1
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Bang J, Kang D, Jung J, Yoo TJ, Shim MS, Gladyshev VN, Tsuji PA, Hatfield DL, Kim JH, Lee BJ. SEPHS1: Its evolution, function and roles in development and diseases. Arch Biochem Biophys 2022; 730:109426. [PMID: 36202216 PMCID: PMC9648052 DOI: 10.1016/j.abb.2022.109426] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/27/2022] [Accepted: 09/29/2022] [Indexed: 11/25/2022]
Abstract
Selenophosphate synthetase (SEPHS) was originally discovered in prokaryotes as an enzyme that catalyzes selenophosphate synthesis using inorganic selenium and ATP as substrates. However, in contrast to prokaryotes, two paralogs, SEPHS1 and SEPHS2, occur in many eukaryotes. Prokaryotic SEPHS, also known as SelD, contains either cysteine (Cys) or selenocysteine (Sec) in the catalytic domain. In eukaryotes, only SEPHS2 carries out selenophosphate synthesis and contains Sec at the active site. However, SEPHS1 contains amino acids other than Sec or Cys at the catalytic position. Phylogenetic analysis of SEPHSs reveals that the ancestral SEPHS contains both selenophosphate synthesis and another unknown activity, and that SEPHS1 lost the selenophosphate synthesis activity. The three-dimensional structure of SEPHS1 suggests that its homodimer is unable to form selenophosphate, but retains ATPase activity to produce ADP and inorganic phosphate. The most prominent function of SEPHS1 is that it is implicated in the regulation of cellular redox homeostasis. Deficiency of SEPHS1 leads to the disturbance in the expression of genes involved in redox homeostasis. Different types of reactive oxygen species (ROS) are accumulated in response to SEPHS deficiency depending on cell or tissue types. The accumulation of ROS causes pleiotropic effects such as growth retardation, apoptosis, DNA damage, and embryonic lethality. SEPHS1 deficiency in mouse embryos affects retinoic signaling and other related signaling pathways depending on the embryonal stage until the embryo dies at E11.5. Dysregulated SEPHS1 is associated with the pathogenesis of various diseases including cancer, Crohn's disease, and osteoarthritis.
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Affiliation(s)
- Jeyoung Bang
- Interdisciplinary Program in Bioinformatics, College of Natural Sciences, Seoul National University, Seoul, South Korea
| | - Donghyun Kang
- School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea
| | - Jisu Jung
- School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea
| | - Tack-Jin Yoo
- School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea
| | - Myoung Sup Shim
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, NC, USA
| | - Vadim N Gladyshev
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Petra A Tsuji
- Department of Biological Sciences, Towson University, 8000 York Rd., Towson, MD, USA
| | - Dolph L Hatfield
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jin-Hong Kim
- School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea.
| | - Byeong Jae Lee
- Interdisciplinary Program in Bioinformatics, College of Natural Sciences, Seoul National University, Seoul, South Korea; School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea.
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2
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Zhang L, Liu J, Dai Z, Wang J, Wu M, Su R, Zhang D. Crosstalk between regulated necrosis and micronutrition, bridged by reactive oxygen species. Front Nutr 2022; 9:1003340. [PMID: 36211509 PMCID: PMC9543034 DOI: 10.3389/fnut.2022.1003340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 08/26/2022] [Indexed: 11/15/2022] Open
Abstract
The discovery of regulated necrosis revitalizes the understanding of necrosis from a passive and accidental cell death to a highly coordinated and genetically regulated cell death routine. Since the emergence of RIPK1 (receptor-interacting protein kinase 1)-RIPK3-MLKL (mixed lineage kinase domain-like) axis-mediated necroptosis, various other forms of regulated necrosis, including ferroptosis and pyroptosis, have been described, which enrich the understanding of pathophysiological nature of diseases and provide novel therapeutics. Micronutrients, vitamins, and minerals, position centrally in metabolism, which are required to maintain cellular homeostasis and functions. A steady supply of micronutrients benefits health, whereas either deficiency or excessive amounts of micronutrients are considered harmful and clinically associated with certain diseases, such as cardiovascular disease and neurodegenerative disease. Recent advance reveals that micronutrients are actively involved in the signaling pathways of regulated necrosis. For example, iron-mediated oxidative stress leads to lipid peroxidation, which triggers ferroptotic cell death in cancer cells. In this review, we illustrate the crosstalk between micronutrients and regulated necrosis, and unravel the important roles of micronutrients in the process of regulated necrosis. Meanwhile, we analyze the perspective mechanism of each micronutrient in regulated necrosis, with a particular focus on reactive oxygen species (ROS).
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Affiliation(s)
- Lei Zhang
- College of Veterinary Medicine, Jilin Agricultural University, Changchun, China
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
- Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Agricultural University, Changchun, China
| | - Jinting Liu
- College of Veterinary Medicine, Jilin Agricultural University, Changchun, China
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
- Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Agricultural University, Changchun, China
| | - Ziyan Dai
- College of Veterinary Medicine, Jilin Agricultural University, Changchun, China
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
- Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Agricultural University, Changchun, China
| | - Jia Wang
- College of Veterinary Medicine, Jilin Agricultural University, Changchun, China
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
- Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Agricultural University, Changchun, China
| | - Mengyang Wu
- College of Veterinary Medicine, Jilin Agricultural University, Changchun, China
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
- Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Agricultural University, Changchun, China
| | - Ruicong Su
- College of Veterinary Medicine, Jilin Agricultural University, Changchun, China
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
- Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Agricultural University, Changchun, China
| | - Di Zhang
- College of Veterinary Medicine, Jilin Agricultural University, Changchun, China
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
- Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Agricultural University, Changchun, China
- *Correspondence: Di Zhang,
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3
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Hayek H, Eriani G, Allmang C. eIF3 Interacts with Selenoprotein mRNAs. Biomolecules 2022; 12:biom12091268. [PMID: 36139107 PMCID: PMC9496622 DOI: 10.3390/biom12091268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/01/2022] [Accepted: 09/05/2022] [Indexed: 11/16/2022] Open
Abstract
The synthesis of selenoproteins requires the co-translational recoding of an in-frame UGASec codon. Interactions between the Selenocysteine Insertion Sequence (SECIS) and the SECIS binding protein 2 (SBP2) in the 3'untranslated region (3'UTR) of selenoprotein mRNAs enable the recruitment of the selenocysteine insertion machinery. Several selenoprotein mRNAs undergo unusual cap hypermethylation and are not recognized by the translation initiation factor 4E (eIF4E) but nevertheless translated. The human eukaryotic translation initiation factor 3 (eIF3), composed of 13 subunits (a-m), can selectively recruit several cellular mRNAs and plays roles in specialized translation initiation. Here, we analyzed the ability of eIF3 to interact with selenoprotein mRNAs. By combining ribonucleoprotein immunoprecipitation (RNP IP) in vivo and in vitro with cross-linking experiments, we found interactions between eIF3 and a subgroup of selenoprotein mRNAs. We showed that eIF3 preferentially interacts with hypermethylated capped selenoprotein mRNAs rather than m7G-capped mRNAs. We identified direct contacts between GPx1 mRNA and eIF3 c, d, and e subunits and showed the existence of common interaction patterns for all hypermethylated capped selenoprotein mRNAs. Differential interactions of eIF3 with selenoprotein mRNAs may trigger specific translation pathways independent of eIF4E. eIF3 could represent a new player in the translation regulation and hierarchy of selenoprotein expression.
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Affiliation(s)
- Hassan Hayek
- Architecture et Réactivité de l’ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
- Department of Microbiology, Immunology, and Inflammation, Center for Inflammation and Lung Research, Temple University, Philadelphia, PA 19140, USA
| | - Gilbert Eriani
- Architecture et Réactivité de l’ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Christine Allmang
- Architecture et Réactivité de l’ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
- Correspondence:
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4
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Chellan B, Zhao L, Landeche M, Carmean CM, Dumitrescu AM, Sargis RM. Selenocysteine insertion sequence binding protein 2 (Sbp2) in the sex-specific regulation of selenoprotein gene expression in mouse pancreatic islets. Sci Rep 2020; 10:18568. [PMID: 33122797 PMCID: PMC7596060 DOI: 10.1038/s41598-020-75595-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 10/09/2020] [Indexed: 12/16/2022] Open
Abstract
Selenoproteins are a group of selenocysteine-containing proteins with major roles in cellular antioxidant defense and thyroid hormone metabolism. Selenoprotein expression is determined by hierarchical mechanisms that result in tissue-specific levels. Current data inadequately explain the abundance of various selenoproteins under normal and pathological conditions, including in pancreatic β-cells. Selenocysteine insertion sequence binding protein 2 (SBP2) is a critical protein in selenoprotein translation that also plays an essential role in stabilizing selenoprotein transcripts by antagonizing nonsense-mediated decay (NMD). Importantly, dysfunctional SBP2 is associated with endocrine disorders in humans. Here we describe the impact of induced Sbp2 deficiency in pancreatic β-cells on selenoprotein transcript profiles in the pancreatic islets of C57BL/6J mice. Sex differences were noted in control mice, in which female islets showed 5 selenoproteins decreased and one increased versus male islets. Induced Sbp2 deficiency in pancreatic β-cells altered expression of only 3 selenoprotein transcripts in male islets, whereas 14 transcripts were reduced in female islets. In all cases, decreased transcription was observed in genes known to be regulated by NMD. The differential impact of Sbp2 deletion on selenoprotein transcription between sexes suggests sex-specific hierarchical mechanisms of selenoprotein expression that may influence islet biology and consequentially metabolic disease risk.
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Affiliation(s)
- B Chellan
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Illinois at Chicago, 835 S. Wolcott, Suite E625; M/C 640, Chicago, IL, 60612, USA
| | - L Zhao
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Illinois at Chicago, 835 S. Wolcott, Suite E625; M/C 640, Chicago, IL, 60612, USA
| | - M Landeche
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Illinois at Chicago, 835 S. Wolcott, Suite E625; M/C 640, Chicago, IL, 60612, USA
| | - C M Carmean
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Illinois at Chicago, 835 S. Wolcott, Suite E625; M/C 640, Chicago, IL, 60612, USA
| | - A M Dumitrescu
- Section of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Chicago, Chicago, IL, USA
| | - R M Sargis
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Illinois at Chicago, 835 S. Wolcott, Suite E625; M/C 640, Chicago, IL, 60612, USA.
- ChicAgo Center for Health and EnvironmenT (CACHET), Chicago, IL, USA.
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5
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Schoenmakers E, Chatterjee K. Human Disorders Affecting the Selenocysteine Incorporation Pathway Cause Systemic Selenoprotein Deficiency. Antioxid Redox Signal 2020; 33:481-497. [PMID: 32295391 PMCID: PMC7409586 DOI: 10.1089/ars.2020.8097] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Significance: Generalized selenoprotein deficiency has been associated with mutations in SECISBP2, SEPSECS, and TRU-TCA1-1, 3 factors that are crucial for incorporation of the amino acid selenocysteine (Sec) into at least 25 human selenoproteins. SECISBP2 and TRU-TCA1-1 defects are characterized by a multisystem phenotype due to deficiencies of antioxidant and tissue-specific selenoproteins, together with abnormal thyroid hormone levels reflecting impaired hormone metabolism by deiodinase selenoenzymes. SEPSECS mutations are associated with a predominantly neurological phenotype with progressive cerebello-cerebral atrophy. Recent Advances: The recent identification of individuals with defects in genes encoding components of the selenocysteine insertion pathway has delineated complex and multisystem disorders, reflecting a lack of selenoproteins in specific tissues, oxidative damage due to lack of oxidoreductase-active selenoproteins and other pathways whose nature is unclear. Critical Issues: Abnormal thyroid hormone metabolism in patients can be corrected by triiodothyronine (T3) treatment. No specific therapies for other phenotypes (muscular dystrophy, male infertility, hearing loss, neurodegeneration) exist as yet, but their severity often requires supportive medical intervention. Future Directions: These disorders provide unique insights into the role of selenoproteins in humans. The long-term consequences of reduced cellular antioxidant capacity remain unknown, and future surveillance of patients may reveal time-dependent phenotypes (e.g., neoplasia, aging) or consequences of deficiency of selenoproteins whose function remains to be elucidated. The role of antioxidant therapies requires evaluation. Antioxid. Redox Signal. 33, 481-497.
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Affiliation(s)
- Erik Schoenmakers
- Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Krishna Chatterjee
- Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, United Kingdom
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6
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Schwenzer H, Jühling F, Chu A, Pallett LJ, Baumert TF, Maini M, Fassati A. Oxidative Stress Triggers Selective tRNA Retrograde Transport in Human Cells during the Integrated Stress Response. Cell Rep 2020; 26:3416-3428.e5. [PMID: 30893612 PMCID: PMC6426654 DOI: 10.1016/j.celrep.2019.02.077] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 02/04/2019] [Accepted: 02/20/2019] [Indexed: 01/05/2023] Open
Abstract
In eukaryotes, tRNAs are transcribed in the nucleus and exported to the cytosol, where they deliver amino acids to ribosomes for protein translation. This nuclear-cytoplasmic movement was believed to be unidirectional. However, active shuttling of tRNAs, named tRNA retrograde transport, between the cytosol and nucleus has been discovered. This pathway is conserved in eukaryotes, suggesting a fundamental function; however, little is known about its role in human cells. Here we report that, in human cells, oxidative stress triggers tRNA retrograde transport, which is rapid, reversible, and selective for certain tRNA species, mostly with shorter 3′ ends. Retrograde transport of tRNASeC, which promotes translation of selenoproteins required to maintain homeostatic redox levels in cells, is highly efficient. tRNA retrograde transport is regulated by the integrated stress response pathway via the PERK-REDD1-mTOR axis. Thus, we propose that tRNA retrograde transport is part of the cellular response to oxidative stress. Oxidative stress triggers nuclear import of cytoplasmic tRNAs Import is selective for certain tRNAs Import requires activation of the unfolded protein response and inhibition of mTOR via REDD1 tRNA nuclear import is a component of the integrated stress response
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Affiliation(s)
- Hagen Schwenzer
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK
| | - Frank Jühling
- INSERM, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, 2 Université de Strasbourg, 67000 Strasbourg, France
| | - Alexander Chu
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK
| | - Laura J Pallett
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK
| | - Thomas F Baumert
- INSERM, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, 2 Université de Strasbourg, 67000 Strasbourg, France; Nouvel Hôpital Civil, Institut Hospitalo-Universitaire, 67000 Strasbourg, France
| | - Mala Maini
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK
| | - Ariberto Fassati
- Division of Infection and Immunity, University College London (UCL), London WC1E 6BT, UK.
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7
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Hariharan S, Dharmaraj S. Selenium and selenoproteins: it's role in regulation of inflammation. Inflammopharmacology 2020; 28:667-695. [PMID: 32144521 PMCID: PMC7222958 DOI: 10.1007/s10787-020-00690-x] [Citation(s) in RCA: 269] [Impact Index Per Article: 67.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 02/06/2020] [Indexed: 12/22/2022]
Abstract
Abstract Selenium is an essential immunonutrient which holds the human’s metabolic activity with its chemical bonds. The organic forms of selenium naturally present in human body are selenocysteine and selenoproteins. These forms have a unique way of synthesis and translational coding. Selenoproteins act as antioxidant warriors for thyroid regulation, male-fertility enhancement, and anti-inflammatory actions. They also participate indirectly in the mechanism of wound healing as oxidative stress reducers. Glutathione peroxidase (GPX) is the major selenoprotein present in the human body, which assists in the control of excessive production of free radical at the site of inflammation. Other than GPX, other selenoproteins include selenoprotein-S that regulates the inflammatory cytokines and selenoprotein-P that serves as an inducer of homeostasis. Previously, reports were mainly focused on the cellular and molecular mechanism of wound healing with reference to various animal models and cell lines. In this review, the role of selenium and its possible routes in translational decoding of selenocysteine, synthesis of selenoproteins, systemic action of selenoproteins and their indirect assimilation in the process of wound healing are explained in detail. Some of the selenium containing compounds which can acts as cancer preventive and therapeutics are also discussed. These compounds directly or indirectly exhibit antioxidant properties which can sustain the intracellular redox status and these activities protect the healthy cells from reactive oxygen species induced oxidative damage. Although the review covers the importance of selenium/selenoproteins in wound healing process, still some unresolved mystery persists which may be resolved in near future. Graphic abstract ![]()
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Affiliation(s)
- Sneha Hariharan
- Department of Biochemistry, Karpagam Academy of Higher Education, Eachanari Post, Pollachi Main Road, Coimbatore, Tamil Nadu, 641021, India
| | - Selvakumar Dharmaraj
- Department of Biochemistry, Karpagam Academy of Higher Education, Eachanari Post, Pollachi Main Road, Coimbatore, Tamil Nadu, 641021, India.
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8
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Howard MT, Copeland PR. New Directions for Understanding the Codon Redefinition Required for Selenocysteine Incorporation. Biol Trace Elem Res 2019; 192:18-25. [PMID: 31342342 PMCID: PMC6801069 DOI: 10.1007/s12011-019-01827-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 07/10/2019] [Indexed: 10/26/2022]
Abstract
The fact that selenocysteine (Sec) is delivered to the elongating ribosome by a tRNA that recognizes a UGA stop codon makes it unique and a thorn in the side of what was originally thought to be a universal genetic code. The mechanism by which this redefinition occurs has been slowly coming to light over the past 30 years, but key questions remain. This review seeks to highlight the prominent mechanistic questions that will guide the direction of work in the near future. These questions arise from two major aspects of Sec incorporation: (1) novel functions for the Sec insertion sequence (SECIS) that resides in all selenoprotein mRNAs and (2) the myriad of RNA-binding proteins, both known and yet to be discovered, that act in concert to modify the translation elongation process to allow Sec incorporation.
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Affiliation(s)
- Michael T Howard
- Department of Human Genetics, University of Utah, Salt Lake City, UT, 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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9
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Translation regulation of mammalian selenoproteins. Biochim Biophys Acta Gen Subj 2018; 1862:2480-2492. [PMID: 29751099 DOI: 10.1016/j.bbagen.2018.05.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 04/28/2018] [Accepted: 05/04/2018] [Indexed: 11/22/2022]
Abstract
BACKGROUND Interest in selenium research has considerably grown over the last decades owing to the association of selenium deficiencies with an increased risk of several human diseases, including cancers, cardiovascular disorders and infectious diseases. The discovery of a genetically encoded 21st amino acid, selenocysteine, is a fascinating breakthrough in molecular biology as it is the first addition to the genetic code deciphered in the 1960s. Selenocysteine is a structural and functional analog of cysteine, where selenium replaces sulfur, and its presence is critical for the catalytic activity of selenoproteins. SCOPE OF REVIEW The insertion of selenocysteine is a non-canonical translational event, based on the recoding of a UGA codon in selenoprotein mRNAs, normally used as a stop codon in other cellular mRNAs. Two RNA molecules and associated partners are crucial components of the selenocysteine insertion machinery, the Sec-tRNA[Ser]Sec devoted to UGA codon recognition and the SECIS elements located in the 3'UTR of selenoprotein mRNAs. MAJOR CONCLUSIONS The translational UGA recoding event is a limiting stage of selenoprotein expression and its efficiency is regulated by several factors. GENERAL SIGNIFICANCE The control of selenoproteome expression is crucial for redox homeostasis and antioxidant defense of mammalian organisms. In this review, we summarize current knowledge on the co-translational insertion of selenocysteine into selenoproteins, and its layers of regulation.
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10
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Oudouhou F, Casu B, Dopgwa Puemi AS, Sygusch J, Baron C. Analysis of Novel Interactions between Components of the Selenocysteine Biosynthesis Pathway, SEPHS1, SEPHS2, SEPSECS, and SECp43. Biochemistry 2017; 56:2261-2270. [DOI: 10.1021/acs.biochem.6b01116] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Flore Oudouhou
- Department of Biochemistry
and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Bastien Casu
- Department of Biochemistry
and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Arnold Steve Dopgwa Puemi
- Department of Biochemistry
and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Jurgen Sygusch
- Department of Biochemistry
and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Christian Baron
- Department of Biochemistry
and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
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11
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Dubey A, Copeland PR. The Selenocysteine-Specific Elongation Factor Contains Unique Sequences That Are Required for Both Nuclear Export and Selenocysteine Incorporation. PLoS One 2016; 11:e0165642. [PMID: 27802322 PMCID: PMC5089774 DOI: 10.1371/journal.pone.0165642] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 10/14/2016] [Indexed: 11/18/2022] Open
Abstract
Selenocysteine (Sec) is a critical residue in at least 25 human proteins that are essential for antioxidant defense and redox signaling in cells. Sec is inserted into proteins cotranslationally by the recoding of an in-frame UGA termination codon to a Sec codon. In eukaryotes, this recoding event requires several specialized factors, including a dedicated, Sec-specific elongation factor called eEFSec, which binds Sec-tRNASec with high specificity and delivers it to the ribosome for selenoprotein production. Unlike most translation factors, including the canonical elongation factor eEF1A, eEFSec readily localizes to the nucleus of mammalian cells and shuttles between the cytoplasmic and nuclear compartments. The functional significance of eEFSec's nuclear localization has remained unclear. In this study, we have examined the subcellular localization of eEFSec in the context of altered Sec incorporation to demonstrate that reduced selenoprotein production does not correlate with changes in the nuclear localization of eEFSec. In addition, we identify several novel sequences of the protein that are essential for localization as well as Sec insertion activity, and show that eEFSec utilizes CRM1-mediated nuclear export pathway. Our findings argue for two distinct pools of eEFSec in the cell, where the cytoplasmic pool participates in Sec incorporation and the nuclear pool may be involved in an as yet unknown function.
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Affiliation(s)
- Aditi Dubey
- Department of Biochemistry and Molecular Biology, Rutgers—Robert Wood Johnson Medical School, Piscataway, NJ, United States of America
| | - Paul R. Copeland
- Department of Biochemistry and Molecular Biology, Rutgers—Robert Wood Johnson Medical School, Piscataway, NJ, United States of America
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12
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Bubenik JL, Miniard AC, Driscoll DM. Characterization of the UGA-recoding and SECIS-binding activities of SECIS-binding protein 2. RNA Biol 2015; 11:1402-13. [PMID: 25692238 PMCID: PMC4615290 DOI: 10.1080/15476286.2014.996472] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Selenium, a micronutrient, is primarily incorporated into human physiology as selenocysteine (Sec). The 25 Sec-containing proteins in humans are known as selenoproteins. Their synthesis depends on the translational recoding of the UGA stop codon to allow Sec insertion. This requires a stem-loop structure in the 3' untranslated region of eukaryotic mRNAs known as the Selenocysteine Insertion Sequence (SECIS). The SECIS is recognized by SECIS-binding protein 2 (SBP2) and this RNA:protein interaction is essential for UGA recoding to occur. Genetic mutations cause SBP2 deficiency in humans, resulting in a broad set of symptoms due to differential effects on individual selenoproteins. Progress on understanding the different phenotypes requires developing robust tools to investigate SBP2 structure and function. In this study we demonstrate that SBP2 protein produced by in vitro translation discriminates among SECIS elements in a competitive UGA recoding assay and has a much higher specific activity than bacterially expressed protein. We also show that a purified recombinant protein encompassing amino acids 517-777 of SBP2 binds to SECIS elements with high affinity and selectivity. The affinity of the SBP2:SECIS interaction correlated with the ability of a SECIS to compete for UGA recoding activity in vitro. The identification of a 250 amino acid sequence that mediates specific, selective SECIS-binding will facilitate future structural studies of the SBP2:SECIS complex. Finally, we identify an evolutionarily conserved core cysteine signature in SBP2 sequences from the vertebrate lineage. Mutation of multiple, but not single, cysteines impaired SECIS-binding but did not affect protein localization in cells.
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Key Words
- DTT, dithiothreitol
- Dio1, deiodinase 1
- Dio2, deiodinase 2
- GPx1, glutathione peroxidase 1
- PHGPx, phospholipid hydroperoxide glutathione peroxidase
- REMSA, RNA electrophoretic mobility shift assay
- RNA-protein interactions
- RRL, rabbit reticulocyte lysate
- SBP2, SECIS binding protein 2
- SECIS, Selenocysteine Insertion Sequence
- SECIS-binding protein 2
- Sec, selenocysteine
- selenium
- selenocysteine
- selenoprotein
- translation
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Affiliation(s)
- Jodi L Bubenik
- a Department of Cellular and Molecular Medicine; Lerner Research Institute; Cleveland Clinic ; Cleveland , OH USA
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Abstract
SIGNIFICANCE Selenium is an essential trace element that is incorporated in the small but vital family of proteins, namely the selenoproteins, as the selenocysteine amino acid residue. In humans, 25 selenoprotein genes have been characterized. The most remarkable trait of selenoprotein biosynthesis is the cotranslational insertion of selenocysteine by the recoding of a UGA codon, normally decoded as a stop signal. RECENT ADVANCES In eukaryotes, a set of dedicated cis- and trans-acting factors have been identified as well as a variety of regulatory mechanisms, factors, or elements that control the selenoprotein expression at the level of the UGA-selenocysteine recoding process, offering a fascinating playground in the field of translational control. It appeared that the central players are two RNA molecules: the selenocysteine insertion sequence (SECIS) element within selenoprotein mRNA and the selenocysteine-tRNA([Ser]Sec); and their interacting partners. CRITICAL ISSUES After a couple of decades, despite many advances in the field and the discovery of many essential and regulatory components, the precise mechanism of UGA-selenocysteine recoding remains elusive and more complex than anticipated, with many layers of control. This review offers an update of selenoproteome biosynthesis and regulation in eukaryotes. FUTURE DIRECTIONS The regulation of selenoproteins in response to a variety of pathophysiological conditions and cellular stressors, including selenium levels, oxidative stress, replicative senescence, or cancer, awaits further detailed investigation. Clearly, the efficiency of UGA-selenocysteine recoding is the limiting stage of selenoprotein synthesis. The sequence of events leading Sec-tRNA([Ser]Sec) delivery to ribosomal A site awaits further analysis, notably at the level of a three-dimensional structure.
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Affiliation(s)
- Anne-Laure Bulteau
- Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, IPREM , CNRS/UPPA, UMR5254, Pau, France
| | - Laurent Chavatte
- Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, IPREM , CNRS/UPPA, UMR5254, Pau, France
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Wurth L, Gribling-Burrer AS, Verheggen C, Leichter M, Takeuchi A, Baudrey S, Martin F, Krol A, Bertrand E, Allmang C. Hypermethylated-capped selenoprotein mRNAs in mammals. Nucleic Acids Res 2014; 42:8663-77. [PMID: 25013170 PMCID: PMC4117793 DOI: 10.1093/nar/gku580] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mammalian mRNAs are generated by complex and coordinated biogenesis pathways and acquire 5′-end m7G caps that play fundamental roles in processing and translation. Here we show that several selenoprotein mRNAs are not recognized efficiently by translation initiation factor eIF4E because they bear a hypermethylated cap. This cap modification is acquired via a 5′-end maturation pathway similar to that of the small nucle(ol)ar RNAs (sn- and snoRNAs). Our findings also establish that the trimethylguanosine synthase 1 (Tgs1) interacts with selenoprotein mRNAs for cap hypermethylation and that assembly chaperones and core proteins devoted to sn- and snoRNP maturation contribute to recruiting Tgs1 to selenoprotein mRNPs. We further demonstrate that the hypermethylated-capped selenoprotein mRNAs localize to the cytoplasm, are associated with polysomes and thus translated. Moreover, we found that the activity of Tgs1, but not of eIF4E, is required for the synthesis of the GPx1 selenoprotein in vivo.
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Affiliation(s)
- Laurence Wurth
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Anne-Sophie Gribling-Burrer
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Céline Verheggen
- Equipe labélisée Ligue contre le cancer, Institut de Génétique Moléculaire, Centre National de la Recherche Scientifique, UMR 5535, 34293 Montpellier, France
| | - Michael Leichter
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Akiko Takeuchi
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Stéphanie Baudrey
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Franck Martin
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Alain Krol
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Edouard Bertrand
- Equipe labélisée Ligue contre le cancer, Institut de Génétique Moléculaire, Centre National de la Recherche Scientifique, UMR 5535, 34293 Montpellier, France
| | - Christine Allmang
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
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Touat-Hamici Z, Legrain Y, Bulteau AL, Chavatte L. Selective up-regulation of human selenoproteins in response to oxidative stress. J Biol Chem 2014; 289:14750-61. [PMID: 24706762 DOI: 10.1074/jbc.m114.551994] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Selenocysteine is inserted into selenoproteins via the translational recoding of a UGA codon, normally used as a stop signal. This process depends on the nature of the selenocysteine insertion sequence element located in the 3' UTR of selenoprotein mRNAs, selenium bioavailability, and, possibly, exogenous stimuli. To further understand the function and regulation of selenoproteins in antioxidant defense and redox homeostasis, we investigated how oxidative stress influences selenoprotein expression as a function of different selenium concentrations. We found that selenium supplementation of the culture media, which resulted in a hierarchical up-regulation of selenoproteins, protected HEK293 cells from reactive oxygen species formation. Furthermore, in response to oxidative stress, we identified a selective up-regulation of several selenoproteins involved in antioxidant defense (Gpx1, Gpx4, TR1, SelS, SelK, and Sps2). Interestingly, the response was more efficient when selenium was limiting. Although a modest change in mRNA levels was noted, we identified a novel translational control mechanism stimulated by oxidative stress that is characterized by up-regulation of UGA-selenocysteine recoding efficiency and relocalization of SBP2, selenocysteine-specific elongation factor, and L30 recoding factors from the cytoplasm to the nucleus.
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Affiliation(s)
- Zahia Touat-Hamici
- From the Centre de Génétique Moléculaire, CNRS, UPR3404, 91198 Gif-sur-Yvette, France
| | - Yona Legrain
- From the Centre de Génétique Moléculaire, CNRS, UPR3404, 91198 Gif-sur-Yvette, France
| | - Anne-Laure Bulteau
- the Centre de Recherche Institut Cochin, INSERM U567, CNRS UMR 8104, 75005 Paris, France, and the Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, CNRS/UPPA, UMR5254, 64000 Pau, France
| | - Laurent Chavatte
- From the Centre de Génétique Moléculaire, CNRS, UPR3404, 91198 Gif-sur-Yvette, France, the Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, CNRS/UPPA, UMR5254, 64000 Pau, France
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Legrain Y, Touat-Hamici Z, Chavatte L. Interplay between selenium levels, selenoprotein expression, and replicative senescence in WI-38 human fibroblasts. J Biol Chem 2014; 289:6299-310. [PMID: 24425862 DOI: 10.1074/jbc.m113.526863] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Selenium is an essential trace element, which is incorporated as selenocysteine into at least 25 selenoproteins using a unique translational UGA-recoding mechanism. Selenoproteins are important enzymes involved in antioxidant defense, redox homeostasis, and redox signaling pathways. Selenium levels decline during aging, and its deficiency is associated with a marked increase in mortality for people over 60 years of age. Here, we investigate the relationship between selenium levels in the culture medium, selenoprotein expression, and replicative life span of human embryonic lung fibroblast WI-38 cells. Selenium levels regulate the entry into replicative senescence and modify the cellular markers characteristic for senescent cells. Whereas selenium supplementation extends the number of population doublings, its deficiency impairs the proliferative capacity of WI-38 cells. We observe that the expression of several selenoproteins involved in antioxidant defense is specifically affected in response to cellular senescence. Their expression is selectively controlled by the modulation of mRNA levels and translational recoding efficiencies. Our data provide novel mechanistic insights into how selenium impacts the replicative life span of mammalian cells by identifying several selenoproteins as new targets of senescence.
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Affiliation(s)
- Yona Legrain
- From the Centre de Génétique Moléculaire, CNRS, UPR3404, Gif-sur-Yvette 91198 Cedex, France and
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17
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Latrèche L, Duhieu S, Touat-Hamici Z, Jean-Jean O, Chavatte L. The differential expression of glutathione peroxidase 1 and 4 depends on the nature of the SECIS element. RNA Biol 2012; 9:681-90. [PMID: 22614831 DOI: 10.4161/rna.20147] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Selenocysteine insertion into selenoproteins involves the translational recoding of UGA stop codons. In mammals, selenoprotein expression further depends on selenium availability, which has been particularly described for glutathione peroxidase 1 and 4 (Gpx1 and Gpx4). The SECIS element located in the 3'UTR of the selenoprotein mRNAs is a modulator of UGA recoding efficiency in adequate selenium conditions. One of the current models for the UGA recoding mechanism proposes that the SECIS binds SECIS-binding protein 2 (SBP2), which then recruits a selenocysteine-specific elongation factor (EFsec) and tRNA (Sec) to the ribosome, where L30 acts as an anchor. The involvement of the SECIS in modulation of UGA recoding activity was investigated, together with SBP2 and EFsec, in Hek293 cells cultured with various selenium levels. Luciferase reporter constructs, in transiently or stably expressing cell lines, were used to analyze the differential expression of Gpx1 and Gpx4. We showed that, upon selenium fluctuation, the modulation of UGA recoding efficiency depends on the nature of the SECIS, with Gpx1 being more sensitive than Gpx4. Attenuation of SBP2 and EFsec levels by shRNAs confirmed that both factors are essential for efficient selenocysteine insertion. Strikingly, in a context of either EFsec or SBP2 attenuation, the decrease in UGA recoding efficiency is dependent on the nature of the SECIS, GPx1 being more sensitive. Finally, the profusion of selenium of the culture medium exacerbates the lack of factors involved in selenocysteine insertion.
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Speijer D. Does constructive neutral evolution play an important role in the origin of cellular complexity? Making sense of the origins and uses of biological complexity. Bioessays 2011; 33:344-9. [PMID: 21381061 DOI: 10.1002/bies.201100010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Recently, constructive neutral evolution has been touted as an important concept for the understanding of the emergence of cellular complexity. It has been invoked to help explain the development and retention of, amongst others, RNA splicing, RNA editing and ribosomal and mitochondrial respiratory chain complexity. The theory originated as a welcome explanation of isolated small scale cellular idiosyncrasies and as a reaction to 'overselectionism'. Here I contend, that in its extended form, it has major conceptual problems, can not explain observed patterns of complex processes, is too easily dismissive of alternative selectionist models, underestimates the creative force of complexity as such, and--if seen as a major evolutionary mechanism for all organisms--could stifle further thought regarding the evolution of highly complex biological processes.
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Affiliation(s)
- Dave Speijer
- Academic Medical Center (AMC), Department of Medical Biochemistry, University of Amsterdam, Amsterdam, The Netherlands.
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Abstract
The co-translational incorporation of selenocysteine (Sec) requires that UGA be recognized as a sense rather than a nonsense codon. This is accomplished by the concerted action of a Sec insertion sequence (SECIS) element, SECIS binding protein 2, and a ternary complex of the Sec specific elongation factor, Sec-tRNA(Sec), and GTP. The mechanism by which they alter the canonical protein synthesis reaction has been elusive. Here we present an overview of the mechanistic perspective on Sec incorporation, highlighting recent advances in the field.
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Affiliation(s)
- Jesse Donovan
- Department of Microbiology, Molecular Genetics, and Immunology, Graduate School of Biomedical Sciences, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 675 Hoes Lane, Piscataway, NJ 08854, USA
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Berry MJ, Howard MT. Reprogramming the Ribosome for Selenoprotein Expression: RNA Elements and Protein Factors. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/978-0-387-89382-2_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/27/2023]
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Reeves MA, Hoffmann PR. The human selenoproteome: recent insights into functions and regulation. Cell Mol Life Sci 2009; 66:2457-78. [PMID: 19399585 PMCID: PMC2866081 DOI: 10.1007/s00018-009-0032-4] [Citation(s) in RCA: 354] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2009] [Revised: 04/01/2009] [Accepted: 04/03/2009] [Indexed: 12/16/2022]
Abstract
Selenium (Se) is a nutritional trace mineral essential for various aspects of human health that exerts its effects mainly through its incorporation into selenoproteins as the amino acid, selenocysteine. Twenty-five selenoprotein genes have been identified in humans and several selenoproteins are broadly classified as antioxidant enzymes. As progress is made on characterizing the individual members of this protein family, however, it is becoming clear that their properties and functions are quite diverse. This review summarizes recent insights into properties of individual selenoproteins such as tissue distribution, subcellular localization, and regulation of expression. Also discussed are potential roles the different selenoproteins play in human health and disease.
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Affiliation(s)
- M. A. Reeves
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo Street, Honolulu, HI 96813 USA
| | - P. R. Hoffmann
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo Street, Honolulu, HI 96813 USA
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22
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Abstract
Selenoproteins are proteins containing selenium in the form of the 21st amino acid, selenocysteine. Members of this protein family have many diverse functions, but their synthesis is dependent on a common set of cofactors and on dietary selenium. Although the functions of many selenoproteins are unknown, several disorders involving changes in selenoprotein structure, activity or expression have been reported. Selenium deficiency and mutations or polymorphisms in selenoprotein genes and synthesis cofactors are implicated in a variety of diseases, including muscle and cardiovascular disorders, immune dysfunction, cancer, neurological disorders and endocrine function. Members of this unusual family of proteins have roles in a variety of cell processes and diseases.
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Allmang C, Wurth L, Krol A. The selenium to selenoprotein pathway in eukaryotes: more molecular partners than anticipated. Biochim Biophys Acta Gen Subj 2009; 1790:1415-23. [PMID: 19285539 DOI: 10.1016/j.bbagen.2009.03.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 03/03/2009] [Accepted: 03/05/2009] [Indexed: 01/23/2023]
Abstract
The amino acid selenocysteine (Sec) is the major biological form of the trace element selenium. Sec is co-translationally incorporated in selenoproteins. There are 25 selenoprotein genes in humans, and Sec was found in the active site of those that have been attributed a function. This review will discuss how selenocysteine is synthesized and incorporated into selenoproteins in eukaryotes. Sec biosynthesis from serine on the tRNA(Sec) requires four enzymes. Incorporation of Sec in response to an in-frame UGA codon, otherwise signaling termination of translation, is achieved by a complex recoding machinery to inform the ribosomes not to stop at this position on the mRNA. A number of the molecular partners acting in this machinery have been identified but their detailed mechanism of action has not been deciphered yet. Here we provide an overview of the literature in the field. Particularly striking is the higher than originally envisaged number of factors necessary to synthesize Sec and selenoproteins. Clearly, selenoprotein synthesis is an exciting and very active field of research.
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Affiliation(s)
- Christine Allmang
- Architecture et Réactivité de l'ARN - Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
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Pappas A, Zoidis E, Surai P, Zervas G. Selenoproteins and maternal nutrition. Comp Biochem Physiol B Biochem Mol Biol 2008; 151:361-72. [DOI: 10.1016/j.cbpb.2008.08.009] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 08/13/2008] [Accepted: 08/20/2008] [Indexed: 11/24/2022]
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25
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Gereben B, Zavacki AM, Ribich S, Kim BW, Huang SA, Simonides WS, Zeöld A, Bianco AC. Cellular and molecular basis of deiodinase-regulated thyroid hormone signaling. Endocr Rev 2008; 29:898-938. [PMID: 18815314 PMCID: PMC2647704 DOI: 10.1210/er.2008-0019] [Citation(s) in RCA: 552] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Accepted: 08/15/2008] [Indexed: 02/06/2023]
Abstract
The iodothyronine deiodinases initiate or terminate thyroid hormone action and therefore are critical for the biological effects mediated by thyroid hormone. Over the years, research has focused on their role in preserving serum levels of the biologically active molecule T(3) during iodine deficiency. More recently, a fascinating new role of these enzymes has been unveiled. The activating deiodinase (D2) and the inactivating deiodinase (D3) can locally increase or decrease thyroid hormone signaling in a tissue- and temporal-specific fashion, independent of changes in thyroid hormone serum concentrations. This mechanism is particularly relevant because deiodinase expression can be modulated by a wide variety of endogenous signaling molecules such as sonic hedgehog, nuclear factor-kappaB, growth factors, bile acids, hypoxia-inducible factor-1alpha, as well as a growing number of xenobiotic substances. In light of these findings, it seems clear that deiodinases play a much broader role than once thought, with great ramifications for the control of thyroid hormone signaling during vertebrate development and metamorphosis, as well as injury response, tissue repair, hypothalamic function, and energy homeostasis in adults.
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Affiliation(s)
- Balázs Gereben
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
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Meno SR, Nelson R, Hintze KJ, Self WT. Exposure to monomethylarsonous acid (MMA(III)) leads to altered selenoprotein synthesis in a primary human lung cell model. Toxicol Appl Pharmacol 2008; 239:130-6. [PMID: 19095002 DOI: 10.1016/j.taap.2008.11.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 11/03/2008] [Accepted: 11/06/2008] [Indexed: 10/21/2022]
Abstract
Monomethylarsonous acid (MMA(III)), a trivalent metabolite of arsenic, is highly cytotoxic and recent cell culture studies suggest that it might act as a carcinogen. The general consensus of studies indicates that the cytotoxicity of MMA(III) is a result of increased levels of reactive oxygen species (ROS). A longstanding relationship between arsenic and selenium metabolism has led to the use of selenium as a supplement in arsenic exposed populations, however the impact of organic arsenicals (methylated metabolites) on selenium metabolism is still poorly understood. In this study we determined the impact of exposure to MMA(III) on the regulation of expression of TrxR1 and its activity using a primary lung fibroblast line, WI-38. The promoter region of the gene encoding the selenoprotein thioredoxin reductase 1 (TrxR1) contains an antioxidant responsive element (ARE) that has been shown to be activated in the presence of electrophilic compounds. Results from radiolabeled selenoproteins indicate that exposure to low concentrations of MMA(III) resulted in increased synthesis of TrxR1 in WI-38 cells, and lower incorporation of selenium into other selenoproteins. MMA(III) treatment led to increased mRNA encoding TrxR1 in WI-38 cells, while lower levels of mRNA coding for cellular glutathione peroxidase (cGpx) were detected in exposed cells. Luciferase activity of TrxR1 promoter fusions increased with addition of MMA(III), as did expression of a rat quinone reductase (QR) promoter fusion construct. However, MMA(III) induction of the TRX1 promoter fusion was abrogated when the ARE was mutated, suggesting that this regulation is mediated via the ARE. These results indicate that MMA(III) alters the expression of selenoproteins based on a selective induction of TrxR1, and this response to exposure to organic arsenicals that requires the ARE element.
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Affiliation(s)
- Sarah R Meno
- Department of Molecular Biology and Microbiology, Burnett School of Biomedical Science, University of Central Florida, Orlando, Florida 32816-2364, USA
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Papp LV, Wang J, Kennedy D, Boucher D, Zhang Y, Gladyshev VN, Singh RN, Khanna KK. Functional characterization of alternatively spliced human SECISBP2 transcript variants. Nucleic Acids Res 2008; 36:7192-206. [PMID: 19004874 PMCID: PMC2602786 DOI: 10.1093/nar/gkn829] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Synthesis of selenoproteins depends on decoding of the UGA stop codon as the amino acid selenocysteine (Sec). This process requires the presence of a Sec insertion sequence element (SECIS) in the 3′-untranslated region of selenoprotein mRNAs and its interaction with the SECIS binding protein 2 (SBP2). In humans, mutations in the SBP2-encoding gene Sec insertion sequence binding protein 2 (SECISBP2) that alter the amino acid sequence or cause splicing defects lead to abnormal thyroid hormone metabolism. Herein, we present the first in silico and in vivo functional characterization of alternative splicing of SECISBP2. We report a complex splicing pattern in the 5′-region of human SECISBP2, wherein at least eight splice variants encode five isoforms with varying N-terminal sequence. One of the isoforms, mtSBP2, contains a mitochondrial targeting sequence and localizes to mitochondria. Using a minigene-based in vivo splicing assay we characterized the splicing efficiency of several alternative transcripts, and show that the splicing event that creates mtSBP2 can be modulated by antisense oligonucleotides. Moreover, we show that full-length SBP2 and some alternatively spliced variants are subject to a coordinated transcriptional and translational regulation in response to ultraviolet type A irradiation-induced stress. Overall, our data broadens the functional scope of a housekeeping protein essential to selenium metabolism.
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Affiliation(s)
- Laura V Papp
- Signal Transduction Laboratory, Queensland Institute of Medical Research, Herston, Queensland, Australia.
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Arsenic trioxide and auranofin inhibit selenoprotein synthesis: implications for chemotherapy for acute promyelocytic leukaemia. Br J Pharmacol 2008; 154:940-8. [PMID: 18587442 DOI: 10.1038/bjp.2008.161] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND AND PURPOSE Arsenicals have been used medicinally for decades to treat both infectious disease and cancer. Arsenic trioxide (As2O3) is effective for treatment of acute promyelocytic leukaemia (APL), yet the mechanism of action of this drug is still widely debated. Recently, As2O3 was shown to inhibit the activity of the selenoenzyme thioredoxin reductase (TrxR). TrxR has been proposed to be required for selenium metabolism. The effect of inhibitors of TrxR on selenium metabolism has yet to be assessed. This study aims to determine whether chemotherapeutics that target selenocysteine within selenoenzymes may also affect the metabolism of selenium. EXPERIMENTAL APPROACH A lung cell line, A549, was used to assess the effect of TrxR inhibitors on selenium metabolism, using 75Se-selenite. The level of mRNA encoding cytosolic TrxR (TrxR1) was determined using real-time reverse transcriptase-PCR. TrxR activity was determined in whole-cell extracts. KEY RESULTS Exposure of cells to As2O3, arsenite or auranofin led to a concentration-dependent reduction of selenium metabolism into selenoproteins. Knockdown of TrxR1, using small inhibitory RNA, did not affect selenium metabolism. Exposure of cells to monomethylarsonic acid, a potent inhibitor of TrxR, did not alter selenium metabolism but did inhibit enzyme activity. CONCLUSIONS AND IMPLICATIONS As2O3 and auranofin block the metabolism of selenium in A549 cells. Because As2O3 is used to treat APL, our findings may reveal the mechanism of this therapeutic action and lead to further research targeting selenium metabolism to find novel chemotherapeutic agents for the treatment of APL.
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Squires JE, Berry MJ. Eukaryotic selenoprotein synthesis: mechanistic insight incorporating new factors and new functions for old factors. IUBMB Life 2008; 60:232-5. [PMID: 18344183 DOI: 10.1002/iub.38] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Selenium is an essential micronutrient that has been linked to various aspects of human health. Selenium exerts its biological activity through the incorporation of the amino acid, selenocysteine (Sec), into a unique class of proteins termed selenoproteins. Sec incorporation occurs cotranslationally at UGA codons in archaea, prokaryotes, and eukaryotes. UGA codons specify Sec coding rather than termination by the presence of specific secondary structures in mRNAs termed selenocysteine insertion (SECIS) elements, and trans-acting factors that associate with SECIS elements. Herein, we discuss the various proteins known to function in eukaryotic selenoprotein biosynthesis, including several players whose roles have only been elucidated very recently.
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Affiliation(s)
- Jeffrey E Squires
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96813, USA.
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Abstract
The oxidizing nature of the extracellular environment is vastly different from the highly reducing nature of the intracellular compartment. The redox potential of the cytosolic compartment of the intracellular environment limits disulfide bond formation, whereas the oxidizing extracellular environment contains proteins rich in disulfide bonds. If not for an extracellular antioxidant system to eliminate reactive oxygen and nitrogen species, lipid peroxidation and protein oxidation would become excessive, resulting in cellular damage. Many reviews have focused on the role of intracellular antioxidants in the elimination of oxidative stress, but this one will focus on the coordinated action of both intracellular and extracellular antioxidants in limiting cellular oxidant stress.
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Squires JE, Stoytchev I, Forry EP, Berry MJ. SBP2 binding affinity is a major determinant in differential selenoprotein mRNA translation and sensitivity to nonsense-mediated decay. Mol Cell Biol 2007; 27:7848-55. [PMID: 17846120 PMCID: PMC2169151 DOI: 10.1128/mcb.00793-07] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2007] [Revised: 05/30/2007] [Accepted: 08/29/2007] [Indexed: 01/23/2023] Open
Abstract
Selenoprotein mRNAs are potential targets for degradation via nonsense-mediated decay due to the presence of in-frame UGA codons that can be decoded as either selenocysteine or termination codons. When UGA decoding is inefficient, as occurs when selenium is limiting, termination occurs at these positions. Based on the predicted exon-intron structure, 14 of the 25 human selenoprotein mRNAs are predicted to be sensitive to nonsense-mediated decay. Among these, sensitivity varies widely, resulting in a hierarchy of preservation or degradation of selenoprotein mRNAs and, thus, of selenoprotein synthesis. Potential factors in dictating the hierarchy of selenoprotein synthesis are the Sec insertion sequence RNA-binding proteins, SBP2 and nucleolin. To investigate the mechanistic basis for this hierarchy and the role of these two proteins, we carried out knockdowns of SBP2 expression and assessed the effects on selenoprotein mRNA levels. We also investigated in vivo binding of selenoprotein mRNAs by SBP2 and nucleolin via immunoprecipitation of the proteins and quantitation of bound mRNAs. We report that SBP2 exhibits strong preferential binding to some selenoprotein mRNAs over others, whereas nucleolin exhibits minimal differences in binding. Thus, SBP2 is a major determinant in dictating the hierarchy of selenoprotein synthesis via differential selenoprotein mRNA translation and sensitivity to nonsense-mediated decay.
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Affiliation(s)
- Jeffrey E Squires
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813, USA
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Papp LV, Lu J, Holmgren A, Khanna KK. From selenium to selenoproteins: synthesis, identity, and their role in human health. Antioxid Redox Signal 2007; 9:775-806. [PMID: 17508906 DOI: 10.1089/ars.2007.1528] [Citation(s) in RCA: 867] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The requirement of the trace element selenium for life and its beneficial role in human health has been known for several decades. This is attributed to low molecular weight selenium compounds, as well as to its presence within at least 25 proteins, named selenoproteins, in the form of the amino acid selenocysteine (Sec). Incorporation of Sec into selenoproteins employs a unique mechanism that involves decoding of the UGA codon. This process requires multiple features such as the selenocysteine insertion sequence (SECIS) element and several protein factors including a specific elongation factor EFSec and the SECIS binding protein 2, SBP2. The function of most selenoproteins is currently unknown; however, thioredoxin reductases (TrxR), glutathione peroxidases (GPx) and thyroid hormone deiodinases (DIO) are well characterised selenoproteins involved in redox regulation of intracellular signalling, redox homeostasis and thyroid hormone metabolism. Recent evidence points to a role for selenium compounds as well as selenoproteins in the prevention of some forms of cancer. A number of clinical trials are either underway or being planned to examine the effects of selenium on cancer incidence. In this review we describe some of the recent progress in our understanding of the mechanism of selenoprotein synthesis, the role of selenoproteins in human health and disease and the therapeutic potential of some of these proteins.
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Affiliation(s)
- Laura Vanda Papp
- Queensland Institute of Medical Research, Cancer and Cell Biology Division, Herston, QLD, Australia
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Hoffmann PR, Höge SC, Li PA, Hoffmann FW, Hashimoto AC, Berry MJ. The selenoproteome exhibits widely varying, tissue-specific dependence on selenoprotein P for selenium supply. Nucleic Acids Res 2007; 35:3963-73. [PMID: 17553827 PMCID: PMC1919489 DOI: 10.1093/nar/gkm355] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Selenoprotein P (Sel P) is a selenium-rich glycoprotein believed to play a key role in selenium (Se) transport throughout the body. Development of a Sel P knockout mouse model has supported this notion and initial studies have indicated that selenium supply to various tissues is differentially affected by genetic deletion of Sel P. Se in the form of the amino acid, selenocysteine, is incorporated into selenoproteins at UGA codons. Thus, Se availability affects not only selenoprotein levels, but also the turnover of selenoprotein mRNAs via the nonsense-mediated decay pathway. We investigated how genetic deletion of Sel P in mice affected levels of the mRNAs encoding all known members of the murine selenoprotein family, as well as three non-selenoprotein factors involved in their synthesis, selenophosphate synthetase 1 (SPS1), SECIS-binding protein 2 (SBP2) and SECp43. Our findings present a comprehensive description of selenoprotein mRNA expression in the following murine tissues: brain, heart, intestine, kidney, liver, lung, spleen and testes. We also describe how abundance of selenoproteins and selenoprotein-synthesis factors are affected by genetic deletion of Sel P in some of these tissues, providing insight into how the presence of this selenoprotein influences selenoprotein mRNA levels, and thus, the selenoproteome.
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Affiliation(s)
- Peter R Hoffmann
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, USA.
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Ganyc D, Talbot S, Konate F, Jackson S, Schanen B, Cullen W, Self WT. Impact of trivalent arsenicals on selenoprotein synthesis. ENVIRONMENTAL HEALTH PERSPECTIVES 2007; 115:346-53. [PMID: 17431482 PMCID: PMC1849912 DOI: 10.1289/ehp.9440] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Accepted: 12/19/2006] [Indexed: 05/04/2023]
Abstract
BACKGROUND Exposure to arsenic has been associated with development of skin, lung, bladder, liver, and kidney cancer. Recent evidence suggests that an increase in oxidative stress in cells treated with arsenicals represents the molecular mechanism behind arsenic-induced carcinogenesis. Selenium, in the form of selenocysteine, is necessary for the activity of several enzymes with a role in defense against reactive oxygen species. A mutual sparing effect between arsenic and selenium has been shown in animal studies when both metalloids are present in high concentrations. OBJECTIVES To determine whether changes in selenoprotein synthesis may be an underlying mechanism behind arsenic-induced carcinogenesis, we analyzed the new synthesis of selenoproteins within cells after exposure to inorganic or methylated arsenicals using a human keratinocyte cell model. RESULTS Addition of arsenite to culture medium blocked new synthesis of selenoproteins when selenium was present in the form of selenite, and appeared to stimulate the use of serum-derived selenium. Monomethylarsonous acid (MMA(III)) treatment of cells, in contrast, did not block all new synthesis of selenoproteins but did result in an increase in cytosolic thioredoxin reductase (TrxR1) at both the mRNA and protein levels. MMA(III) also reduced the new synthesis of cellular glutatione peroxidase (cGpx) and other smaller selenoproteins. Dimethylarsinous acid (DMA(III)) stimulated selenoprotein synthesis by an as yet unknown mechanism. CONCLUSIONS These results suggest that arsenite and MMA(III) are key metabolites that trigger higher levels of TrxR1, and both lead to a reduction in the expression of cGpx. Together these effects certainly could lead to carcinogenesis given the knowledge that many cancers have higher levels of TrxR, and reduced Gpx levels will reduce the cell's ability to defend against reactive oxygen species. Based on these results, the impact of the trivalent arsenicals arsenite and MMA(III) on selenoprotein synthesis may indeed represent a potential molecular mechanism for the higher rates of cancer observed in populations exposed to high levels of arsenic.
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Affiliation(s)
- Denis Ganyc
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Science, University of Central Florida, Orlando, Florida, USA
| | - Sarah Talbot
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Science, University of Central Florida, Orlando, Florida, USA
| | - Fanta Konate
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Science, University of Central Florida, Orlando, Florida, USA
| | - Sarah Jackson
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Science, University of Central Florida, Orlando, Florida, USA
| | - Brian Schanen
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Science, University of Central Florida, Orlando, Florida, USA
| | - William Cullen
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada
| | - William T. Self
- Department of Molecular Biology and Microbiology, Burnett College of Biomedical Science, University of Central Florida, Orlando, Florida, USA
- Address correspondence to W. Self, Department of Molecular Biology and Microbiology, Burnett College of Biomedical Science, 4000 Central Florida Blvd., Bldg. 20, Rm. 124, University of Central Florida, Orlando, FL 32816-2364 USA. Telephone: (407) 823-4262. Fax: (407) 823-0956. E-mail:
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Cléry A, Bourguignon-Igel V, Allmang C, Krol A, Branlant C. An improved definition of the RNA-binding specificity of SECIS-binding protein 2, an essential component of the selenocysteine incorporation machinery. Nucleic Acids Res 2007; 35:1868-84. [PMID: 17332014 PMCID: PMC1874613 DOI: 10.1093/nar/gkm066] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
By binding to SECIS elements located in the 3′-UTR of selenoprotein mRNAs, the protein SBP2 plays a key role in the assembly of the selenocysteine incorporation machinery. SBP2 contains an L7Ae/L30 RNA-binding domain similar to that of protein 15.5K/Snu13p, which binds K-turn motifs with a 3-nt bulge loop closed by a tandem of G.A and A.G pairs. Here, by SELEX experiments, we demonstrate the capacity of SBP2 to bind such K-turn motifs with a protruding U residue. However, we show that conversion of the bulge loop into an internal loop reinforces SBP2 affinity and to a greater extent RNP stability. Opposite variations were found for Snu13p. Accordingly, footprinting assays revealed strong contacts of SBP2 with helices I and II and the 5′-strand of the internal loop, as opposed to the loose interaction of Snu13p. Our data also identifies new determinants for SBP2 binding which are located in helix II. Among the L7Ae/L30 family members, these determinants are unique to SBP2. Finally, in accordance with functional data on SECIS elements, the identity of residues at positions 2 and 3 in the loop influences SBP2 affinity. Altogether, the data provide a very precise definition of the SBP2 RNA specificity.
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Affiliation(s)
- A. Cléry
- Laboratoire de Maturation des ARN et Enzymologie Moléculaire – UMR 7567 CNRS-UHP, Nancy Université, Faculté des Sciences et Techniques – BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France and Architecture et Réactivité de l'arN – CNRS-Université Louis Pasteur, Institut de Biologie Moléculaire et Cellulaire 15 Rue René Descartes, 67084 Strasbourg Cedex, France
| | - V. Bourguignon-Igel
- Laboratoire de Maturation des ARN et Enzymologie Moléculaire – UMR 7567 CNRS-UHP, Nancy Université, Faculté des Sciences et Techniques – BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France and Architecture et Réactivité de l'arN – CNRS-Université Louis Pasteur, Institut de Biologie Moléculaire et Cellulaire 15 Rue René Descartes, 67084 Strasbourg Cedex, France
| | - C. Allmang
- Laboratoire de Maturation des ARN et Enzymologie Moléculaire – UMR 7567 CNRS-UHP, Nancy Université, Faculté des Sciences et Techniques – BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France and Architecture et Réactivité de l'arN – CNRS-Université Louis Pasteur, Institut de Biologie Moléculaire et Cellulaire 15 Rue René Descartes, 67084 Strasbourg Cedex, France
| | - A. Krol
- Laboratoire de Maturation des ARN et Enzymologie Moléculaire – UMR 7567 CNRS-UHP, Nancy Université, Faculté des Sciences et Techniques – BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France and Architecture et Réactivité de l'arN – CNRS-Université Louis Pasteur, Institut de Biologie Moléculaire et Cellulaire 15 Rue René Descartes, 67084 Strasbourg Cedex, France
| | - C. Branlant
- Laboratoire de Maturation des ARN et Enzymologie Moléculaire – UMR 7567 CNRS-UHP, Nancy Université, Faculté des Sciences et Techniques – BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France and Architecture et Réactivité de l'arN – CNRS-Université Louis Pasteur, Institut de Biologie Moléculaire et Cellulaire 15 Rue René Descartes, 67084 Strasbourg Cedex, France
- *To whom the correspondence should be addressed. 33 38368430333 383684307
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Allmang C, Krol A. Selenoprotein synthesis: UGA does not end the story. Biochimie 2006; 88:1561-71. [PMID: 16737768 DOI: 10.1016/j.biochi.2006.04.015] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Accepted: 04/24/2006] [Indexed: 11/15/2022]
Abstract
It is well established that the beneficial effects of the trace element selenium are mediated by its major biological product, the amino acid selenocysteine, present in the active site of selenoproteins. These fulfill different functions, as varied as oxidation-reduction of metabolites in bacteria, reduction of reactive oxygen species, control of the redox status of the cell or thyroid hormone maturation. This review will focus on the singularities of the selenocysteine biosynthesis pathway and its unique incorporation mechanism into eukaryal selenoproteins. Selenocysteine biosynthesis from serine is achieved on tRNA(Sec) and requires four proteins. As this amino acid is encoded by an in-frame UGA codon, otherwise signaling termination of translation, ribosomes must be told not to stop at this position in the mRNA. Several molecular partners acting in cis or in trans have been identified, but their knowledge has not enabled yet to firmly establish the molecular events underlying this mechanism. Data suggest that other, so far uncharacterized factors might exist. In this survey, we attempted to compile all the data available in the literature and to describe the latest developments in the field.
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Affiliation(s)
- C Allmang
- Institut de Biologie Moléculaire et Cellulaire, UPR 9002 du CNRS Architecture et Réactivité de l'ARN. Université Louis-Pasteur, 15, rue René-Descartes, 67084 Strasbourg Cedex, France
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Small-Howard A, Morozova N, Stoytcheva Z, Forry EP, Mansell JB, Harney JW, Carlson BA, Xu XM, Hatfield DL, Berry MJ. Supramolecular complexes mediate selenocysteine incorporation in vivo. Mol Cell Biol 2006; 26:2337-46. [PMID: 16508009 PMCID: PMC1430297 DOI: 10.1128/mcb.26.6.2337-2346.2006] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Selenocysteine incorporation in eukaryotes occurs cotranslationally at UGA codons via the interactions of RNA-protein complexes, one comprised of selenocysteyl (Sec)-tRNA([Ser]Sec) and its specific elongation factor, EFsec, and another consisting of the SECIS element and SECIS binding protein, SBP2. Other factors implicated in this pathway include two selenophosphate synthetases, SPS1 and SPS2, ribosomal protein L30, and two factors identified as binding tRNA([Ser]Sec), termed soluble liver antigen/liver protein (SLA/LP) and SECp43. We report that SLA/LP and SPS1 interact in vitro and in vivo and that SECp43 cotransfection increases this interaction and redistributes all three proteins to a predominantly nuclear localization. We further show that SECp43 interacts with the selenocysteyl-tRNA([Ser]Sec)-EFsec complex in vitro, and SECp43 coexpression promotes interaction between EFsec and SBP2 in vivo. Additionally, SECp43 increases selenocysteine incorporation and selenoprotein mRNA levels, the latter presumably due to circumvention of nonsense-mediated decay. Thus, SECp43 emerges as a key player in orchestrating the interactions and localization of the other factors involved in selenoprotein biosynthesis. Finally, our studies delineating the multiple, coordinated protein-nucleic acid interactions between SECp43 and the previously described selenoprotein cotranslational factors resulted in a model of selenocysteine biosynthesis and incorporation dependent upon both cytoplasmic and nuclear supramolecular complexes.
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Affiliation(s)
- Andrea Small-Howard
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96822, USA
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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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