1
|
Vindry C, Guillin O, Wolff P, Marie P, Mortreux F, Mangeot P, Ohlmann T, Chavatte L. A homozygous mutation in the human selenocysteine tRNA gene impairs UGA recoding activity and selenoproteome regulation by selenium. Nucleic Acids Res 2023; 51:7580-7601. [PMID: 37254812 PMCID: PMC10415148 DOI: 10.1093/nar/gkad482] [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: 11/21/2022] [Revised: 05/04/2023] [Accepted: 05/22/2023] [Indexed: 06/01/2023] Open
Abstract
The selenocysteine (Sec) tRNA (tRNA[Ser]Sec) governs Sec insertion into selenoproteins by the recoding of a UGA codon, typically used as a stop codon. A homozygous point mutation (C65G) in the human tRNA[Ser]Sec acceptor arm has been reported by two independent groups and was associated with symptoms such as thyroid dysfunction and low blood selenium levels; however, the extent of altered selenoprotein synthesis resulting from this mutation has yet to be comprehensively investigated. In this study, we used CRISPR/Cas9 technology to engineer homozygous and heterozygous mutant human cells, which we then compared with the parental cell lines. This C65G mutation affected many aspects of tRNA[Ser]Sec integrity and activity. Firstly, the expression level of tRNA[Ser]Sec was significantly reduced due to an altered recruitment of RNA polymerase III at the promoter. Secondly, selenoprotein expression was strongly altered, but, more surprisingly, it was no longer sensitive to selenium supplementation. Mass spectrometry analyses revealed a tRNA isoform with unmodified wobble nucleotide U34 in mutant cells that correlated with reduced UGA recoding activities. Overall, this study demonstrates the pleiotropic effect of a single C65G mutation on both tRNA phenotype and selenoproteome expression.
Collapse
Affiliation(s)
- Caroline Vindry
- CIRI, Centre International de Recherche en Infectiologie, 69007 Lyon, France
- INSERM U1111, 69007 Lyon, France
- Ecole Normale Supérieure de Lyon, Lyon, France
- Université Lyon 1, Lyon, France
- CNRS/ENS/UCBL1 UMR5308, 69007 Lyon, France
| | - Olivia Guillin
- CIRI, Centre International de Recherche en Infectiologie, 69007 Lyon, France
- INSERM U1111, 69007 Lyon, France
- Ecole Normale Supérieure de Lyon, Lyon, France
- Université Lyon 1, Lyon, France
- CNRS/ENS/UCBL1 UMR5308, 69007 Lyon, France
| | - Philippe Wolff
- Architecture et Réactivité de l’ARN, Institut de Biologie Moléculaire et Cellulaire du CNRS, Université de Strasbourg, F-67084 Strasbourg, France
| | - Paul Marie
- Ecole Normale Supérieure de Lyon, Lyon, France
- Université Lyon 1, Lyon, France
- LBMC, Laboratoire de Biologie et Modélisation de la Cellule, 69007 Lyon, France
- CNRS/ENS/UCBL1 UMR5239, 69007 Lyon, France
- INSERM U1210, 69007 Lyon, France
| | - Franck Mortreux
- Ecole Normale Supérieure de Lyon, Lyon, France
- Université Lyon 1, Lyon, France
- LBMC, Laboratoire de Biologie et Modélisation de la Cellule, 69007 Lyon, France
- CNRS/ENS/UCBL1 UMR5239, 69007 Lyon, France
- INSERM U1210, 69007 Lyon, France
| | - Philippe E Mangeot
- CIRI, Centre International de Recherche en Infectiologie, 69007 Lyon, France
- INSERM U1111, 69007 Lyon, France
- Ecole Normale Supérieure de Lyon, Lyon, France
- Université Lyon 1, Lyon, France
- CNRS/ENS/UCBL1 UMR5308, 69007 Lyon, France
| | - Théophile Ohlmann
- CIRI, Centre International de Recherche en Infectiologie, 69007 Lyon, France
- INSERM U1111, 69007 Lyon, France
- Ecole Normale Supérieure de Lyon, Lyon, France
- Université Lyon 1, Lyon, France
- CNRS/ENS/UCBL1 UMR5308, 69007 Lyon, France
| | - Laurent Chavatte
- CIRI, Centre International de Recherche en Infectiologie, 69007 Lyon, France
- INSERM U1111, 69007 Lyon, France
- Ecole Normale Supérieure de Lyon, Lyon, France
- Université Lyon 1, Lyon, France
- CNRS/ENS/UCBL1 UMR5308, 69007 Lyon, France
| |
Collapse
|
2
|
Jenkins T, Gouge J. Nrf2 in Cancer, Detoxifying Enzymes and Cell Death Programs. Antioxidants (Basel) 2021; 10:1030. [PMID: 34202320 PMCID: PMC8300779 DOI: 10.3390/antiox10071030] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 06/18/2021] [Accepted: 06/21/2021] [Indexed: 12/15/2022] Open
Abstract
Reactive oxygen species (ROS) play an important role in cell proliferation and differentiation. They are also by-products of aerobic living conditions. Their inherent reactivity poses a threat for all cellular components. Cells have, therefore, evolved complex pathways to sense and maintain the redox balance. Among them, Nrf2 (Nuclear factor erythroid 2-related factor 2) plays a crucial role: it is activated under oxidative conditions and is responsible for the expression of the detoxification machinery and antiapoptotic factors. It is, however, a double edge sword: whilst it prevents tumorigenesis in healthy cells, its constitutive activation in cancer promotes tumour growth and metastasis. In addition, recent data have highlighted the importance of Nrf2 in evading programmed cell death. In this review, we will focus on the activation of the Nrf2 pathway in the cytoplasm, the molecular basis underlying Nrf2 binding to the DNA, and the dysregulation of this pathway in cancer, before discussing how Nrf2 contributes to the prevention of apoptosis and ferroptosis in cancer and how it is likely to be linked to detoxifying enzymes containing selenium.
Collapse
Affiliation(s)
- Tabitha Jenkins
- Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, UK
| | - Jerome Gouge
- Institute of Structural and Molecular Biology, Birkbeck College, University of London, London WC1E 7HX, UK
| |
Collapse
|
3
|
The Interaction between Dietary Selenium Intake and Genetics in Determining Cancer Risk and Outcome. Nutrients 2020; 12:nu12082424. [PMID: 32806741 PMCID: PMC7468715 DOI: 10.3390/nu12082424] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 08/05/2020] [Accepted: 08/07/2020] [Indexed: 02/06/2023] Open
Abstract
There is considerable interest in the trace element selenium as a possible cancer chemopreventive dietary component, but supplementation trials have not indicated a clear benefit. Selenium is a critical component of selenium-containing proteins, or selenoproteins. Members of this protein family contain selenium in the form of selenocysteine. Selenocysteine is encoded by an in-frame UGA codon recognized as a selenocysteine codon by a regulatory element, the selenocysteine insertion sequence (SECIS), in the 3′-untranslated region of selenoprotein mRNAs. Epidemiological studies have implicated several selenoprotein genes in cancer risk or outcome based on associations between allelic variations and disease risk or mortality. These polymorphisms can be found in or near the SECIS or in the selenoprotein coding sequence. These variations both function to control protein synthesis and impact the efficiency of protein synthesis in response to the levels of available selenium. Thus, an individual’s genetic makeup and nutritional intake of selenium may interact to predispose them to acquiring cancer or affect cancer progression to lethality.
Collapse
|
4
|
Zoidis E, Seremelis I, Kontopoulos N, Danezis GP. Selenium-Dependent Antioxidant Enzymes: Actions and Properties of Selenoproteins. Antioxidants (Basel) 2018; 7:E66. [PMID: 29758013 PMCID: PMC5981252 DOI: 10.3390/antiox7050066] [Citation(s) in RCA: 203] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 05/07/2018] [Accepted: 05/09/2018] [Indexed: 12/23/2022] Open
Abstract
Unlike other essential trace elements that interact with proteins in the form of cofactors, selenium (Se) becomes co-translationally incorporated into the polypeptide chain as part of 21st naturally occurring amino acid, selenocysteine (Sec), encoded by the UGA codon. Any protein that includes Sec in its polypeptide chain is defined as selenoprotein. Members of the selenoproteins family exert various functions and their synthesis depends on specific cofactors and on dietary Se. The Se intake in productive animals such as chickens affect nutrient utilization, production performances, antioxidative status and responses of the immune system. Although several functions of selenoproteins are unknown, many disorders are related to alterations in selenoprotein expression or activity. Selenium insufficiency and polymorphisms or mutations in selenoproteins' genes and synthesis cofactors are involved in the pathophysiology of many diseases, including cardiovascular disorders, immune dysfunctions, cancer, muscle and bone disorders, endocrine functions and neurological disorders. Finally, heavy metal poisoning decreases mRNA levels of selenoproteins and increases mRNA levels of inflammatory factors, underlying the antagonistic effect of Se. This review is an update on Se dependent antioxidant enzymes, presenting the current state of the art and is focusing on results obtained mainly in chicken.
Collapse
Affiliation(s)
- Evangelos Zoidis
- Department of Nutritional Physiology and Feeding, Faculty of Animal Science and Aquaculture, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Greece.
| | - Isidoros Seremelis
- Chemistry Laboratory, Department of Food Science and Human Nutrition, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Greece.
| | - Nikolaos Kontopoulos
- Chemistry Laboratory, Department of Food Science and Human Nutrition, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Greece.
| | - Georgios P Danezis
- Chemistry Laboratory, Department of Food Science and Human Nutrition, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Greece.
| |
Collapse
|
5
|
Gouge J, Vannini A. New tricks for an old dog: Brf2-dependent RNA Polymerase III transcription in oxidative stress and cancer. Transcription 2017; 9:61-66. [PMID: 28854119 PMCID: PMC5791813 DOI: 10.1080/21541264.2017.1335269] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 05/22/2017] [Accepted: 05/22/2017] [Indexed: 01/07/2023] Open
Abstract
Here, we discuss the role of Brf2, an RNA Polymerase III core transcription factor, as a master switch of the oxidative stress response. We highlight the interplay of Brf2 with the Nrf2/Keap1 pathway, as well as the role of Brf2 in cancer and other possible regulations.
Collapse
|
6
|
Gouge J, Satia K, Guthertz N, Widya M, Thompson AJ, Cousin P, Dergai O, Hernandez N, Vannini A. Redox Signaling by the RNA Polymerase III TFIIB-Related Factor Brf2. Cell 2016; 163:1375-87. [PMID: 26638071 PMCID: PMC4671959 DOI: 10.1016/j.cell.2015.11.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 10/14/2015] [Accepted: 10/23/2015] [Indexed: 01/06/2023]
Abstract
TFIIB-related factor 2 (Brf2) is a member of the family of TFIIB-like core transcription factors. Brf2 recruits RNA polymerase (Pol) III to type III gene-external promoters, including the U6 spliceosomal RNA and selenocysteine tRNA genes. Found only in vertebrates, Brf2 has been linked to tumorigenesis but the underlying mechanisms remain elusive. We have solved crystal structures of a human Brf2-TBP complex bound to natural promoters, obtaining a detailed view of the molecular interactions occurring at Brf2-dependent Pol III promoters and highlighting the general structural and functional conservation of human Pol II and Pol III pre-initiation complexes. Surprisingly, our structural and functional studies unravel a Brf2 redox-sensing module capable of specifically regulating Pol III transcriptional output in living cells. Furthermore, we establish Brf2 as a central redox-sensing transcription factor involved in the oxidative stress pathway and provide a mechanistic model for Brf2 genetic activation in lung and breast cancer. Architectural conservation of TFIIB and TFIIB-related factors Brf2 is a redox-sensing RNA polymerase III core transcription factor Brf2 regulates cellular responses to oxidative stress Brf2 amplification enables cancer cells to evade oxidative stress-induced apoptosis
Collapse
Affiliation(s)
- Jerome Gouge
- Division of Structural Biology, The Institute of Cancer Research, London SW7 3RP, UK
| | - Karishma Satia
- Division of Structural Biology, The Institute of Cancer Research, London SW7 3RP, UK
| | - Nicolas Guthertz
- Division of Structural Biology, The Institute of Cancer Research, London SW7 3RP, UK
| | - Marcella Widya
- Division of Structural Biology, The Institute of Cancer Research, London SW7 3RP, UK
| | - Andrew James Thompson
- Division of Structural Biology, The Institute of Cancer Research, London SW7 3RP, UK
| | - Pascal Cousin
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland
| | - Oleksandr Dergai
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland
| | - Nouria Hernandez
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland
| | - Alessandro Vannini
- Division of Structural Biology, The Institute of Cancer Research, London SW7 3RP, UK.
| |
Collapse
|
7
|
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]
|
8
|
Suzuki T, Kelly VP, Motohashi H, Nakajima O, Takahashi S, Nishimura S, Yamamoto M. Deletion of the Selenocysteine tRNA Gene in Macrophages and Liver Results in Compensatory Gene Induction of Cytoprotective Enzymes by Nrf2. J Biol Chem 2008; 283:2021-30. [DOI: 10.1074/jbc.m708352200] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
|
9
|
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: 856] [Impact Index Per Article: 50.4] [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.
Collapse
Affiliation(s)
- Laura Vanda Papp
- Queensland Institute of Medical Research, Cancer and Cell Biology Division, Herston, QLD, Australia
| | | | | | | |
Collapse
|
10
|
Venardos K, Ashton K, Headrick J, Perkins A. Effects of dietary selenium on post-ischemic expression of antioxidant mRNA. Mol Cell Biochem 2005; 270:131-8. [PMID: 15792362 DOI: 10.1007/s11010-005-5279-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cardiac ischemia reperfusion leads to oxidative stress and poor physiological recovery. Selenium deficiency down-regulates thioredoxin reductase (Txnrd) and glutathione peroxidase (Gpx) activity, impairing recovery from ischemia-reperfusion. Furthermore, selenium supplementation has been shown to be cardioprotective and lessens oxidative stress in reperfused rat hearts. In this study we have investigated the role of selenium in the mRNA expression of these, and related antioxidant proteins, post ischemia-reperfusion. Male rats were fed varying doses of selenium for five weeks. Hearts were isolated and perfused using the Langendorff method with 22.5 min of global ischemia and 45 min reperfusion. RNA was extracted for quantitative real-time PCR analysis of glutathione peroxidase (Gpx)-1 and 4, glutathione reductase (Gsr), thioredoxin peroxidase-2 (Prdx2), thioredoxin (Txn) and thioredoxin reductase (Txnrd)-1 and 2 gene expression. Selenium deficiency produced significant reductions in Gpx-1, Gpx-4, Prdx2, Txnrd-1 and Txnrd-2 expression. Conversely, selenium supplementation of 1000 microg/kg significantly up-regulated Gpx-1, Gpx-4, Txn, Txnrd-1 and Txnrd-2 transcription. Our results show selenium modulates the cardiac mRNA expression of thioredoxin and glutathione related enzymes post ischemia-reperfusion, and impacts on tolerance to ischemia-reperfusion.
Collapse
Affiliation(s)
- Kylie Venardos
- Heart Foundation Research Centre, School of Health Science, Griffith University Gold Coast Campus, Southport, Australia
| | | | | | | |
Collapse
|
11
|
Gu W, Li M, Zhao WM, Fang NX, Bu S, Frazer IH, Zhao KN. tRNASer(CGA) differentially regulates expression of wild-type and codon-modified papillomavirus L1 genes. Nucleic Acids Res 2004; 32:4448-61. [PMID: 15319446 PMCID: PMC516046 DOI: 10.1093/nar/gkh748] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Exogenous transfer RNAs (tRNAs) favor translation of bovine papillomavirus 1 wild-type (wt) L1 mRNA in in vitro translation systems (Zhou et al. 1999, J. Virol., 73, 4972-4982). We, therefore, investigated whether papillomavirus (PV) wt L1 protein expression could be enhanced in eukaryotic cells following exogenous tRNA supplementation. Both Chinese hamster ovary (CHO) and Cos1 cells, transfected with PV1 wt L1 genes, effectively transcribed the genes but did not translate them. However, L1 protein translation was demonstrated following co-transfection with the L1 gene and a gene expressing tRNA(Ser)(CGA). Cell lines, stably transfected with a bovine papillomavirus 1 (BPV1) wt L1 expression construct, produced L1 protein after the transfection of the tRNA(Ser)(CGA) gene, but not following the transfection with basal vectors, suggesting that tRNA(Ser)(CGA) gene enhanced wt L1 translation as a result of endogenous tRNA alterations and phosphorylation of translation initiation factors elF4E and elF2alpha in the tRNA(Ser)(CGA) transfected L1 cell lines. The tRNA(Ser)(CGA) gene expression significantly reduced translation of L1 proteins expressed from codon-modified (HB) PV L1 genes utilizing mammalian preferred codons, but had variable effects on translation of green fluorescent proteins (GFPs) expressed from six serine GFP variants. The changes of tRNA pools appear to match the codon composition of PV wt and HB L1 genes and serine GFP variants to regulate translation of their mRNAs. These findings demonstrate for the first time in eukaryotic cells that translation of the target genes can be differentially influenced by the provision of a single tRNA expression construct.
Collapse
Affiliation(s)
- Wenyi Gu
- Centre for Immunology and Cancer Research, University of Queensland, Princess Alexandra Hospital, Woolloongabba, Queensland 4102, Australia
| | | | | | | | | | | | | |
Collapse
|
12
|
Jameson RR, Diamond AM. A regulatory role for Sec tRNA[Ser]Sec in selenoprotein synthesis. RNA (NEW YORK, N.Y.) 2004; 10:1142-1152. [PMID: 15208449 PMCID: PMC1370604 DOI: 10.1261/rna.7370104] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2004] [Accepted: 04/20/2004] [Indexed: 05/24/2023]
Abstract
Selenium is biologically active through the functions of selenoproteins that contain the amino acid selenocysteine. This amino acid is translated in response to in-frame UGA codons in mRNAs that include a SECIS element in its 3' untranslated region, and this process requires a unique tRNA, referred to as tRNA([Ser]Sec). The translation of UGA as selenocysteine, rather than its use as a termination signal, is a candidate restriction point for the regulation of selenoprotein synthesis by selenium. A specialized reporter construct was used that permits the evaluation of SECIS-directed UGA translation to examine mechanisms of the regulation of selenoprotein translation. Using SECIS elements from five different selenoprotein mRNAs, UGA translation was quantified in response to selenium supplementation and alterations in tRNA([Ser]Sec) levels and isoform distributions. Although each of the evaluated SECIS elements exhibited differences in their baseline activities, each was stimulated to a similar extent by increased selenium or tRNA([Ser]Sec) levels and was inhibited by diminished levels of the methylated isoform of tRNA([Ser]Sec) achieved using a dominant-negative acting mutant tRNA([Ser]Sec). tRNA([Ser]Sec) was found to be limiting for UGA translation under conditions of high selenoprotein mRNA in both a transient reporter assay and in cells with elevated GPx-1 mRNA. This and data indicating increased amounts of the methylated isoform of tRNA([Ser]Sec) during selenoprotein translation indicate that it is this isoform that is translationally active and that selenium-induced tRNA methylation is a mechanism of regulation of the synthesis of selenoproteins.
Collapse
Affiliation(s)
- Ruth R Jameson
- Department of Human Nutrition, University of Illinois at Chicago, 1919 West Taylor Street, MC517, Chicago, IL 60612, USA
| | | |
Collapse
|
13
|
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.
Collapse
Affiliation(s)
- Donna M Driscoll
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
| | | |
Collapse
|