scholarly journals Evidence That Ternary Complex (eIF2-GTP-tRNAi Met)–Deficient Preinitiation Complexes Are Core Constituents of Mammalian Stress Granules

2002 ◽  
Vol 13 (1) ◽  
pp. 195-210 ◽  
Author(s):  
Nancy Kedersha ◽  
Samantha Chen ◽  
Natalie Gilks ◽  
Wei Li ◽  
Ira J. Miller ◽  
...  
Keyword(s):  
Ternary Complex ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Stress Granules ◽  
Direct Consequence ◽  
Protein Translation ◽  
Preinitiation Complex ◽  
Translational Initiation ◽  
Stressed Cells ◽  
As Stress

Environmental stress-induced phosphorylation of eIF2α inhibits protein translation by reducing the availability of eIF2-GTP-tRNAiMet, the ternary complex that joins initiator tRNAMet to the 43S preinitiation complex. The resulting untranslated mRNA is dynamically routed to discrete cytoplasmic foci known as stress granules (SGs), a process requiring the related RNA-binding proteins TIA-1 and TIAR. SGs appear to be in equilibrium with polysomes, but the nature of this relationship is obscure. We now show that most components of the 48S preinitiation complex (i.e., small, but not large, ribosomal subunits, eIF3, eIF4E, eIF4G) are coordinately recruited to SGs in arsenite-stressed cells. In contrast, eIF2 is not a component of newly assembled SGs. Cells expressing a phosphomimetic mutant (S51D) of eIF2α assemble SGs of similar composition, confirming that the recruitment of these factors is a direct consequence of blocked translational initiation and not due to other effects of arsenite. Surprisingly, phospho-eIF2α is recruited to SGs that are disassembling in cells recovering from arsenite-induced stress. We discuss these results in the context of a translational checkpoint model wherein TIA and eIF2 are functional antagonists of translational initiation, and in which lack of ternary complex drives SG assembly.

Stress granules: sites of mRNA triage that regulate mRNA stability and translatability

2002 ◽  
Vol 30 (6) ◽  
pp. 963-969 ◽  
Author(s):  
N. Kedersha ◽  
P. Anderson
Keyword(s):  
Mrna Stability ◽  
Ternary Complex ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Stress Granules ◽  
Initiation Factor ◽  
Cytoplasmic Domains ◽  
Hsp70 Mrna ◽  
Translational Initiation

Mammalian stress granules (SGs) are cytoplasmic domains into which mRNAs are sorted dynamically in response to phosphorylation of eukaryotic initiation factor (eIF) 2α, a key regulatory step in translational initiation. The activation of one or more of the eIF2α kinases leads to SG assembly by decreasing the levels of eIF2-GTP-tRNAMet, the ternary complex that is normally required for loading the initiator methionine onto the 48 S preinitiation complex to begin translation. This stress-induced scarcity of eIF2-GTP-tRNAMet allows the RNA-binding proteins TIA-1 (T-cell internal antigen-1) and TIAR (TIA-1-related protein) to bind the 48 S complex in lieu of the ternary complex, thereby promoting polysome disassembly and the concurrent routing of the mRNA into a SG. The actual formation of SGs occurs upon auto-aggregation of the prion-like C-termini of TIA-1 proteins; this aggregation is reversed in vivo by overexpression of the heat-shock protein (HSP) chaperone HSP70. Remarkably, HSP70 mRNA is excluded from SGs and is preferentially translated during stress, indicating that the RNA composition of the SG is selective. Moreover, the effects of HSP70 on TIA aggregation suggest a feedback loop whereby HSP70 synthesis is auto-regulated. Proteins that promote mRNA stability [e.g. HuR (Hu protein R)] and destabilize mRNA [i.e. tristetraprolin (TTP)] are also recruited to SGs, suggesting that SGs effect a process of mRNA triage, by promoting polysome disassembly and routing mRNAs to cytoplasmic domains enriched for HuR and TTP. This model reveals connections between the eIF2α kinase system, mRNA stability and cellular chaperone levels.

Stressful initiations

2002 ◽  
Vol 115 (16) ◽  
pp. 3227-3234 ◽  
Author(s):  
Paul Anderson ◽  
Nancy Kedersha
Keyword(s):  
Environmental Stress ◽  
Uv Irradiation ◽  
Ternary Complex ◽  
Rna Binding ◽  
Dynamic Equilibrium ◽  
Rna Binding Proteins ◽  
Ribosomal Subunit ◽  
Eukaryotic Cells ◽  
Translational Initiation ◽  
The Core

Stress granules (SGs) are phase-dense particles that appear in the cytoplasm of eukaryotic cells that have been exposed to environmental stress(e.g. heat, oxidative conditions, hyperosmolarity and UV irradiation). SG assembly is a consequence of abortive translational initiation: SGs appear when translation is initiated in the absence of eIF2-GTP-tRNAiMet, the ternary complex that normally loads tRNAiMet onto the small ribosomal subunit. Stress-induced depletion of eIF2-GTP-tRNAiMet allows the related RNA-binding proteins TIA-1 and TIAR to promote the assembly of eIF2-eIF5-deficient preinitiation complexes, the core constituents of SGs. The mRNP components that make up the SG are in a dynamic equilibrium with polysomes. As such, the SG appears to constitute a metabolic domain through which mRNPs are continually routed and subjected to triage — they are first monitored for integrity and composition, and then sorted for productive translational initiation or targeted degradation.

scholarly journals SINEUP long non-coding RNA acts via PTBP1 and HNRNPK to promote translational initiation assemblies

2019 ◽  
Author(s):  
Naoko Toki ◽  
Hazuki Takahashi ◽  
Silvia Zucchelli ◽  
Stefano Gustincich ◽  
Piero Carninci
Keyword(s):  
Translational Regulation ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Mrna Translation ◽  
Protein Translation ◽  
Expression Vectors ◽  
Translational Initiation ◽  
Target Mrna ◽  
Target Mrnas ◽  
Wide Range

AbstractSINEUPs are long non-coding RNAs (lncRNAs) that contain a SINE element, which up-regulate the translation of target mRNA and have been studied in a wide range of applications for biological and therapeutic tools, although the molecular mechanism is unclear. Here, we focused on the kinetic distribution of target mRNAs and SINEUP RNAs by performing co-transfection of expression vectors for these transcripts into human embryonic normal kidney cells (HEK293T/17) to investigate the network of translational regulation. The results showed that co-localization of target mRNAs and SINEUP RNAs in the cytoplasm was one of the key phenomena. We identified PTBP1 and HNRNPK as essential RNA binding proteins. These proteins contributed to SINEUP RNA sub-cellular distribution and to assembly of translational initiation complexes, leading to enhanced target mRNA translation. These findings will promote a better understanding of the mechanisms on the fate of regulatory RNAs implicated in efficient protein translation.

scholarly journals SINEUP long non-coding RNA acts via PTBP1 and HNRNPK to promote translational initiation assemblies

2020 ◽  
Vol 48 (20) ◽  
pp. 11626-11644
Author(s):  
Naoko Toki ◽  
Hazuki Takahashi ◽  
Harshita Sharma ◽  
Matthew N Z Valentine ◽  
Ferdous-Ur M Rahman ◽  
...  
Keyword(s):  
Rna Binding ◽  
Rna Binding Proteins ◽  
Mrna Translation ◽  
Protein Translation ◽  
Expression Vectors ◽  
Cellular Distribution ◽  
Translational Initiation ◽  
Target Mrna ◽  
Target Mrnas ◽  
Wide Range

Abstract SINEUPs are long non-coding RNAs (lncRNAs) that contain a SINE element, and which up-regulate the translation of target mRNA. They have been studied in a wide range of applications, as both biological and therapeutic tools, although the underpinning molecular mechanism is unclear. Here, we focused on the sub-cellular distribution of target mRNAs and SINEUP RNAs, performing co-transfection of expression vectors for these transcripts into human embryonic kidney cells (HEK293T/17), to investigate the network of translational regulation. The results showed that co-localization of target mRNAs and SINEUP RNAs in the cytoplasm was a key phenomenon. We identified PTBP1 and HNRNPK as essential RNA binding proteins. These proteins contributed to SINEUP RNA sub-cellular distribution and to assembly of translational initiation complexes, leading to enhanced target mRNA translation. These findings will promote a better understanding of the mechanisms employed by regulatory RNAs implicated in efficient protein translation.

The Therapeutic Potential and Role of miRNA, lncRNA, and circRNA in Osteoarthritis

2019 ◽  
Vol 19 (4) ◽  
pp. 255-263 ◽  
Author(s):  
Yuangang Wu ◽  
Xiaoxi Lu ◽  
Bin Shen ◽  
Yi Zeng
Keyword(s):  
Gene Expression ◽  
Gene Therapy ◽  
Extracellular Matrix ◽  
Inflammatory Reaction ◽  
Noncoding Rna ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Protein Translation ◽  
Cochrane Library

Background: Osteoarthritis (OA) is a disease characterized by progressive degeneration, joint hyperplasia, narrowing of joint spaces, and extracellular matrix metabolism. Recent studies have shown that the pathogenesis of OA may be related to non-coding RNA, and its pathological mechanism may be an effective way to reduce OA. Objective: The purpose of this review was to investigate the recent progress of miRNA, long noncoding RNA (lncRNA) and circular RNA (circRNA) in gene therapy of OA, discussing the effects of this RNA on gene expression, inflammatory reaction, apoptosis and extracellular matrix in OA. Methods: The following electronic databases were searched, including PubMed, EMBASE, Web of Science, and the Cochrane Library, for published studies involving the miRNA, lncRNA, and circRNA in OA. The outcomes included the gene expression, inflammatory reaction, apoptosis, and extracellular matrix. Results and Discussion: With the development of technology, miRNA, lncRNA, and circRNA have been found in many diseases. More importantly, recent studies have found that RNA interacts with RNA-binding proteins to regulate gene transcription and protein translation, and is involved in various pathological processes of OA, thus becoming a potential therapy for OA. Conclusion: In this paper, we briefly introduced the role of miRNA, lncRNA, and circRNA in the occurrence and development of OA and as a new target for gene therapy.

scholarly journals Long noncoding RNAs as tumorigenic factors and therapeutic targets for renal cell carcinoma

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Haiyan Shen ◽  
Guomin Luo ◽  
Qingjuan Chen
Keyword(s):  
Renal Cell Carcinoma ◽  
Cell Carcinoma ◽  
Renal Cell ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Noncoding Rnas ◽  
Protein Translation ◽  
Long Noncoding Rnas ◽  
In Vivo Studies

AbstractApproximately 338,000 patients are diagnosed with kidney cancer worldwide each year, and renal cell carcinoma (RCC), which is derived from renal epithelium, accounts for more than ninety percent of the malignancy. Next generation RNA sequencing has enabled the identification of novel long noncoding RNAs (lncRNAs) in the past 10 years. Recent studies have provided extensive evidence that lncRNAs bind to chromatin modification proteins, transcription factors, RNA-binding proteins and microRNAs, and thereby modulate gene expression through regulating chromatin status, gene transcription, pre-mRNA splicing, mRNA decay and stability, protein translation and stability. In vitro and in vivo studies have demonstrated that over-expression of oncogenic lncRNAs and silencing of tumor suppressive lncRNAs are a common feature of human RCC, and that aberrant lncRNA expression is a marker for poor patient prognosis, and is essential for the initiation and progression of RCC. Because lncRNAs, compared with mRNAs, are expressed in a tissue-specific manner, aberrantly expressed lncRNAs can be better targeted for the treatment of RCC through screening small molecule compounds which block the interaction between lncRNAs and their binding proteins or microRNAs.

scholarly journals Ras Suppresses TXNIP Expression by Restricting Ribosome Translocation

2018 ◽  
Author(s):  
Zhizhou Ye ◽  
Donald E. Ayer
Keyword(s):  
Protein Synthesis ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Aerobic Glycolysis ◽  
Protein Translation ◽  
Underlying Mechanism ◽  
Metabolic Reprogramming ◽  
Coding Region ◽  
Interacting Protein ◽  
Thioredoxin Interacting Protein

ABSTRACTOncogenic Ras upregulates aerobic glycolysis to meet the bioenergetic and biosynthetic demands of rapidly growing cells. In contrast, Thioredoxin interacting protein (TXNIP) is a potent inhibitor of glucose uptake and is frequently downregulated in human cancers. Our lab previously discovered that Ras activation suppresses TXNIP transcription and translation. In this report, we developed a system to study how Ras affects TXNIP translation in the absence of transcriptional affects. We show that whereas Ras drives a global increase in protein translation, it suppresses TXNIP protein synthesis by reducing the rate at which ribosomes transit the coding region of TXNIP mRNA. To investigate the underlying mechanism(s), we randomized or optimized the codons in the TXNIP message without altering the TXNIP primary amino acid sequence. Translation from these mRNA variants is still repressed by Ras, intimating that mRNA secondary structure, miRNAs, RNA binding proteins, or codon usage do not contribute to the blockade of TXNIP synthesis. Rather, we show that the N-terminus of the growing TXNIP polypeptide is the target for Ras-dependent translational repression. Our work demonstrates how Ras suppresses TXNIP translation elongation in the face of a global upregulation of protein synthesis and provides new insight into Ras-dependent metabolic reprogramming.

scholarly journals The RNA-binding protein, Rasputin/G3BP, enhances the stability and translation of its target mRNAs

2020 ◽  
Author(s):  
John D. Laver ◽  
Jimmy Ly ◽  
Allison K. Winn ◽  
Angelo Karaiskakis ◽  
Sichun Lin ◽  
...  
Keyword(s):  
Microarray Analysis ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Rna Binding Protein ◽  
Stress Granules ◽  
Direct Role ◽  
Target Mrnas ◽  
Core Components ◽  
The Stability

SUMMARYG3BP RNA-binding proteins are important components of stress granules (SGs). Here we analyze the role of Drosophila G3BP, Rasputin (RIN), in unstressed cells, where RIN is not SG associated. Immunoprecipitation followed by microarray analysis identified over 550 mRNAs that copurify with RIN. The mRNAs found in SGs are long and translationally silent. In contrast, we find that RIN-bound mRNAs, which encode core components of the transcription, splicing and translation machinery, are short, stable and highly translated. We show that RIN is associated with polysomes and provide evidence for a direct role for RIN and its human homologs in stabilizing and upregulating the translation of their target mRNAs. We propose that when cells are stressed the resulting incorporation of RIN/G3BPs into SGs sequesters them away from their short target mRNAs. This would downregulate the expression of these transcripts, even though they are not incorporated into stress granules.

scholarly journals Transite: A computational motif-based analysis platform that identifies RNA-binding proteins modulating changes in gene expression

2018 ◽  
Author(s):  
Konstantin Krismer ◽  
Shohreh Varmeh ◽  
Molly A. Bird ◽  
Anna Gattinger ◽  
Yi Wen Kong ◽  
...  
Keyword(s):  
Gene Expression ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Rna Stability ◽  
Protein Translation ◽  
State Transitions ◽  
Global Changes ◽  
Expression Data ◽  
Platinum Based Chemotherapy

AbstractRNA-binding proteins (RBPs) play critical roles in regulating gene expression by modulating splicing, RNA stability, and protein translation. In response to various stimuli, alterations in RBP function contribute to global changes in gene expression, but identifying which specific RBPs are responsible for the observed changes in gene expression patterns remains an unmet need. Here, we presentTransitea multi-pronged computational approach that systematically infers RBPs influencing gene expression changes through alterations in RNA stability and degradation. As a proof of principle, we applied Transite to public RNA expression data from human patients with non-small cell lung cancer whose tumors were sampled at diagnosis, or after recurrence following treatment with platinum-based chemotherapy. Transite implicated known RBP regulators of the DNA damage response and identified hnRNPC as a new modulator of chemotherapeutic resistance, which we subsequently validated experimentally. Transite serves as a generalizable framework for the identification of RBPs responsible for gene expression changes that drive cell-state transitions and adds additional value to the vast wealth of publicly-available gene expression data.

scholarly journals Selective recruitment of endoplasmic reticulum-targeted and cytosolic mRNAs into membrane-associated stress granules

2021 ◽  
Author(s):  
Jessica R Child ◽  
Qiang Chen ◽  
David W Reid ◽  
Sujatha Jagannathan ◽  
Christopher V Nicchitta
Keyword(s):  
Endoplasmic Reticulum ◽  
Translation Initiation ◽  
Nuclear Export ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Signal Sequence ◽  
Stress Granules ◽  
Cell Fractionation ◽  
Functional Link ◽  
Translational Inhibition

Stress granules (SGs) are membraneless organelles composed of mRNAs and RNA binding proteins which undergo assembly in response to stress-induced inactivation of translation initiation. The biochemical criteria for mRNA recruitment into SGs are largely unknown. In general, SG recruitment is limited to a subpopulation of a given mRNA species and RNA-seq analyses of purified SGs revealed that signal sequence-encoding (i.e. endoplasmic reticulum (ER)-targeted) transcripts are significantly under-represented, consistent with prior reports that ER-localized mRNAs are excluded from SGs. Using translational profiling, cell fractionation, and single molecule mRNA imaging, we examined SG biogenesis during the unfolded protein response (UPR) and report that UPR-elicited SG formation is gene selective. Combined immunofluorescence-smFISH studies demonstrated that UPR-induced mRNA granules co-localized with SG protein markers and were in close physical proximity to or directly associated with the ER membrane. mRNA recruitment into ER-associated SGs required stress-induced translational inhibition, though translational inhibition was not solely predictive of mRNA accumulation in SGs. SG formation in response to UPR activation or arsenite addition was blocked by the transcriptional inhibitors actinomycin D or triptolide, suggesting a functional link between gene transcriptional state and SG biogenesis. These data demonstrate that ER-targeted mRNAs can be recruited into SGs and identify the ER as a subcellular site of SG assembly. On the basis of the transcriptional inhibitor studies, we propose that newly transcribed mRNAs undergoing nuclear export during conditions of suppressed translation initiation are key substrates for SG biogenesis

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