA Decay and Calculation of Codon Occurrence to mRNA Stability Correlation Coefficients after 5-EU Metabolic Labeling.

mRNA translation and decay are tightly connected. This chapter describes a method to assess the influence of each codon identity on mRNA stability in cultured cells. The technique involves metabolic labeling of the nascent mRNAs by addition of the nucleoside analog 5-ethynyluridine (5-EU), purification of the RNA at different time-points after chase of the 5-EU, then biotinylation with Click chemistry, pull-down, and sequencing. The transcripts' half-lives are calculated from the expression level of each mRNA at the different time-points. Finally, the method describes the calculation of the Codon occurrence to mRNA Stability correlation Coefficient, or CSC, as a correlation between the codon occurrence in a transcript and the transcript half-life, for each codon.

RNA Stability

Using the Tether Function Assay to Identify Potential Regulators of mRNA Translation and mRNA Decay.

RNA binding proteins (RBPs) and their associated partners are key factors of posttranscriptional control of gene expression. To study and manipulate the functional consequences of binding of these regulators to their targets, several tethering assays have been developed, in which a protein of interest is brought to a reporter mRNA through heterologous RNA-protein interaction motifs. The effect of such constrained binding is then monitored by measuring the accumulation of the reporter protein and mRNA. This chapter describes a protocol for the λN-BoxB tether system in transiently transfected mammalian cells. Combining the luciferase reporter technology to quantify protein amounts by light measurement and RNA amounts by RT-qPCR, this assay provides a simple and robust way to analyze the consequences of any protein binding in a controlled and defined manner.

RNA, Messenger

Genome-Wide Impact of Human DBR1 Depletion on RNA Processing Networks Reveal a Connection Between Pre-mRNA Splicing, mRNA Surveillance and Stress Granule Dynamics.

The RNA lariat debranching enzyme DBR1 is essential for intron turnover and RNA metabolism, yet its broader impact on transcriptome regulation remains incompletely defined. To elucidate the consequences of DBR1 depletion, we performed transcriptome-wide RNA sequencing of DBR1-knockdown and wild-type HEK293 cells. Differential expression analysis revealed widespread perturbations in pathways linked to RNA splicing, mRNA surveillance, translational control, and stress-granule biology. Many of the most significantly altered transcripts encode splicing factors and RNA quality-control components, underscoring DBR1's influence on post-transcriptional regulation. Alternative splicing analysis showed changes across multiple event types, with exon skipping accounting for >50% of events, followed by mutually exclusive exons, alternative 5' and 3' splice sites, and retained introns, indicating that DBR1 depletion induces pervasive splicing defects. Direct spliceosome inhibition using isoginkgetin (blocks tri-snRNP recruitment) and pladienolide B (targets SF3B1) reproduced the DBR1-KD mis-splicing patterns of cell signaling genes and factors involved in RNA metabolism, supporting a functional link between DBR1 activity and alternative splicing. Notably, DBR1 knockdown revealed a subset of transcripts that are both NMD-sensitive and enriched within stress granules. Consistent with this observation, G3BP1 immunopurification and confocal microscopy further support a role for DBR1 and UPF1 in stress-granule dynamics, suggesting that these factors may participate at distinct stages to influence mRNA fate under stress conditions. Together, these findings indicate that DBR1 functions beyond lariat RNA turnover as a common regulator of RNA processing, transcriptome stability, and stress granule homeostasis, revealing intricate crosstalk between RNA splicing and RNA quality control pathways in human cells.

Humans

Rho-dependent termination and RNase E-mediated cleavage: dual pathways for RNA 3' end processing in polycistronic mRNA.

"Pre-full-length" transcripts are produced at the end of the polycistronic galactose (gal) operon, 5' galE-galT-galK-galM 3', via Rho-dependent transcription termination (RDT) and -independent transcription termination. The 3' end of the full-length galETKM mRNA is acquired by exonucleolytic processing of the 3'-OH ends of the pre-full-length transcripts. However, the gal operon produces an mRNA termed galE whose 3' end forms approximately 120 nucleotides downstream of the galE stop codon, within the subsequent gene, galT, thereby establishing polarity in gene expression. In this study, we investigated the molecular processes that generate the 3' end of galE mRNA. We discovered that the 3' ends of pre-galE mRNA are produced in the middle of galT as a result of the combination of two separate molecular processes-one previously reported as RDT and the other as unreported RNase E-mediated transcript cleavage. The 3' ends of pre-galE mRNA undergo exonucleolytic processing to the 3' end of galE mRNA observed in vivo. A hairpin structure containing an 8 bp stem and a 4-nucleotide loop, located 5-10 nucleotides upstream of the 3' ends of galE mRNA, blocks exoribonuclease digestion and renders transcript stability. These findings demonstrate that RNase E-contrary to its general role in mRNA degradation-produces RNA 3' ends that regulate polarity in gene expression.IMPORTANCEThis study reports the findings of two molecular mechanisms that generate the 3' ends of pre-galE mRNA in the gal operon, viz., Rho-dependent transcription termination and RNase E-mediated cleavage. These 3' ends are subsequently processed to produce stable galE mRNA with a hairpin structure that prevents exoribonuclease degradation. This mechanism establishes gene expression polarity by generating the 3' end of galE mRNA within galT in contrast to the usual mRNA degradation role of RNase E. The study reveals a unique role of RNase E in mRNA processing and stability.

RNA, Messenger

mRNA therapy: A novel approach for retinal neurodegenerative diseases.

Retinal neurodegeneration remains a major cause of irreversible vision loss, yet current therapeutic options are limited in effectiveness. Although gene therapies have shown clinical potential, the overexpression platforms they rely on, such as adeno-associated virus DNA, are constrained by safety concerns, limited efficacy, and cargo size restrictions. In contrast, mRNA therapy has gained recognition as a compelling alternative, enabling rapid and efficient protein expression without the risk of genomic integration. This review synthesizes recent advances in mRNA engineering, delivery systems, and administration routes for retinal applications, and highlight strategies to enhance targeting, penetration, and controlled release through interdisciplinary collaboration between ophthalmology and bioengineering. In recent years, engineered mRNA formats, including chemically modified linear, circular, and self-amplifying RNA, can achieve higher translation efficiency within a tunable expression window. The transient nature and relatively low immunogenicity of in vitro transcribed mRNA support repeat dosing without insertional mutagenesis. Advances in nanocarriers, particularly lipid nanoparticles, have enabled preferential delivery to retinal neurons, Müller glia, and pigment epithelium via intraocular administration, while improving mRNA stability and transfection efficiency. In preclinical studies, mRNA has been widely used to deliver gene-editing tools, transcription factors, and supplementary functional proteins. In disease models such as optic nerve crush and laser-induced choroidal neovascularization, mRNA-based therapies enhance neuroprotection and suppress pathological angiogenesis in the injured retina, with favorable ocular safety profiles. However, it remains largely unexplored how the intrinsic advantages of mRNA therapy can be leveraged to develop tailored strategies for complex retinal disorders. Consistent with this gap, mRNA platforms have not yet been widely incorporated into retinal research or clinical practice. In parallel, clinical translation also lags: despite encouraging outcomes of lipid nanoparticle-mRNA formulations in preclinical models, no candidates have progressed into retinal clinical trials. This review draws on the complex pathology and therapeutic logic of retinal neurodegeneration. It proposes that mRNA therapy enables multitarget, repeatable, stage-specific interventions that align with the dynamic evolution of diseases and the requirements of combination therapy in retinal diseases. It may be used to support neuroprotection, axon regeneration, and neurovascular regulation. By integrating data across experimental models and modalities, this review outlines representative cases and experimental paradigms to guide rational trial design and carrier selection. Taken together, technical progress and evolving application strategies position mRNA therapy as a compelling therapeutic avenue for retinal neurodegeneration.

administration

Safety and immunogenicity of an mRNA COVID-19 vaccine administered to adults: A phase 2, randomized, active-controlled trial.

We conducted a phase 2, randomized, active-controlled, observer-blind study (NCT05960097) among healthy adults ≥18 y of age who completed a primary COVID-19 mRNA vaccination series, with or without a booster, ≥3 months earlier. Participants were randomized (1:1:1:1:1) to either receive an investigational bivalent mRNA COVID-19 vaccine encoding ancestral D614G and Omicron BA.4-5 spike proteins (CV0701 mRNA vaccine) at one of three dose levels, an investigational monovalent mRNA COVID-19 vaccine encoding the Omicron BA.4-5 spike protein (CV0601 mRNA vaccine), or a licensed Original Wuhan/Omicron BA.4-5 bivalent mRNA COVID-19 vaccine. The primary objectives were to evaluate reactogenicity, safety and immunogenicity post-vaccination. Secondary and tertiary objectives were to further evaluate humoral and cell-mediated immunity post-vaccination. In total, 425 participants were vaccinated and 381 were included in the Day 29 per-protocol immunogenicity analysis. Most solicited events were mild to moderate. No vaccine-related serious adverse events or myocarditis/pericarditis cases were reported. For the CV0701 mRNA vaccine, a dose-dependent increase in Day 29 neutralizing titers against ancestral D614G and Omicron BA.4-5 was observed. Neutralizing titers against ancestral D614G and Omicron BA.4-5 declined by Days 91 and 181, but remained above baseline. Similar immune responses were observed for the CV0601 mRNA vaccine. At Day 8, CD4+ T cells (Th1 profile) increased in all study groups and CD8+ T cells increased in all study groups, except the lowest CV0701 dose group. The CV0701 and CV0601 mRNA vaccines elicited robust humoral and cellular immunity with an acceptable safety profile, comparable to a licensed, bivalent mRNA vaccine. Clinical Trial Registration EU CT number: 2023-504596-25-00 ClinicalTrials.gov: NCT05960097.

Humans

mRNA vaccine immunity is enhanced by hepatocyte detargeting and not dependent on dendritic cell expression.

Proteins encoded by mRNA vaccines can be expressed by a diversity of transfected cell types but how cell-type-specific expression influences immunity is poorly understood. To investigate this, we incorporated synthetic microRNA target sites (miRT) into lipid nanoparticle (LNP)-delivered mRNA vaccines to silence mRNA expression specifically in professional antigen-presenting cells (pAPCs), hepatocytes or myocytes. We found that mRNA expression in pAPCs was dispensable for priming antigen-specific T cells, whereas mRNA expression in myocytes induced similar or stronger immune responses, including for SARS-CoV-2, suggesting that antigen cross-presentation or cross-dressing may be more impactful than direct mRNA expression in pAPCs. In contrast, mRNA expression in hepatocytes suppressed the antigen-specific T cell response, partly through PD1/PDL1. In mice bearing tumor-associated antigen (TAA)-expressing lymphoma cells, miRT-mediated hepatocyte-silenced TAA mRNA vaccine enhanced immune response and reduced tumor burden. Thus, non-pAPC expression shapes immunity to mRNA-encoded protein and inclusion of miRTs can boost or blunt mRNA-LNP immunogenicity.

Journal Article

mRNA turnover dynamics are affected by cell differentiation and loss of the cytosine methyltransferase Nsun2.

Nsun2 catalyzes 5-methylcytosine (m5C) formation in several types of RNA, including messenger RNAs (mRNAs), transfer RNAs, and other non-coding RNAs. In mRNA, m5C was reported to influence transcript stability. However, it is unclear if it has stabilizing or destabilizing effects. To address the role of Nsun2 in mRNA stability, we characterized the landscape of mRNA turnover dynamics during embryonic stem cell (ESC) differentiation in wild-type and Nsun2-mutant cells. By using an RNA labeling approach combined with thiouridine-to-cytidine-sequencing (TUC-seq), we demonstrate that mRNA synthesis and stability undergo extensive changes during normal cellular differentiation. Remarkably, a large proportion of these changes did not result in altered mRNA abundance, providing evidence for robust transcript buffering during ESC differentiation. Importantly, also the loss of Nsun2 affected mRNA turnover dynamics but not the steady-state levels of transcripts. Furthermore, our data indicate that the effect of Nsun2 on mRNA turnover was not mediated by m5C deposition in mRNA, which is corroborated by catalysis-independent effects of Nsun2 on translation in early ESC differentiation. In conclusion, this study demonstrates that differentiation as well as loss of Nsun2 can induce changes in mRNA turnover dynamics that are independent of mRNA methylation but consistent with a buffering mechanism to maintain constant RNA levels.

Cell Differentiation

Investigating the miRNA-mRNA interactome of human trabecular meshwork cells treated with TGF-β1 provides insights into the pathogenesis of pseudoexfoliation glaucoma.

Pseudoexfoliation glaucoma is a severe form of secondary open angle glaucoma and is associated with activation of the TGF-β pathway by TGF-β1. MicroRNAs (miRNAs) are small non-coding RNA species that are involved in regulation of mRNA expression and translation. To investigate what glaucomatous changes occur in the trabecular meshwork and how these changes may be regulated by miRNAs, we performed a bioinformatics analysis resulting in a miRNA-mRNA interactome. Primary human trabecular meshwork cells originating from normal donors were treated with TGF-β1 at 5 ng/mL for 24h; total RNA was extracted followed by RNA-Seq and miRNA-Seq. For both mRNA and miRNA species, differential expression was determined using a bioinformatics pipeline consisting of FastQC, STAR, FeatureCounts, edgeR (for miRNA) and DESeq2 (for mRNA). Putative mRNA-miRNA interactions between differentially expressed mRNA and miRNA species were determined using interaction databases miRWalk, miRTarBase, TarBase and TargetScan. To classify mRNA species by function and pathway, gene enrichment was performed using Enrichr. The resulting miRNA-mRNA interactome consisted of 1202 interactions. Some highly connected microRNAs were hsa-let-7e-5p, hsa-miR-20a-5p, hsa-miR-122-5p, and hsa-miR-29c-3p. Most differentially expressed genes were indicated to be regulated by miRNAs. The sub-interactomes of genes involved in specific pseudoexfoliation glaucoma related enrichment terms such as oxidative stress, unfolded protein response, signal molecules and ECM remodelling were determined. This is the first study to present a genome-wide microRNA-mRNA regulatory network for human trabecular meshwork cells treated with TGF-β1 and may serve to generate unbiased hypotheses about regulatory functions and mRNA targets of miRNAs in pseudoexfoliation glaucoma and may help to develop miRNA-based therapeutics.

Humans

A hormone-dependent tRNA half promotes cell cycle progression via destabilization of p21 mRNA.

tRNA halves are among the most abundant short non-coding RNAs in the cellular transcriptome. Here we report that in androgen receptor-positive LNCaP prostate cancer cells, the hormone-dependent 5'-tRNALysCUU half promoted cell proliferation by facilitating cell cycle progression. Global mRNA profiling upon the 5'-tRNALysCUU half depletion revealed that the mRNA of p21, a negative regulator of the cell cycle, is post-transcriptionally destabilized via a 5'-tRNALysCUU half-driven mechanism. YBX1, identified as a protein interacting with 5'-tRNALysCUU half in the cytosol, was shown to stabilize p21 mRNA. Specific sequences resembling the 5'-tRNALysCUU half, located in the 3'-UTR of p21 mRNA and termed LL588, were identified as the binding site for YBX1 and are required for p21 mRNA stability. In vitro binding assays demonstrated that the 5'-tRNALysCUU half is capable of displacing YBX1 from LL588. Collectively, our findings suggest that the 5'-tRNALysCUU half directly binds to and displaces YBX1 from p21 mRNA, leading to the destabilization of p21 mRNA and the promotion of cell cycle progression in hormone-dependent cancers. Our study illuminates the role of tRNA halves in regulating mRNA stability and suggests that this may be part of broader regulatory networks affecting mRNA levels, orchestrated by various tRNA halves and their interacting proteins.

Humans

Codon Composition in Human Oocytes Reveals Age-Associated Defects in mRNA Decay.

Oocytes from women of advanced reproductive age exhibit diminished developmental potential, but the underlying mechanisms remain incompletely defined. Oocyte maturation depends on translational control of maternal mRNA synthesized during growth. We performed a computational analysis on human oocytes from women <30 versus &#x2265;40 years and observed that mRNA GC content correlates negatively with half-life in oocytes from young (<30 yr) but positively with oocytes from aged (>40 yr) women. In young oocytes, longer mRNA half-life is associated with lower protein abundance, whereas in aged oocytes GC content correlates positively with protein abundance. During the GV-to-MII transition, codon composition stratifies stability: codons that support rapid translation (optimal) stabilize mRNA, while slow-translating codons (non-optimal) promote decay. With reproductive aging, GC-containing codons become more optimal and align with increased protein abundance. These findings indicate that reproductive aging remodels codon-optimality-linked, translation-coupled mRNA decay, stabilizing a subset of GC-rich maternal mRNA that may be prone to excess translation during maturation. Our analysis is explicitly within human reproductive aging; it does not revisit cross-species stability rules. Instead, it shows that sequence-stability relations are reprogrammed with age within human oocytes, including an inversion of the GC-stability association during GV-to-MII transition. Disruption of the normal mRNA clearance program in aged oocytes may compromise oocyte competence and alter maternal mRNA dosage, with downstream consequences for early embryonic development.

Humans

Nitric oxide-assisted lipid nanoparticles amplify mRNA vaccine responses.

mRNA vaccines have made substantial clinical advances, yet their full clinical potential can be further expanded by enhancing cytosolic delivery. Here, we integrate a nitric oxide (NO) generator with lipid nanoparticles (LNPs) to boost mRNA delivery efficiency and mRNA-based vaccine efficacy. SM-102/DEA LNPs, the lead formulation, achieved significantly higher mRNA delivery compared with the FDA approved SM-102 LNPs in both cellular and animal models. The intramuscular administration of SM-102/DEA LNPs encapsulating mRNA encoding SARS-CoV-2 spike protein elicited substantially higher anti-spike IgG levels and robust CD8+ and CD4+ T cell responses compared to SM-102 LNPs. Mechanistic studies revealed that DEA incorporation promotes endosomal escape of mRNA cargos in SM-102/DEA LNPs. These findings establish NO-assisted LNPs as a unique platform for potent mRNA delivery, which provides a new paradigm for overcoming endosomal barriers and improving the efficacy of mRNA vaccines.

COVID-19

Hexokinase 2 is an RNA-binding protein that regulates mRNA translation independently of glycolysis and induces melanoma cell proliferation.

Although metabolic benefits of glycolysis have been extensively described in tumor cells, the extra-metabolic functions linked to this energetic pathway in tumor growth and cell proliferation have not been clearly established yet. Recently, some key glycolytic enzymes, such as glyceraldehyde-3-phosphate dehydrogenase and pyruvate kinase 2, were reported to regulate mRNA translation. Translational control of gene expression is considered as a critical effector in cancer biology, representing a highly promising area of research. Here, we report that Hexokinase 2 (HK2), a glucose kinase that catalyzes the first step of glycolysis at the outer mitochondrial membrane (OMM), is an RNA-binding protein (RBP) that regulates mRNA translation in melanoma cell lines. Polysome profiling experiments followed by RNA sequencing indicate that the translational regulation exerted by HK2 is partly independent of the metabolic status or the glycolytic pathway. We found that HK2 specifically regulates translation of the mRNA encoding SOX10, a transcription factor implicated in the regulation of tumor initiation, maintenance, and progression in melanoma. RNA-protein interaction assays, including CrossLinking ImmunoPrecipitation (CLIP), indicate that HK2 is an RBP whose interaction with RNA is independent of its enzymatic activity, its ability to bind glucose or its association with the OMM. HK2 directly interacts with the 5' untranslated region (5'UTR) of the SOX10 mRNA through a stem-loop RNA secondary structure. Using RNA-protein proximity ligation assays and a fluorescence-based ribosome-bound mRNA mapping method, we found that high glucose conditions, which promote the release of HK2 from the OMM, induce an increase in HK2-SOX10 mRNA interaction and SOX10 mRNA translation in the cytoplasm. We further showed that HK2-dependent SOX10 mRNA translation is involved in melanoma cell proliferation and colony formation. Collectively, our data highlight a nonmetabolic function of HK2 acting as an RBP and translation regulator.

Hexokinase

Sequence optimization targeting mRNA stability enhances monoclonal antibody titers in CHO cells.

This study presents a DNA sequence optimization approach that integrates mRNA stability as a tunable design parameter to enhance monoclonal antibody expression in Chinese hamster ovary (CHO) cells. A comprehensive combinatorial library of synonymous coding-sequence variants of an IgG1 light chain was integrated as single copies at a defined genomic locus in CHO cells with identical regulatory elements. Steady-state mRNA abundance, quantified by deep sequencing of gDNA and mRNA, served as a proxy for mRNA stability. These data were used to train a machine learning model that predicts mRNA abundance from coding sequence using embeddings from a pre-trained nucleotide transformer. This abundance predictor, together with established translational metrics, was incorporated into a genetic algorithm for multi-objective codon optimization. As proof-of-concept, we optimized sequences encoding Trastuzumab to either maximize or minimize the abundance criterion and obtained benchmark sequences from two commercial providers. Using targeted integration, we generated CHO cell lines and measured protein titer and cell-specific productivity. Sequences optimized for high abundance significantly increased intracellular mRNA levels (+41%), protein titer (+59%), and cell-specific productivity (+85%) relative to low-abundance designs, while viable cell densities remained comparable. Compared to commercial benchmarks, high-abundance sequences achieved significantly higher titer (+70%) and cell-specific productivity (+98%). These findings establish mRNA stability as a practical and complementary design parameter for codon optimization in monoclonal antibody production, with potential applicability to other proteins and expression systems.

CHO

Cytoplasmic mRNA decay and quality control machineries in eukaryotes.

mRNA degradation pathways have key regulatory roles in gene expression. The intrinsic stability of mRNAs in the cytoplasm of eukaryotic cells varies widely in a gene- and isoform-dependent manner and can be regulated by cellular cues, such as kinase signalling, to control mRNA levels and spatiotemporal dynamics of gene expression. Moreover, specialized quality control pathways exist to rid cells of non-functional mRNAs produced by errors in mRNA processing or mRNA damage that negatively impact translation. Recent advances in structural, single-molecule and genome-wide methods have provided new insights into the central machineries that carry out mRNA turnover, the mechanisms by which mRNAs are targeted for degradation and the general principles that govern mRNA stability at a global level. This improved understanding of mRNA degradation in the cytoplasm of eukaryotic cells is finding practical applications in the design of therapeutic mRNAs.

RNA Stability

Long-range mRNA folding shapes expression and sequence of bacterial genes.

Bacterial gene expression is strongly influenced by local mRNA secondary structure, yet the impact of long-range folding remains poorly understood. Here, we show that sequences hundreds of nucleotides from the mRNA 5' end can act as potent repressors of gene expression through long-range base pairing to the ribosome binding site (RBS), subjecting anti-RBS sequences to negative selection. Using massively parallel reporter assays in Bacillus subtilis, we identify anti-RBS sequences as among the strongest determinants of reduced mRNA abundance across the transcript body. We demonstrate that distal anti-RBS elements engage in long-range folding with the Shine-Dalgarno sequence, blocking ribosome entry and promoting mRNA decay. Consistent with these repressive effects, anti-RBS-like sequences are depleted throughout diverse bacterial coding sequences but not from leaderless transcripts, and introducing distal anti-RBS to native genes reduces expression. Our findings establish that long-range mRNA folding is a conserved force shaping gene expression and constrains coding sequence evolution.

Bacillus subtilis

Abundant mRNA m1A modification in dinoflagellates: a new layer of gene regulation.

Dinoflagellates, a class of unicellular eukaryotic phytoplankton, exhibit minimal transcriptional regulation, representing a unique model for exploring gene expression. The biosynthesis, distribution, regulation, and function of mRNA N1-methyladenosine (m1A) remain controversial due to its limited presence in typical eukaryotic mRNA. This study provides a comprehensive map of m1A in dinoflagellate mRNA and shows that m1A, rather than N6-methyladenosine (m6A), is the most prevalent internal mRNA modification in various dinoflagellate species, with an asymmetric distribution along mature transcripts. In Amphidinium carterae, we identify 6549 m1A sites characterized by a non-tRNA T-loop-like sequence motif within the transcripts of 3196 genes, many of which are involved in regulating carbon and nitrogen metabolism. Enriched within 3'UTRs, dinoflagellate mRNA m1A levels negatively correlate with translation efficiency. Nitrogen depletion further decreases mRNA m1A levels. Our data suggest that distinctive patterns of m1A modification might influence the expression of metabolism-related genes through translational control.

Dinoflagellida

Cold-adapted RNA polymerase from Pseudomonas phage Njord improves synthesis of therapeutic mRNA.

An RNA polymerase identified in the genome of Pseudomonas phage Njord offers a promising tool for the synthesis of mRNA and other therapeutic nucleic acids. Originating from a marine microbial ecosystem, Njord RNAP transcribes RNA at high yield even under low temperature conditions. Key properties of the enzyme relevant to mRNA synthesis are presented including transcriptional fidelity, promoter specificity, incorporation of modified nucleotides, and the impurity profile of the RNA. Specific attention is given to the formation of contaminating double-stranded RNA (dsRNA) species. Analysis of transcription reactions shows that DNA-templated promoter-independent transcription is a major source of detectable dsRNA impurities and that Njord RNAP displays a minimal level of this activity. Consistent with the known inflammatory role of dsRNA in synthetic mRNA, transcriptomic analysis of cell culture and a live animal study demonstrates that mRNA synthesized with Njord RNAP elicits only a minimal immune response. This natural enzyme enables efficient mRNA synthesis at ambient temperature and produces transcripts essentially free of dsRNA, offering significant potential to streamline mRNA manufacturing processes.

DNA-Directed RNA Polymerases