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Nicchitta CV. An emerging role for the endoplasmic reticulum in stress granule biogenesis. Semin Cell Dev Biol 2024; 156:160-166. [PMID: 36202692 PMCID: PMC10208384 DOI: 10.1016/j.semcdb.2022.09.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 09/07/2022] [Accepted: 09/26/2022] [Indexed: 11/07/2022]
Abstract
Stress granules (SGs), structurally dynamic, optically resolvable, macromolecular assemblies of mRNAs, RNA binding proteins (RBPs), translation factors, ribosomal subunits, as well as other interacting proteins, assemble in response to cell stress conditions that elicit phosphorylation of eukaryotic initiation factor 2α (eIF2α) and consequently, the inactivation of translation initiation. SG biology is conserved throughout eukaryotes and has recently been linked to the pathological sequelae of neurodegenerative disorders, cancer biology, and viral infection. Substantial insights into mechanisms of SG biogenesis, and more broadly the phenomenon of biological liquid-liquid phase separation (LLPS), have been aided by detailed proteomic and transcriptomic studies as well as in vitro reconstitution approaches. A particularly interesting and largely unexplored element of SG biology is the cell biological context of SG biogenesis, including its subcellular organization and more recently, evidence that the endoplasmic reticulum (ER) membrane may serve important functions in RNA granule biology generally and SG biogenesis specifically. A central role for the ER in SG biogenesis is discussed and a hypothesis linking SG formation on the ER to the trafficking, localization and de novo translation of newly exported mRNAs is presented.
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Xu L, Liu T, Xiong X, Liu W, Yu Y, Cao J. AtC3H18L is a stop-codon read-through gene and encodes a novel non-tandem CCCH zinc-finger protein that can form cytoplasmic foci similar to mRNP granules. Biochem Biophys Res Commun 2020; 528:140-145. [PMID: 32451083 DOI: 10.1016/j.bbrc.2020.05.081] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 05/12/2020] [Indexed: 11/18/2022]
Abstract
The membraneless messenger ribonucleoprotein (mRNP) granules, including processing bodies (PBs) and stress granules (SGs), are important cytoplasmic structures in eukaryotes that can participate in gene expression through mRNA regulation. It has been verified that mRNP granules are mainly composed of proteins and translation-repressed mRNAs. Here, we reported a stop-codon read-through gene, At3g52980, in plants for the first time. At3g52980 encodes a novel non-tandem CCCH zinc-finger (non-TZF) protein named AtC3H18-Like (AtC3H18L), which contains two putative RNA-binding domains. By using transient expression system, we showed that heat treatment can induce the aggregation of diffuse distributed AtC3H18L to form cytoplasmic foci, which were similar to PBs and SGs in morphology. Further analysis did find that AtC3H18L can co-localize with markers of PB and SG. The aggregation of AtC3H18L was closely related to the cytoskeleton, and AtC3H18L-foci were highly dynamic and can move frequently along cytoskeleton. Moreover, analysis in transgenic plants showed that AtC3H18L was specifically expressed in pollen and can form cytoplasmic foci without heat treatment. It will be fascinating in future studies to discover whether and how AtC3H18L affects pollen development by participating in the assembly of mRNP granules as a protein component, especially under heat stress.
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Affiliation(s)
- Liai Xu
- Laboratory of Cell & Molecular Biology, Institute of Vegetable Science, Zhejiang University, Hangzhou, 310058, China; Key Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Hangzhou, 310058, China.
| | - Tingting Liu
- Laboratory of Cell & Molecular Biology, Institute of Vegetable Science, Zhejiang University, Hangzhou, 310058, China; Key Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Hangzhou, 310058, China.
| | - Xingpeng Xiong
- Laboratory of Cell & Molecular Biology, Institute of Vegetable Science, Zhejiang University, Hangzhou, 310058, China; Key Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Hangzhou, 310058, China.
| | - Weimiao Liu
- Laboratory of Cell & Molecular Biology, Institute of Vegetable Science, Zhejiang University, Hangzhou, 310058, China; Key Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Hangzhou, 310058, China.
| | - Youjian Yu
- Department of Horticulture, College of Agriculture and Food Science, Zhejiang A & F University, Lin'an, 311300, China.
| | - Jiashu Cao
- Laboratory of Cell & Molecular Biology, Institute of Vegetable Science, Zhejiang University, Hangzhou, 310058, China; Key Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Hangzhou, 310058, China.
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Park J, Ahn S, Jayabalan AK, Ohn T, Koh HC, Hwang J. Insulin Signaling Augments eIF4E-Dependent Nonsense-Mediated mRNA Decay in Mammalian Cells. Biochim Biophys Acta 2015; 1859:896-905. [PMID: 26708722 DOI: 10.1016/j.bbagrm.2015.12.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 12/14/2015] [Accepted: 12/17/2015] [Indexed: 12/13/2022]
Abstract
Nonsense-mediated mRNA decay (NMD) modulates the level of mRNA harboring a premature termination codon (PTC) in a translation-dependent manner. Inhibition of translation is known to impair NMD; however, few studies have investigated the correlation between enhanced translation and increased NMD. Here, we demonstrate that insulin signaling events increase translation, leading to an increase in NMD of eIF4E-bound transcripts. We provide evidence that (i) insulin-mediated enhancement of translation augments NMD and rapamycin abrogates this enhancement; (ii) an increase in AKT phosphorylation due to inhibition of PTEN facilitates NMD; (iii) insulin stimulation increases the binding of up-frameshift factor 1 (UPF1), most likely to eIF4E-bound PTC-containing transcripts; and (iv) insulin stimulation induces the colocalization of UPF1 and eIF4E in processing bodies. These results illustrate how extracellular signaling promotes the removal of eIF4E-bound NMD targets.
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Affiliation(s)
- Jungyun Park
- Graduate School for Biomedical Science & Engineering, FTC1202-8, Hanyang University, 222 Wangimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Seyoung Ahn
- Graduate School for Biomedical Science & Engineering, FTC1202-8, Hanyang University, 222 Wangimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Aravinth K Jayabalan
- Department of Cellular and Molecular Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Takbum Ohn
- Department of Cellular and Molecular Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Hyun Chul Koh
- Department of Pharmacology, College of Medicine, Hanyang University, 222 Wangimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea.
| | - Jungwook Hwang
- Graduate School for Biomedical Science & Engineering, FTC1202-8, Hanyang University, 222 Wangimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea; Department of Medical Genetics, College of Medicine, FTC1202-8, Hanyang University, 222 Wangimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea.
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Terrell AM, Anand D, Smith SF, Dang CA, Waters SM, Pathania M, Beebe DC, Lachke SA. Molecular characterization of mouse lens epithelial cell lines and their suitability to study RNA granules and cataract associated genes. Exp Eye Res 2014; 131:42-55. [PMID: 25530357 DOI: 10.1016/j.exer.2014.12.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 12/02/2014] [Accepted: 12/18/2014] [Indexed: 01/10/2023]
Abstract
The discovery of cytosolic RNA granule (RG) component proteins associated with human cataract has initiated investigations on post-transcriptional mechanisms of gene expression control in the lens. Application of established mouse lens epithelial cell lines (LECs) can provide rapid insights on RG function in lens cells, especially because mouse mutants in several RG components are not available. However, although these LECs represent potential reagents for such analyses, they are uncharacterized for lens gene expression or RG formation. Therefore, a detailed molecular and cellular characterization of three permanent mouse LECs 17EM15, 21EM15 and αTN4 is performed in this study. Comparative analysis between microarray gene expression datasets on LEC 21EM15 and iSyTE lens tissue demonstrates that 30% of top 200 iSyTE identified lens-enriched genes are expressed in these cells. Majority of these candidates are independently validated to either have lens expression, function or linkage to cataract. Moreover, analysis of microarray data with genes described in Cat-Map, an online database of cataract associated genes and loci, demonstrates that 131 genes linked to cataract loci are expressed in 21EM15 cells. Furthermore, gene expression in LECs is compared to isolated lens epithelium or fiber cells by qRT-PCR and by comparative analyses with publically available epithelium or fiber-specific microarray and RNA-seq (sequencing) datasets. Expression of select candidate genes was validated by regular and real-time quantitative RT-PCR. Expression of lens epithelium-enriched genes Foxe3, Pax6, Anxa4 and Mcm4 is up-regulated in LEC lines, compared to isolated lens fiber cells. Moreover, similar to isolated lens epithelium, all three LECs exhibit down-regulation of fiber cell-expressed genes Crybb1, Mip and Prox1 when compared to fiber cells. These data indicate that the LEC lines exhibit greater similarity to lens epithelium than to fiber cells. Compared to non-lens cell line NIH3T3, LECs exhibit significantly enriched expression of transcription factors with important function in the lens, namely Pax6, Foxe3 and Prox1. In addition to these genes, all three LECs also express key lens- and cataract-associated genes, namely Dkk3, Epha2, Hsf4, Jag1, Mab21l1, Meis1, Pknox1, Pou2f1, Sfrp1, Sparc, Tdrd7 and Trpm3. Additionally, 21EM15 microarrays indicate expression of Chmp4b, Cryab and Tcfap2a among others important genes. Immunostaining with makers for Processing bodies (P-bodies) and Stress granules (SGs) demonstrates that these classes of RGs are robustly expressed in all three LECs. Moreover, under conditions of stress, 17EM15 and αTN4 exhibit significantly higher numbers of P-bodies and SGs compared to NIH3T3 cells. In sum, these data indicate that mouse LECs 21EM15, 17EM15 and αTN4 express key lens or cataract genes, are similar to lens epithelium than fiber cells, and exhibit high levels of P-bodies and SGs, indicating their suitability for investigating gene expression control and RG function in lens-derived cells.
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Affiliation(s)
- Anne M Terrell
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Deepti Anand
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Sylvie F Smith
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Christine A Dang
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Stephanie M Waters
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Mallika Pathania
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - David C Beebe
- Department of Ophthalmology and Visual Sciences, Washington University, St. Louis, MO, USA
| | - Salil A Lachke
- Department of Biological Sciences, University of Delaware, Newark, DE, USA; Center for Bioinformatics & Computational Biology, University of Delaware, Newark, DE, USA.
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