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Sumioka A, Usuki F, Fujimura M. Development of a sensor to detect methylmercury toxicity. Sci Rep 2024; 14:21832. [PMID: 39294331 PMCID: PMC11411131 DOI: 10.1038/s41598-024-72788-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Accepted: 09/10/2024] [Indexed: 09/20/2024] Open
Abstract
Methylmercury (MeHg) is a well-known neurotoxicant that induces various cellular functions depending on cellular- and developmental-specific vulnerabilities. MeHg has a high affinity for selenol and thiol groups, thus impairing the antioxidant system. Such affinity characteristics of MeHg led us to develop sensor vectors to assess MeHg toxicity. In this study, MeHg-mediated defects in selenocysteine (Sec) incorporation were demonstrated using thioredoxin reductase 1 cDNA fused with the hemagglutinin tag sequence at the C-terminus. Taking advantage of such MeHg-mediated defects in Sec incorporation, a cDNA encoding luciferase with a Sec substituted for cysteine-491 was constructed. This construct showed MeHg-induced decreases in signaling in a dose-dependent manner. To directly detect truncated luciferase under MeHg exposure, we further constructed a new sensor vector fused with a target for proteasomal degradation. However, this construct was inadequate because of the low rate of Sec insertion, even in the absence of MeHg. Finally, a Krab transcriptional suppressor fused with Sec was constructed and assessed to demonstrate MeHg-dependent increases in signal intensity. We confirmed that the vector responded specifically and in a dose-dependent manner to MeHg in cultured cerebellar granule cells. This vector is expected to allow monitoring of MeHg-specific toxicity via spatial and temporal imaging.
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Affiliation(s)
- Akio Sumioka
- Department of Basic Medical Sciences, National Institute for Minamata Disease, 4058-18 Hama, Minamata, Kumamoto, 867-0008, Japan.
| | - Fusako Usuki
- Division of Neuroimmunology, Joint Research Center for Human Retrovirus Infection, Kagoshima University, Kagoshima, 890-8544, Japan
| | - Masatake Fujimura
- Department of Basic Medical Sciences, National Institute for Minamata Disease, 4058-18 Hama, Minamata, Kumamoto, 867-0008, Japan
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Lava Kumar S, Kushawaha B, Mohanty A, Kumari A, Kumar A, Beniwal R, Kiran Kumar P, Athar M, Krishna Rao D, Rao HBDP. Glutathione peroxidase (GPX1) - Selenocysteine metabolism preserves the follicular fluid's (FF) redox homeostasis via IGF-1- NMD cascade in follicular ovarian cysts (FOCs). Biochim Biophys Acta Mol Basis Dis 2024; 1870:167235. [PMID: 38744343 DOI: 10.1016/j.bbadis.2024.167235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 04/18/2024] [Accepted: 05/09/2024] [Indexed: 05/16/2024]
Abstract
Follicular ovarian cysts (FOCs) are characterized by follicles in the ovaries that are >20 mm in diameter and persist for >10 days without the corpus luteum, leading to anovulation, dysregulation of folliculogenesis and subfertility in humans and livestock species. Despite their clinical significance, the precise impact of FOCs on oocyte reserve, maturation, and quality still needs to be explored. While FOCs are observed in both human and livestock populations, they are notably prevalent in livestock species. Consequently, livestock species serve as valuable models for investigating the molecular intricacies of FOCs. Thus, in this study, using goat FOCs, we performed integrated proteomic, metabolomic and functional analyses to demonstrate that oocyte maturation is hampered due to increased reactive oxygen species (ROS) in FOCs follicular fluid (FF) via downregulation of glutathione peroxidase (GPX1), a critical antioxidant seleno enzyme required to negate oxidative stress. Notably, GPX1 reduction was positively correlated with the FF's decline of free selenium and selenocysteine metabolic enzymes, O-phosphoryl-tRNA (Sec) selenium transferase (SEPSECS) and selenocysteine lyase (SCLY) levels. Adding GPX1, selenocysteine, or selenium to the culture media rescued the oocyte maturation abnormalities caused by FOCs FF by down-regulating the ROS. Additionally, we demonstrate that substituting GPX1 regulator, Insulin-like growth factor-I (IGF-1) in the in vitro maturation media improved the oocyte maturation in the cystic FF by down-regulating the ROS activity via suppressing Non-sense-mediated decay (NMD) of GPX1. In contrast, inhibition of IGF-1R and the target of rapamycin complex 1 (mTORC1) hampered the oocyte maturation via NMD up-regulation. These findings imply that the GPX1 regulation via selenocysteine metabolism and the IGF-1-mediated NMD may be critical for the redox homeostasis of FF. We propose that GPX1 enhancers hold promise as therapeutics for enhancing the competence of FOCs oocytes. However, further in vivo studies are necessary to validate these findings observed in vitro.
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Affiliation(s)
- S Lava Kumar
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India; Graduate studies, Regional Center for Biotechnology, Faridabad 121 001, India
| | - Bhawna Kushawaha
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India
| | - Aradhana Mohanty
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India; Graduate studies, Regional Center for Biotechnology, Faridabad 121 001, India
| | - Anjali Kumari
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India; Graduate studies, Regional Center for Biotechnology, Faridabad 121 001, India
| | - Ajith Kumar
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India; Graduate studies, Regional Center for Biotechnology, Faridabad 121 001, India
| | - Rohit Beniwal
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India; Graduate studies, Regional Center for Biotechnology, Faridabad 121 001, India
| | - P Kiran Kumar
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India
| | - Mohd Athar
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India; Graduate studies, Regional Center for Biotechnology, Faridabad 121 001, India
| | - D Krishna Rao
- Tata Institute of Fundamental Research, Hyderabad, Telangana 500032, India
| | - H B D Prasada Rao
- National Institute of Animal Biotechnology, Hyderabad, Telangana 500032, India.
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Kurosaki T, Rambout X, Maquat LE. FMRP-mediated spatial regulation of physiologic NMD targets in neuronal cells. Genome Biol 2024; 25:31. [PMID: 38263082 PMCID: PMC10804635 DOI: 10.1186/s13059-023-03146-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 12/14/2023] [Indexed: 01/25/2024] Open
Abstract
In non-polarized cells, nonsense-mediated mRNA decay (NMD) generally begins during the translation of newly synthesized mRNAs after the mRNAs are exported to the cytoplasm. Binding of the FMRP translational repressor to UPF1 on NMD targets mainly inhibits NMD. However, in polarized cells like neurons, FMRP additionally localizes mRNAs to cellular projections. Here, we review the literature and evaluate available transcriptomic data to conclude that, in neurons, the translation of physiologic NMD targets bound by FMRP is partially inhibited until the mRNAs localize to projections. There, FMRP displacement in response to signaling induces a burst in protein synthesis followed by rapid mRNA decay.
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Affiliation(s)
- Tatsuaki Kurosaki
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY, 14642, USA
- Center for RNA Biology, University of Rochester, Rochester, NY, 14642, USA
| | - Xavier Rambout
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY, 14642, USA
- Center for RNA Biology, University of Rochester, Rochester, NY, 14642, USA
| | - Lynne E Maquat
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY, 14642, USA.
- Center for RNA Biology, University of Rochester, Rochester, NY, 14642, USA.
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Burkart V, Kowalski K, Disch A, Hilfiker-Kleiner D, Lal S, Dos Remedios C, Perrot A, Zeug A, Ponimaskin E, Kosanke M, Dittrich-Breiholz O, Kraft T, Montag J. Nonsense mediated decay factor UPF3B is associated with cMyBP-C haploinsufficiency in hypertrophic cardiomyopathy patients. J Mol Cell Cardiol 2023; 185:26-37. [PMID: 37797718 DOI: 10.1016/j.yjmcc.2023.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 09/08/2023] [Accepted: 09/28/2023] [Indexed: 10/07/2023]
Abstract
Hypertrophic cardiomyopathy (HCM) is the most prevalent inherited cardiac disease. Up to 40% of cases are associated with heterozygous mutations in myosin binding protein C (cMyBP-C, MYBPC3). Most of these mutations lead to premature termination codons (PTC) and patients show reduction of functional cMyBP-C. This so-called haploinsufficiency most likely contributes to disease development. We analyzed mechanisms underlying haploinsufficiency using cardiac tissue from HCM-patients with truncation mutations in MYBPC3 (MYBPC3trunc). We compared transcriptional activity, mRNA and protein expression to donor controls. To differentiate between HCM-specific and general hypertrophy-induced mechanisms we used patients with left ventricular hypertrophy due to aortic stenosis (AS) as an additional control. We show that cMyBP-C haploinsufficiency starts at the mRNA level, despite hypertrophy-induced increased transcriptional activity. Gene set enrichment analysis (GSEA) of RNA-sequencing data revealed an increased expression of NMD-components. Among them, Up-frameshift protein UPF3B, a regulator of NMD was upregulated in MYBPC3trunc patients and not in AS-patients. Strikingly, we show that in sarcomeres UPF3B but not UPF1 and UPF2 are localized to the Z-discs, the presumed location of sarcomeric protein translation. Our data suggest that cMyBP-C haploinsufficiency in HCM-patients is established by UPF3B-dependent NMD during the initial translation round at the Z-disc.
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Affiliation(s)
- Valentin Burkart
- Institute for Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany.
| | - Kathrin Kowalski
- Institute for Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Alina Disch
- Institute for Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | | | - Sean Lal
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Cristobal Dos Remedios
- Mechanosensory Biophysics Laboratory, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Andreas Perrot
- Charité - Universitätsmedizin Berlin, Experimental & Clinical Research Center, Berlin, Germany
| | - Andre Zeug
- Institute of Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Evgeni Ponimaskin
- Institute of Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Maike Kosanke
- Research Core Unit Genomics, Hannover Medical School, Hannover, Germany
| | | | - Theresia Kraft
- Institute for Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
| | - Judith Montag
- Institute for Molecular and Cell Physiology, Hannover Medical School, Hannover, Germany
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Andjus S, Morillon A, Wery M. From Yeast to Mammals, the Nonsense-Mediated mRNA Decay as a Master Regulator of Long Non-Coding RNAs Functional Trajectory. Noncoding RNA 2021; 7:ncrna7030044. [PMID: 34449682 PMCID: PMC8395947 DOI: 10.3390/ncrna7030044] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 07/22/2021] [Accepted: 07/25/2021] [Indexed: 12/22/2022] Open
Abstract
The Nonsense-Mediated mRNA Decay (NMD) has been classically viewed as a translation-dependent RNA surveillance pathway degrading aberrant mRNAs containing premature stop codons. However, it is now clear that mRNA quality control represents only one face of the multiple functions of NMD. Indeed, NMD also regulates the physiological expression of normal mRNAs, and more surprisingly, of long non-coding (lnc)RNAs. Here, we review the different mechanisms of NMD activation in yeast and mammals, and we discuss the molecular bases of the NMD sensitivity of lncRNAs, considering the functional roles of NMD and of translation in the metabolism of these transcripts. In this regard, we describe several examples of functional micropeptides produced from lncRNAs. We propose that translation and NMD provide potent means to regulate the expression of lncRNAs, which might be critical for the cell to respond to environmental changes.
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Affiliation(s)
- Sara Andjus
- ncRNA, Epigenetic and Genome Fluidity, Institut Curie, PSL University, Sorbonne Université, CNRS UMR3244, 26 Rue d’Ulm, CEDEX 05, F-75248 Paris, France;
| | - Antonin Morillon
- ncRNA, Epigenetic and Genome Fluidity, Institut Curie, Sorbonne Université, CNRS UMR3244, 26 Rue d’Ulm, CEDEX 05, F-75248 Paris, France
- Correspondence: (A.M.); (M.W.)
| | - Maxime Wery
- ncRNA, Epigenetic and Genome Fluidity, Institut Curie, Sorbonne Université, CNRS UMR3244, 26 Rue d’Ulm, CEDEX 05, F-75248 Paris, France
- Correspondence: (A.M.); (M.W.)
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Dietary selenium sources differentially regulate selenium concentration, mRNA and protein expression of representative selenoproteins in various tissues of yellow catfish Pelteobagrus fulvidraco. Br J Nutr 2021; 127:490-502. [PMID: 34085611 DOI: 10.1017/s000711452100194x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The study was conducted to determine the effects of three dietary Se sources, such as sodium-selenite (S-S), seleno-yeast (S-Y) and seleno-methionine (S-M), on Se concentration, glutathione peroxidase (GPX) and TXNRD activities, and mRNA expression of fifteen representative selenoproteins, and protein expression of four endoplasmic reticulum-resided selenoproteins in a wide range of tissues of yellow catfish. Compared with S-S and S-M groups, dietary S-Y significantly decreased growth performance and feed utilisation of yellow catfish. Dietary Se sources significantly influenced Se contents in the spleen, dorsal muscle and the kidney, GPX activities in spleen, kidney, intestine, muscle and mesenteric fat, and TXNRD activities in the heart, intestine and mesenteric fat. Among ten tested tissues, dietary Se sources influenced mRNA expression of GPX4 and SELENOK in three tissues; GPX3, SELENOS and TXNRD2 in four tissues; SELENOF, SELENON and DIO2 in five tissues; SELENOM, GPX1/2 and TXNRD3 in six tissues; SELENOW in seven tissue and SELENOP and SELENOT in eight tissues. Based on these observations above, S-S and S-M seem to be suitable Se sources for improving growth performance and feed utilisation of yellow catfish. Dietary Se sources differentially influence the expression of selenoproteins in various tissues of yellow catfish. For the first time, we determined the expression of selenoproteins in fish in responses to dietary Se sources, which contributes to a better understanding of the functions and regulatory mechanisms of selenoporteins.
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Su Y, Li L, Farooq MU, Huang X, Zheng T, Zhang YJ, Ei HH, Panhwar FH, Tang Z, Zeng R, Liang Y, Ye X, Jia X, Zhu J. Rescue effects of Se-enriched rice on physiological and biochemical characteristics in cadmium poisoning mice. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:20023-20033. [PMID: 33409993 DOI: 10.1007/s11356-020-11854-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 11/26/2020] [Indexed: 06/12/2023]
Abstract
Cadmium (Cd) is an element injurious for human health and is possibly toxic to organisms at minor concentrations. While some of other trace metallic elements have antagonistic features to it. One of them is the interaction between selenium (Se) and Cd in plant different organs. Literature review disclosed that the intake of Se to some extent can reduce the accumulation of Cd in plants, while the research on of trace metallic elements (Cd) and Se-enriched food (rice) in the living body has rarely been reported. This study intended to explore whether there was a mitigating effect of Se-enriched rice on mice poisoned with Cd. A mouse model of low-dose and high-dose Cd poisoning was established (supplemented with cadmium chloride(CdCl2·2½H20)), followed by feeding two groups (1) Se-enriched rice and (2) setting an equal amount of inorganic Se group. After that, the impact of Se-enriched rice on the antioxidant activity was evaluated. The Se-enriched diet enhanced the total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and enzyme activities of GSH peroxidase (GSH-Px) in mice livers and kidney whereas significantly decreased the malondialdehyde (MDA) contents. Moreover, the degree of physiological damage in mice with low cadmium poisoning was significantly alleviated, and the expression of antioxidant genes (Nrf-2, GPX1, TrxR2, TNF-2) was increased. In conclusion, the Se-enriched diet has a positive effect on the biological effects in mice, and it can be used as a daily diet to resist damage to the body's low Cd state and support enzymatic antioxidant systems by eliminating oxidative injury.
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Affiliation(s)
- Yang Su
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Ling Li
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Muhammad Umer Farooq
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
- Department of Botany, Faculty of Life Sciences, University of Okara, Okara, 56130, Pakistan
| | - Xin Huang
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Tengda Zheng
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Yu Jie Zhang
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Hla Hla Ei
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Faiz Hussain Panhwar
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Zhichen Tang
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Rui Zeng
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
- College of Chemistry and Life Science, Chengdu Normal University, Chengdu, 611130, China
| | - Yuanke Liang
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Xiaoying Ye
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Xiaomei Jia
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China
| | - Jianqing Zhu
- Rice Research Institute, Sichuan Agricultural University, 211, Huimin Road, Wenjiang District, Chengdu, 611130, Sichuan, China.
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Neonatal Selenoenzyme Expression Is Variably Susceptible to Duration of Maternal Selenium Deficiency. Antioxidants (Basel) 2021; 10:antiox10020288. [PMID: 33672905 PMCID: PMC7917816 DOI: 10.3390/antiox10020288] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/03/2021] [Accepted: 02/08/2021] [Indexed: 12/16/2022] Open
Abstract
Maternal selenium (Se) deficiency is associated with decreased neonatal Se levels, which increases the risk for neonatal morbidities. There is a hierarchy to selenoprotein expression after Se deficiency in adult rodents, depending on the particular protein and organ evaluated. However, it is unknown how limited Se supply during pregnancy impacts neonatal selenoprotein expression. We used an Se-deficient diet to induce perinatal Se deficiency (SeD), initiated 2–4 weeks before onset of breeding and continuing through gestation. Neonatal plasma, liver, heart, kidney, and lung were collected on the day of birth and assessed for selenoproteins, factors required for Se processing, and non-Se containing antioxidant enzymes (AOE). Maternal SeD reduced neonatal circulating and hepatic glutathione peroxidase (GPx) activity, as well as hepatic expression of Gpx1 and selenophosphate synthetase 2 (Sps2). In contrast, the impact of maternal SeD on hepatic thioredoxin reductase 1, hepatic non-Se containing AOEs, as well as cardiac, renal, and pulmonary GPx activity, varied based on duration of maternal exposure to SeD diet. We conclude that the neonatal liver and circulation demonstrate earlier depletion in selenoenzyme activity after maternal SeD. Our data indicate that prolonged maternal SeD may escalate risk to the neonate by progressively diminishing Se-containing AOE across multiple organs.
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Giuliani ME, Filippini G, Nardi A. Season specific influence of projected ocean changes on the response to cadmium of stress-related genes in Mytilus galloprovincialis. MARINE ENVIRONMENTAL RESEARCH 2020; 162:105091. [PMID: 32798697 DOI: 10.1016/j.marenvres.2020.105091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 07/17/2020] [Accepted: 07/21/2020] [Indexed: 06/11/2023]
Abstract
Anthropogenic inputs of carbon dioxide in the atmosphere are driving ocean warming and acidification. The potential threat represented by these changes for marine species could be amplified in coastal areas, characterized by higher levels of pollutants. In addition, temperate organisms may exhibit a different seasonal tolerance to stressors influenced by fluctuations of environmental and physiological factors. In this study, Mediterranean mussels Mytilus galloprovincialis collected both in summer and winter were exposed to combinations of two temperatures (SST, seasonal surface temperature and SST+5 °C) and two levels of pH (8.20 and 7.40) in clean or cadmium contaminated seawater (20 μg/L Cd). mRNA levels of genes related to metal-induced stress response were investigated, including metallothionein mt-20, heat-shock protein hsp70, superoxide dismutase Cu/Zn-sod, catalase cat, glutathione peroxidase gpx1 and glutathione S-transferase gst-pi. To further elucidate if tissues with different physiological roles could exhibit different responsiveness, such analyses were carried out in digestive gland and in gills of exposed mussels. mt-20 mRNA increase after Cd-exposure was higher in the digestive gland than in the gills, with few modulations by temperature or pH only in the latter. Acidification, alone or in combination with other stressors, increased hsp70 mRNA, with seasonal- and tissue-specificities (higher in summer and in digestive gland). Among antioxidants, gpx1 mRNA was affected by Cd in both tissues and seasons, with further modulations due to pH and temperature variation tissue- and season-specific; in winter the combination of Cd, warming and acidification affected Cu/Zn-sod both in digestive gland and gills and cat only in gills, while weak seasonal variations were observed for gst-pi transcripts only in digestive gland. The overall results highlighted the importance of considering seasonality and responsiveness of different tissues to predict the effects of sudden changes in environmental parameters on responsiveness to and toxicity of chemicals in marine coastal organisms.
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Affiliation(s)
- Maria Elisa Giuliani
- Dipartimento di Scienze della Vita e dell'Ambiente (DiSVA), Università Politecnica delle Marche, Ancona, Italy
| | - Giulia Filippini
- Department of Environmental Sciences, Macquarie University, North Ryde, NSW 2109, Australia
| | - Alessandro Nardi
- Dipartimento di Scienze della Vita e dell'Ambiente (DiSVA), Università Politecnica delle Marche, Ancona, Italy.
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Fujimura M, Usuki F. Methylmercury-Mediated Oxidative Stress and Activation of the Cellular Protective System. Antioxidants (Basel) 2020; 9:antiox9101004. [PMID: 33081221 PMCID: PMC7602710 DOI: 10.3390/antiox9101004] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/09/2020] [Accepted: 10/14/2020] [Indexed: 12/17/2022] Open
Abstract
Methylmercury (MeHg) is a well-known neurotoxicant that causes severe intoxication in humans. In Japan, it is referred to as Minamata disease, which involves two characteristic clinical forms: fetal type and adult type depending on the exposed age. In addition to MeHg burden level, individual susceptibility to MeHg plays a role in the manifestation of MeHg toxicity. Research progress has pointed out the importance of oxidative stress in the pathogenesis of MeHg toxicity. MeHg has a high affinity for selenohydryl groups, sulfhydryl groups, and selenides. It has been clarified that such affinity characteristics cause the impairment of antioxidant enzymes and proteins, resulting in the disruption of antioxidant systems. Furthermore, MeHg-induced intracellular selenium deficiency due to the greater affinity of MeHg for selenohydryl groups and selenides leads to failure in the recoding of a UGA codon for selenocysteine and results in the degradation of antioxidant selenoenzyme mRNA by nonsense-mediated mRNA decay. The defect of antioxidant selenoenzyme replenishment exacerbates MeHg-mediated oxidative stress. On the other hand, it has also been revealed that MeHg can directly activate the antioxidant Keap1/Nrf2 signaling pathway. This review summarizes the incidence of MeHg-mediated oxidative stress from the viewpoint of the individual intracellular redox system interactions and the MeHg-mediated aforementioned intracellular events. In addition, the mechanisms of cellular stress pathways and neuronal cell death triggered by MeHg-mediated oxidative stress and direct interactions of MeHg with reactive residues of proteins are mentioned.
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Affiliation(s)
- Masatake Fujimura
- Department of Basic Medical Sciences, National Institute for Minamata Disease, Kumamoto 867-0008, Japan;
| | - Fusako Usuki
- Division of Neuroimmunology, Joint Research Center for Human Retrovirus Infection, Kagoshima University, Kagoshima 890-8544, Japan
- Correspondence: ; Tel.: +81-99-275-6246; Fax: +81-99-275-5942
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Dietary selenium deficiency or selenomethionine excess drastically alters organ selenium contents without altering the expression of most selenoproteins in mice. J Nutr Biochem 2019; 69:120-129. [DOI: 10.1016/j.jnutbio.2019.03.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 02/27/2019] [Accepted: 03/25/2019] [Indexed: 12/24/2022]
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Lejeune F. Nonsense-mediated mRNA decay at the crossroads of many cellular pathways. BMB Rep 2018; 50:175-185. [PMID: 28115040 PMCID: PMC5437961 DOI: 10.5483/bmbrep.2017.50.4.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Indexed: 12/22/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is a surveillance mechanism ensuring the fast decay of mRNAs harboring a premature termination codon (PTC). As a quality control mechanism, NMD distinguishes PTCs from normal termination codons in order to degrade PTC-carrying mRNAs only. For this, NMD is connected to various other cell processes which regulate or activate it under specific cell conditions or in response to mutations, mis-regulations, stresses, or particular cell programs. These cell processes and their connections with NMD are the focus of this review, which aims both to illustrate the complexity of the NMD mechanism and its regulation and to highlight the cellular consequences of NMD inhibition.
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Affiliation(s)
- Fabrice Lejeune
- University Lille, UMR8161 - M3T - Mechanisms of Tumorigenesis and Target Therapies; CNRS, UMR 8161, 3Institut Pasteur de Lille, F-59000 Lille, France
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Carlson BA, Gupta N, Pinkerton MH, Hatfield DL, Copeland PR. The utilization of selenocysteine-tRNA [Ser]Sec isoforms is regulated in part at the level of translation in vitro. ACTA ACUST UNITED AC 2017; 5:e1314240. [PMID: 28702279 DOI: 10.1080/21690731.2017.1314240] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 03/27/2017] [Accepted: 03/28/2017] [Indexed: 10/19/2022]
Abstract
The tRNA for the 21st proteinogenic amino acid, selenocysteine, exists in mammalian cells as 2 isoforms differing by a single 2'-O-methylribosyl moiety at position 34 (Um34). These isoforms contain either 5-methoxycarbonylmethyluridine (mcm5U) or 5-methoxycarbonylmethyl-2'-O-methyluridine (mcm5Um) at position 34. The accumulation of the mcm5Um isoform is tightly correlated with the expression of nonessential "stress response" selenoproteins such as glutathione peroxidase 1 (GPX1). The expression of essential selenoproteins, such as thioredoxin reductase 1 (TXNRD1), is not affected by changes in Sec-tRNA[Ser]Sec isoform accumulation. In this work we used purified mcm5U and mcm5Um Sec-tRNA[Ser]Sec isoforms to analyze possible differences in binding to the selenocysteine-specific elongation factor, EEFSEC, and the translation of GPX1 and TXNRD1in vitro. Our results indicate that no major distinction between mcm5U and mcm5Um isoforms is made by the translation machinery, but a small consistent increase in GPX1 translation is associated with the mcm5Um isoform. These results implicate fundamental differences in translation efficiency in playing a role in regulating selenoprotein expression as a function of isoform accumulation.
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Affiliation(s)
- Bradley A Carlson
- Molecular Biology of Selenium Section, Mouse Cancer Genetics Program, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Nirupama Gupta
- Department of Biochemistry and Molecular Biology, Rutgers - Robert Wood Johnson Medical School, Piscataway, NJ, USA
| | - Mark H Pinkerton
- Department of Biochemistry and Molecular Biology, Rutgers - Robert Wood Johnson Medical School, Piscataway, NJ, USA
| | - Dolph L Hatfield
- Molecular Biology of Selenium Section, Mouse Cancer Genetics Program, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Paul R Copeland
- Department of Biochemistry and Molecular Biology, Rutgers - Robert Wood Johnson Medical School, Piscataway, NJ, USA
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Gonzalez-Flores JN, Shetty SP, Dubey A, Copeland PR. The molecular biology of selenocysteine. Biomol Concepts 2015; 4:349-65. [PMID: 25436585 DOI: 10.1515/bmc-2013-0007] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 03/22/2013] [Indexed: 01/11/2023] Open
Abstract
Selenium is an essential trace element that is incorporated into 25 human proteins as the amino acid selenocysteine (Sec). The incorporation of this amino acid turns out to be a fascinating problem in molecular biology because Sec is encoded by a stop codon, UGA. Layered on top of the canonical translation elongation machinery is a set of factors that exist solely to incorporate this important amino acid. The mechanism by which this process occurs, put into the context of selenoprotein biology, is the focus of this review.
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Shetty SP, Copeland PR. Selenocysteine incorporation: A trump card in the game of mRNA decay. Biochimie 2015; 114:97-101. [PMID: 25622574 DOI: 10.1016/j.biochi.2015.01.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 01/14/2015] [Indexed: 11/16/2022]
Abstract
The incorporation of the 21st amino acid, selenocysteine (Sec), occurs on mRNAs that harbor in-frame stop codons because the Sec-tRNA(Sec) recognizes a UGA codon. This sets up an intriguing interplay between translation elongation, translation termination and the complex machinery that marks mRNAs that contain premature termination codons for degradation, leading to nonsense mediated mRNA decay (NMD). In this review we discuss the intricate and complex relationship between this key quality control mechanism and the process of Sec incorporation in mammals.
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Affiliation(s)
- Sumangala P Shetty
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, 675 Hoes Ln, Piscataway, NJ 08854, USA
| | - Paul R Copeland
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, 675 Hoes Ln, Piscataway, NJ 08854, USA.
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Seyedali A, Berry MJ. Nonsense-mediated decay factors are involved in the regulation of selenoprotein mRNA levels during selenium deficiency. RNA (NEW YORK, N.Y.) 2014; 20:1248-1256. [PMID: 24947499 PMCID: PMC4105750 DOI: 10.1261/rna.043463.113] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 05/08/2014] [Indexed: 06/03/2023]
Abstract
Selenoproteins contain the unique amino acid selenocysteine (Sec), which is encoded by the triplet UGA. Since UGA also serves as a stop codon, it has been postulated that selenoprotein mRNAs are targeted for degradation by the nonsense-mediated mRNA decay pathway (NMD). Several reports have observed a hierarchy of selenoprotein mRNA expression when selenium (Se) is limiting, whereby the abundance of certain transcripts decline while others do not. We sought to investigate the role of NMD in this hierarchical response that selenoprotein mRNAs exhibit to environmental Se status. Selenoprotein mRNAs were categorized as being predicted sensitive or resistant to NMD based on the requirements held by the current model. About half of the selenoprotein transcriptome was predicted to be sensitive to NMD and showed significant changes in mRNA abundance in response to cellular Se status. The other half that was predicted to be resistant to NMD did not respond to Se status. RNA immunoprecipitation with essential NMD factor UPF1 revealed that the mRNAs that were the most sensitive to Se status were also the most enriched on UPF1 during Se deficiency. Furthermore, depletion of SMG1, the kinase responsible for UPF1 phosphorylation and NMD activation, abrogated the decline in transcript abundance of Se-responsive transcripts. Lastly, mRNA decay rates of Se-responsive transcripts were altered upon the addition of Se to resemble the slower decay rates of nonresponsive transcripts. Taken together, these results present novel evidence in support of a crucial role for the NMD pathway in regulating selenoprotein mRNA levels when Se is limiting.
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Affiliation(s)
- Ali Seyedali
- Department of Cell and Molecular Biology, John A. Burn School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813, USA
| | - Marla J Berry
- Department of Cell and Molecular Biology, John A. Burn School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813, USA
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17
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Fang Y, Bateman JF, Mercer JF, Lamandé SR. Nonsense-mediated mRNA decay of collagen -emerging complexity in RNA surveillance mechanisms. J Cell Sci 2013; 126:2551-60. [PMID: 23729740 DOI: 10.1242/jcs.120220] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is an evolutionarily conserved mRNA surveillance system that degrades mRNA transcripts that harbour a premature translation-termination codon (PTC), thus reducing the synthesis of truncated proteins that would otherwise have deleterious effects. Although extensive research has identified a conserved repertoire of NMD factors, these studies have been performed with a restricted set of genes and gene constructs with relatively few exons. As a consequence, NMD mechanisms are poorly understood for genes with large 3' terminal exons, and the applicability of the current models to large multi-exon genes is not clear. In this Commentary, we present an overview of the current understanding of NMD and discuss how analysis of nonsense mutations in the collagen gene family has provided new mechanistic insights into this process. Although NMD of the collagen genes with numerous small exons is consistent with the widely accepted exon-junction complex (EJC)-dependent model, the degradation of Col10a1 transcripts with nonsense mutations cannot be explained by any of the current NMD models. Col10a1 NMD might represent a fail-safe mechanism for genes that have large 3' terminal exons. Defining the mechanistic complexity of NMD is important to allow us to understand the pathophysiology of the numerous genetic disorders caused by PTC mutations.
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Affiliation(s)
- Yiwen Fang
- Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville 3052, Australia
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18
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Yamashita A. Role of SMG-1-mediated Upf1 phosphorylation in mammalian nonsense-mediated mRNA decay. Genes Cells 2013; 18:161-75. [DOI: 10.1111/gtc.12033] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Accepted: 12/06/2012] [Indexed: 12/14/2022]
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Banerjee S, Yang S, Foster CB. A luciferase reporter assay to investigate the differential selenium-dependent stability of selenoprotein mRNAs. J Nutr Biochem 2011; 23:1294-301. [PMID: 22209284 DOI: 10.1016/j.jnutbio.2011.07.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 07/01/2011] [Accepted: 07/22/2011] [Indexed: 11/29/2022]
Abstract
The mechanisms regulating the differential selenium (Se)-dependent stability of selenoprotein mRNAs are partially characterized. To further study the Se-dependent regulation of selenoproteins, we developed a novel chemiluminescent reporter to monitor the steady-state mRNA level of an artificial selenoprotein. Our reporter is a fusion of the Renilla luciferase gene and of the β-globin gene, but contains features required for incorporation of selenocysteine (SEC), namely, a UGA-SEC codon and a 3' untranslated region RNA stem loop called a SEC incorporation sequence (SECIS). At various levels of Se, the activity of reporters containing GPX1 or GPX4 SECIS elements is proportional to the steady-state mRNA level of the reporter construct and reflects the level of the corresponding endogenous mRNA. In a reporter containing a UGA codon and a functional GPX1 SECIS, Se-dependent nonsense-mediated decay (NMD) occurred in the cytoplasm, as opposed to the more typical nuclear location. To validate the reporter system, we used genetic and pharmacologic approaches to inhibit or promote NMD. Modulation of UPF1 by siRNA, overexpression, or by inhibition of SMG1 altered NMD in this system. Our reporter is derived from a Renilla luciferase reporter gene fused to an intron containing B-globin gene and is subject to degradation by NMD when a stop codon is inserted before the second intron.
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Affiliation(s)
- Shuvojit Banerjee
- Department of Cancer Biology, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH 44195, USA
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20
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Wang SK, Weaver JD, Zhang S, Lei XG. Knockout of SOD1 promotes conversion of selenocysteine to dehydroalanine in murine hepatic GPX1 protein. Free Radic Biol Med 2011; 51:197-204. [PMID: 21420488 PMCID: PMC3109192 DOI: 10.1016/j.freeradbiomed.2011.03.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 02/22/2011] [Accepted: 03/11/2011] [Indexed: 12/23/2022]
Abstract
Se-dependent glutathione peroxidase-1 (GPX1) and Cu,Zn-superoxide dismutase (SOD1) are two major intracellular antioxidant enzymes. The purpose of this study was to elucidate the biochemical mechanisms for the 40% loss of hepatic GPX1 activity in SOD1(-/-) mice. Compared with the wild type (WT), the SOD1(-/-) mice showed no change in the total amount of GPX1 protein. However, their total enzyme protein exhibited 31 and 38% decreases (P<0.05) in the apparent k(cat) for hydrogen peroxide and tert-butylperoxide (at 2mM GSH), respectively. Most striking, mass spectrometry revealed two chemical forms of the 47th residue of GPX1: the projected native selenocysteine (Sec) and the Se-lacking dehydroalanine (DHA). The hepatic GPX1 protein of the SOD1(-/-) mice contained 38% less Sec and 77% more DHA than that of WT and showed aggravated dissociation of the tetramer structure. In conclusion, knockout of SOD1 elevated the conversion of Sec to DHA in the active site of hepatic GPX1, leading to proportional decreases in the apparent k(cat) and activity of the enzyme protein as a whole. Our data reveal a structural and kinetic mechanism for the in vivo functional dependence of GPX1 on SOD1 in mammals and provide a novel mass spectrometric method for the assay of oxidative modification of the GPX1 protein.
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Affiliation(s)
- Shi Kui Wang
- Department of Animal Science, Cornell University, Ithaca, NY 14853, USA
| | - Jeremy D. Weaver
- Department of Animal Science, Cornell University, Ithaca, NY 14853, USA
| | - Sheng Zhang
- Department of Proteomics and Mass Spectrometry Core Facility, Cornell University, Ithaca, NY 14853, USA
| | - Xin Gen Lei
- Department of Animal Science, Cornell University, Ithaca, NY 14853, USA
- Contact information of the corresponding author: Dr. X. G. Lei, Professor, Department of Animal Science, Cornell University, Ithaca, NY 14853, USA, Tel: (607)-254-4703, Fax: (607)-255-9829,
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Mistry HD, Kurlak LO, Williams PJ, Ramsay MM, Symonds ME, Broughton Pipkin F. Differential expression and distribution of placental glutathione peroxidases 1, 3 and 4 in normal and preeclamptic pregnancy. Placenta 2010; 31:401-8. [PMID: 20303587 DOI: 10.1016/j.placenta.2010.02.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 02/17/2010] [Accepted: 02/19/2010] [Indexed: 10/19/2022]
Abstract
UNLABELLED Preeclampsia is a pregnancy-specific condition affecting 2-7% of women and a leading cause of perinatal and maternal morbidity and mortality; it may also predispose the mother and fetus to increased risks of adult cardiovascular disease. The selenoprotein glutathione peroxidases (GPxs) have critical roles in regulating antioxidant status. OBJECTIVES, STUDY DESIGN AND MAIN OUTCOME MEASURES Immunohistochemical measurements of GPx1, GPx3 and GPx4 protein expression were performed on samples taken from three standardised sampling sites between the cord insertion and the periphery of the placenta from 12 normotensive, and 12 preeclamptic women to establish if their expression differed between sampling sites. Total GPx activities were also examined from the three sampling sites of these placentae. RESULTS There were highly significant reductions in overall immunohistochemical staining of all 3 GPxs in the preeclampsia compared to normotensive placentae (GPx1: P=0.016; GPx3: P=0.003; GPx4: P<0.001). Furthermore, graded differences in expression between the standardised placental sampling sites were also found for GPx3 (higher in the inner region, P=0.05) and GPx4 (higher in the periphery, P=0.02) but not GPx1. Placental GPx enzyme activity was also significantly reduced in tissue from preeclamptic women as compared to normotensive women (P=0.007; the difference was more pronounced nearest the cord insertion). CONCLUSIONS We have shown highly significant reductions in expression of all three major classes of GPx in placentae from women with preeclampsia, and distribution gradients in activity, which may relate to the differential oxygenation of regions of the placenta.
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Affiliation(s)
- H D Mistry
- Maternal and Fetal Research Unit, Division of Reproduction & Endocrinology, King's College London, London SE1 7EH, UK.
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22
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Schomburg L, Schweizer U. Hierarchical regulation of selenoprotein expression and sex-specific effects of selenium. Biochim Biophys Acta Gen Subj 2009; 1790:1453-62. [PMID: 19328222 DOI: 10.1016/j.bbagen.2009.03.015] [Citation(s) in RCA: 176] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 03/17/2009] [Accepted: 03/18/2009] [Indexed: 02/07/2023]
Abstract
The expression of selenoproteins is controlled on each one of the textbook steps of protein biosynthesis, i.e., during gene transcription, RNA processing, translation and posttranslational events as well as via control of the stability of the involved intermediates and final products. Selenoproteins are unique in their dependence on the trace element Se which they incorporate as the 21st proteinogenic amino acid, selenocysteine. Higher mammals have developed unique pathways to enable a fine-tuned expression of all their different selenoproteins according to developmental stage, actual needs, and current availability of the trace element. Tightly controlled and dynamic expression patterns of selenoproteins are present in different tissues. Interestingly, these patterns display some differences in male and female individuals, and can be grossly modified during disease, e.g. in cancer, inflammation or neurodegeneration. Likewise, important health issues related to the selenium status show unexpected sexual dimorphisms. Some detailed molecular insights have recently been gained on how the hierarchical Se distribution among the different tissues is achieved, how the selenoprotein biosynthesis machinery discriminates among the individual selenoprotein transcripts and how impaired selenoprotein biosynthesis machinery becomes phenotypically evident in humans. This review tries to summarize these fascinating findings and highlights some interesting and surprising sex-specific differences.
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Affiliation(s)
- Lutz Schomburg
- Institute for Experimental Endocrinology, Südring 10, CVK, Charité - Universitätsmedizin Berlin, 13353-Berlin, Germany.
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23
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Neu-Yilik G, Kulozik AE. NMD: multitasking between mRNA surveillance and modulation of gene expression. ADVANCES IN GENETICS 2008; 62:185-243. [PMID: 19010255 DOI: 10.1016/s0065-2660(08)00604-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Gene expression is a highly specific and regulated multilayer process with a plethora of interconnections as well as safeguard and feedback mechanisms. Messenger RNA, long neglected as a mere subcarrier of genetic information, is more recently recognized as a linchpin of regulation and control of gene expression. Moreover, the awareness of not only proteins but also mRNA as a modulator of genetic disorders has vastly increased in recent years. Nonsense-mediated mRNA decay (NMD) is a posttranscriptional surveillance mechanism that uses an intricate network of nuclear and cytoplasmic processes to eliminate mRNAs, containing premature termination codons. It thus helps limit the synthesis of potentially harmful truncated proteins. However, recent results suggest functions of NMD that go far beyond this role and affect the expression of wild-type genes and the modulation of whole pathways. In both respects--the elimination of faulty transcripts and the regulation of error-free mRNAs--NMD has many medical implications. Therefore, it has earned increasing interest from researchers of all fields of the life sciences. In the following text, we (1) present current knowledge about the NMD mechanism and its targets, (2) define its relevance in the regulation of important biochemical pathways, (3) explore its medical significance and the prospects of therapeutic interventions, and (4) discuss additional functions of NMD effectors, some of which may be networked to NMD. The main focus of this chapter lies on mammalian NMD and resorts to the features and factors of NMD in other organisms if these help to complete or illuminate the picture.
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Affiliation(s)
- Gabriele Neu-Yilik
- Department for Pediatric Oncology, Hematology and Immunology, University Hospital Heidelberg and Molecular Medicine Partnership Unit, University of Heidelberg and European Molecular Biology Laboratory, Im Neuenheimer Feld 156, 69120 Heidelberg, Germany
| | - Andreas E Kulozik
- Department for Pediatric Oncology, Hematology and Immunology, University Hospital Heidelberg and Molecular Medicine Partnership Unit, University of Heidelberg and European Molecular Biology Laboratory, Im Neuenheimer Feld 156, 69120 Heidelberg, Germany
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24
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Isken O, Maquat LE. Quality control of eukaryotic mRNA: safeguarding cells from abnormal mRNA function. Genes Dev 2007; 21:1833-56. [PMID: 17671086 DOI: 10.1101/gad.1566807] [Citation(s) in RCA: 433] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cells routinely make mistakes. Some mistakes are encoded by the genome and may manifest as inherited or acquired diseases. Other mistakes occur because metabolic processes can be intrinsically inefficient or inaccurate. Consequently, cells have developed mechanisms to minimize the damage that would result if mistakes went unchecked. Here, we provide an overview of three quality control mechanisms--nonsense-mediated mRNA decay, nonstop mRNA decay, and no-go mRNA decay. Each surveys mRNAs during translation and degrades those mRNAs that direct aberrant protein synthesis. Along with other types of quality control that occur during the complex processes of mRNA biogenesis, these mRNA surveillance mechanisms help to ensure the integrity of protein-encoding gene expression.
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Affiliation(s)
- Olaf Isken
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
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25
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Barbier J, Dutertre M, Bittencourt D, Sanchez G, Gratadou L, de la Grange P, Auboeuf D. Regulation of H-ras splice variant expression by cross talk between the p53 and nonsense-mediated mRNA decay pathways. Mol Cell Biol 2007; 27:7315-33. [PMID: 17709397 PMCID: PMC2168895 DOI: 10.1128/mcb.00272-07] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
When cells are exposed to a genotoxic stress, a DNA surveillance pathway that involves p53 is activated, allowing DNA repair. Eukaryotic cells have also evolved a mechanism called mRNA surveillance that controls the quality of mRNAs. Indeed, mutant mRNAs carrying premature translation termination codons (PTCs) are selectively degraded by the nonsense-mediated mRNA decay (NMD) pathway. However, in the case of particular genes, such as proto-oncogenes, mutations that do not create PTCs and therefore that do not induce mRNA degradation, can be harmful to cells. In this study, we showed that the H-ras gene in the absence of mutations produces an NMD-target splice variant that is degraded in the cytosol. We observed that a treatment with the genotoxic stress inducer camptothecin for 6 h favored the production of the H-ras NMD-target transcript degraded in the cytosol by the NMD process. Our data indicated that the NMD process allowed the elimination of transcripts produced in response to a short-term treatment with camptothecin from the major proto-oncogene H-ras, independently of PTCs induced by mutations. The camptothecin effects on H-ras gene expression were p53 dependent and involved in part modulation of the SC35 splicing factor. Interestingly, a long-term treatment with camptothecin as well as p53 overexpression for 24 h resulted in the accumulation of the H-ras NMD target in the cytosol, although the NMD process was not completely inhibited as other NMD targets are not stabilized. Finally, Upf1, a major NMD effector, was necessary for optimal p53 activation by camptothecin, which is consistent with recent data showing that NMD effectors are required for genome stability. In conclusion, we identified cross talk between the p53 and NMD pathways that regulates the expression levels of H-ras splice variants.
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Affiliation(s)
- Jérôme Barbier
- INSERM U685, Equipe AVENIR, Hopital Saint-Louis, 1 Avenue Claude Vellefaux, Paris 75010, France
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26
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Rebsch CM, Penna FJ, Copeland PR. Selenoprotein expression is regulated at multiple levels in prostate cells. Cell Res 2006; 16:940-8. [PMID: 17160069 DOI: 10.1038/sj.cr.7310117] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Selenium supplementation in a population with low basal blood selenium levels has been reported to decrease the incidence of several cancers including prostate cancer. Based on the clinical findings, it is likely that the antioxidant function of one or more selenoproteins is responsible for the chemopreventive effect, although low molecular weight seleno-compounds have also been posited to selectively induce apoptosis in transformed cells. To address the effects of selenium supplementation on selenoprotein expression in prostate cells, we have undertaken an analysis of antioxidant selenoprotein expression as well as selenium toxicity in non-tumorigenic prostate epithelial cells (RWPE-1) and prostate cancer cells (LNCaP and PC-3). Our results show that two of the glutathione peroxidase family members (GPX1 and GPX4) are highly induced by supplemental selenium in prostate cancer cells but only slightly induced in RWPE-1 cells. In addition, GPX1 levels are dramatically lower in PC-3 cells as compared to RWPE-1 or LNCaP cells. GPX2 protein and mRNA, however, are only detectable in RWPE-1 cells. Of the three selenium compounds tested (sodium selenite, sodium selenate and selenomethionine), only sodium selenite shows toxicity in a physiological range of selenium concentrations. Notably and in contrast to previous studies, RWPE-1 cells were significantly more sensitive to selenite than either of the prostate cancer cell lines. These results demonstrate that selenoproteins and selenium metabolism are regulated at multiple levels in prostate cells.
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Affiliation(s)
- Cheryl M Rebsch
- Department of Molecular Genetics, Microbiology and Immunology, UMDNJ--Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA
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27
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Baykal U, Moyne AL, Tuzun S. A frameshift in the coding region of a novel tomato class I basic chitinase gene makes it a pseudogene with a functional wound-responsive promoter. Gene 2006; 376:37-46. [PMID: 16716538 DOI: 10.1016/j.gene.2006.01.039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 01/10/2006] [Accepted: 01/27/2006] [Indexed: 11/28/2022]
Abstract
A putative class I basic chitinase gene, assigned as psiBCH, was cloned from a tomato breeding line NC 24E. The gene contains a coding region with two introns. The predicted psiBCH open reading frame (ORF) is 971 bp and exhibits 81-88% identity at the nucleotide level with known class I basic chitinase genes from the Solanaceae family. However, the presence of a stop codon caused by a frameshift in the ORF of psiBCH makes it unusual among the other class I plant basic chitinases. This stop codon might be involved in the lower accumulation of fully spliced psiBCH RNA caused by nonsense-mediated decay (NMD), which is an RNA surveillance system universally found in eukaryotes. Sequence analysis of the 1883-bp 5'-flanking region of the psiBCH gene revealed the presence of potential wound-response promoter elements. To study the transcriptional regulation of the psiBCH gene, its 5'-flanking region containing the putative promoter was fused to the gus reporter gene and introduced into the tobacco genome via Agrobacterium tumefaciens-mediated transformation. Transgenic plants were functionally assayed for beta-glucuronidase activity. The psiBCH promoter drives the reporter gene expression in response to wounding stimuli. psiBCH promoter-GUS analysis indicates that wound-response of the tobacco transgene was rapid and localized in the wounded area following mechanical wounding. Therefore, our results suggest that the psiBCH promoter can provide targeted expression of genes, such as protease inhibitors in response to pest attack.
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Affiliation(s)
- Ulku Baykal
- Department of Entomology and Plant Pathology, 209 Life Sciences Building, Auburn University, Auburn AL 36849, USA.
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28
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Atanasova S, von Ahsen N, Schlumbohm C, Wieland E, Oellerich M, Armstrong V. Marmoset glutathione peroxidases: cDNA sequences, molecular evolution, and gene expression. J Med Primatol 2006; 35:155-64. [PMID: 16764674 DOI: 10.1111/j.1600-0684.2006.00158.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Dysfunction of the cellular antioxidant system and accumulation of reactive oxygen species are involved in the pathophysiology of diseases such as cardiovascular disease, neurodegenerative disorders, tumors, male infertility and aging. Two gluthathione peroxidases play key roles in the cellular protection against oxidative damage. Glutathione peroxidase (GPx-1) removes cytosolic hydroperoxides while phospholipid-hydroperoxide glutathione peroxidase (GPx-4) is a unique enzyme that reduces phospholipid peroxides in membranes. METHODS We cloned and sequenced the full-length cDNA for GPx-1 (GenBank: AY966403) and GPx-4 (GenBank: AY966404) from the common marmoset (Callithrix jacchus) in order to create a suitable model for studying human diseases related with oxidative stress. RESULTS The cDNAs encode a 202 amino acid protein for GPx-1 and a 197 amino acid protein for GPx-4. Both proteins include selenocysteine (Sec, in Gpx-1 at position 48; in GPx-4 at position 73) and showed high homology (>90%) with other mammalian GPxs. The relative levels of mRNA expression for GPx-1 and GPx-4 were determined in different marmoset tissues by quantitative real-time reverse transcriptase-polymerase chain reaction using transcription elongation factor-2 as a reference gene. GPx-1 showed increased levels of expression in the liver, heart and kidney while the highest mRNA levels for GPx-4 were detected in the testis, followed by the liver, lung, kidney and spinal cord. CONCLUSIONS These findings will be of value for studies designed to assess the role of glutathione peroxidases in non-human primate models for a variety of diseases in which increased oxidative stress has been implicated.
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Affiliation(s)
- Srebrena Atanasova
- Department of Clinical Chemistry, Georg-August University, Goettingen, Germany
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29
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Thiele A, Nagamine Y, Hauschildt S, Clevers H. AU-rich elements and alternative splicing in the beta-catenin 3'UTR can influence the human beta-catenin mRNA stability. Exp Cell Res 2006; 312:2367-78. [PMID: 16696969 DOI: 10.1016/j.yexcr.2006.03.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Revised: 03/24/2006] [Accepted: 03/27/2006] [Indexed: 12/12/2022]
Abstract
Beta-catenin, the central player of the Wnt signaling cascade, is a well-known oncogene. The regulation of beta-catenin protein stability has been studied extensively while other mechanisms that control cellular levels of beta-catenin have hardly been addressed. In this study, we show that there are three beta-catenin mRNA splice variants that differ solely in their 3'-untranslated region (3'UTR) due to alternative splicing or retaining of an intron. The three isoforms were found to be ubiquitously expressed though in different quantities. Upon induction of the beta-catenin protein in peripheral blood mononuclear leukocytes (PBMC), the beta-catenin mRNA is induced in an isoform-specific manner. All three variants occur in the cytoplasm and contribute to the synthesis of beta-catenin acting as a transcriptional coactivator but have different cytoplasmic stabilities in Hela cells. AU-rich elements (AREs), sequence elements implicated in the regulation of mRNA stability, are found in each of the three transcripts. Surprisingly, the AREs contribute to stabilization of the beta-catenin mRNA transcripts in a splicing-dependent manner. The isoform most affected is the one found to be most induced when beta-catenin protein accumulates. These results suggest that alternative splicing and AREs can act together in regulating beta-catenin mRNA stability and thereby provide a step of controlling the cellular beta-catenin concentration.
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Affiliation(s)
- Andrea Thiele
- Hubrecht Laboratory, The Netherlands Institute of Developmental Biology, Uppsalalaan 8, NL-3584 CT Utrecht, The Netherlands.
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30
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Abstract
Analysis of the selenoproteome identified five glutathione peroxidases (GPxs) in mammals: cytosolic GPx (cGPx, GPx1), phospholipid hydroperoxide GPx (PHGPX, GPx4), plasma GPx (pGPX, GPx3), gastrointestinal GPx (GI-GPx, GPx2) and, in humans, GPx6, which is restricted to the olfactory system. GPxs reduce hydroperoxides to the corresponding alcohols by means of glutathione (GSH). They have long been considered to only act as antioxidant enzymes. Increasing evidence, however, suggests that nature has not created redundant GPxs just to detoxify hydroperoxides. cGPx clearly acts as an antioxidant, as convincingly demonstrated in GPx1-knockout mice. PHGPx specifically interferes with NF-kappaB activation by interleukin-1, reduces leukotriene and prostanoid biosynthesis, prevents COX-2 expression, and is indispensable for sperm maturation and embryogenesis. GI-GPx, which is not exclusively expressed in the gastrointestinal system, is upregulated in colon and skin cancers and in certain cultured cancer cells. GI-GPx is a target for Nrf2, and thus is part of the adaptive response by itself, while PHGPx might prevent cancer by interfering with inflammatory pathways. In conclusion, cGPx, PHGPx and GI-GPx have distinct roles, particularly in cellular defence mechanisms. Redox sensing and redox regulation of metabolic events have become attractive paradigms to unravel the specific and in part still enigmatic roles of GPxs.
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Affiliation(s)
- Regina Brigelius-Flohé
- German Institute of Human Nutrition, Potsdam-Rehbrücke, Arthur-Scheunert-Allee 114-116, D-14558 Nuthetal, Germany.
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31
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Weil JE, Beemon KL. A 3' UTR sequence stabilizes termination codons in the unspliced RNA of Rous sarcoma virus. RNA (NEW YORK, N.Y.) 2006; 12:102-10. [PMID: 16301601 PMCID: PMC1370890 DOI: 10.1261/rna.2129806] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Eukaryotic cells target mRNAs to the nonsense-mediated mRNA decay (NMD) pathway when translation terminates within the coding region. In mammalian cells, this is presumably due to a downstream signal deposited during pre-mRNA splicing. In contrast, unspliced retroviral RNA undergoes NMD in chicken cells when premature termination codons (PTCs) are present in the gag gene. Surprisingly, deletion of a 401-nt 3' UTR sequence immediately downstream of the normal gag termination codon caused this termination event to be recognized as premature. We termed this 3' UTR region the Rous sarcoma virus (RSV) stability element (RSE). The RSE also stabilized the viral RNA when placed immediately downstream of a PTC in the gag gene. Deletion analysis of the RSE indicated a smaller functional element. We conclude that this 3' UTR sequence stabilizes termination codons in the RSV RNA, and termination codons not associated with such an RSE sequence undergo NMD.
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Affiliation(s)
- Jason E Weil
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
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32
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Hatfield DL, Carlson BA, Xu XM, Mix H, Gladyshev VN. Selenocysteine Incorporation Machinery and the Role of Selenoproteins in Development and Health. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2006; 81:97-142. [PMID: 16891170 DOI: 10.1016/s0079-6603(06)81003-2] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Dolph L Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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33
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Handy DE, Hang G, Scolaro J, Metes N, Razaq N, Yang Y, Loscalzo J. Aminoglycosides decrease glutathione peroxidase-1 activity by interfering with selenocysteine incorporation. J Biol Chem 2005; 281:3382-8. [PMID: 16354666 PMCID: PMC1472404 DOI: 10.1074/jbc.m511295200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellular glutathione peroxidase is a key intracellular antioxidant enzyme that contains a selenocysteine residue at its active site. Selenium, a selenocysteine incorporation sequence in the 3'-untranslated region of the glutathione peroxidase mRNA, and other translational cofactors are necessary for "read-through" of a UGA stop codon that specifies selenocysteine incorporation. Aminoglycoside antibiotics facilitate read-through of premature stop codons in prokayotes and eukaryotes. We studied the effects of G418, an aminoglycoside, on cellular glutathione peroxidase expression and function in mammalian cells. Insertion of a selenocysteine incorporation element along with a UGA codon into a reporter construct allows for read-through only in the presence of selenium. G418 increased read-through in selenium-replete cells as well as in the absence of selenium. G418 treatment increased immunodetectable endogenous or recombinant glutathione peroxidase but reduced the specific activity of the enzyme. Tandem mass spectrometry experiments indicated that G418 caused a substitution of l-arginine for selenocysteine. These data show that G418 can affect the biosynthesis of this key antioxidant enzyme by promoting substitution at the UGA codon.
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Affiliation(s)
- Diane E Handy
- Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
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34
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Unique features of selenocysteine incorporation function within the context of general eukaryotic translational processes. Biochem Soc Trans 2005; 33:1493-7. [PMID: 16246153 DOI: 10.1042/bst0331493] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Unlike other essential dietary trace elements, selenium exerts its biological actions through its direct incorporation into selenoproteins, as a part of the 21st amino acid, selenocysteine. Fundamental studies have elucidated the unique structures and putative functions of multiple co-translational factors required for the incorporation of selenocysteine into selenoproteins. The current challenge is to understand how these selenocysteine incorporation factors function within the framework of translation. In eukaryotes, co-ordinating nuclear transcription with cytoplasmic translation of genes is a challenge involving complex spatial and temporal regulation. Selenoproteins utilize the common cellular machinery required for synthesis of non-selenoproteins. This machinery includes the elements involved in transcription, mRNA splicing and transport, and translational processes. Many investigators have emphasized the differences between the expression of selenoproteins and other eukaryotic proteins, whereas this review will attempt to highlight common themes and point out where additional interactions may be discovered.
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35
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Streckfuss F, Hamann I, Schomburg L, Michaelis M, Sapin R, Klein MO, Köhrle J, Schweizer U. Hepatic deiodinase activity is dispensable for the maintenance of normal circulating thyroid hormone levels in mice. Biochem Biophys Res Commun 2005; 337:739-45. [PMID: 16202981 DOI: 10.1016/j.bbrc.2005.09.102] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Accepted: 09/15/2005] [Indexed: 10/25/2022]
Abstract
Thyroid hormone (TH) homeostasis depends on peripheral activation and inactivation of iodothyronines by selenoenzymes of the deiodinase (Dio) family. We genetically inactivated hepatic selenoenzyme expression, including Dio1, in order to determine the contribution of hepatic Dio to circulating TH levels. Serum levels of TSH, total T(4), and total T(3) were not different from controls. We measured Dio1 and Dio2 in kidney, skeletal muscle, heart, brown adipose tissue, and brain, but did not find compensatory up-regulation in these tissues. Finally, we determined expression in the liver of the following T(3) target genes: Spot14, alpha-glycerophosphate dehydrogenase (alphaGPD), and malic enzyme (ME). On the transcript level, both Spot14 and alphaGPD were reduced in Dio-deficient liver to about 60-70% of controls. However, mRNA and activity of ME were significantly increased in the same mice. Together, our results indicate that hepatic Dio1 activity is not absolutely required to sustain the euthyroid state in mice.
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Affiliation(s)
- Florian Streckfuss
- Neurobiology of Selenium, Neuroscience Research Center, Charité Universitätsmedizin, Berlin, Germany
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36
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Wang J, Xu G, Li H, Gonzales V, Fromholt D, Karch C, Copeland NG, Jenkins NA, Borchelt DR. Somatodendritic accumulation of misfolded SOD1-L126Z in motor neurons mediates degeneration: alphaB-crystallin modulates aggregation. Hum Mol Genet 2005; 14:2335-47. [PMID: 16000321 DOI: 10.1093/hmg/ddi236] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mice expressing variants of superoxide dismutase-1 (SOD1) encoding C-terminal truncation mutations linked to familial amyotrophic lateral sclerosis (FALS) have begun to define the role of misfolding and aggregation in the pathogenesis of disease. Here, we examine transgenic mice expressing SOD1-L126Z (Z = stop-truncation of last 28 amino acids), finding that detergent-insoluble mutant protein specifically accumulates in somatodendritic compartments. Soluble forms of the SOD1-L126Z were virtually undetectable in spinal cord at any age and the levels of accumulated protein directly correlated with disease symptoms. Neither soluble nor insoluble forms of SOD1-L126Z were transported to distal axons. In vitro, small heat shock protein (Hsp) alphaB-crystallin suppressed the in vitro aggregation of SOD1-L126Z. In vivo, alphaB-crystallin immunoreactivity was most abundant in oligodendrocytes and up-regulated in astrocytes of symptomatic mice; neither of these cell-types accumulated mutant SOD1 immunoreactivity. These results suggest that damage to motor neuron cell bodies and dendrites within the spinal cord can be sufficient to induce motor neuron disease and that the activities of chaperones may modulate the cellular specificity of mutant SOD1 accumulation.
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Affiliation(s)
- Jiou Wang
- Departement of Pathology, The John's Hopkins University School of Medicine, Baltimore, MD 21205, USA
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37
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Jankowsky JL, Slunt HH, Gonzales V, Jenkins NA, Copeland NG, Borchelt DR. APP processing and amyloid deposition in mice haplo-insufficient for presenilin 1. Neurobiol Aging 2004; 25:885-92. [PMID: 15212842 DOI: 10.1016/j.neurobiolaging.2003.09.008] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2003] [Revised: 07/29/2003] [Accepted: 09/24/2003] [Indexed: 11/25/2022]
Abstract
More than 70 different mutations in presenilin 1 (PS1) have been associated with inherited early onset Alzheimer's disease (AD). How all these different mutations cause disease has not been clearly delineated. Our laboratory has previously shown that co-expression of mutant PS1 in mice transgenic for amyloid precursor protein (APPswe) dramatically accelerates the rate of amyloid deposition in the brain. In our original animals mutant PS1 was substantially over-expressed, and the stabilized pool of mouse PS1 fragments was largely replaced by the human protein. In this setting the accelerated amyloid pathology in the double transgenic mice could have been due, in part, to decreased endogenous PS1 activity. To investigate this possibility, we generated APP transgenic mice with reduced levels of endogenous PS1. We find that mice harboring only one functional PS1 allele and co-expressing Mo/HuAPPswe do not develop amyloid deposits at ages comparable to mice expressing mutant PS1. We next tested whether hypo-expression of mutant PS1 could accelerate the rate of amyloid deposition using an unusual line of transgenic mice expressing PS1dE9 at low levels, finding no significant acceleration. Our findings demonstrate that the accelerated amyloid pathology, caused by so many different mutations in PS1, is clearly not a result of haplo-insufficiency that might result from inactivating mutations. Instead, our data are consistent with a gain of property mechanism.
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Affiliation(s)
- Joanna L Jankowsky
- Department of Pathology, The Johns Hopkins University School of Medicine, 558 Ross Research Building, 720 Rutland Ave., Baltimore, MD 21205, USA
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38
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Schweizer U, Bräuer AU, Köhrle J, Nitsch R, Savaskan NE. Selenium and brain function: a poorly recognized liaison. ACTA ACUST UNITED AC 2004; 45:164-78. [PMID: 15210302 DOI: 10.1016/j.brainresrev.2004.03.004] [Citation(s) in RCA: 244] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/09/2004] [Indexed: 01/08/2023]
Abstract
Molecular biology has recently contributed significantly to the recognition of selenium (Se)2 and Se-dependent enzymes as modulators of brain function. Increased oxidative stress has been proposed as a pathomechanism in neurodegenerative diseases including, among others, Parkinson's disease, stroke, and epilepsy. Glutathione peroxidases (GPx), thioredoxin reductases, and one methionine-sulfoxide-reductase are selenium-dependent enzymes involved in antioxidant defense and intracellular redox regulation and modulation. Selenium depletion in animals is associated with decreased activities of Se-dependent enzymes and leads to enhanced cell loss in models of neurodegenerative disease. Genetic inactivation of cellular GPx increases the sensitivity towards neurotoxins and brain ischemia. Conversely, increased GPx activity as a result of increased Se supply or overexpression ameliorates the outcome in the same models of disease. Genetic inactivation of selenoprotein P leads to a marked reduction of brain Se content, which has not been achieved by dietary Se depletion, and to a movement disorder and spontaneous seizures. Here we review the role of Se for the brain under physiological as well as pathophysiological conditions and highlight recent findings which open new vistas on an old essential trace element.
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Affiliation(s)
- Ulrich Schweizer
- Neurobiology of Selenium, Neuroscience Research Center, Charité, University Medical School, Berlin, Germany
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39
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Gadjieva R, Axelsson E, Olsson U, Vallon-Christersson J, Hansson M. Nonsense-mediated mRNA decay in barley mutants allows the cloning of mutated genes by a microarray approach. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2004; 42:681-685. [PMID: 15331098 DOI: 10.1016/j.plaphy.2004.06.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2004] [Accepted: 06/15/2004] [Indexed: 05/24/2023]
Abstract
We have previously described a microarray approach to identify and clone genes from mutants of higher organisms. In the method cDNA of two mutants with similar phenotype are competitively hybridized to DNA clones arrayed on a glass slide. Clones corresponding to an mRNA that is not expressed in one of the strains due to a mutation will be specifically highlighted in the hybridization, which provides a possibility to identify and eventually clone the mutated gene. The approach is dependent on mutations that affect the amount of mRNA. Nonsense mutations, which prematurely terminate translation, can be such mutations as a surveillance system known as nonsense-mediated decay (NMD) has been developed by organisms to reduce the abundance of mRNA with nonsense codons. In the present study, we have analysed the barley (Hordeum vulgare L.) magnesium chelatase mutants xantha-f26, xantha-f27 and xantha-f40 in order to investigate the presence of NMD in barley, as well as the importance of the position of the stop codon for NMD. Both nonsense-mutants xantha-f27 and xantha-f40, but not the missense mutant xantha-f26, showed NMD. This was not expected for xantha-f27 as its mutation is in the last exon of the gene. We conclude the NMD expands the number of mutants that can be used for gene cloning by our described microarray approach.
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Affiliation(s)
- Rena Gadjieva
- Department of Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
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40
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Bühler M, Paillusson A, Mühlemann O. Efficient downregulation of immunoglobulin mu mRNA with premature translation-termination codons requires the 5'-half of the VDJ exon. Nucleic Acids Res 2004; 32:3304-15. [PMID: 15210863 PMCID: PMC443527 DOI: 10.1093/nar/gkh651] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Premature translation-termination codons (PTCs) elicit rapid degradation of the mRNA by a process called nonsense-mediated mRNA decay (NMD). NMD appears to be significantly more efficient for mRNAs of genes belonging to the immunoglobulin superfamily, which frequently acquire PTCs during VDJ rearrangment, than for mRNAs of other genes. To identify determinants for efficient NMD, we developed a minigene system derived from a mouse immunoglobulin micro gene (Ig-micro) and measured the effect of PTCs at different positions on the mRNA level. This revealed that PTCs located downstream of the V-D junction in the VDJ exon of Ig-micro minigenes and of endogenous Ig-micro genes elicit very strong mRNA downregulation, whereas NMD efficiency decreases gradually further upstream in the V segment where a PTC was inserted. Interestingly, two PTCs are in positions where they usually do not trigger NMD (<50 nt from the 3'-most 5' splice site) still resulted in reduced mRNA levels. Using a set of hybrid constructs comprised of Ig-micro and an inefficient substrate for NMD, we identified a 177 nt long element in the V segment that is necessary for efficient downregulation of PTC-containing hybrid transcripts. Moreover, deletion of this NMD-promoting element from the Ig-micro minigene results in loss of strong NMD.
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Affiliation(s)
- Marc Bühler
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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41
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Olsson U, Sirijovski N, Hansson M. Characterization of eight barley xantha-f mutants deficient in magnesium chelatase. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2004; 42:557-564. [PMID: 15246070 DOI: 10.1016/j.plaphy.2004.05.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Accepted: 05/17/2004] [Indexed: 05/24/2023]
Abstract
Magnesium chelatase (EC 6.6.1.1) catalyses the insertion of magnesium into protoporphyrin IX, the first unique step of the chlorophyll biosynthetic pathway. The enzyme is composed of three different subunits of approximately 40, 70 and 140 kDa. In barley (Hordeum vulgare L.) the subunits are encoded by the genes Xantha-h, Xantha-g and Xantha-f. In the 1950s, eight induced xantha-f mutants were isolated. In this work we characterized these mutations at the DNA level and provided explanations for their phenotypes. The xantha-f10 mutation is a 3 bp deletion, resulting in a polypeptide lacking the glutamate residue at position 424. The leaky mutation xantha-f26 has a missense mutation leading to a M632R exchange. The xantha-f27 and -f40 are deletions of 14 and 2 bp, respectively, resulting in truncated polypeptides of 1104 and 899 amino acid residues, respectively. Mutation xantha-f41 is an in-frame deletion that removes A439, L440, Q441 and V442 from the resulting protein. Mutation xantha-f58 is most likely a deletion of the whole Xantha-f gene, as no DNA fragments could be detected by PCR or southern blot experiments. The slightly leaky xantha-f60 and non-leaky -f68 mutations each have a missense mutation causing a P393L and G794E exchange in the polypeptide, respectively.
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Affiliation(s)
- Ulf Olsson
- Department of Biochemistry, Lund University, Box 124, 22100 Lund, Sweden
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42
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Abstract
Studies of nonsense-mediated mRNA decay in mammalian cells have proffered unforeseen insights into changes in mRNA-protein interactions throughout the lifetime of an mRNA. Remarkably, mRNA acquires a complex of proteins at each exon-exon junction during pre-mRNA splicing that influences the subsequent steps of mRNA translation and nonsense-mediated mRNA decay. Complex-loaded mRNA is thought to undergo a pioneer round of translation when still bound by cap-binding proteins CBP80 and CBP20 and poly(A)-binding protein 2. The acquisition and loss of mRNA-associated proteins accompanies the transition from the pioneer round to subsequent rounds of translation, and from translational competence to substrate for nonsense-mediated mRNA decay.
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Affiliation(s)
- Lynne E Maquat
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, 601 Elmwood Avenue, Box 712, University of Rochester, Rochester, New York 14642, USA.
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Ladd AN, Nguyen NH, Malhotra K, Cooper TA. CELF6, a Member of the CELF Family of RNA-binding Proteins, Regulates Muscle-specific Splicing Enhancer-dependent Alternative Splicing. J Biol Chem 2004; 279:17756-64. [PMID: 14761971 DOI: 10.1074/jbc.m310687200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously described a family of five RNA-binding proteins: CUG-binding protein, embryonic lethal abnormal vision-type RNA-binding protein 3, and the CUG-binding protein and embryonic lethal abnormal vision-type RNA-binding protein 3-like factors (CELFs) 3, 4, and 5. We demonstrated that all five of these proteins specifically activate exon inclusion of cardiac troponin T minigenes in vivo via muscle-specific splicing enhancer (MSE) sequences. We also predicted that a sixth family member, CELF6, was located on chromosome 15. Here, we describe the isolation and characterization of CELF6. Like the previously described CELF proteins, CELF6 shares a domain structure containing three RNA-binding domains and a divergent domain of unknown function. CELF6 is strongly expressed in kidney, brain, and testis and is expressed at very low levels in most other tissues. In the brain, expression is widespread and maintained from the fetus to the adult. CELF6 activates exon inclusion of a cardiac troponin T minigene in transient transfection assays in an MSE-dependent manner and can activate inclusion via multiple copies of a single element, MSE2. These results place CELF6 in a functional subfamily of CELF proteins that includes CELFs 3, 4, and 5. CELF6 also promotes skipping of exon 11 of insulin receptor, a known target of CELF activity that is expressed in kidney.
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Affiliation(s)
- Andrea N Ladd
- Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA
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44
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Abstract
Selenium is an essential trace element that is incorporated into proteins as selenocysteine (Sec), the twenty-first amino acid. Sec is encoded by a UGA codon in the selenoprotein mRNA. The decoding of UGA as Sec requires the reprogramming of translation because UGA is normally read as a stop codon. The translation of selenoprotein mRNAs requires cis-acting sequences in the mRNA and novel trans-acting factors dedicated to Sec incorporation. Selenoprotein synthesis in vivo is highly selenium-dependent, and there is a hierarchy of selenoprotein expression in mammals when selenium is limiting. This review describes emerging themes from studies on the mechanism, kinetics, and efficiency of Sec insertion in prokaryotes. Recent developments that provide mechanistic insight into how the eukaryotic ribosome distinguishes between UGA/Sec and UGA/stop codons are discussed. The efficiency and regulation of mammalian selenoprotein synthesis are considered in the context of current models for Sec insertion.
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Affiliation(s)
- Donna M Driscoll
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
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45
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Noé V, MacKenzie S, Ciudad CJ. An intron is required for dihydrofolate reductase protein stability. J Biol Chem 2003; 278:38292-300. [PMID: 12865433 DOI: 10.1074/jbc.m212746200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We compared the expression of dihydrofolate reductase minigenes with and without an intron. The levels of protein were significantly higher in the presence of dihydrofolate reductase intron 1. However, mRNA levels in both constructs were comparable. In addition, the RNA transcribed from either construct was correctly polyadenylated and exported to the cytoplasm. The intron-mediated increase in dihydrofolate reductase protein levels was position-independent and was also observed when dihydrofolate reductase intron 1 was replaced by heterologous introns. The translational rate of dihydrofolate reductase protein was increased in transfectants from the intron-containing minigene. In addition, the protein encoded by the intronless construct was unstable and subject to lysosomal degradation, thus showing a shorter half-life than the protein encoded by the intron-containing minigene. We conclude that an intron is required for the translation and stability of dihydrofolate reductase protein.
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Affiliation(s)
- Véronique Noé
- Department of Biochemistry and Molecular Biology, School of Pharmacy, University of Barcelona E-08028, Spain.
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46
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Abstract
The regulation of gene expression at the translational level not only allows for rapid changes in specific protein levels but also provides an opportunity to alter codon specificity. For the incorporation of selenocysteine (Sec) into protein, the UGA codon is transformed from one that signals translation termination to one specific for Sec. This review provides a look at Sec incorporation from the perspective of the individual steps involved in protein synthesis: initiation, elongation and termination. The roles of the factors known to be required for Sec incorporation are considered in the context of each step in translation including structural modeling of the differences between the standard elongation factor eEF1A and the Sec-specific counterpart, eEFSec.
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Affiliation(s)
- Paul R Copeland
- Department of Molecular Genetics, Microbiology and Immunology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 675 Hoes Ln Rm 728, Piscataway, NJ 08854, USA.
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47
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Maquat LE, Serin G. Nonsense-mediated mRNA decay: insights into mechanism from the cellular abundance of human Upf1, Upf2, Upf3, and Upf3X proteins. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 66:313-20. [PMID: 12762033 DOI: 10.1101/sqb.2001.66.313] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- L E Maquat
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
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48
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Abstract
Messenger RNAs with premature translation termination codons (PTCs) are degraded by nonsense-mediated mRNA decay (NMD). In mammals, PTCs are discriminated from physiological stop codons by a process thought to involve the splicing-dependent deposition of an exon junction complex (EJC), EJC-mediated recruitment of Upf3, and Upf2 binding to the N terminus of Upf3. Here, we identify a conserved domain of hUpf3b that mediates an interaction with the EJC protein Y14. Tethered function analysis shows that the Y14/hUpf3b interaction is essential for NMD, while surprisingly the interaction between hUpf3b and hUpf2 is not. Nonetheless, hUpf2 is necessary for NMD mediated by tethered Y14. RNAi-induced knockdown and Y14 repletion of siRNA-treated cells implicates Y14 in the degradation of beta-globin NS39 mRNA and demonstrates that Y14 is required for NMD induced by tethered hUpf3b. These results uncover a direct role of Y14 in NMD and suggest an unexpected hierarchy in the assembly of NMD complexes.
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Affiliation(s)
- Niels H Gehring
- Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Germany
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Maderazo AB, Belk JP, He F, Jacobson A. Nonsense-containing mRNAs that accumulate in the absence of a functional nonsense-mediated mRNA decay pathway are destabilized rapidly upon its restitution. Mol Cell Biol 2003; 23:842-51. [PMID: 12529390 PMCID: PMC140708 DOI: 10.1128/mcb.23.3.842-851.2003] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is a conserved proofreading mechanism that protects eukaryotic cells from the potentially deleterious effects of truncated proteins. Studies of Saccharomyces cerevisiae imply that NMD is a predominantly cytoplasmic decay pathway, while studies of mammalian systems suggest that decay of most substrate mRNAs may occur while they are still associated with the nucleus, possibly during a round of translation that occurs during their export to the cytoplasm. Complete entry of the latter mRNAs into the cytoplasm appears to render them immune to further NMD; i.e., they escape further susceptibility to this decay pathway. To determine if yeast cytoplasmic nonsense-containing mRNAs that evade decay are subsequently immune to NMD, we examined the consequences of placing each of the three UPF/NMD genes under the control of a galactose-inducible promoter. The decay kinetics of ADE2 and PGK1 nonsense-containing mRNAs were then analyzed when expression of UPF1, NMD2, or UPF3 was either repressed or subsequently induced. Results from these experiments demonstrated that activation of NMD caused rapid and immediate degradation of both substrate transcripts, with half-lives of both stable mRNA populations shortened to approximately 7 min. These findings make it unlikely that yeast nonsense-containing mRNAs can escape degradation by NMD and indicate that such mRNAs are available to this decay pathway at each round of translation.
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Affiliation(s)
- Alan B Maderazo
- Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655-0122, USA
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Chiu SY, Serin G, Ohara O, Maquat LE. Characterization of human Smg5/7a: a protein with similarities to Caenorhabditis elegans SMG5 and SMG7 that functions in the dephosphorylation of Upf1. RNA (NEW YORK, N.Y.) 2003; 9:77-87. [PMID: 12554878 PMCID: PMC1370372 DOI: 10.1261/rna.2137903] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2002] [Accepted: 10/08/2002] [Indexed: 05/20/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) in mammalian cells depends on phosphorylation of Upf1, an RNA-dependent ATPase and 5'-to-3' helicase. Upf1 phosphorylation is mediated by Smg1, a phosphoinositol 3-kinase-related protein kinase. Here, we describe a human protein, which we call hSmg5/7a, that manifests similarity to Caenorhabditis elegans NMD factors CeSMG5 and CeSMG7, as well as two Drosophila melanogaster proteins that are also similar to the C. elegans NMD factors. Results indicate that hSmg5/7a functions in the dephosphorylation of Upf1. Furthermore, hSmg5/7a copurifies with Upf1, Upf2, Upf3X, Smg1, and the catalytic subunit of protein phosphatase 2A. We also demonstrate that Upf2, another factor involved in NMD, is a phosphoprotein. However, hSmg5/7a plays no role in the dephosphorylation of Upf2. These data indicate that hSmg5/7a targets protein phosphatase 2A to Upf1 but not Upf2. Results of Western blotting reveal that hSmg5/7a is mostly cytoplasmic in HEK293T cells.
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Affiliation(s)
- Shang-Yi Chiu
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, New York 14642, USA
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