1
|
Transcript Regulation of the Recoded Archaeal α-l-Fucosidase In Vivo. Molecules 2021; 26:molecules26071861. [PMID: 33806142 PMCID: PMC8037382 DOI: 10.3390/molecules26071861] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 02/22/2021] [Accepted: 03/19/2021] [Indexed: 11/17/2022] Open
Abstract
Genetic decoding is flexible, due to programmed deviation of the ribosomes from standard translational rules, globally termed "recoding". In Archaea, recoding has been unequivocally determined only for termination codon readthrough events that regulate the incorporation of the unusual amino acids selenocysteine and pyrrolysine, and for -1 programmed frameshifting that allow the expression of a fully functional α-l-fucosidase in the crenarchaeon Saccharolobus solfataricus, in which several functional interrupted genes have been identified. Increasing evidence suggests that the flexibility of the genetic code decoding could provide an evolutionary advantage in extreme conditions, therefore, the identification and study of interrupted genes in extremophilic Archaea could be important from an astrobiological point of view, providing new information on the origin and evolution of the genetic code and on the limits of life on Earth. In order to shed some light on the mechanism of programmed -1 frameshifting in Archaea, here we report, for the first time, on the analysis of the transcription of this recoded archaeal α-l-fucosidase and of its full-length mutant in different growth conditions in vivo. We found that only the wild type mRNA significantly increased in S. solfataricus after cold shock and in cells grown in minimal medium containing hydrolyzed xyloglucan as carbon source. Our results indicated that the increased level of fucA mRNA cannot be explained by transcript up-regulation alone. A different mechanism related to translation efficiency is discussed.
Collapse
|
2
|
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: 217] [Impact Index Per Article: 36.2] [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
|
3
|
Gharipour M, Sadeghi M, Behmanesh M, Salehi M, Nezafati P, Gharpour A. Selenium Homeostasis and Clustering of Cardiovascular Risk Factors: A Systematic Review. ACTA BIO-MEDICA : ATENEI PARMENSIS 2017; 88:263-270. [PMID: 29083329 PMCID: PMC6142834 DOI: 10.23750/abm.v88i3.5701] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 09/06/2016] [Indexed: 02/07/2023]
Abstract
Selenium is a trace element required for a range of cellular functions. It is widely used for the biosynthesis of the unique amino acid selenocysteine [Sec], which is a structural element of selenoproteins. This systematic review focused on the possible relation between selenium and metabolic risk factors. The literature was searched via PubMed, Scopus, ISI Web of Science, and Google Scholar. Searches were not restricted by time or language. Relevant studies were selected in three phases. After an initial quality assessment, two reviewers extracted all the relevant data, whereas the third reviewer checked their extracted data. All evidence came from experimental and laboratory studies. Selenoprotein P is the best indicator for selenium nutritional levels. In addition, high levels of selenium may increase the risk of metabolic syndrome while the lack of sufficient selenium may also promote metabolic syndrome. selenium supplementation in subjects with sufficient serum selenium levels has a contrary effect on blood pressure, LDL, and total cholesterol. According to the bioavailability of different types of selenium supplementation such as selenomethionine, selenite and selenium-yeast, it seems that the best nutritional type of selenium is selenium-yeast. Regarding obtained results of longitudinal studies and randomized controlled trials, selenium supplementation should not be recommended for primary or secondary cardio-metabolic risk prevention in populations with adequate selenium status.
Collapse
|
4
|
Li M, Cheng W, Luo J, Hu X, Nie T, Lai H, Zheng X, Li F, Li H. Loss of selenocysteine insertion sequence binding protein 2 suppresses the proliferation, migration/invasion and hormone secretion of human trophoblast cells via the PI3K/Akt and ERK signaling pathway. Placenta 2017. [DOI: 10.1016/j.placenta.2017.05.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
5
|
Gharipour M, Sadeghi M, Behmanesh M, Salehi M, Nezafati P, Gharipour A. Selenium Homeostasis and Clustering of Cardiovascular Risk Factors: A Systematic Review. ACTA BIO-MEDICA : ATENEI PARMENSIS 2017; 88. [PMID: 29083329 PMCID: PMC6142834 DOI: 10.23750/abm.v%vi%i.5701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Selenium is a trace element required for a range of cellular functions. It is widely used for the biosynthesis of the unique amino acid selenocysteine [Sec], which is a structural element of selenoproteins. This systematic review focused on the possible relation between selenium and metabolic risk factors. The literature was searched via PubMed, Scopus, ISI Web of Science, and Google Scholar. Searches were not restricted by time or language. Relevant studies were selected in three phases. After an initial quality assessment, two reviewers extracted all the relevant data, whereas the third reviewer checked their extracted data. All evidence came from experimental and laboratory studies. Selenoprotein P is the best indicator for selenium nutritional levels. In addition, high levels of selenium may increase the risk of metabolic syndrome while the lack of sufficient selenium may also promote metabolic syndrome. selenium supplementation in subjects with sufficient serum selenium levels has a contrary effect on blood pressure, LDL, and total cholesterol. According to the bioavailability of different types of selenium supplementation such as selenomethionine, selenite and selenium-yeast, it seems that the best nutritional type of selenium is selenium-yeast. Regarding obtained results of longitudinal studies and randomized controlled trials, selenium supplementation should not be recommended for primary or secondary cardio-metabolic risk prevention in populations with adequate selenium status.
Collapse
Affiliation(s)
- Mojgan Gharipour
- Cardiac Rehabilitation Research Center, Isfahan Cardiovascular Research Institute, Isfahan University of Medicine Sciences, Isfahan, Iran
| | - Masoumeh Sadeghi
- Cardiac Rehabilitation Research Center, Cardiovascular Research Institute, Isfahan University of Medical Sciences, Isfahan, Iran,Correspondence: Dr. Masoumeh Sadeghi Associate Professor in Cardiology, Cardiac Rehabilitation Research Center, Cardiovascular Research Institute, Isfahan University of Medical Sciences, Isfahan, Iran E-mail:
| | - Mehrdad Behmanesh
- Department of Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Mansour Salehi
- Dept. of Genetics and Molecular Biology Medical School, Isfahan University of Medical Sciences
| | - Pouya Nezafati
- Department of Cardiac Surgery, Imam Reza Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Amin Gharipour
- School of Information and Communication Technology, Gold Coast Campus, Griffith University, QLD4222, Australia
| |
Collapse
|
6
|
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.
Collapse
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
| |
Collapse
|
7
|
Martitz J, Hofmann PJ, Johannes J, Köhrle J, Schomburg L, Renko K. Factors impacting the aminoglycoside-induced UGA stop codon readthrough in selenoprotein translation. J Trace Elem Med Biol 2016; 37:104-110. [PMID: 27157664 DOI: 10.1016/j.jtemb.2016.04.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/13/2016] [Accepted: 04/18/2016] [Indexed: 01/24/2023]
Abstract
Aminoglycosides (AG) are oligosaccharide antibiotics that interfere with the small ribosomal subunit in aerobic, Gram-negative bacteria, causing pathogen-destructing error rates in their protein biosynthesis. Aminoglycosides also induce mRNA misinterpretation in eukaryotic cells, especially of the UGA (Opal)-stop codon, albeit to a lower extent. UGA recoding is essentially required for the incorporation of selenocysteine (Sec) into growing selenoproteins during translation. Selenocysteine incorporation requires the presence of a selenoprotein-specific stem-loop structure within the 3'-untranslated region of the mRNA, the so-called Sec-insertion sequence (SECIS) element. Interestingly, selenoprotein genes differ in their SECIS-element sequence and in their UGA base context. We hypothesized that the SECIS-element and the specific codon context synergize in controlling the effects of AG on stop codon readthrough. To this end, the SECIS-elements of glutathione peroxidase 1, glutathione peroxidase 4 and selenoprotein P transcripts were cloned into a reporter system and analyzed in combination with different UGA codon contexts. Our results indicate that a cytosine in position 4 (directly downstream of UGA) confers strongest effects on both the Se- and AG-dependent readthrough. Overall selenoprotein biosynthesis rate depends on the Se-status, AG concentration and the specific SECIS-element present in the transcript. These findings help to get a better understanding for the susceptibility of different transcripts towards AG-mediated interference with the biosynthesis of functional Se-containing selenoproteins, and highlight the importance of the Se-status for successful selenoprotein biosynthesis under antibiotic therapy.
Collapse
Affiliation(s)
- Janine Martitz
- Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, D - 13353 Berlin, Germany
| | - Peter Josef Hofmann
- Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, D - 13353 Berlin, Germany
| | - Jörg Johannes
- Rheinische Friedrich-Wilhelms-Universität, Institut für Biochemie und Molekularbiologie, Bonn, Germany
| | - Josef Köhrle
- Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, D - 13353 Berlin, Germany
| | - Lutz Schomburg
- Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, D - 13353 Berlin, Germany
| | - Kostja Renko
- Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, D - 13353 Berlin, Germany.
| |
Collapse
|
8
|
Gonzalez-Flores JN, Shetty SP, Dubey A, Copeland PR. The molecular biology of selenocysteine. Biomol Concepts 2015; 4:349-65. [PMID: 25436585 DOI: 10.1515/bmc-2013-0007] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 03/22/2013] [Indexed: 01/11/2023] Open
Abstract
Selenium is an essential trace element that is incorporated into 25 human proteins as the amino acid selenocysteine (Sec). The incorporation of this amino acid turns out to be a fascinating problem in molecular biology because Sec is encoded by a stop codon, UGA. Layered on top of the canonical translation elongation machinery is a set of factors that exist solely to incorporate this important amino acid. The mechanism by which this process occurs, put into the context of selenoprotein biology, is the focus of this review.
Collapse
|
9
|
Abstract
Selenium is regulated in the body to maintain vital selenoproteins and to avoid toxicity. When selenium is limiting, cells utilize it to synthesize the selenoproteins most important to them, creating a selenoprotein hierarchy in the cell. The liver is the central organ for selenium regulation and produces excretory selenium forms to regulate whole-body selenium. It responds to selenium deficiency by curtailing excretion and secreting selenoprotein P (Sepp1) into the plasma at the expense of its intracellular selenoproteins. Plasma Sepp1 is distributed to tissues in relation to their expression of the Sepp1 receptor apolipoprotein E receptor-2, creating a tissue selenium hierarchy. N-terminal Sepp1 forms are taken up in the renal proximal tubule by another receptor, megalin. Thus, the regulated whole-body pool of selenium is shifted to needy cells and then to vital selenoproteins in them to supply selenium where it is needed, creating a whole-body selenoprotein hierarchy.
Collapse
Affiliation(s)
- Raymond F Burk
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0252; ,
| | | |
Collapse
|
10
|
Shetty SP, Copeland PR. Selenocysteine incorporation: A trump card in the game of mRNA decay. Biochimie 2015; 114:97-101. [PMID: 25622574 DOI: 10.1016/j.biochi.2015.01.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 01/14/2015] [Indexed: 11/16/2022]
Abstract
The incorporation of the 21st amino acid, selenocysteine (Sec), occurs on mRNAs that harbor in-frame stop codons because the Sec-tRNA(Sec) recognizes a UGA codon. This sets up an intriguing interplay between translation elongation, translation termination and the complex machinery that marks mRNAs that contain premature termination codons for degradation, leading to nonsense mediated mRNA decay (NMD). In this review we discuss the intricate and complex relationship between this key quality control mechanism and the process of Sec incorporation in mammals.
Collapse
Affiliation(s)
- Sumangala P Shetty
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, 675 Hoes Ln, Piscataway, NJ 08854, USA
| | - Paul R Copeland
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, 675 Hoes Ln, Piscataway, NJ 08854, USA.
| |
Collapse
|
11
|
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.
Collapse
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
| |
Collapse
|
12
|
Howard MT, Carlson BA, Anderson CB, Hatfield DL. Translational redefinition of UGA codons is regulated by selenium availability. J Biol Chem 2013; 288:19401-13. [PMID: 23696641 DOI: 10.1074/jbc.m113.481051] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Incorporation of selenium into ~25 mammalian selenoproteins occurs by translational recoding whereby in-frame UGA codons are redefined to encode the selenium containing amino acid, selenocysteine (Sec). Here we applied ribosome profiling to examine the effect of dietary selenium levels on the translational mechanisms controlling selenoprotein synthesis in mouse liver. Dietary selenium levels were shown to control gene-specific selenoprotein expression primarily at the translation level by differential regulation of UGA redefinition and Sec incorporation efficiency, although effects on translation initiation and mRNA abundance were also observed. Direct evidence is presented that increasing dietary selenium causes a vast increase in ribosome density downstream of UGA-Sec codons for a subset of selenoprotein mRNAs and that the selenium-dependent effects on Sec incorporation efficiency are mediated in part by the degree of Sec-tRNA([Ser]Sec) Um34 methylation. Furthermore, we find evidence for translation in the 5'-UTRs for a subset of selenoproteins and for ribosome pausing near the UGA-Sec codon in those mRNAs encoding the selenoproteins most affected by selenium availability. These data illustrate how dietary levels of the trace element selenium can alter the readout of the genetic code to affect the expression of an entire class of proteins.
Collapse
Affiliation(s)
- Michael T Howard
- Department of Human Genetics, University of Utah, Salt Lake City, Utah 84112, USA.
| | | | | | | |
Collapse
|
13
|
Lukashenko NP. Expanding genetic code: Amino acids 21 and 22, selenocysteine and pyrrolysine. RUSS J GENET+ 2010. [DOI: 10.1134/s1022795410080016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
14
|
Esposito AM, Mateyak M, He D, Lewis M, Sasikumar AN, Hutton J, Copeland PR, Kinzy TG. Eukaryotic polyribosome profile analysis. J Vis Exp 2010:1948. [PMID: 20567211 PMCID: PMC3149985 DOI: 10.3791/1948] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Protein synthesis is a complex cellular process that is regulated at many levels. For example, global translation can be inhibited at the initiation phase or the elongation phase by a variety of cellular stresses such as amino acid starvation or growth factor withdrawal. Alternatively, translation of individual mRNAs can be regulated by mRNA localization or the presence of cognate microRNAs. Studies of protein synthesis frequently utilize polyribosome analysis to shed light on the mechanisms of translation regulation or defects in protein synthesis. In this assay, mRNA/ribosome complexes are isolated from eukaryotic cells. A sucrose density gradient separates mRNAs bound to multiple ribosomes known as polyribosomes from mRNAs bound to a single ribosome or monosome. Fractionation of the gradients allows isolation and quantification of the different ribosomal populations and their associated mRNAs or proteins. Differences in the ratio of polyribosomes to monosomes under defined conditions can be indicative of defects in either translation initiation or elongation/termination. Examination of the mRNAs present in the polyribosome fractions can reveal whether the cohort of individual mRNAs being translated changes with experimental conditions. In addition, ribosome assembly can be monitored by analysis of the small and large ribosomal subunit peaks which are also separated by the gradient. In this video, we present a method for the preparation of crude ribosomal extracts from yeast cells, separation of the extract by sucrose gradient and interpretation of the results. This procedure is readily adaptable to mammalian cells.
Collapse
Affiliation(s)
- Anthony M Esposito
- Department of Molecular Genetics, Microbiology, and Immunology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, NJ, USA
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Donovan J, Copeland PR. The efficiency of selenocysteine incorporation is regulated by translation initiation factors. J Mol Biol 2010; 400:659-64. [PMID: 20488192 DOI: 10.1016/j.jmb.2010.05.026] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Revised: 05/10/2010] [Accepted: 05/11/2010] [Indexed: 10/19/2022]
Abstract
Selenocysteine (Sec) incorporation is an essential process required for the production of at least 25 human selenoproteins. This unique amino acid is co-translationally incorporated at specific UGA codons that normally serve as termination signals. Recoding from stop to Sec involves a cis-acting Sec insertion sequence element in the 3' untranslated region of selenoprotein mRNAs as well as Sec insertion sequence binding protein 2, Sec-tRNA(Sec), and the Sec-specific elongation factor, eEFSec. The interplay between recoding and termination at Sec codons has served as a focal point in researching the mechanism of Sec insertion, but the role of translation initiation has not been addressed. In this report, we show that the cricket paralysis virus intergenic internal ribosome entry site is able to support Sec incorporation, thus providing evidence that the canonical functions of translation initiation factors are not required. Additionally, we show that neither a 5' cap nor a 3' poly(A) tail enhances Sec incorporation. Interestingly, however, the presence of the internal ribosome entry site significantly decreases Sec incorporation efficiency, suggesting a role for translation initiation in regulating the efficiency of UGA recoding.
Collapse
Affiliation(s)
- Jesse Donovan
- Department of Molecular Genetics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA
| | | |
Collapse
|
16
|
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]
|
17
|
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.
Collapse
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.
| | | |
Collapse
|
18
|
Zafiriou MP, Deva R, Ciccoli R, Siafaka-Kapadai A, Nigam S. Biological role of hepoxilins: upregulation of phospholipid hydroperoxide glutathione peroxidase as a cellular response to oxidative stress? Prostaglandins Leukot Essent Fatty Acids 2007; 77:209-15. [PMID: 17997296 DOI: 10.1016/j.plefa.2007.08.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 08/08/2007] [Accepted: 08/14/2007] [Indexed: 10/22/2022]
Abstract
The 12S-lipoxygenase (12S-LOX) pathway of arachidonic acid (AA) metabolism is bifurcated at 12(S)-hydroperoxy-5Z,8Z,10E (12S-HpETE) in the reduction route to form 12S-hydroxy-eicosatetraenoic acid (12S-HETE) and in 8(S/R)-hydroxy-11(S),12S-trans-epoxyeicosa-5Z,9E,14Z-trienoic acid (HXA3) synthase pathway, previously known as isomerization route, to form hepoxilins. Earlier we showed that the HXA3 formation is restricted to cellular systems devoid of hydroperoxide reducing enzymes, e.g. GPxs, thus causing a persistent oxidative stress situation. Here, we show that HXA3 at as low as 100 nM concentration upregulates phospholipid hydroperoxide glutathione peroxidase (PHGPx) mRNA and protein expressions, whereas other metabolites of AA metabolism 12S-HpETE and 12S-HETE failed to stimulate the PHGPx. Moreover, the decrease in 12S-HpETE below a threshold value of the hydroperoxide tone causes both suppression of the overall 12S-LOX activity and a shift from HXA3 formation towards 12S-HETE formation. We therefore propose that under persistent oxidative stress the formation of HXA3 and the HXA3-induced upregulation of PHGPx constitute a compensatory defense response to protect the vitality and functionality of the cell.
Collapse
Affiliation(s)
- M P Zafiriou
- Centre for Experimental Gynecology & Breast Research and Eicosanoid Research Division, Charité - Campus University Medical Centre Benjamin Franklin, Berlin, D-12200 Berlin, German.
| | | | | | | | | |
Collapse
|
19
|
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.
Collapse
Affiliation(s)
- Laura Vanda Papp
- Queensland Institute of Medical Research, Cancer and Cell Biology Division, Herston, QLD, Australia
| | | | | | | |
Collapse
|
20
|
Mix H, Lobanov AV, Gladyshev VN. SECIS elements in the coding regions of selenoprotein transcripts are functional in higher eukaryotes. Nucleic Acids Res 2006; 35:414-23. [PMID: 17169995 PMCID: PMC1802603 DOI: 10.1093/nar/gkl1060] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Expression of selenocysteine (Sec)-containing proteins requires the presence of a cis-acting mRNA structure, called selenocysteine insertion sequence (SECIS) element. In bacteria, this structure is located in the coding region immediately downstream of the Sec-encoding UGA codon, whereas in eukaryotes a completely different SECIS element has evolved in the 3′-untranslated region. Here, we report that SECIS elements in the coding regions of selenoprotein mRNAs support Sec insertion in higher eukaryotes. Comprehensive computational analysis of all available viral genomes revealed a SECIS element within the ORF of a naturally occurring selenoprotein homolog of glutathione peroxidase 4 in fowlpox virus. The fowlpox SECIS element supported Sec insertion when expressed in mammalian cells as part of the coding region of viral or mammalian selenoproteins. In addition, readthrough at UGA was observed when the viral SECIS element was located upstream of the Sec codon. We also demonstrate successful de novo design of a functional SECIS element in the coding region of a mammalian selenoprotein. Our data provide evidence that the location of the SECIS element in the untranslated region is not a functional necessity but rather is an evolutionary adaptation to enable a more efficient synthesis of selenoproteins.
Collapse
Affiliation(s)
| | | | - Vadim N. Gladyshev
- To whom correspondence should be addressed. Tel: +1 402 472 4948; Fax: +1 402 472 7842;
| |
Collapse
|
21
|
Stoytcheva Z, Tujebajeva RM, Harney JW, Berry MJ. Efficient incorporation of multiple selenocysteines involves an inefficient decoding step serving as a potential translational checkpoint and ribosome bottleneck. Mol Cell Biol 2006; 26:9177-84. [PMID: 17000762 PMCID: PMC1698516 DOI: 10.1128/mcb.00856-06] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Selenocysteine is incorporated into proteins via "recoding" of UGA from a stop codon to a sense codon, a process that requires specific secondary structures in the 3' untranslated region, termed selenocysteine incorporation sequence (SECIS) elements, and the protein factors that they recruit. Whereas most selenoprotein mRNAs contain a single UGA codon and a single SECIS element, selenoprotein P genes encode multiple UGAs and two SECIS elements. We have identified evolutionary adaptations in selenoprotein P genes that contribute to the efficiency of incorporating multiple selenocysteine residues in this protein. The first is a conserved, inefficiently decoded UGA codon in the N-terminal region, which appears to serve both as a checkpoint for the presence of factors required for selenocysteine incorporation and as a "bottleneck," slowing down the progress of elongating ribosomes. The second adaptation involves the presence of introns downstream of this inefficiently decoded UGA which confer the potential for nonsense-mediated decay when factors required for selenocysteine incorporation are limiting. Third, the two SECIS elements in selenoprotein P mRNA function with differing efficiencies, affecting both the rate and the efficiency of decoding different UGAs. The implications for how these factors contribute to the decoding of multiple selenocysteine residues are discussed.
Collapse
Affiliation(s)
- Zoia Stoytcheva
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, HI 96813, USA
| | | | | | | |
Collapse
|
22
|
Chavatte L, Brown BA, Driscoll DM. Ribosomal protein L30 is a component of the UGA-selenocysteine recoding machinery in eukaryotes. Nat Struct Mol Biol 2005; 12:408-16. [PMID: 15821744 DOI: 10.1038/nsmb922] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Accepted: 03/14/2005] [Indexed: 11/08/2022]
Abstract
The translational recoding of UGA as selenocysteine (Sec) is directed by a SECIS element in the 3' untranslated region (UTR) of eukaryotic selenoprotein mRNAs. The selenocysteine insertion sequence (SECIS) contains two essential tandem sheared G.A pairs that bind SECIS-binding protein 2 (SBP2), which recruits a selenocysteine-specific elongation factor and Sec-tRNA(Sec) to the ribosome. Here we show that ribosomal protein L30 is a component of the eukaryotic selenocysteine recoding machinery. L30 binds SECIS elements in vitro and in vivo, stimulates UGA recoding in transfected cells and competes with SBP2 for SECIS binding. Magnesium, known to induce a kink-turn in RNAs that contain two tandem G.A pairs, decreases the SBP2-SECIS complex in favor of the L30-SECIS interaction. We propose a model in which SBP2 and L30 carry out different functions in the UGA recoding mechanism, with the SECIS acting as a molecular switch upon protein binding.
Collapse
Affiliation(s)
- Laurent Chavatte
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
| | | | | |
Collapse
|
23
|
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
|
24
|
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
|
25
|
Abstract
The regulation of gene expression at the translational level not only allows for rapid changes in specific protein levels but also provides an opportunity to alter codon specificity. For the incorporation of selenocysteine (Sec) into protein, the UGA codon is transformed from one that signals translation termination to one specific for Sec. This review provides a look at Sec incorporation from the perspective of the individual steps involved in protein synthesis: initiation, elongation and termination. The roles of the factors known to be required for Sec incorporation are considered in the context of each step in translation including structural modeling of the differences between the standard elongation factor eEF1A and the Sec-specific counterpart, eEFSec.
Collapse
Affiliation(s)
- Paul R Copeland
- Department of Molecular Genetics, Microbiology and Immunology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 675 Hoes Ln Rm 728, Piscataway, NJ 08854, USA.
| |
Collapse
|
26
|
Affiliation(s)
- Dolph L Hatfield
- Molecular Biology of Selenium Section, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
| | | |
Collapse
|
27
|
Fletcher JE, Copeland PR, Driscoll DM, Krol A. The selenocysteine incorporation machinery: interactions between the SECIS RNA and the SECIS-binding protein SBP2. RNA (NEW YORK, N.Y.) 2001; 7:1442-1453. [PMID: 11680849 PMCID: PMC1370188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The decoding of UGA as a selenocysteine (Sec) codon in mammalian selenoprotein mRNAs requires a selenocysteine insertion sequence (SECIS) element in the 3' untranslated region. The SECIS is a hairpin structure that contains a non-Watson-Crick base-pair quartet with a conserved G.A/A.G tandem in the core of the upper helix. Another essential component of the Sec insertion machinery is SECIS-binding protein 2 (SBP2). In this study, we define the binding site of SBP2 on six different SECIS RNAs using enzymatic and hydroxyl radical footprinting, gel mobility shift analysis, and phosphate-ethylation binding interference. We show that SBP2 binds to a variety of mammalian SECIS elements with similar affinity and that the SBP2 binding site is conserved across species. Based on footprinting studies, SBP2 protects the proximal part of the hairpin and both strands of the lower half of the upper helix that contains the non-Watson-Crick base pair quartet. Gel mobility shift assays showed that the G.A/A.G tandem and internal loop are critical for the binding of SBP2. Modification of phosphates by ethylnitrosourea along both strands of the non-Watson-Crick base pair quartet, on the 5' strand of the lower helix and part of the 5' strand of the internal loop, prevented binding of SBP2. We propose a model in which SBP2 covers the central part of the SECIS RNA, binding to the non-Watson-Crick base pair quartet and to the 5' strands of the lower helix and internal loop. Our results suggest that the affinity of SBP2 for different SECIS elements is not responsible for the hierarchy of selenoprotein expression that is observed in vivo.
Collapse
Affiliation(s)
- J E Fletcher
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Ohio 44195, USA
| | | | | | | |
Collapse
|
28
|
Sun X, Li X, Moriarty PM, Henics T, LaDuca JP, Maquat LE. Nonsense-mediated decay of mRNA for the selenoprotein phospholipid hydroperoxide glutathione peroxidase is detectable in cultured cells but masked or inhibited in rat tissues. Mol Biol Cell 2001; 12:1009-17. [PMID: 11294903 PMCID: PMC32283 DOI: 10.1091/mbc.12.4.1009] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Previous studies of mRNA for classical glutathione peroxidase 1 (GPx1) demonstrated that hepatocytes of rats fed a selenium-deficient diet have less cytoplasmic GPx1 mRNA than hepatocytes of rats fed a selenium-adequate diet. This is because GPx1 mRNA is degraded by the surveillance pathway called nonsense-mediated mRNA decay (NMD) when the selenocysteine codon is recognized as nonsense. Here, we examine the mechanism by which the abundance of phospholipid hydroperoxide glutathione peroxidase (PHGPx) mRNA, another selenocysteine-encoding mRNA, fails to decrease in the hepatocytes and testicular cells of rats fed a selenium-deficient diet. We demonstrate with cultured NIH3T3 fibroblasts or H35 hepatocytes transiently transfected with PHGPx gene variants under selenium-supplemented or selenium-deficient conditions that PHGPx mRNA is, in fact, a substrate for NMD when the selenocysteine codon is recognized as nonsense. We also demonstrate that the endogenous PHGPx mRNA of untransfected H35 cells is subject to NMD. The failure of previous reports to detect the NMD of PHGPx mRNA in cultured cells is likely attributable to the expression of PHGPx cDNA rather than the PHGPx gene. We conclude that 1) the sequence of the PHGPx gene is adequate to support the NMD of product mRNA, and 2) there is a mechanism in liver and testis but not cultured fibroblasts and hepatocytes that precludes or masks the NMD of PHGPx mRNA.
Collapse
Affiliation(s)
- X Sun
- Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
| | | | | | | | | | | |
Collapse
|
29
|
Copeland PR, Stepanik VA, Driscoll DM. Insight into mammalian selenocysteine insertion: domain structure and ribosome binding properties of Sec insertion sequence binding protein 2. Mol Cell Biol 2001; 21:1491-8. [PMID: 11238886 PMCID: PMC86695 DOI: 10.1128/mcb.21.5.1491-1498.2001] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cotranslational incorporation of the unusual amino acid selenocysteine (Sec) into both prokaryotic and eukaryotic proteins requires the recoding of a UGA stop codon as one specific for Sec. The recognition of UGA as Sec in mammalian selenoproteins requires a Sec insertion sequence (SECIS) element in the 3' untranslated region as well as the SECIS binding protein SBP2. Here we report a detailed analysis of SBP2 structure and function using truncation and site-directed mutagenesis. We have localized the RNA binding domain to a conserved region shared with several ribosomal proteins and eukaryotic translation termination release factor 1. We also identified a separate and novel functional domain N-terminal to the RNA binding domain which was required for Sec insertion but not for SECIS binding. Conversely, we showed that the RNA binding domain was necessary but not sufficient for Sec insertion and that the conserved glycine residue within this domain was required for SECIS binding. Using glycerol gradient sedimentation, we found that SBP2 was stably associated with the ribosomal fraction of cell lysates and that this interaction was not dependent on its SECIS binding activity. This interaction also occurred with purified components in vitro, and we present data which suggest that the SBP2-ribosome interaction occurs via 28S rRNA. SBP2 may, therefore, have a distinct function in selecting the ribosomes to be used for Sec insertion.
Collapse
MESH Headings
- 3' Untranslated Regions
- Amino Acid Sequence
- Animals
- Centrifugation, Density Gradient
- Codon, Terminator
- Electrophoresis, Polyacrylamide Gel
- Glycerol/metabolism
- Humans
- Models, Genetic
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Peptide Termination Factors/metabolism
- Point Mutation
- Protein Binding
- Protein Biosynthesis
- Protein Structure, Tertiary
- RNA/metabolism
- RNA, Ribosomal, 28S/metabolism
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/physiology
- Rats
- Recombinant Proteins/metabolism
- Ribosomes/metabolism
- Selenocysteine/chemistry
- Selenocysteine/genetics
- Sequence Homology, Amino Acid
- Tumor Cells, Cultured
Collapse
Affiliation(s)
- P R Copeland
- Department of Cell Biology, Cleveland Clinic Foundation, Lerner Research Institute, Cleveland, Ohio 44195, USA
| | | | | |
Collapse
|