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Nonsense-mediated RNA decay (NMD) degrades transcripts carrying premature termination codons. NMD is thought to prevent the synthesis of toxic truncated proteins. However, whether loss of NMD results in widespread production of truncated proteins is unclear. A human genetic disease, facioscapulohumeral muscular dystrophy (FSHD), features acute inhibition of NMD upon expression of the disease-causing transcription factor, DUX4. Using a cell-based model of FSHD, we show production of truncated proteins from physiological NMD targets and find that RNA-binding proteins are enriched for aberrant truncations. The NMD isoform of one RNA-binding protein, SRSF3, is translated to produce a stable truncated protein, which is detected in FSHD patient-derived myotubes. Ectopic expression of truncated SRSF3 confers toxicity, and its downregulation is cytoprotective. Our results delineate the genome-scale impact of NMD loss. This widespread production of potentially deleterious truncated proteins has implications for FSHD biology as well as other genetic diseases where NMD is therapeutically modulated., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

The presence of the m 6 A modification in mammalian mRNAs is proposed to promote mRNA recruitment to stress granules through the interaction with YTHDF proteins. We test this possibility by examining the accumulation of mRNAs in stress granules in both WT and ∆METTL3 mES cells, which are deficient in m 6 A modification. A critical observation is that all m 6 A modified mRNAs partition similarly into stress granules in both wild-type and m 6 A-deficient cells by single-molecule FISH. Moreover, multiple linear regression analysis indicates m 6 A modification explains only 6% of the variance in stress granule localization when controlled for length. Finally, the artificial tethering of 25 YTHDF proteins on reporter mRNAs leads to only a modest increase in mRNA partitioning to stress granules. Since most mammalian mRNAs have 4 or fewer m 6 A sites, and those sites are not fully modified, this argues m 6 A modifications are unlikely to play a significant role in recruiting mRNAs to stress granules. Taken together, these observations argue that m 6 A modifications play a minimal, if any, role in mRNA partitioning into stress granules., (© 2022. The Author(s).)

This review summarizes the pathogenic mechanisms that underpin the monogenic epilepsies and discusses the potential of novel precision therapeutics to treat these disorders. Pathogenic mechanisms of epilepsy include recessive (null alleles), haploinsufficiency, imprinting, gain-of-function, and dominant negative effects. Understanding which pathogenic mechanism(s) that underlie each genetic epilepsy is pivotal to design precision therapies that are most likely to be beneficial for the patient. Novel therapeutics discussed include gene therapy, gene editing, antisense oligonucleotides, and protein replacement. Discussions are illustrated and reinforced with examples from the literature., (© 2021. The American Society for Experimental NeuroTherapeutics, Inc.)

Stress granules (SGs) are stress-induced RNA-protein assemblies formed from a complex transcriptome of untranslating ribonucleoproteins (RNPs). Although RNAs can be either enriched or depleted from SGs, the rules that dictate RNA partitioning into SGs are unknown. We demonstrate that the SG-enriched NORAD RNA is sufficient to enrich a reporter RNA within SGs through the combined effects of multiple elements. Moreover, artificial tethering of G3BP1, TIA1, or FMRP can target mRNAs into SGs in a dose-dependent manner with numerous interactions required for efficient SG partitioning, which suggests individual protein interactions have small effects on the SG partitioning of mRNPs. This is supported by the observation that the SG transcriptome is largely unchanged in cell lines lacking the abundant SG RNA-binding proteins G3BP1 and G3BP2. We suggest the targeting of RNPs into SGs is due to a summation of potential RNA-protein, protein-protein, and RNA-RNA interactions with no single interaction dominating RNP recruitment into SGs., (© 2021 Matheny et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.)

The eukaryotic cytosol contains multiple RNP granules, including P-bodies and stress granules. Three different methods have been used to describe the transcriptome of stress granules or P-bodies, but how these methods compare and how RNA partitioning occurs between P-bodies and stress granules have not been addressed. Here, we compare the analysis of the stress granule transcriptome based on differential centrifugation with and without subsequent stress granule immunopurification. We find that while differential centrifugation alone gives a first approximation of the stress granule transcriptome, this methodology contains nonspecific transcripts that play a confounding role in the interpretation of results. We also immunopurify and compare the RNAs in stress granules and P-bodies under arsenite stress and compare those results to those for the P-body transcriptome described under nonstress conditions. We find that the P-body transcriptome is dominated by poorly translated mRNAs under nonstress conditions, but during arsenite stress, when translation is globally repressed, the P-body transcriptome is very similar to the stress granule transcriptome. This suggests that translation is a dominant factor in targeting mRNAs into both P-bodies and stress granules, and during stress, when most mRNAs are untranslated, the composition of P-bodies reflects this broader translation repression., (Copyright © 2019 American Society for Microbiology.)

In response to foreign and endogenous double-stranded RNA (dsRNA), protein kinase R (PKR) and ribonuclease L (RNase L) reprogram translation in mammalian cells. PKR inhibits translation initiation through eIF2α phosphorylation, which triggers stress granule (SG) formation and promotes translation of stress responsive mRNAs. The mechanisms of RNase L-driven translation repression, its contribution to SG assembly, and its regulation of dsRNA stress-induced mRNAs are unknown. We demonstrate that RNase L drives translational shut-off in response to dsRNA by promoting widespread turnover of mRNAs. This alters stress granule assembly and reprograms translation by allowing translation of mRNAs resistant to RNase L degradation, including numerous antiviral mRNAs such as interferon (IFN)-β. Individual cells differentially activate dsRNA responses revealing variation that can affect cellular outcomes. This identifies bulk mRNA degradation and the resistance of antiviral mRNAs as the mechanism by which RNase L reprograms translation in response to dsRNA., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Aberrant translational repression is a feature of multiple neurodegenerative diseases. The association between disease-linked proteins and stress granules further implicates impaired stress responses in neurodegeneration. However, our knowledge of the proteins that evade translational repression is incomplete. It is also unclear whether disease-linked proteins influence the proteome under conditions of translational repression. To address these questions, a quantitative proteomics approach was used to identify proteins that evade stress-induced translational repression in arsenite-treated cells expressing either wild-type or amyotrophic lateral sclerosis (ALS)-linked mutant FUS. This study revealed hundreds of proteins that are actively synthesized during stress-induced translational repression, irrespective of FUS genotype. In addition to proteins involved in RNA- and protein-processing, proteins associated with neurodegenerative diseases such as ALS were also actively synthesized during stress. Protein synthesis under stress was largely unperturbed by mutant FUS, although several proteins were found to be differentially expressed between mutant and control cells. One protein in particular, COPBI, was downregulated in mutant FUS-expressing cells under stress. COPBI is the beta subunit of the coat protein I (COPI), which is involved in Golgi to endoplasmic reticulum (ER) retrograde transport. Further investigation revealed reduced levels of other COPI subunit proteins and defects in COPBI-relatedprocesses in cells expressing mutant FUS. Even in the absence of stress, COPBI localization was altered in primary and human stem cell-derived neurons expressing ALS-linked FUS variants. Our results suggest that Golgi to ER retrograde transport may be important under conditions of stress and is perturbed upon the expression of disease-linked proteins such as FUS., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Stress granules are higher order assemblies of nontranslating mRNAs and proteins that form when translation initiation is inhibited. Stress granules are thought to form by protein-protein interactions of RNA-binding proteins. We demonstrate RNA homopolymers or purified cellular RNA forms assemblies in vitro analogous to stress granules. Remarkably, under conditions representative of an intracellular stress response, the mRNAs enriched in assemblies from total yeast RNA largely recapitulate the stress granule transcriptome. We suggest stress granules are formed by a summation of protein-protein and RNA-RNA interactions, with RNA self-assembly likely to contribute to other RNP assemblies wherever there is a high local concentration of RNA. RNA assembly in vitro is also increased by GR and PR dipeptide repeats, which are known to increase stress granule formation in cells. Since GR and PR dipeptides are involved in neurodegenerative diseases, this suggests that perturbations increasing RNA-RNA assembly in cells could lead to disease., Competing Interests: The authors declare no conflict of interest.

Stress granules are mRNA-protein assemblies formed from nontranslating mRNAs. Stress granules are important in the stress response and may contribute to some degenerative diseases. Here, we describe the stress granule transcriptome of yeast and mammalian cells through RNA-sequencing (RNA-seq) analysis of purified stress granule cores and single-molecule fluorescence in situ hybridization (smFISH) validation. While essentially every mRNA, and some noncoding RNAs (ncRNAs), can be targeted to stress granules, the targeting efficiency varies from <1% to >95%. mRNA accumulation in stress granules correlates with longer coding and UTR regions and poor translatability. Quantifying the RNA-seq analysis by smFISH reveals that only 10% of bulk mRNA molecules accumulate in mammalian stress granules and that only 185 genes have more than 50% of their mRNA molecules in stress granules. These results suggest that stress granules may not represent a specific biological program of messenger ribonucleoprotein (mRNP) assembly, but instead form by condensation of nontranslating mRNPs in proportion to their length and lack of association with ribosomes., (Copyright © 2017 Elsevier Inc. All rights reserved.)

RNAs besides tRNA and rRNA contain chemical modifications, including the recently described 5' nicotinamide-adenine dinucleotide (NAD + ) RNA in bacteria. Whether 5' NAD-RNA exists in eukaryotes remains unknown. We demonstrate that 5' NAD-RNA is found on subsets of nuclear and mitochondrial encoded mRNAs in Saccharomyces cerevisiae NAD-mRNA appears to be produced cotranscriptionally because NAD-RNA is also found on pre-mRNAs, and only on mitochondrial transcripts that are not 5' end processed. These results define an additional 5' RNA cap structure in eukaryotes and raise the possibility that this 5' NAD + cap could modulate RNA stability and translation on specific subclasses of mRNAs., Competing Interests: The authors declare no conflict of interest.

Stress granules are non-membrane bound RNA-protein (RNP) assemblies that form when translation initiation is limited and contain a biphasic structure with stable core structures surrounded by a less concentrated shell. The order of assembly and disassembly of these two structures remains unknown. Time course analysis of granule assembly suggests that core formation is an early event in granule assembly. Stress granule disassembly is also a stepwise process with shell dissipation followed by core clearance. Perturbations that alter liquid-liquid phase separations (LLPS) driven by intrinsically disordered protein regions (IDR) of RNA binding proteins in vitro have the opposite effect on stress granule assembly in vivo. Taken together, these observations argue that stress granules assemble through a multistep process initiated by stable assembly of untranslated mRNPs into core structures, which could provide sufficient high local concentrations to allow for a localized LLPS driven by IDRs on RNA binding proteins., Competing Interests: The authors declare that no competing interests exist.

Background: Child abuse presents in many different forms: physical, sexual, psychological, and neglect. The orthopaedic surgeon is involved mostly with physical abuse but should be aware of the other forms. There is limited training regarding child abuse, and the documentation is poor when a patient is at risk for abuse. There is a considerable risk to children when abuse is not recognized., Questions/purposes: In this review, we (1) define abuse, (2) describe the incidence and demographic characteristics of abuse, (3) describe the orthopaedic manifestations of abuse, and (4) define the orthopaedic surgeon's role in cases of abuse., Methods: We performed a PubMed literature review and a search of the Department of Health and Human Services Web site. The Pediatric Orthopaedic Surgery of North America trauma symposium was referenced and expanded to create this review., Results: Recognition and awareness of child abuse are the primary tasks of the orthopaedic surgeon. Skin trauma is more common than fractures, yet fractures are the most common radiographic finding. Patients with fractures who are younger than 3 years, particularly those younger than 1 year, should be evaluated for abuse. No fracture type or location is pathognomonic. Management in the majority of fracture cases resulting from abuse is nonoperative casting or splinting., Conclusions: The role of the orthopaedic surgeon in suspected cases of child abuse includes (1) obtaining a good history and making a thorough physical examination; (2) obtaining the appropriate radiographs and notifying the appropriate services; and (3) participating in and communicating with a multidisciplinary team to manage the patients.