Phosphorylation of G3BP1 is involved in the regulation of PDCoV-induced inflammatory response.

Stress granules (SGs), the main component is GTPase-activating protein-binding protein 1 (G3BP1), which are assembled during viral infection and function to sequester host and viral mRNAs and proteins, are part of the antiviral responses. In this study, we found that porcine deltacoronavirus (PDCoV) infection induced stable formation of robust SGs in cells through a PERK (protein kinase R-like endoplasmic reticulum kinase)-dependent mechanism. Overexpression of SGs marker proteins G3BP1 significantly reduced PDCoV replication in vitro, while inhibition of endogenous G3BP1 enhanced PDCoV replication. Moreover, PDCoV infected LLC-PK1 cells raise the phosphorylation level of G3BP1. By overexpression of the G3BP1 phosphorylated protein or the G3BP1 dephosphorylated protein, we found that phosphorylation of G3BP1 is involved in the regulation of PDCoV-induced inflammatory response. Taken together, our study presents a vital aspect of the host innate response to invading pathogens and reveals attractive host targets for antiviral target.

Escherichia coli-Induced cGLIS3-Mediated Stress Granules Activate the NF-κB Pathway to Promote Intrahepatic Cholangiocarcinoma Progression.

Patients with concurrent intrahepatic cholangiocarcinoma (ICC) and hepatolithiasis generally have poor prognoses. Hepatolithiasis is once considered the primary cause of ICC, although recent insights indicate that bacteria in the occurrence of hepatolithiasis can promote the progression of ICC. By constructing in vitro and in vivo ICC models and patient-derived organoids (PDOs), it is shown that Escherichia coli induces the production of a novel RNA, circGLIS3 (cGLIS3), which promotes tumor growth. cGLIS3 binds to hnRNPA1 and G3BP1, resulting in the assembly of stress granules (SGs) and suppression of hnRNPA1 and G3BP1 ubiquitination. Consequently, the IKKα mRNA is blocked in SGs, decreasing the production of IKKα and activating the NF-κB pathway, which finally results in chemoresistance and produces metastatic phenotypes of ICC. This study shows that a combination of Icaritin (ICA) and gemcitabine plus cisplatin (GP) chemotherapy can be a promising treatment strategy for ICC.

G3BP1 Interact with JAK2 mRNA to Promote the Malignant Progression of Nasopharyngeal Carcinoma via Activating JAK2/STAT3 Signaling Pathway.

Ras-GTPase-activating protein (GAP)-binding protein 1 (G3BP1) is an RNA-binding protein implicated in various malignancies. However, its role in nasopharyngeal carcinoma (NPC) remains elusive. This study elucidates the potential regulation mechanisms of G3BP1 and its significance in NPC advancement. Through knockdown and overexpression approaches, we validate G3BP1's oncogenic role by promoting proliferation, migration, and invasion in vitro and in vivo. Moreover, G3BP1 emerges as a key regulator of the JAK2/STAT3 signaling pathway, augmenting JAK2 expression via mRNA binding. Notably, epigallocatechin gallate (EGCG), a green tea-derived antioxidant, counteracts G3BP1-mediated pathway activation. Clinical analysis reveals heightened G3BP1, JAK2, and p-STAT3 as powerful prognostic markers, with G3BP1's expression standing as an independent indicator of poorer outcomes for NPC patients. In conclusion, the study unveils the oncogenic prowess of G3BP1, its orchestration of the JAK2/STAT3 signaling pathway, and its pivotal role in NPC progression.

Identification of small molecule inhibitors of G3BP-driven stress granule formation.

Stress granule formation is triggered by the release of mRNAs from polysomes and is promoted by the action of the RNA-binding proteins G3BP1/2. Stress granules have been implicated in several disease states, including cancer and neurodegeneration. Consequently, compounds that limit stress granule formation or promote their dissolution have potential as both experimental tools and novel therapeutics. Herein, we describe two small molecules, G3BP inhibitor a and b (G3Ia and G3Ib), designed to bind to a specific pocket in G3BP1/2 that is targeted by viral inhibitors of G3BP1/2 function. In addition to disrupting the co-condensation of RNA, G3BP1, and caprin 1 in vitro, these compounds inhibit stress granule formation in cells treated prior to or concurrent with stress and dissolve pre-existing stress granules. These effects are consistent across multiple cell types and a variety of initiating stressors. Thus, these compounds represent powerful tools to probe the biology of stress granules and hold promise for therapeutic interventions designed to modulate stress granule formation.

Profiling of RNA-binding protein binding sites by in situ reverse transcription-based sequencing.

RNA-binding proteins (RBPs) regulate diverse cellular processes by dynamically interacting with RNA targets. However, effective methods to capture both stable and transient interactions between RBPs and their RNA targets are still lacking, especially when the interaction is dynamic or samples are limited. Here we present an assay of reverse transcription-based RBP binding site sequencing (ARTR-seq), which relies on in situ reverse transcription of RBP-bound RNAs guided by antibodies to identify RBP binding sites. ARTR-seq avoids ultraviolet crosslinking and immunoprecipitation, allowing for efficient and specific identification of RBP binding sites from as few as 20 cells or a tissue section. Taking advantage of rapid formaldehyde fixation, ARTR-seq enables capturing the dynamic RNA binding by RBPs over a short period of time, as demonstrated by the profiling of dynamic RNA binding of G3BP1 during stress granule assembly on a timescale as short as 10 minutes.

CircNUP50 is a novel therapeutic target that promotes cisplatin resistance in ovarian cancer by modulating p53 ubiquitination.

BACKGROUND: Most patients with ovarian cancer (OC) treated with platinum-based chemotherapy have a dismal prognosis owing to drug resistance. However, the regulatory mechanisms of circular RNA (circRNA) and p53 ubiquitination are unknown in platinum-resistant OC. We aimed to identify circRNAs associated with platinum-resistant OC to develop a novel treatment strategy. METHODS: Platinum-resistant circRNAs were screened through circRNA sequencing and validated using quantitative reverse-transcription PCR in OC cells and tissues. The characteristics of circNUP50 were analysed using Sanger sequencing, oligo (dT) primers, ribonuclease R and fluorescence in situ hybridisation assays. Functional experimental studies were performed in vitro and in vivo. The mechanism underlying circNUP50-mediated P53 ubiquitination was investigated through circRNA pull-down analysis and mass spectrometry, luciferase reporters, RNA binding protein immunoprecipitation, immunofluorescence assays, cycloheximide chase assays, and ubiquitination experiments. Finally, a platinum and si-circNUP50 co-delivery nanosystem (Psc@DPP) was constructed to treat platinum-resistant OC in an orthotopic animal model. RESULTS: We found that circNUP50 contributes to platinum-resistant conditions in OC by promoting cell proliferation, affecting the cell cycle, and reducing apoptosis. The si-circNUP50 mRNA sequencing and circRNA pull-down analysis showed that circNUP50 mediates platinum resistance in OC by binding p53 and UBE2T, accelerating p53 ubiquitination. By contrast, miRNA sequencing and circRNA pull-down experiments indicated that circNUP50 could serve as a sponge for miR-197-3p, thereby upregulating G3BP1 to mediate p53 ubiquitination, promoting OC platinum resistance. Psc@DPP effectively overcame platinum resistance in an OC tumour model and provided a novel idea for treating platinum-resistant OC using si-circNUP50. CONCLUSIONS: This study reveals a novel molecular mechanism by which circNUP50 mediates platinum resistance in OC by modulating p53 ubiquitination and provides new insights for developing effective therapeutic strategies for platinum resistance in OC.

G3BP1 and SLU7 Jointly Promote Immune Evasion by Downregulating MHC-I via PI3K/Akt Activation in Bladder Cancer.

Immune checkpoint inhibitors (ICIs) show promise as second-line treatment for advanced bladder cancer (BLCA); however, their responsiveness is limited by the immune evasion mechanisms in tumor cells. This study conduct a Cox regression analysis to screen mRNA-binding proteins and reveals an association between Ras GTPase-activating protein-binding protein 1 (G3BP1) and diminished effectiveness of ICI therapy in patients with advanced BLCA. Subsequent investigation demonstrates that G3BP1 enhances immune evasion in BLCA cells by downregulating major histocompatibility complex class I (MHC-I) through phosphoinositide 3-kinase (PI3K)/Akt signaling activation. Mechanistically, G3BP1 interacts with splicing factor synergistic lethal with U5 snRNA 7 (SLU7) to form a complex with poly(A)-binding protein cytoplasmic 1 and eukaryotic translation initiation factor 4 gamma 1. This complex stabilizes the closed-loop structure of the mRNAs of class IA PI3Ks and consequently facilitates their translation and stabilization, thereby activating PI3K/Akt signaling to downregulate MHC-I. Consistently, targeting G3BP1 with epigallocatechin gallate (EGCG) impedes immune evasion and sensitizes BLCA cells to anti-programmed cell death (PD)-1 antibodies in mice. Thus, G3BP1 and SLU7 collaboratively contribute to immune evasion in BLCA, indicating that EGCG is a precision therapeutic agent to enhance the effectiveness of anti-PD-1 therapy.

A novel G3BP1-GFP reporter human lung cell system enabling real-time monitoring of stress granule dynamics for in vitro lung toxicity assessment.

Under various cellular stress conditions, including exposure to toxic chemicals, RNA-binding proteins (RBPs), including Ras GTPase-activating protein-binding protein 1 (G3BP1), aggregate and form stress granule complexes, which serve as hallmarks of cellular stress. The existing methods for analyzing stress granule assembly have limitations in the rapid detection of dynamic cellular stress and ignore the effects of constitutively overexpressed RBP on cellular stress and stress-related processes. Therefore, to overcome these limitations, we established a G3BP1-GFP reporter in a human lung epithelial cell line using CRISPR/Cas9-based knock-in as an alternative system for stress granule analysis. We showed that the G3BP1-GFP reporter system responds to stress conditions and forms a stress granule complex similar to that of native G3BP1. Furthermore, we validated the stress granule response of an established cell line under exposure to various household chemicals. Overall, this novel G3BP1-GFP reporter human lung cell system is capable of monitoring stress granule dynamics in real time and can be used for assessing the lung toxicity of various substances in vitro.

Convergent gene pair dSH3 and irr regulate Pi and Fe homeostasis in Bradyrhizobium diazoefficiens USDA110 and symbiotic nitrogen fixation efficiency.

The nitrogen-fixing bacteroids inhabit inside legume root nodules must manage finely the utilization of P and Fe, the two most critical elements, due to their antagonistic interactions. While the balance mechanism for them remains unclear. A double SH3 domain-containing protein (dSH3) in the Bradyrhizobium diazoefficiens USDA110 was found to inhibit the alkaline phosphatase activity, thereby reducing P supply from organophosphates. The dSH3 gene is adjacent to the irr gene, which encodes the iron response repressor and regulates Fe homeostasis under Fe-limited conditions. Their transcription directions converge to a common intergenic sequence (IGS) region, forming a convergent transcription. Extending the IGS region through Tn5 transposon or pVO155 plasmid insertion significantly down-regulated expression of this gene pair, leading to a remarkable accumulation of P and an inability to grow under Fe-limited conditions. Inoculation of soybean with either of the insertion mutants resulted in N2-fixing failure. However, the IGS-deleted mutant showed no visible changes in N2-fixing efficiency on soybean compared to that inoculated with wild type. These findings reveal a novel regulative strategy in the IGS region and its flanking convergent gene pair for antagonistic utilization of P and Fe in rhizobia and coordination of N2-fixing efficiency.

Gadd45ß is critical for regulation of type I interferon signaling by facilitating G3BP-mediated stress granule formation.

Stress granules (SGs) constitute a signaling hub that plays a critical role in type I interferon responses. Here, we report that growth arrest and DNA damage-inducible beta (Gadd45ß) act as a positive regulator of SG-mediated interferon signaling by targeting G3BP upon RNA virus infection. Gadd45ß deficiency markedly impairs SG formation and SG-mediated activation of interferon signaling in vitro. Gadd45ß knockout mice are highly susceptible to RNA virus infection, and their ability to produce interferon and cytokines is severely impaired. Specifically, Gadd45ß interacts with the RNA-binding domain of G3BP, leading to conformational expansion of G3BP1 via dissolution of its autoinhibitory electrostatic intramolecular interaction. The acidic loop 1- and RNA-binding properties of Gadd45ß markedly increase the conformational expansion and RNA-binding affinity of the G3BP1-Gadd45ß complex, thereby promoting assembly of SGs. These findings suggest a role for Gadd45ß as a component and critical regulator of G3BP1-mediated SG formation, which facilitates RLR-mediated interferon signaling.

RBM25 binds to and regulates alternative splicing levels of Slc38a9, Csf1, and Coro6 to affect immune and inflammatory processes in H9c2 cells.

Background: Alternative splicing (AS) is a biological process that allows genes to be translated into diverse proteins. However, aberrant AS can predispose cells to aberrations in biological mechanisms. RNA binding proteins (RBPs), closely affiliated with AS, have gained increased attention in recent years. Among these RBPs, RBM25 has been reported to participate in the cardiac pathological mechanism through regulating AS; however, the involvement of RBM25 as a splicing factor in heart failure remains unclarified. Methods: RBM25 was overexpressed in H9c2 cells to explore the target genes bound and regulated by RBM25 during heart failure. RNA sequencing (RNA-seq) was used to scrutinize the comprehensive transcriptional level before identifying AS events influenced by RBM25. Further, improved RNA immunoprecipitation sequencing (iRIP-seq) was employed to pinpoint RBM25-binding sites, and RT-qPCR was used to validate specific genes modulated by RBM25. Results: RBM25 was found to upregulate the expression of genes pertinent to the inflammatory response and viral processes, as well as to mediate the AS of genes associated with cellular apoptosis and inflammation. Overlap analysis between RNA-seq and iRIP-seq suggested that RBM25 bound to and manipulated the AS of genes associated with inflammation in H9c2 cells. Moreover, qRT-PCR confirmed Slc38a9, Csf1, and Coro6 as the binding and AS regulatory targets of RBM25. Conclusion: Our research implies that RBM25 plays a contributory role in cardiac inflammatory responses via its ability to bind to and regulate the AS of related genes. This study offers preliminary evidence of the influence of RBM25 on inflammation in H9c2 cells.

Endometrial cancer (EC) derived G3BP1 overexpression and mutant promote EC tumorigenesis and metastasis via SPOP/ERα axis.

BACKGROUND: Ras-GTPase-activating protein binding protein 1 (G3BP1) is an oncogenic factor, which highly expressed in a variety of cancers. In recent years, G3BP1 has been reported to promote the development of prostate cancer by inhibiting the degradation of AR through inhibiting SPOP. However, whether G3BP1 contributes in a similar manner to the abnormal accumulation of ERα, which is also an important target for hormone therapy, remains unknown. This article addresses this issue and explores potential mechanisms. METHODS: Bioinformatics tools were used for G3BP1 expression analysis, survival analysis, and clinical association analysis. Immunohistochemical staining was used to examine the correlation between G3BP1 and ERα in EC patients. In addition, western blot and co-immunoprecipitation were used to detect the half-life of G3BP1 and mutant, and the effect of G3BP1 and mutant on the ubiquitination and degradation of ERα mediated by SPOP. Then, the oncogenic functions of G3BP1 dependent on the SPOP/ERα axis were determined by CCK8 cell proliferation assay, colony formation assay and cell migration assay. Finally, we established the EC cells treated or untreated with fulvestrant, exploring the possibility of fulvestrant combined with the reduction of G3BP1 to improve the efficacy of fulvestrant. RESULTS: G3BP1 is abnormally high expressed and characterized by high-frequency mutation in EC. In addition, there is a positive correlation between G3BP1 protein and ERα protein. Mechanistically, both G3BP1 and mutant, the latter is displaying the longer half-life, competitively bind SPOP with ERα, thereby inhibiting SPOP-mediated ubiquitination and degradation of ERα. Functionally, G3BP1 and mutant promote the proliferation and migration of EC cells by regulating the G3BP1/SPOP/ERα axis. However, fulvestrant can reverse the cancer-promoting effects of G3BP1 and mutant. CONCLUSIONS: G3BP1 and its mutant positively regulate ERα signaling pathway by inhibiting SPOP-mediated ubiquitination and degradation of ERα, indicating the promising effect of fulvestrant on the suppression the occurrence and development of EC with high expressed G3BP1 and G3BP1 mutants. Video Abstract.

In silico identification, characterization, and expression analysis of RNA recognition motif (RRM) containing RNA-binding proteins in Aedes aegypti.

RNA-binding proteins (RBPs) are the proteins that bind RNAs and regulate their functioning. RBPs in mosquitoes are gaining attention due to their ability to bind flaviviruses and regulate their replication and transmission. Despite their relevance, RBPs in mosquitoes are not explored much. In this study, we screened the whole genome of Aedes aegypti, the primary vector of several pathogenic viruses, and identified the proteins containing RNA recognition motif (RRM), the most abundant protein domain in eukaryotes. Using several in silico strategies, a total of 135 RRM-containing RBPs were identified in Ae. aegypti. The proteins were characterized based on their available annotations and the sequence similarity with Drosophila melanogaster. Ae. aegypti RRM-containing RBPs included serine/arginine-rich (SR) proteins, polyadenylate-binding proteins (PABP), heteronuclear ribonucleoproteins (hnRNP), small nuclear ribonucleoproteins (snRNP), splicing factors, eukaryotic initiation factors, transformers, and nucleolysins. Phylogenetic analysis revealed that the proteins and the domain organization are conserved among Ae. aegypti, Bombyx mori, and Drosophila melanogaster. However, the gene length and the intron-exon organization varied across the insect species. Expression analysis of the genes encoding RBPs using publicly available RNA sequencing data for different developmental time points of the mosquito life cycle starting from the ovary and eggs up to the adults revealed stage-specific expression with several genes preferentially expressed in early embryonic stages and blood-fed female ovaries. This is the first database for the Ae. aegypti RBPs that can serve as the reference base for future investigations. Stage-specific genes can be further explored to determine their role in mosquito growth and development with a focus on developing novel mosquito control strategies.

SARS-CoV-2 nucleocapsid protein inhibits the PKR-mediated integrated stress response through RNA-binding domain N2b.

The nucleocapsid protein N of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enwraps and condenses the viral genome for packaging but is also an antagonist of the innate antiviral defense. It suppresses the integrated stress response (ISR), purportedly by interacting with stress granule (SG) assembly factors G3BP1 and 2, and inhibits type I interferon responses. To elucidate its mode of action, we systematically deleted and over-expressed distinct regions and domains. We show that N via domain N2b blocks PKR-mediated ISR activation, as measured by suppression of ISR-induced translational arrest and SG formation. N2b mutations that prevent dsRNA binding abrogate these activities also when introduced in the intact N protein. Substitutions reported to block post-translation modifications of N or its interaction with G3BP1/2 did not have a detectable additive effect. In an encephalomyocarditis virus-based infection model, N2b - but not a derivative defective in RNA binding-prevented PKR activation, inhibited ß-interferon expression and promoted virus replication. Apparently, SARS-CoV-2 N inhibits innate immunity by sequestering dsRNA to prevent activation of PKR and RIG-I-like receptors. Similar observations were made for the N protein of human coronavirus 229E, suggesting that this may be a general trait conserved among members of other orthocoronavirus (sub)genera.

The translation initiating factor eIF4E and arginine methylation underlie G3BP1 function in dendritic spine development of neurons.

Communication between neurons relies on neurotransmission that takes place at synapses. Excitatory synapses are located primarily on dendritic spines that possess diverse morphologies, ranging from elongated filopodia to mushroom-shaped spines. Failure in the proper development of dendritic spines has detrimental consequences on neuronal connectivity, but the molecular mechanism that controls the balance of filopodia and mushroom spines is not well understood. G3BP1 is the key RNA-binding protein that assembles the stress granules in non-neuronal cells to adjust protein synthesis upon exogenous stress. Emerging evidence suggests that the biological significance of G3BP1 extends beyond its role in stress response, especially in the nervous system. However, the mechanism underlying the regulation and function of G3BP1 in neurons remains elusive. Here we found that G3BP1 suppresses protein synthesis and binds to the translation initiation factor eIF4E via its NTF2-like domain. Notably, the over-production of filopodia caused by G3BP1 depletion can be alleviated by blocking the formation of the translation initiation complex. We further found that the interaction of G3BP1 with eIF4E is regulated by arginine methylation. Knockdown of the protein arginine methyltransferase PRMT8 leads to elevated protein synthesis and filopodia production, which is reversed by the expression of methylation-mimetic G3BP1. Our study, therefore, reveals arginine methylation as a key regulatory mechanism of G3BP1 during dendritic spine morphogenesis and identifies eIF4E as a novel downstream target of G3BP1 in neuronal development independent of stress response.

Role(s) of G3BPs in Human Pathogenesis.

Ras-GTPase-activating protein (SH3 domain)-binding proteins (G3BP) are RNA binding proteins that play a critical role in stress granule (SG) formation. SGs protect critical mRNAs from various environmental stress conditions by regulating mRNA stability and translation to maintain regulated gene expression. Recent evidence suggests that G3BPs can also regulate mRNA expression through interactions with RNA outside of SGs. G3BPs have been associated with a number of disease states, including cancer progression, invasion, metastasis, and viral infections, and may be useful as a cancer therapeutic target. This review summarizes the biology of G3BP including their structure, function, localization, role in cancer progression, virus replication, mRNA stability, and SG formation. We will also discuss the potential of G3BPs as a therapeutic target. SIGNIFICANCE STATEMENT: This review will discuss the molecular mechanism(s) and functional role(s) of Ras-GTPase-activating protein (SH3 domain)-binding proteins in the context of stress granule formation, interaction with viruses, stability of RNA, and tumorigenesis.

QKI shuttles internal m7G-modified transcripts into stress granules and modulates mRNA metabolism.

N7-methylguanosine (m7G) modification, routinely occurring at mRNA 5' cap or within tRNAs/rRNAs, also exists internally in messenger RNAs (mRNAs). Although m7G-cap is essential for pre-mRNA processing and protein synthesis, the exact role of mRNA internal m7G modification remains elusive. Here, we report that mRNA internal m7G is selectively recognized by Quaking proteins (QKIs). By transcriptome-wide profiling/mapping of internal m7G methylome and QKI-binding sites, we identified more than 1,000 high-confidence m7G-modified and QKI-bound mRNA targets with a conserved "GANGAN (N = A/C/U/G)" motif. Strikingly, QKI7 interacts (via C terminus) with the stress granule (SG) core protein G3BP1 and shuttles internal m7G-modified transcripts into SGs to regulate mRNA stability and translation under stress conditions. Specifically, QKI7 attenuates the translation efficiency of essential genes in Hippo signaling pathways to sensitize cancer cells to chemotherapy. Collectively, we characterized QKIs as mRNA internal m7G-binding proteins that modulate target mRNA metabolism and cellular drug resistance.

The Arabidopsis RRM domain proteins EDM3 and IBM2 coordinate the floral transition and basal immune responses.

The transition from vegetative to reproductive development (floral transition) is a costly process in annual plants requiring increased investments in metabolic resources. The Arabidopsis thaliana (Arabidopsis) PHD finger protein EDM2 and RRM domain proteins EDM3 and IBM2 are known to form chromatin-associated complexes controlling transcript processing. We are reporting that distinct splice isoforms of EDM3 and IBM2 cooperate in the coordination of the floral transition with basal immune responses. These cooperating splice isoforms, termed EDM3L and IBM2L, control the intensity of basal immunity and, via a separate pathway, the timing of the floral transition. During the developmental phase prior to the floral transition expression of EDM3L and IBM2L strongly and gradually increases, while these isoforms simultaneously down-regulate expression of the floral suppressor gene FLC and promote the transition to reproductive growth. At the same time these accumulating EDM3 and IBM2 splice isoforms gradually suppress basal immunity against the virulent Noco2 isolate of the pathogenic oomycete Hyaloperonospora arabidopsidis and down-regulate expression of a set of defense-associated genes and immune receptor genes. We are providing clear evidence for a functional link between the floral transition and basal immunity in the annual plant Arabidopsis. Coordination of these two biological processes, which compete for metabolic resources, is likely critical for plant survival and reproductive success.

Stress granules sequester Alzheimer's disease-associated gene transcripts and regulate disease-related neuronal proteostasis.

Environmental and physiological stresses can accelerate Alzheimer's disease (AD) pathogenesis. Under stress, a cytoplasmic membraneless structure termed a stress granule (SG) is formed and is associated with various neurodegenerative disorders, including AD. SGs contain translationally arrested mRNAs, suggesting that impaired RNA metabolism in neurons causes AD progression; however, the underlying mechanism remains unclear. Here, we identified numerous mRNAs and long non-coding RNAs that are directly targeted by the SG core proteins G3BP1 and G3BP2. They redundantly target RNAs before and after stress conditions. We further identified RNAs within SGs, wherein AD-associated gene transcripts accumulated, suggesting that SGs can directly regulate AD development. Furthermore, gene-network analysis revealed a possible link between the sequestration of RNAs by SGs and the impairment of protein neurohomeostasis in AD brains. Together, our study provides a comprehensive RNA regulatory mechanism involving SGs, which could be targeted therapeutically to slow AD progression mediated by SGs.

The association of UBAP2L and G3BP1 mediated by small nucleolar RNA is essential for stress granule formation.

Stress granules (SGs) are dynamic, non-membranous structures composed of non-translating mRNAs and various proteins and play critical roles in cell survival under stressed conditions. Extensive proteomics analyses have been performed to identify proteins in SGs; however, the molecular functions of these components in SG formation remain unclear. In this report, we show that ubiquitin-associated protein 2-like (UBAP2L) is a crucial component of SGs. UBAP2L localized to SGs in response to various stresses, and its depletion significantly suppressed SG organization. Proteomics and RNA sequencing analyses found that UBAP2L formed a protein-RNA complex with Ras-GTP-activating protein SH3 domain binding protein 1 (G3BP1) and small nucleolar RNAs (snoRNAs). In vitro binding analysis demonstrated that snoRNAs were required for UBAP2L association with G3BP1. In addition, decreased expression of snoRNAs reduced the interaction between UBAP2L and G3BP1 and suppressed SG formation. Our results reveal a critical role of SG component, the UBAP2L/snoRNA/G3BP1 protein-RNA complex, and provide new insights into the regulation of SG assembly.