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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

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, M&#xfc;ller 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

A change in the stability of globin mRNA during the induction of murine erythroleukemia cells.

The stability of globin mRNA in murine erythroleukemia cells (Friend cells) before and during DMSO-induced differentiation was investigated. Cells were exposed to 3H-uridine for 2 hr and then transferred to medium without the radioactive precursor. The loss of radioactivity in total RNA, poly(A)-containing RNA and globin mRNA was followed. The globin mRNA was isolated using a highly specific globin cDNA column. In uninduced cells and cells early in differentiation, the globin mRNA decays with a half-life of less than 50 hr. After 4 days of induction, the globin mRNA decays with a half-life of 17 hr, demonstrating a change in stability during the induction process. Although the stability of globin mRNA changes during induction, this is not true for total poly(A)-containing RNA. At all times of induction, the poly(A)-containing RNA decays as two populations, one with a half-life of 6 hr and the other with a half-life of 36 hr. The half-life of the rRNA also remains unchanged during differentiation.

Cell Differentiation

Dual regulation of the receptor-like kinase BIR1 involves site-directed transcript cleavage and 5'-leader-mediated translational control.

In Arabidopsis, BRASSINOSTEROID INSENSITIVE1-ASSOCIATED RECEPTOR KINASE 1 (BAK1)-INTERACTING RECEPTOR-LIKE KINASE 1 (BIR1) is a negative regulator of plant immunity and cell death. BIR1 was earlier described as a target of epigenetic and post-transcriptional degradation. During virus infections, degradome analysis of BIR1 transcripts mapped predominant mRNA cleavage sites at the 5'-untranslated leader region (site A) and the protein-coding sequence (sites B and C). Here, we identified another virus-associated cleavage site (D) within the BIR1 coding region and investigated the contribution of site-directed mRNA cleavage to BIR1 regulation. Mutations at B, C, and D sites enhanced mRNA stability by impairing transcript cleavage, resulting in increased BIR1 mRNA and protein accumulation. This regulation is disrupted in RNA silencing mutants, supporting a model of cis-directed small interfering RNA (siRNA)-mediated degradation. We next demonstrate that virus infection reduces BIR1 translation in Arabidopsis. Furthermore, our data reveal a repressive role for the 5'-leader in regulating BIR1 translation, potentially mediated by upstream open reading frames (uORFs) and a virus-responsive long non-coding RNA (lncRNA) derived from the natural antisense At4g39838 locus. Together, these findings reveal a multilayered regulatory mechanism that integrates sRNA-mediated cleavage with translational control, with broader implications for the fine-tuning of stress-responsive gene expression during infection.

Arabidopsis

m1A methylase TRMT6 promotes neuroblastoma development by demethylating SST mRNA in an m1A/YTHDF2-dependent manner.

BACKGROUND: m1A, a prevalent RNA modification found in various RNA species, has recently been reported to modulate cancer progression. However, its effects on neuroblastoma remain uninvestigated. METHODS: The PCAT database was utilized to analyze the mRNA levels and survival probabilities of m1A regulator genes (TRMT6, TRMT61A, ALKBH1, and ALKBH3) in neuroblastoma patients. Silencing and recovery of TRMT6 were employed to investigate its role in neuroblastoma in vitro and in vivo. m1A-seq and RIP-qPCR were performed to identify and confirm the downstream targets of TRMT6. Additionally, Actinomycin D treatment was administered to assess mRNA stability. RESULTS: m1A transmethylase TRMT6 expression was significantly elevated in high-risk and late-stage neuroblastoma patients. Functionally, TRMT6 promotes the malignancy of neuroblastoma cells in vitro and promotes tumor growth and metastasis in vivo. Mechanistically, TRMT6 reduces SST mRNA levels by inhibiting its stability in an m1A-YTHDF2-dependent manner, thereby promoting the development of neuroblastoma. Furthermore, SST analog octreotide suppresses neuroblastoma cell malignancy, tumor growth, and metastasis. CONCLUSIONS: TRMT6 mediates m1A modification of SST to promote neuroblastoma progression, suggesting that targeting TRMT6 may be a novel potential therapeutic approach for treating neuroblastoma.

Neuroblastoma

Control of synthesis of mRNA's for T4 bacteriophage-specific dihydrofolate reductase and deoxycytidylate hydroxymethylase.

A 30 degrees C, functional messengers for dCMP hydroxymethylase first appeared 3 to 6 min postinfection and reached their maximum levels at 12 min. Chloramphenicol, added before the phage, reduced the rate of mRNA accumulation. When the antibiotic was added 6 min postinfection, mRNA levels increased at their normal rate but there was no obvious repression of messenger accumulation. Delaying the addition of drug until 8 or 12 min had progressively less effect on the pattern of hydroxymethylase mRNA metabolism. When chloramphenicol was present from preinfection times or from 6 min postinfection, all hydroxymethylase mRNA's synthesized were stable; at later times, however, the ability of the drug to stabilize mRNA decreased with its ability to delay the turnoff of mRNA production. An overaccumulation of hydroxymethylase mRNA was also seen when phage-specific DNA synthesis was inhibited either by mutational lesion in an essential viral gene or by 5-fluorodeoxyuridine. By min 20 of a DNA-negative program, hydroxymethylase mRNA synthesis was repressed to the point where it no longer compensated for decay. However, a finite level of hydroxymethylase mRNA synthesis was maintained at later times of a DNA-negative infection. Such results indicate that replication of the phage chromosome is necessary but not sufficient for a complete turnoff of hydroxymethylase mRNA production. Functions controlled by the maturation-defective proteins (the products of genes 55 and 33) played only a minor role in the regulation of hydroxymethylase mRNA, metabolism. Thus, we favor the hypothesis that a complete turnoff of hydroxymethylase messenger production requires one or more new proteins as well as an interval of DNA replication. The absence of DNA synthesis had no particular effect upon dihydrofolate reductase messenger production. The preinfection addition of chloramphenicol likewise had little effect on dihydrofolate reductase messenger metabolism. These latter data imply that prior synthesis of a phage-coded protein synthesis may not be required for the turnoff of reductase messenger production.

Chloramphenicol

[Stabilization of polyribosomal mRNA in rat liver cells under protein synthesis inhibition by cycloheximide].

It was found that in the course of centrifugation of the postmitochondrial fraction from rat liver in the sucrose concentration gradient, mRNA located in the EDTA-resistant structures sedimented together with polyribosomes. The same structures were detected in the polyribosomal fraction of liver cells after injection of ethionine to the animals. Centrifugation of polyribosomes through a layer of 2.0 M sucrose at 105 000 g for 4 hrs and subsequent centrifugation through a layer of 1.0 M sucrose resulted in the disappearance of the complexes from the polyribosomal fraction. Evidence for the absence of destruction of labelled polyribosomal mRNA in liver cells following the injection of cycloheximide were obtained. Actinomycin D also stabilized polyribosomal mRNA in liver cells, however, in a much lesser degree as compared to cycloheximide. Possible mechanisms of the stabilizing effects of cycloheximide and actinomycin D on polyribosomal mRNA in liver cells are discussed.

Animals

Programmable in vivo mRNA circularization for enhanced gene expression in bacteria.

The minute-scale lifetime of mRNA strongly influences bacterial gene expression, whereas a robust and programmable approach to directly control the mRNA stability and topology remains elusive. Here, we develop CRESEnT (Circular RNA Expression for Stable and Enhanced Translation), a programmable in vivo mRNA circularization system based on a permuted intron-exon architecture to engineer mRNA topology. CRESEnT enables facile circularization of mRNA, which led to a substantial increase in protein expression across diverse promoters, RBS variants, genetic cargos, and bacterial hosts. Furthermore, application of CRESEnT to biosynthetic pathways increased the production of several value-added metabolites, demonstrating that mRNA circularization can be harnessed to improve the metabolic performance of microbial cell factories. Together, these results establish RNA topology engineering via circularization as a transformative axis for controlling bacterial gene expression and enhancing the functionality of microbial cells.

RNA, Messenger

Post-transcriptional control of KRAS: functional roles of 5'UTR RNA G-quadruplexes, long noncoding RNA, and hnRNPA1.

Previous studies have shown that human KRAS expression is regulated at the transcriptional level by G-quadruplex DNA structures within its promoter. Here we show an additional level of regulation involving a post-transcriptional mechanism centred on the 5'-untranslated region (5'UTR) of the messenger RNA (mRNA) characterized by G4 structures (rG4s). Long noncoding RNAs (lncRNAs) and the protein hnRNPA1 are also involved in this mechanism. RIP-seq confirmed the presence of rG4s in the 5'UTR. Deletion of the rG4 region using CRISPR/Cas9 resulted in a significant increase in KRAS mRNA levels, indicating the role of the 5'UTR in controlling mRNA levels. RIP shows that hnRNPA1 is recruited to the 5'UTR, where it unfolds the rG4 structures and potentially affects mRNA stability. In addition, lncRNAs transcribed from the LINC01750 locus can hybridize to the rG4 region of 5'UTR and form RNA duplexes leading to RNase III-assisted degradation of the targeted mRNA. Activation of the LINC01750 locus with dCas9-VP64 resulted in downregulation of KRAS mRNA, whereas its suppression with dCas9-KRAB led to upregulation of both KRAS mRNA and protein. Since lncRNA-mediated regulation of mRNA appears to be a crucial aspect of cellular homeostasis and its disruption contributes to various diseases, understanding these mechanisms may&#xa0;reveal promising new therapeutic targets.

Humans

Non-Coding c.*6C>T Variant in RBM8A Associated With Thrombocytopenia-Absent Radius (TAR) Syndrome in Three Indian Patients.

Thrombocytopenia-absent radius (TAR) syndrome is a rare genetic disorder characterized by the absence of radius in the forearms and a decrease in platelet count. The molecular basis of TAR syndrome is linked to a heterozygous minimal deletion within the 1q21.1 region spanning 200&#x2009;k bases (kb), resulting in a null allele and a nucleotide variation in RBM8A resulting in a hypomorphic allele. Previous studies have identified pathogenic variants in the coding regions of the RBM8A gene as the cause of TAR syndrome. However, the involvement of non-coding variants in disease pathogenesis remains largely unexplored. We investigated the association of a non-coding 3' UTR variant, c.*6C>T, in RBM8A with TAR syndrome in three individuals from two unrelated families of Indian origin. Our study provides evidence that this variant is associated with decreased stability of the transcript and is a hypomorphic allele with disease-causing impact when in trans with a null allele (1q21.1 deletion). The present work is the first application of an mRNA stability assay to directly detect RNA degradation in patients with non-coding RBM8A variants causing TAR syndrome.

Humans

Molecular genetics of human hemoglobin synthesis.

Molecular analysis of normal and abnormal human globin genes and their gene products has recently provided information on the precise genetic events that result in hemoglobinopathies. In the case of structurally abnormal hemoglobins, the following mechanisms can be invoked: single nucleotide base substitutions leading to amino acid replacement or chain termination variants; nucleotide deletions (or additions) leading to deletion and frameshift variants; and nonhomologous crossing over leading to the production of fused globin chains. The molecular basis of the thalassemia syndromes, disorders characterized by absent or decreased synthesis of alpha- or beta-globin chains, is quite heterogeneous. In some cases globin gene deletions have been demonstrated; whereas in others there is probably either a defect in globin gene transcription or a defect in nuclear globin messenger RNA (mRNA) processing, mRNA transport or globin mRNA stability. In one form of beta(0)-thalassemia a nonsense mutation has recently been demonstrated, and other cases are also associated with some as yet undetermined functional abnormality of beta-globin mRNA.

Amino Acid Sequence

Identification of a Novel Splice-Site variant in TACR3 (c.888&#x2009;+&#x2009;1G&#x2009;>&#x2009;A) Associated with Asthenozoospermia and Hypogonadotropic Hypogonadism in an Iranian Family.

BACKGROUND: TACR3 encodes the receptor for neurokinin B, a key regulator of the hypothalamic-pituitary-gonadal axis. Disruption of this pathway can impair gonadotropin release and male reproductive function. Given the genetic heterogeneity of male infertility, this study aimed to identify novel variants in TACR3 that may underlie asthenozoospermia and related hormonal abnormalities. METHODS: Fifteen infertile men with confirmed asthenozoospermia were enrolled. Whole-exome sequencing (WES) was performed on genomic DNA from peripheral blood, and the candidate variant was validated by Sanger sequencing. Functional predictions were made using PolyPhen-2, SIFT, MutationTaster, and REVEL. TACR3 mRNA expression levels were assessed by real-time PCR in available samples. RESULTS: A novel splice-site variant, TACR3 (NM_001059.3:c.888&#x2009;+&#x2009;1G&#x2009;>&#x2009;A), was detected and found to segregate with infertility in one family, appearing homozygously in two infertile brothers and heterozygously in the proband with severe asthenozoospermia. The variant was absent in public and local genomic databases, suggesting its extremely rare frequency. Furthermore, RT-PCR showed a dramatic reduction or complete loss of TACR3 expression in affected individuals, confirming its deleterious effect on splicing and mRNA stability. CONCLUSION: We identified a previously unreported splice-site mutation in TACR3 (c.888&#x2009;+&#x2009;1G&#x2009;>&#x2009;A) that likely causes familial infertility by disrupting the neurokinin B/NK3R signaling pathway. While the heterozygous proband exhibited severe asthenozoospermia, the homozygous brothers displayed hormonal profiles typical of hypogonadotropic hypogonadism. These findings extend the mutational landscape of TACR3 and highlight its essential contribution to male reproductive endocrinology.

Humans

Detection of mitochondrial tDRs in killifish embryos and other non-model organisms.

In recent years a diversity of small noncoding RNAs have been identified that originate from the mitochondrial genome. These mitosRNAs are often dominated by tRNA-derived small RNAs (mito-tDRs). Differential expression of mito-tDRs is associated with responses to stress. They also appear to be expressed differentially during development and their expression may be enriched in stress-tolerant animals. Very little is currently known about roles or modes of action of these sequences, although they are implicated in a diversity of processes such as cell cycle regulation, mRNA stability, regulation of ROS production, and import of proteins into the mitochondrion. To better understand the various roles these sequences may play, it is critical that we understand their diversity, cellular location, and the context for their expression. This protocol outlines the methodologies used to detect mitosRNAs, including mito-tDRs, in embryos and cells of the annual killifish Austrofundulus limnaeus. We highlight critical steps in the isolation of RNA, creation of sequencing libraries, bioinformatics processing of sequence data, and methods for validation of expression that support a robust discovery pipeline for mitosRNAs even from species with incomplete reference genome sequences.

Animals

Pseudogene-Derived Long Noncoding RNAs GSTM3P1/Gstm2-ps1 Exacerbate Sepsis-Associated Acute Kidney Injury by Suppressing Their Parent Gene Translation.

Long noncoding RNAs are emerging as critical regulators of acute kidney injury (AKI). In this study, the pathologic role of pseudogene-derived long noncoding RNAs GSTM3P1 (human)/Gstm2-ps1 (mouse) in sepsis-associated AKI (SA-AKI) was investigated. Glutathione S-transferase mu 3, pseudogene 1 (GSTM3P1)/glutathione S-transferase mu 2, pseudogene 1 (Gstm2-ps1) were transiently up-regulated in kidney proximal tubular cells at the early stage of SA-AKI in mice treated with lipopolysaccharide (LPS) or cecal ligation and puncture, as well as in LPS-treated proximal tubular cells. Functionally, overexpression of GSTM3P1/Gstm2-ps1 exacerbated LPS-induced proximal tubular cell apoptosis and oxidative stress. In contrast, proximal tubule-specific Gstm2-ps1 knockout mice were significantly protected from LPS-induced AKI, as evidenced by improved renal function and reduced apoptosis, kidney injury markers, and reactive oxygen species. Similarly, these mice showed renal protective effects against cecal ligation and puncture-induced AKI. Mechanistically, overexpression of GSTM3P1/Gstm2-ps1 in proximal tubular cells markedly suppressed parent gene GSTM3/GSTM2 protein but not mRNA expression, indicating a translational repression. Restoration of GSTM3/GSTM2 rescued proximal tubular cells from LPS-induced apoptosis. Furthermore, an RNA pulldown assay revealed that Gstm2-ps1 binds to human antigen R (HuR), a known post-transcriptional regulator for mRNA stability and translation. Overexpression of HuR antagonized Gstm2-ps1-mediated repression of GSTM2, associated with increased cell survival after LPS injury. In conclusion, the early induction of GSTM3P1/Gstm2-ps1 in SA-AKI exacerbates kidney injury by a novel mechanism to sequester HuR and inhibit the translation of parent gene GSTM3/gstm2 for oxidative stress detoxification.

Animals

Integrative multi-omics and machine learning identify the SPI1-METTL16-PLIN4 axis as a candidate driver of steatosis in HepG2 cells.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is a prevalent metabolic disorder with limited therapeutic options. This study aimed to identify potential regulators and explore their functional roles in a cellular model of NAFLD. METHODS: WGCNA was performed on the hepatic transcriptomic dataset GSE126848 (31 NAFLD vs. 26 controls), followed by integration with serum proteomic data from 12 NAFLD patients and 12 healthy controls. Hub genes were prioritized using three machine learning algorithms. Functional validation was conducted in a HepG2 cellular steatosis model induced by high fructose (3.2&#x202f;g/L) and oleic acid (400&#x202f;&#x3bc;M) for 48&#x202f;h. Lipid accumulation was assessed by Oil Red O staining and triglyceride/total cholesterol measurement. Inflammation was evaluated by TNF-&#x3b1; and IL-6 secretion (ELISA), and oxidative stress by ROS levels (flow cytometry). The binding interaction between METTL16 and PLIN4 mRNA was validated by RNA immunoprecipitation (RIP)-quantitative PCR. METTL16-mediated m6A modification of PLIN4 was assessed by Methylated RIP (MeRIP)-quantitative PCR. Transcriptional regulation of METTL16 by SPI1 was examined by chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays. RESULTS: Integrative analysis identified PLIN4 as a core hub gene. PLIN4 was upregulated in the HepG2 steatosis model (P&#x202f;<&#x202f;0.001). PLIN4 knockdown alleviated lipid droplet accumulation (P&#x202f;<&#x202f;0.001), reduced TNF-&#x3b1; and IL-6 secretion (P&#x202f;<&#x202f;0.01), and decreased ROS levels (P&#x202f;<&#x202f;0.001) in fructose/oleic acid-treated HepG2 cells. Mechanistically, METTL16 mediated its m6A modification to enhance PLIN4 mRNA stability. Furthermore, SPI1 was found to transcriptionally activate METTL16 by binding to its promoter (P&#x202f;<&#x202f;0.001). PLIN4 re-expression partially reversed the protective effects of SPI1 knockdown on lipid accumulation (P&#x202f;=&#x202f;0.01), inflammation (P&#x202f;<&#x202f;0.05), and oxidative stress (P&#x202f;<&#x202f;0.001). CONCLUSION: This study identifies the SPI1/METTL16/PLIN4 axis as a potential regulatory mechanism contributing to in vitro steatosis, inflammation, and oxidative stress in steatotic HepG2 cells.

Humans

Genome-scale CRISPR screening uncovers SRSF6 as a target to sensitize hepatocellular carcinoma to radiotherapy.

BACKGROUND & AIMS: Radiotherapy confers clinical benefits to patients with hepatocellular carcinoma (HCC) across all stages, yet its clinical efficacy is limited by radioresistance. This study aimed to identify key regulators of HCC radiosensitivity through genome-wide functional screening. METHODS: A genome-wide CRISPR-Cas9 screen in Huh7 cells identified radiosensitivity regulators, with SRSF6 validated by siRNA knockdown and &#x3b3;-H2AX assessment. Stable shRNA-mediated SRSF6 knockdown was established in Huh7 and HepG2 cells, followed by clonogenic, EdU incorporation, apoptosis, micronucleus, and comet assays. Mechanistically, RNA-seq, Western blotting, mRNA stability assays, RIP-qPCR, and RAD51 overexpression rescue assays were performed. The therapeutic potential of the SRSF6 inhibitor indacaterol was evaluated using MTS assays, HCC xenograft mouse models (BALB/c-nu/nu, n = 28), and HCC patient-derived organoids (PDOs) (n = 3). In addition, SRSF6 expression and its correlation with patient survival were analyzed using data from The Cancer Genome Atlas and a tissue microarray (n = 14 HCC and 14 paired adjacent non-tumorous liver samples). RESULTS: We identified the RNA-binding protein SRSF6 as a driver of HCC radioresistance. SRSF6 depletion enhanced the radiosensitivity of HCC cells (p <0.05-0.0001) by post-transcriptionally destabilizing the mRNAs of critical DNA repair genes (p <0.05-0.0001), thereby impairing radiation-induced DNA damage repair. The radiosensitizing effect of SRSF6 depletion was partially abrogated by ectopic overexpression of the core DNA repair protein RAD51 (p <0.05-0.001). Indacaterol exhibited cytotoxic effects on HCC cells (p <0.05-0.0001) and enhanced the antitumor efficacy of radiation in vivo (p <0.05-0.0001), as further validated across multiple HCC patient-derived organoids (p <0.05-0.0001). CONCLUSIONS: SRSF6 is a key regulator of HCC radioresistance through its post-transcriptional control of DNA repair capacity, and represents a novel therapeutic target to sensitize HCC to radiotherapy. IMPACT AND IMPLICATIONS: In this study, we performed a genome-wide CRISPR-Cas9 knockout library screen to dissect the molecular determinants governing HCC radiosensitivity, and identified RNA-binding protein SRSF6 as a driver of HCC radioresistance. We demonstrate that SRSF6 depletion disrupts the post-transcriptional stability of key DNA repair gene mRNAs and enhances HCC radiosensitivity. These findings are important for radiation oncologists and translational researchers, as they identify SRSF6-dependent RNA regulation as a critical determinant of radiotherapy response in HCC. Practically, we show that the clinically approved bronchodilator indacaterol suppresses SRSF6 function and enhances the antitumor efficacy of radiotherapy, offering a readily repurposable pharmacological strategy to overcome radioresistance. These implications are based on preclinical evidence across multiple models; however, future clinical trials are needed to validate the safety and efficacy of indacaterol-based radiosensitization in patients with HCC.

DNA repair

Stabilization of casein mRNA by prolactin and glucocorticoids.

Prolactin injected into pseudopregnant rabbits led to a parallel enhancement of casein synthesis and casein mRNA concentration. When this stimulation was followed by a withdrawal of prolactin obtained by injections of bromocriptine, the rate of casein synthesis progressively diminished. In the presence of endogenous prolactin after the initial stimulation, the decline of casein synthesis was delayed. Hydrocortisone acetate injected with bromocriptine after the initial stimulation by prolactin was able to maintain a high rate of casein synthesis. Measurements of casein mRNA concentration by hybridization with casein cDNA indicated that in all cases the amount of casein mRNA was correlated with the magnitude of casein synthesis. This suggests that the lactogenic hormones, prolactin and glucocorticoids, which were previously demonstrated to be responsible for the enhancement of casein mRNA concentration are involved in their stabilization.

Animals

Messenger ribonucleic acid metabolism in mammalian mitochondria: relationship between the decay of mitochondrial mRNA and their poly(A).

The mitochondrial poly(adenylic acid)-containing mRNAs in mouse ascites cells pulsed with radioactive precursors contain 35-55 nucleotide long poly(adenylic acid) sequences. These sequences are shortened with age in cells chased with cold medium. The possible relationship between the decay rates of mRNA and their poly(adenylic acid) sequences has been investigated by using mitochondrial RNA and protein synthesis inhibitors. The pattern of mRNA decay as determined by a new solid-phase-bound complementary DNA procedure indicates the presence of two classes of poly(adenylic acid) containing mRNA in mammalian mitochondria: one decaying with a t1/2 of 45 min and the other class with a t1/2 of 210 min. Inhibitors such as ethidium bromide and puromycin which accelerate the decay of mitochondrial mRNA also cause an enhanced decay of poly(adenylic acid) sequences. These results have been interpreted as evidence supporting the involvement of poly(adenylic acid) sequences in the mRNA stability.

Animals