101
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Ganichkin OM, Xu XM, Carlson BA, Mix H, Hatfield DL, Gladyshev VN, Wahl MC. Structure and catalytic mechanism of eukaryotic selenocysteine synthase. J Biol Chem 2007; 283:5849-65. [PMID: 18093968 DOI: 10.1074/jbc.m709342200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In eukaryotes and Archaea, selenocysteine synthase (SecS) converts O-phospho-L-seryl-tRNA [Ser]Sec into selenocysteyl-tRNA [Ser]Sec using selenophosphate as the selenium donor compound. The molecular mechanisms underlying SecS activity are presently unknown. We have delineated a 450-residue core of mouse SecS, which retained full selenocysteyl-tRNA [Ser]Sec synthesis activity, and determined its crystal structure at 1.65 A resolution. SecS exhibits three domains that place it in the fold type I family of pyridoxal phosphate (PLP)-dependent enzymes. Two SecS monomers interact intimately and together build up two identical active sites around PLP in a Schiff-base linkage with lysine 284. Two SecS dimers further associate to form a homotetramer. The N terminus, which mediates tetramer formation, and a large insertion that remodels the active site set SecS aside from other members of the family. The active site insertion contributes to PLP binding and positions a glutamate next to the PLP, where it could repel substrates with a free alpha-carboxyl group, suggesting why SecS does not act on free O-phospho-l-serine. Upon soaking crystals in phosphate buffer, a previously disordered loop within the active site insertion contracted to form a phosphate binding site. Residues that are strictly conserved in SecS orthologs but variant in related enzymes coordinate the phosphate and upon mutation corrupt SecS activity. Modeling suggested that the phosphate loop accommodates the gamma-phosphate moiety of O-phospho-l-seryl-tRNA [Ser]Sec and, after phosphate elimination, binds selenophosphate to initiate attack on the proposed aminoacrylyl-tRNA [Ser]Sec intermediate. Based on these results and on the activity profiles of mechanism-based inhibitors, we offer a detailed reaction mechanism for the enzyme.
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Affiliation(s)
- Oleg M Ganichkin
- Max-Planck-Institut für Biophysikalische Chemie, Zelluläre Biochemie/Makromolekulare Röntgenkristallographie, Am Fassberg 11, D-37077 Göttingen, Germany
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102
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Xu XM, Carlson BA, Zhang Y, Mix H, Kryukov GV, Glass RS, Berry MJ, Gladyshev VN, Hatfield DL. New developments in selenium biochemistry: selenocysteine biosynthesis in eukaryotes and archaea. Biol Trace Elem Res 2007; 119:234-41. [PMID: 17916946 DOI: 10.1007/s12011-007-8003-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 12/14/2022]
Abstract
We used comparative genomics and experimental analyses to show that (1) eukaryotes and archaea, which possess the selenocysteine (Sec) protein insertion machinery contain an enzyme, O-phosphoseryl-transfer RNA (tRNA) [Ser]Sec kinase (designated PSTK), which phosphorylates seryl-tRNA [Ser]Sec to form O-phosphoseryl-tRNA [Ser]Sec and (2) the Sec synthase (SecS) in mammals is a pyridoxal phosphate-containing protein previously described as the soluble liver antigen (SLA). SecS uses the product of PSTK, O-phosphoseryl-tRNA[Ser]Sec, and selenophosphate as substrates to generate selenocysteyl-tRNA [Ser]Sec. Sec could be synthesized on tRNA [Ser]Sec from selenide, adenosine triphosphate (ATP), and serine using tRNA[Ser]Sec, seryl-tRNA synthetase, PSTK, selenophosphate synthetase, and SecS. The enzyme that synthesizes monoselenophosphate is a previously identified selenoprotein, selenophosphate synthetase 2 (SPS2), whereas the previously identified mammalian selenophosphate synthetase 1 did not serve this function. Monoselenophosphate also served directly in the reaction replacing ATP, selenide, and SPS2, demonstrating that this compound was the active selenium donor. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that contain selenoproteins.
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Affiliation(s)
- Xue-Ming Xu
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Institutes of Health, Bethesda, MD 20892, USA
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103
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Sengupta A, Carlson BA, Hoffmann VJ, Gladyshev VN, Hatfield DL. Loss of housekeeping selenoprotein expression in mouse liver modulates lipoprotein metabolism. Biochem Biophys Res Commun 2007; 365:446-52. [PMID: 17996733 DOI: 10.1016/j.bbrc.2007.10.189] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Accepted: 10/28/2007] [Indexed: 11/20/2022]
Abstract
Selenium is incorporated into proteins as selenocysteine (Sec), which is dependent on its specific tRNA, designated tRNA([Ser]Sec). Targeted removal of the tRNA([Ser]Sec) gene (Trsp) in mouse hepatocytes previously demonstrated the importance of selenoproteins in liver function. Herein, analysis of plasma proteins in this Trsp knockout mouse revealed increases in apolipoprotein E (ApoE) that was accompanied by elevated plasma cholesterol levels. The expression of genes involved in cholesterol biosynthesis, metabolism and transport were also altered in knockout mice. Additionally, in two transgenic Trsp mutant mouse lines (wherein only housekeeping selenoprotein synthesis was restored), the expression of ApoE, as well as genes involved in cholesterol biosynthesis, metabolism and transport were similar to those observed in wild type mice. These data correlate with reports that selenium deficiency results in increased levels of ApoE, indicating for the first time that housekeeping selenoproteins have a role in regulating lipoprotein biosynthesis and metabolism.
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Affiliation(s)
- Aniruddha Sengupta
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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104
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Yoo MH, Xu XM, Carlson BA, Patterson AD, Gladyshev VN, Hatfield DL. Targeting thioredoxin reductase 1 reduction in cancer cells inhibits self-sufficient growth and DNA replication. PLoS One 2007; 2:e1112. [PMID: 17971875 PMCID: PMC2040202 DOI: 10.1371/journal.pone.0001112] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 10/12/2007] [Indexed: 01/11/2023] Open
Abstract
Thioredoxin reductase 1 (TR1) is a major redox regulator in mammalian cells. As an important antioxidant selenoprotein, TR1 is thought to participate in cancer prevention, but is also known to be over-expressed in many cancer cells. Numerous cancer drugs inhibit TR1, and this protein has been proposed as a target for cancer therapy. We previously reported that reduction of TR1 levels in cancer cells reversed many malignant characteristics suggesting that deficiency in TR1 function is antitumorigenic. The molecular basis for TR1's role in cancer development, however, is not understood. Herein, we found that, among selenoproteins, TR1 is uniquely overexpressed in cancer cells and its knockdown in a mouse cancer cell line driven by oncogenic k-ras resulted in morphological changes characteristic of parental (normal) cells, without significant effect on cell growth under normal growth conditions. When grown in serum-deficient medium, TR1 deficient cancer cells lose self-sufficiency of growth, manifest a defective progression in their S phase and a decreased expression of DNA polymerase α, an enzyme important in DNA replication. These observations provide evidence that TR1 is critical for self-sufficiency in growth signals of malignant cells, that TR1 acts largely as a pro-cancer protein and it is indeed a primary target in cancer therapy.
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Affiliation(s)
- Min-Hyuk Yoo
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Xue-Ming Xu
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Bradley A. Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Andrew D. Patterson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Vadim N. Gladyshev
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Dolph L. Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail:
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105
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Carlson BA, Moustafa ME, Sengupta A, Schweizer U, Shrimali R, Rao M, Zhong N, Wang S, Feigenbaum L, Lee BJ, Gladyshev VN, Hatfield DL. Selective restoration of the selenoprotein population in a mouse hepatocyte selenoproteinless background with different mutant selenocysteine tRNAs lacking Um34. J Biol Chem 2007; 282:32591-602. [PMID: 17848557 DOI: 10.1074/jbc.m707036200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Novel mouse models were developed in which the hepatic selenoprotein population was targeted for removal by disrupting the selenocysteine (Sec) tRNA([Ser]Sec) gene (trsp), and selenoprotein expression was then restored by introducing wild type or mutant trsp transgenes. The selenoprotein population was partially replaced in liver with mutant transgenes encoding mutations at either position 34 (34T-->A) or 37 (37A-->G) in tRNA([Ser]Sec). The A34 transgene product lacked the highly modified 5-methoxycarbonylmethyl-2'-O-methyluridine, and its mutant base A was converted to I34. The G37 transgene product lacked the highly modified N(6)-isopentenyladenosine. Both mutant tRNAs lacked the 2'-methylribose at position 34 (Um34), and both supported expression of housekeeping selenoproteins (e.g. thioredoxin reductase 1) in liver but not stress-related proteins (e.g. glutathione peroxidase 1). Thus, Um34 is responsible for synthesis of a select group of selenoproteins rather than the entire selenoprotein population. The ICA anticodon in the A34 mutant tRNA decoded Cys codons, UGU and UGC, as well as the Sec codon, UGA. However, metabolic labeling of A34 transgenic mice with (75)Se revealed that selenoproteins incorporated the label from the A34 mutant tRNA, whereas other proteins did not. These results suggest that the A34 mutant tRNA did not randomly insert Sec in place of Cys, but specifically targeted selected selenoproteins. High copy numbers of A34 transgene, but not G37 transgene, were not tolerated in the absence of wild type trsp, further suggesting insertion of Sec in place of Cys in selenoproteins.
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Affiliation(s)
- Bradley A Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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106
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Abstract
Selenocysteine insertion during decoding of eukaryotic selenoprotein mRNA requires several trans-acting factors and a cis-acting selenocysteine insertion sequence (SECIS) usually located in the 3' UTR. A second cis-acting selenocysteine codon redefinition element (SRE) has recently been described that resides near the UGA-Sec codon of selenoprotein N (SEPN1). Similar phylogenetically conserved elements can be predicted in a subset of eukaryotic selenoprotein mRNAs. Previous experimental analysis of the SEPN1 SRE revealed it to have a stimulatory effect on readthrough of the UGA-Sec codon, which was not dependent upon the presence of a SECIS element in the 3' UTR; although, as expected, readthrough efficiency was further elevated by inclusion of a SECIS. In order to examine the nature of the redefinition event stimulated by the SEPN1 SRE, we have modified an experimentally tractable in vitro translation system that recapitulates efficient selenocysteine insertion. The results presented here illustrate that the SRE element has a stimulatory effect on decoding of the UGA-Sec codon by both the methylated and unmethylated isoforms of Sec tRNA([Ser]Sec), and confirm that efficient selenocysteine insertion is dependent on the presence of a 3'-UTR SECIS. The variation in recoding elements predicted near UGA-Sec codons implies that these elements may play a differential role in determining the amount of selenoprotein produced by acting as controllers of UGA decoding efficiency.
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Affiliation(s)
- Michael T Howard
- Department of Human Genetics, University of Utah, Salt Lake City, Utah 84112, USA.
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107
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Yoo MH, Xu XM, Turanov AA, Carlson BA, Gladyshev VN, Hatfield DL. A new strategy for assessing selenoprotein function: siRNA knockdown/knock-in targeting the 3'-UTR. RNA 2007; 13:921-9. [PMID: 17468436 PMCID: PMC1869036 DOI: 10.1261/rna.533007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Selenocysteine insertion into protein in mammalian cells requires RNA elements in the 3'-untranslated regions (3'-UTRs) of selenoprotein genes. The occurrence of these conserved sequences should make selenoproteins particularly amenable for knockdown/knock-in strategies to examine selenoprotein functions. Herein, we utilized the 3'-UTR of various selenoproteins to knock down their expression using siRNAs and then knock in expression using constructs containing mutations within the target region. Thioredoxin reductase 1 (TR1) knockdown in a mouse kidney cell line resulted in the cells growing about 10% more slowly, being more sensitive to UV radiation, and having increased apoptosis in response to UV than control cells. The knockdown cells transfected with a construct encoding the wild-type TR1 gene and having mutations in the sequences targeted by siRNA restored TR1 expression and catalytic activity, rendered the knockdown cells less sensitive to UV, and protected the cells against apoptosis. We also applied this technique to other selenoproteins, selenophosphate synthetase 2 and glutathione peroxidase 1, and found that mRNA and protein levels were restored following transfection of knockdown cells with the corresponding knock-in constructs. In addition to important new insights into the functions of key mammalian selenoproteins, the data suggest that the RNAi-based knock-in technology could distinguish phenotypes due to off-targeting and provide a new method for examining many of the subtleties of selenoprotein function not available using RNAi technology alone.
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Affiliation(s)
- Min-Hyuk Yoo
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Institutes of Health, Bethesda, Maryland 20892, USA
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108
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Sheridan PA, Zhong N, Carlson BA, Perella CM, Hatfield DL, Beck MA. Decreased selenoprotein expression alters the immune response during influenza virus infection in mice. J Nutr 2007; 137:1466-71. [PMID: 17513408 DOI: 10.1093/jn/137.6.1466] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Previous work from our laboratory demonstrated that host selenium (Se) deficiency results in greater lung pathology and altered immune function in mice infected with influenza virus. Because selenoproteins play a key role in determining the oxidant status of the host, we utilized a transgenic mouse line carrying a mutant selenocysteine (Sec) tRNA ([Ser]Sec) transgene (t-trspi(6)A(-)). The levels of selenoproteins are decreased in these mice in a protein- and tissue-specific manner. Male t-trspi(6)A(-) and wild-type (WT) mice were infected with influenza and killed at various time points postinfection (p.i.). Lung mRNA levels for innate and pro-inflammatory cytokines increased with infection but did not differ between groups. However, at d 2 p.i., chemokine levels were greater in the t-trspi(6)A(-) mice compared with WT mice. Additionally, IFN-gamma was higher at d 7 p.i. in the t-trspi(6)A(-) mice and viral clearance slower. Despite these immune system changes, lung pathology was similar in t-trspi(6)A(-) and WT mice. (75)Se labeling experiments demonstrated that glutathione peroxidase (GPX)-1 and thioredoxin reductase, although greatly diminished in the lungs of t-trspi(6)A(-) mice, were not altered as a result of infection. GPX-1 activity in the lungs of the t-trspi(6)A(-) mice was approximately 82% of the WT mice. In addition, the GPX-1 activity in the lungs of Se-deficient mice was 125% less than in the t-trspi(6)A(-) mice. These results suggest that although selenoproteins are important for immune function, there is a threshold of GPX-1 activity that can prevent an increase in lung pathology during influenza infection.
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Affiliation(s)
- Patricia A Sheridan
- Department of Nutrition, University of North Carolina, Chapel Hill, NC 27599, USA
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109
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Xu XM, Carlson BA, Mix H, Zhang Y, Saira K, Glass RS, Berry MJ, Gladyshev VN, Hatfield DL. Biosynthesis of selenocysteine on its tRNA in eukaryotes. PLoS Biol 2007; 5:e4. [PMID: 17194211 PMCID: PMC1717018 DOI: 10.1371/journal.pbio.0050004] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Accepted: 11/01/2006] [Indexed: 12/02/2022] Open
Abstract
Selenocysteine (Sec) is cotranslationally inserted into protein in response to UGA codons and is the 21st amino acid in the genetic code. However, the means by which Sec is synthesized in eukaryotes is not known. Herein, comparative genomics and experimental analyses revealed that the mammalian Sec synthase (SecS) is the previously identified pyridoxal phosphate-containing protein known as the soluble liver antigen. SecS required selenophosphate and O-phosphoseryl-tRNA[Ser]Sec as substrates to generate selenocysteyl-tRNA[Ser]Sec. Moreover, it was found that Sec was synthesized on the tRNA scaffold from selenide, ATP, and serine using tRNA[Ser]Sec, seryl-tRNA synthetase, O-phosphoseryl-tRNA[Ser]Sec kinase, selenophosphate synthetase, and SecS. By identifying the pathway of Sec biosynthesis in mammals, this study not only functionally characterized SecS but also assigned the function of the O-phosphoseryl-tRNA[Ser]Sec kinase. In addition, we found that selenophosphate synthetase 2 could synthesize monoselenophosphate in vitro but selenophosphate synthetase 1 could not. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that synthesize selenoproteins. Sec synthase, a conserved protein responsible for the biosynthesis of the rare 21st amino acid, selenocysteine, is identified in eukaryotes, and the underlying biochemical pathway is characterized. Biosynthesis of the 20 canonical amino acids is well established in eukaryotes. However, many eukaryotes also have a rare selenium-containing amino acid, selenocysteine, which is the 21st amino acid in the genetic code. Selenium is essential for human health, and its health benefits, including preventing cancer and heart disease and delaying aging, have been attributed to the presence of selenocysteine in protein. How selenocysteine is made in eukaryotes has not been established. To gain insight into its biosynthesis, we used computational analyses to search completely sequenced genomes for proteins that occur exclusively in organisms that utilize selenocysteine. This approach revealed a putative selenocysteine synthase, which had been previously identified as a pyridoxal phosphate–containing protein dubbed soluble liver antigen. We were able to characterize the activity of this synthase using selenophosphate and a tRNA aminoacylated with phosphoserine as substrates to generate selenocysteine. Moreover, identification of selenocysteine synthase allowed us to delineate the entire pathway of selenocysteine biosynthesis in mammals. Interestingly, selenocysteine synthase is present only in those archaea and eukaryotes that make selenoproteins, indicating that the newly defined pathway of selenocysteine biosynthesis is active in these domains of life.
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Affiliation(s)
- Xue-Ming Xu
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Bradley A Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Heiko Mix
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Yan Zhang
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Kazima Saira
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Richard S Glass
- Department of Chemistry, The University of Arizona, Tucson, Arizona, United States of America
| | - Marla J Berry
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
| | - Vadim N Gladyshev
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Dolph L Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail:
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110
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Dikiy A, Novoselov SV, Fomenko DE, Sengupta A, Carlson BA, Cerny RL, Ginalski K, Grishin NV, Hatfield DL, Gladyshev VN. SelT, SelW, SelH, and Rdx12: genomics and molecular insights into the functions of selenoproteins of a novel thioredoxin-like family. Biochemistry 2007; 46:6871-82. [PMID: 17503775 DOI: 10.1021/bi602462q] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Selenium is an essential trace element in many life forms due to its occurrence as a selenocysteine (Sec) residue in selenoproteins. The majority of mammalian selenoproteins, however, have no known function. Herein, we performed extensive sequence similarity searches to define and characterize a new protein family, designated Rdx, that includes mammalian selenoproteins SelW, SelV, SelT and SelH, bacterial SelW-like proteins and cysteine-containing proteins of unknown function in all three domains of life. An additional member of this family is a mammalian cysteine-containing protein, designated Rdx12, and its fish selenoprotein orthologue. Rdx proteins are proposed to possess a thioredoxin-like fold and a conserved CxxC or CxxU (U is Sec) motif, suggesting a redox function. We cloned and characterized three mammalian members of this family, which showed distinct expression patterns in mouse tissues and different localization patterns in cells transfected with the corresponding GFP fusion proteins. By analogy to thioredoxin, Rdx proteins can use catalytic cysteine (or Sec) to form transient mixed disulfides with substrate proteins. We employed this property to identify cellular targets of Rdx proteins using affinity columns containing mutant versions of these proteins. Rdx12 was found to interact with glutathione peroxidase 1, whereas 14-3-3 protein was identified as one of the targets of mammalian SelW, suggesting a mechanism for redox regulation of the 14-3-3 family of proteins.
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Affiliation(s)
- Alexander Dikiy
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588, USA
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111
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Affiliation(s)
- Xue‐Ming Xu
- CCR/LCPNIH/NCI, 9000 Rockville PikeBethesdaMD20878
| | | | - Heiko Mix
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588
| | - Yan Zhang
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588
| | - Kazima Saira
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588
| | - Richard S. Glass
- Department of ChemistryThe University of Arizona, 1306 E. University BlvdTusconAZ85721
| | - Marla J. Berry
- Department of Cell and Molecular BiologyUniversity of Hawaii at Manoa1960 East West RoadHonoluluHI96822
| | - Vadim N. Gladyshev
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588
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112
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Sengupta A, Carlson BA, Hoffmann VJ, Gladyshev VN, Hatfield DL. Conditional knockout of selenocysteine tRNA gene (
trsp
) in liver modulates lipoprotein metabolism. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Aniruddha Sengupta
- LCP, CCR, NCI, NIH9000 Rockville Pike, Bldg. 37, Rm. 6032BethesdaMD20892
| | - Bradley A Carlson
- LCP, CCR, NCI, NIH9000 Rockville Pike, Bldg. 37, Rm. 6032BethesdaMD20892
| | - Victoria J Hoffmann
- OD, ORS, DIRS, NIH9000 Rockville Pike, Building 14A, Room A100BethesdaMD20892
| | - Vadim N Gladyshev
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588
| | - Dolph L Hatfield
- LCP, CCR, NCI, NIH9000 Rockville Pike, Bldg. 37, Rm. 6032BethesdaMD20892
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113
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Shrimali RK, Irons RD, Carlson BA, Park JM, Hatfield DL. Selenoprotein deficiency adversely affects T cell development, proliferation, TCR signaling and cell mediated immunity. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a114-b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Robert D Irons
- MBSS, LCP, CCR, NCI, NIH6032/37, Convent driveBethesdaMD20892
- NSRG, DCP, NCI, NIH6016/37, Convent driveBethesdaMD20892
| | | | - Jin M Park
- CBRC, MGH, Harvard Medical School149 Thirteenth StreetCharlestownMA02129
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114
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Yoo M, Xu X, Carlson BA, Gladyshev VN, Hatfield DL. Examination of anticancer mechanisms in ras‐induced cancer cells by targeting thioredoxin reductase 1 knockdown. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Min‐Hyuk Yoo
- LCP, CCR, NIH9000 Rockville Pike Building 37 room 6032BethesdaMD20892
| | - Xue‐Ming Xu
- LCP, CCR, NIH9000 Rockville Pike Building 37 room 6032BethesdaMD20892
| | - Bradley A Carlson
- LCP, CCR, NIH9000 Rockville Pike Building 37 room 6032BethesdaMD20892
| | - Vadim N Gladyshev
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588
| | - Dolph L Hatfield
- LCP, CCR, NIH9000 Rockville Pike Building 37 room 6032BethesdaMD20892
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115
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Turanov A, Kehr S, Carlson BA, Hatfield DL, Gladyshev VN. Mammalian thioredoxin reductases: roles in redox homeostasis and analysis of cellular targets. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a718-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Anton Turanov
- University of Nebraska‐Lincoln, Beadle CenterLincolnNE68588
| | - Sebastian Kehr
- University of Nebraska‐Lincoln, Beadle CenterLincolnNE68588
| | - Bradley A Carlson
- Molecular Biology of Selenium SectionCenter for Cancer Research, National Institute of HealthBethesdaMD20892
| | - Dolph L Hatfield
- Molecular Biology of Selenium SectionCenter for Cancer Research, National Institute of HealthBethesdaMD20892
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116
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Carlson BA, Shrimali RK, Irons R, Park JM, Hatfield DL. Targeted removal of the selenocysteine tRNA
[Ser]Sec
gene (
trsp
) in mouse macrophages. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a717-d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Bradley A Carlson
- LCP, CCR, NCI, NIH9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
| | - Rajeev K Shrimali
- LCP, CCR, NCI, NIH9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
| | - Robert Irons
- LCP, CCR, NCI, NIH9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
| | - Jin Mo Park
- Massachusetts General Hospital, Harvard Medical School149 Thirteenth StreetCharlestownMA02129
| | - Dolph L Hatfield
- LCP, CCR, NCI, NIH9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
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117
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Novoselov SV, Kryukov GV, Xu XM, Carlson BA, Hatfield DL, Gladyshev VN. Selenoprotein H is a nucleolar thioredoxin-like protein with a unique expression pattern. J Biol Chem 2007; 282:11960-8. [PMID: 17337453 DOI: 10.1074/jbc.m701605200] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human selenoproteome consists of 25 known selenoproteins, but functions of many of these proteins are not known. Selenoprotein H (SelH) is a recently discovered 14-kDa mammalian protein with no sequence homology to functionally characterized proteins. By sensitive sequence and structure analyses, we identified SelH as a thioredoxin fold-like protein in which a conserved CXXU motif (cysteine separated by two other residues from selenocysteine) corresponds to the CXXC motif in thioredoxins. These data suggest a redox function of SelH. Indeed, a recombinant SelH shows significant glutathione peroxidase activity. In addition, SelH has a conserved RKRK motif in the N-terminal sequence. We cloned wild-type and cysteine mutant forms of SelH either upstream or downstream of green fluorescent protein (GFP) and localized this fusion protein to the nucleus in transfected mammalian cells, whereas mutations in the RKRK motif resulted in the cytosolic protein. Interestingly, the full-length SelH-GFP fusion protein localized specifically to nucleoli, whereas the N-terminal sequence of SelH fused to GFP had a diffuse nucleoplasm location. Northern blot analyses revealed low expression levels of SelH mRNA in various mouse tissues, but it was elevated in the early stages of embryonic development. In addition, SelH mRNA was overexpressed in human prostate cancer LNCaP and mouse lung cancer LCC1 cells. Down-regulation of SelH by RNA interference made LCC1 cells more sensitive to hydrogen peroxide but not to other peroxides tested. Overall, these data establish SelH as a novel nucleolar oxidoreductase and suggest that some functions in this compartment are regulated by redox and dependent on the trace element selenium.
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Affiliation(s)
- Sergey V Novoselov
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588, USA
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118
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Shrimali RK, Weaver JA, Miller GF, Starost MF, Carlson BA, Novoselov SV, Kumaraswamy E, Gladyshev VN, Hatfield DL. Selenoprotein expression is essential in endothelial cell development and cardiac muscle function. Neuromuscul Disord 2006; 17:135-42. [PMID: 17142041 PMCID: PMC1894657 DOI: 10.1016/j.nmd.2006.10.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Revised: 10/06/2006] [Accepted: 10/11/2006] [Indexed: 01/18/2023]
Abstract
LoxP-Cre technology was used to remove the selenocysteine tRNA gene, trsp, in either endothelial cells or myocytes of skeletal and heart muscle to elucidate the role of selenoproteins in cardiovascular disease. Loss of selenoprotein expression in endothelial cells was embryonic lethal. A 14.5-day-old embryo had numerous abnormalities including necrosis of the central nervous system, subcutaneous hemorrhage and erythrocyte immaturity. Loss of selenoprotein expression in myocytes manifested no apparent phenotype until about day 12 after birth. Affected mice had decreased mobility and an increased respiratory rate, which proceeded rapidly to death. Pathological analysis revealed that mice lacking trsp had moderate to severe myocarditis with inflammation extending into the mediastinitis. Thus, ablation of selenoprotein expression demonstrated an essential role of selenoproteins in endothelial cell development and in proper cardiac muscle function. The data suggest a direct connection between the loss of selenoprotein expression in these cell types and cardiovascular disease.
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Affiliation(s)
- Rajeev K. Shrimali
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - James A. Weaver
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Georgina F. Miller
- Division of Veterinary Resources, Office of Research Services, Division of Intramural Research Services, National Institutes of Health, Bethesda, MD 20892, USA
| | - Matthew F. Starost
- Division of Veterinary Resources, Office of Research Services, Division of Intramural Research Services, National Institutes of Health, Bethesda, MD 20892, USA
| | - Bradley A. Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | | - Easwari Kumaraswamy
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Vadim N. Gladyshev
- Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, USA
| | - Dolph L. Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
- * Corresponding author. Tel.: +1 301 496 2797; fax: +1 301 435 4957. E-mail address: (D.L. Hatfield)
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119
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Chen CL, Shim MS, Chung J, Yoo HS, Ha JM, Kim JY, Choi J, Zang SL, Hou X, Carlson BA, Hatfield DL, Lee BJ. G-rich, a Drosophila selenoprotein, is a Golgi-resident type III membrane protein. Biochem Biophys Res Commun 2006; 348:1296-301. [PMID: 16920070 DOI: 10.1016/j.bbrc.2006.07.203] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2006] [Accepted: 07/26/2006] [Indexed: 11/15/2022]
Abstract
G-rich is a Drosophila melanogaster selenoprotein, which is a homologue of human and mouse SelK. Subcellular localization analysis using GFP-tagged G-rich showed that G-rich was localized in the Golgi apparatus. The fusion protein was co-localized with the Golgi marker proteins but not with an endoplasmic reticulum (ER) marker protein in Drosophila SL2 cells. Bioinformatic analysis of G-rich suggests that this protein is either type II or type III transmembrane protein. To determine the type of transmembrane protein experimentally, GFP-G-rich in which GFP was tagged at the N-terminus of G-rich, or G-rich-GFP in which GFP was tagged at the C-terminus of G-rich, were expressed in SL2 cells. The tagged proteins were then digested with trypsin, and analyzed by Western blot analysis. The results showed that the C-terminus of the G-rich protein was exposed to the cytoplasm indicating it is a type III microsomal membrane protein. G-rich is the first selenoprotein identified in the Golgi apparatus.
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Affiliation(s)
- Chang Lan Chen
- School of Biological Sciences and Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Republic of Korea
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120
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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121
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Yoo MH, Xu XM, Carlson BA, Gladyshev VN, Hatfield DL. Thioredoxin Reductase 1 Deficiency Reverses Tumor Phenotype and Tumorigenicity of Lung Carcinoma Cells. J Biol Chem 2006; 281:13005-13008. [PMID: 16565519 DOI: 10.1074/jbc.c600012200] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dietary selenium has potent cancer prevention activity. Both low molecular weight selenocompounds and selenoproteins are implicated in this effect. Thioredoxin reductase 1 (TR1) is one of the major antioxidant and redox regulators in mammals that supports p53 function and other tumor suppressor activities. However, this selenium-containing oxidoreductase is also overexpressed in many malignant cells and has been proposed as a target for cancer therapy. To further assess the role of TR1 in the malignancy process, we used RNA interference technology to decrease its expression in mouse lung carcinoma (LLC1) cells. Stable transfection of LLC1 cells with a small interfering RNA construct that specifically targets TR1 removal manifested a reversal in the morphology and anchorage-independent growth properties of these cancer cells that made them similar to those of normal cells. The expression of at least two cancer-related protein mRNAs, Hgf and Opn1, were reduced dramatically in the TR1 knockdown cells. Mice injected with the TR1 knockdown showed a dramatic reduction in tumor progression and metastasis compared with those mice injected with the corresponding control vector. In addition, tumors that arose from injected TR1 knockdown cells lost the targeting construct, suggesting that TR1 is essential for tumor growth in mice. These observations provide direct evidence that the reduction of TR1 levels in malignant cells is antitumorigenic and suggest that the enzyme is a prime target for cancer therapy.
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Affiliation(s)
- Min-Hyuk Yoo
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Institutes of Health, Bethesda, Maryland 20892
| | - Xue-Ming Xu
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Institutes of Health, Bethesda, Maryland 20892
| | - Bradley A Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Institutes of Health, Bethesda, Maryland 20892
| | - Vadim N Gladyshev
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588
| | - Dolph L Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Institutes of Health, Bethesda, Maryland 20892.
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122
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Irons R, Carlson BA, Hatfield DL, Davis CD. Both selenoproteins and low molecular weight selenocompounds reduce colon cancer risk in mice with genetically impaired selenoprotein expression. J Nutr 2006; 136:1311-7. [PMID: 16614422 DOI: 10.1093/jn/136.5.1311] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Selenium has cancer protective effects in a variety of experimental systems. Currently, it is not known whether selenoproteins or low molecular weight selenocompounds are responsible for this activity. To evaluate the contribution of selenoproteins to the cancer protective effects of selenium, we used transgenic mice that carry a mutant selenocysteine transfer RNA gene, which causes reduced selenoprotein synthesis. Selenium homeostasis was characterized in liver and colon of wild-type and transgenic mice fed selenium-deficient diets supplemented with 0, 0.1, or 2.0 microg selenium (as selenite)/g diet. (75)Se-labeling, Western blot analysis, and enzymatic activities revealed that transgenic mice have reduced (P < 0.05) liver and colon glutathione peroxidase expression, but conserved thioredoxin reductase expression compared with wild-type mice, regardless of selenium status. Transgenic mice had more (P < 0.05) selenium in the nonprotein fraction of the liver and colon than wild-type mice, indicating a greater amount of low molecular weight selenocompounds. Compared with wild-type mice, transgenic mice had more (P < 0.05) azoxymethane-induced aberrant crypt formation (a preneoplastic lesion for colon cancer). Supplemental selenium decreased (P < 0.05) the number of aberrant crypts and aberrant crypt foci in both wild-type and transgenic mice. These results provide evidence that a lack of selenoprotein activity increases colon cancer susceptibility. Furthermore, low molecular weight selenocompounds reduced preneoplastic lesions independent of the selenoprotein genotype. These results are, to our knowledge, the first to provide evidence that both selenoproteins and low molecular weight selenocompounds are important for the cancer-protective effects of selenium.
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Affiliation(s)
- Robert Irons
- Nutritional Science Research Group, National Cancer Institute, Rockville, MD 20852, USA
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123
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Shrimali RK, Park JM, Irons R, Carlson BA, Hatfield DL. Selenoproteins play a major role in immune function. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a68-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Jin Mo Park
- Cutaneous Biology Research CenterMassachusetts General Hospital149 Thirteenth StreetCharlestownMA02129
| | - Robert Irons
- Nutrition Science Research GroupDCPNCINIHRoom 6016, 37 Convent DriveBethesdaMD20892
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124
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Yoo M, Xu X, Turanov AA, Carlson BA, Gladyshev VN, Hatfield DL. siRNA knockdown‐mRNA knock‐in as a means of assessing elenoprotein function. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a427-c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Min‐Hyuk Yoo
- LCPNIH/NCI9000 Rockville Pike Building 37 Room 6032BethesdaMD20892
| | - Xue‐Ming Xu
- LCPNIH/NCI9000 Rockville Pike Building 37 Room 6032BethesdaMD20892
| | - Anton A Turanov
- Department of BiochemistryUniversity of Nebraska, N151 Beadle centerLincolnNE68588
| | | | - Vadim N Gladyshev
- Department of BiochemistryUniversity of Nebraska, N151 Beadle centerLincolnNE68588
| | - Dolph L Hatfield
- LCPNIH/NCI9000 Rockville Pike Building 37 Room 6032BethesdaMD20892
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125
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Xu X, Carlson BA, Mix H, Irons R, Berry MJ, Gladyshev VN, Hatfield DL. Selenophosphate synthetase 2 is essential for selenoprotein biosynthesis. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Heiko Mix
- Department of BiochemistryUniversity of Nebraska, N147 Beadle CenterLincolnNE68588‐0664
| | - Robert Irons
- LCP
- Nutritional Science Research GroupNIH/NCI9000 Rockville PikeBethesdaMD20892
| | - Marla J Berry
- University of Hawaii1960 East West Road, T514HonoluluHI96822
| | - Vadim N Gladyshev
- Department of BiochemistryUniversity of Nebraska, N147 Beadle CenterLincolnNE68588‐0664
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126
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Carlson BA, Jeong SJ, Shrimali RK, Hatfield D. The selenocysteine tRNA Staf region is essential for adequate selenoprotein levels and mouse longevity. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a428-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Bradley A Carlson
- LCPNIH/NCI9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
| | - Soon Jeong Jeong
- LCPNIH/NCI9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
| | - Rajeev K Shrimali
- LCPNIH/NCI9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
| | - Dolph Hatfield
- LCPNIH/NCI9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
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127
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Sengupta A, Weaver JA, Novoselov SV, Fomenko DE, Carlson BA, Gladyshev VN, Hatfield DL. A comparative analysis of selenoproteins and global gene expression in liver selenocysteine tRNA knockout mice and its rescued variants. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a427-d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - James A Weaver
- NCINIH9000 Rockville Pike, Bldg. 37, Rm 6032BethesdaMaryland20892
| | - Sergey V Novoselov
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588‐0664
| | - Dmitri E Fomenko
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588‐0664
| | | | - Vadim N Gladyshev
- Department of BiochemistryUniversity of Nebraska, N151 Beadle CenterLincolnNE68588‐0664
| | - Dolph L Hatfield
- NCINIH9000 Rockville Pike, Bldg. 37, Rm 6032BethesdaMaryland20892
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128
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Irons R, Carlson BA, Hatfield DL, Davis CD. Both selenoproteins and low molecular weight selenocompounds reduce colon cancer risk in mice with genetically impaired selenoprotein expression. FASEB J 2006. [DOI: 10.1096/fasebj.20.4.a428-d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Robert Irons
- LCPNIH/NCI9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
- Nutritional Science Research GroupNIH/NCI6130 Executive BlvdRockvilleMD20852
| | - Bradley A Carlson
- LCPNIH/NCI9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
| | - Dolph L Hatfield
- LCPNIH/NCI9000 Rockville Pike, Building 37, Room 6032BethesdaMD20892
| | - Cindy D Davis
- Nutritional Science Research GroupNIH/NCI6130 Executive BlvdRockvilleMD20852
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129
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Sheridan PA, Carlson BA, Hatfeild DL, Beck MA. Decreased selenoprotein expression results in an altered immune response post influenza virus infection. FASEB J 2006. [DOI: 10.1096/fasebj.20.5.a1067-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Patricia A Sheridan
- NutritionUniversity of North CarolinaChapel Hill, 2215 MHRB, CB#7461, Columbia StreetChapel HillNC27599
| | - Bradley A Carlson
- Molecular Biology of Selenium, NCINational Institutes of HealthBethesdaMD20892
| | - Dolph L Hatfeild
- Molecular Biology of Selenium, NCINational Institutes of HealthBethesdaMD20892
| | - Melinda A Beck
- NutritionUniversity of North CarolinaChapel Hill, 2215 MHRB, CB#7461, Columbia StreetChapel HillNC27599
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130
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Hatfield DL, Carlson BA, Xu XM, Mix H, Gladyshev VN. Selenocysteine Incorporation Machinery and the Role of Selenoproteins in Development and Health. Progress in Nucleic Acid Research and Molecular Biology 2006; 81:97-142. [PMID: 16891170 DOI: 10.1016/s0079-6603(06)81003-2] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Dolph L Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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131
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Novoselov SV, Calvisi DF, Labunskyy VM, Factor VM, Carlson BA, Fomenko DE, Moustafa ME, Hatfield DL, Gladyshev VN. Selenoprotein deficiency and high levels of selenium compounds can effectively inhibit hepatocarcinogenesis in transgenic mice. Oncogene 2005; 24:8003-11. [PMID: 16170372 DOI: 10.1038/sj.onc.1208940] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The micronutrient element selenium (Se) has been shown to be effective in reducing the incidence of cancer in animal models and human clinical trials. Selenoproteins and low molecular weight Se compounds were implicated in the chemopreventive effect, but specific mechanisms are not clear. We examined the role of Se and selenoproteins in liver tumor formation in TGFalpha/c-Myc transgenic mice, which are characterized by disrupted redox homeostasis and develop liver cancer by 6 months of age. In these mice, both Se deficiency and high levels of Se compounds suppressed hepatocarcinogenesis. In addition, both treatments induced expression of detoxification genes, increased apoptosis and inhibited cell proliferation. Within low-to-optimal levels of dietary Se, tumor formation correlated with expression of most selenoproteins. These data suggest that changes in selenoprotein expression may either suppress or promote tumorigenesis depending on cell type and genotype. Since dietary Se may have opposing effects on cancer, it is important to identify the subjects who will benefit from Se supplementation as well as those who will not.
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Affiliation(s)
- Sergey V Novoselov
- Department of Biochemistry, University of Nebraska, N 151 Beadle Center, 1901 Vine Street, Lincoln, NE 68588, USA
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132
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Xu XM, Mix H, Carlson BA, Grabowski PJ, Gladyshev VN, Berry MJ, Hatfield DL. Evidence for Direct Roles of Two Additional Factors, SECp43 and Soluble Liver Antigen, in the Selenoprotein Synthesis Machinery. J Biol Chem 2005; 280:41568-75. [PMID: 16230358 DOI: 10.1074/jbc.m506696200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Selenocysteine (Sec) is inserted into selenoproteins co-translationally with the help of various cis- and trans-acting factors. The specific mechanisms of Sec biosynthesis and insertion into protein in eukaryotic cells, however, are not known. Two proteins, SECp43 and the soluble liver antigen (SLA), were previously reported to interact with tRNA([Ser]Sec), but their functions remained elusive. Herein, we report that knockdown of SECp43 in NIH3T3 or TCMK-1 cells using RNA interference technology resulted in a reduction in the level of methylation at the 2'-hydroxylribosyl moiety in the wobble position (Um34) of Sec tRNA([Ser]Sec), and consequently reduced glutathione peroxidase 1 expression. Double knockdown of SECp43 and SLA resulted in decreased selenoprotein expression. SECp43 formed a complex with Sec tRNA([Ser]Sec) and SLA, and the targeted removal of one of these proteins affected the binding of the other to Sec tRNA([Ser]Sec). SECp43 was located primarily in the nucleus, whereas SLA was found in the cytoplasm. Co-transfection of both proteins resulted in the nuclear translocation of SLA suggesting that SECp43 may also promote shuttling of SLA and Sec tRNA([Ser]Sec) between different cellular compartments. Taken together, these data establish the role of SECp43 and SLA in selenoprotein biosynthesis through interaction with tRNA([Ser]Sec) in a multiprotein complex. The data also reveal a role of SECp43 in regulation of selenoprotein expression by affecting the synthesis of Um34 on tRNA([Ser]Sec) and the intracellular location of SLA.
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MESH Headings
- Animals
- Antigens/chemistry
- Autoantigens/chemistry
- Autoantigens/physiology
- Blotting, Northern
- Blotting, Western
- CHO Cells
- Cell Line
- Cell Nucleus/metabolism
- Chromatography
- Cricetinae
- Cytoplasm/metabolism
- Glutathione Peroxidase/biosynthesis
- Green Fluorescent Proteins/chemistry
- Green Fluorescent Proteins/metabolism
- Immunoprecipitation
- Liver/metabolism
- Mice
- Mice, Knockout
- Microscopy, Confocal
- Microscopy, Fluorescence
- Models, Biological
- NIH 3T3 Cells
- Protein Binding
- Protein Biosynthesis
- Protein Structure, Tertiary
- RNA Interference
- RNA, Messenger/metabolism
- RNA, Small Interfering/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer, Amino Acyl/chemistry
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/physiology
- Recombinant Fusion Proteins/chemistry
- Selenocysteine/chemistry
- Selenoprotein P/chemistry
- Selenoproteins/chemistry
- Serine/chemistry
- Transcriptional Activation
- Transfection
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Affiliation(s)
- Xue-Ming Xu
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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133
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Sun QA, Su D, Novoselov SV, Carlson BA, Hatfield DL, Gladyshev VN. Reaction Mechanism and Regulation of Mammalian Thioredoxin/Glutathione Reductase†. Biochemistry 2005; 44:14528-37. [PMID: 16262253 DOI: 10.1021/bi051321w] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thioredoxin/glutathione reductase (TGR) is a recently discovered member of the selenoprotein thioredoxin reductase family in mammals. In contrast to two other mammalian thioredoxin reductases, it contains an N-terminal glutaredoxin domain and exhibits a wide spectrum of enzyme activities. To elucidate the reaction mechanism and regulation of TGR, we prepared a recombinant mouse TGR in the selenoprotein form as well as various mutants and individual domains of this enzyme. Using these proteins, we showed that the glutaredoxin and thioredoxin reductase domains of TGR could independently catalyze reactions normally associated with each domain. The glutaredoxin domain is a monothiol glutaredoxin containing a CxxS motif at the active site, which could receive electrons from either the thioredoxin reductase domain of TGR or thioredoxin reductase 1. We also found that the C-terminal penultimate selenocysteine was required for transfer of reducing equivalents from the thiol/disulfide active site of TGR to the glutaredoxin domain. Thus, the physiologically relevant NADPH-dependent activities of TGR were dependent on this residue. In addition, we examined the effects of selenium levels in the diet and perturbations in selenocysteine tRNA function on TGR biosynthesis and found that expression of this protein was regulated by both selenium and tRNA status in liver, but was more resistant to this regulation in testes.
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Affiliation(s)
- Qi-An Sun
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68588-0664, USA
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134
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Schweizer U, Streckfuss F, Pelt P, Carlson BA, Hatfield DL, Köhrle J, Schomburg L. Hepatically derived selenoprotein P is a key factor for kidney but not for brain selenium supply. Biochem J 2005; 386:221-6. [PMID: 15638810 PMCID: PMC1134785 DOI: 10.1042/bj20041973] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Liver-specific inactivation of Trsp, the gene for selenocysteine tRNA, removes SePP (selenoprotein P) from plasma, causing serum selenium levels to fall from 298 microg/l to 50 microg/l and kidney selenium to decrease to 36% of wild-type levels. Likewise, glutathione peroxidase activities decreased in plasma and kidney to 43% and 18% respectively of wild-type levels. This agrees nicely with data from SePP knockout mice, supporting a selenium transport role for hepatically expressed SePP. However, brain selenium levels remain unaffected and neurological defects do not occur in the liver-specific Trsp knockout mice, while SePP knockout mice suffer from neurological defects. This indicates that a transport function in plasma is exerted by hepatically derived SePP, while in brain SePP fulfils a second, hitherto unexpected, essential role.
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Affiliation(s)
- Ulrich Schweizer
- Neurobiologie des Selens, Neurowissenschaftliches Forschungszentrum, Charité-Universitätsmedizin Berlin, Schumannstrasse 20/21, 10117 Berlin, Germany.
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135
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Shrimali RK, Lobanov AV, Xu XM, Rao M, Carlson BA, Mahadeo DC, Parent CA, Gladyshev VN, Hatfield DL. Selenocysteine tRNA identification in the model organisms Dictyostelium discoideum and Tetrahymena thermophila. Biochem Biophys Res Commun 2005; 329:147-51. [PMID: 15721286 DOI: 10.1016/j.bbrc.2005.01.120] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Indexed: 11/24/2022]
Abstract
Characterizing Sec tRNAs that decode UGA provides one of the most direct and easiest means of determining whether an organism possesses the ability to insert selenocysteine (Sec) into protein. Herein, we used a combination of two techniques, computational to identify Sec tRNA genes and RT-PCR to sequence the gene products, to unequivocally demonstrate that two widely studied, model protozoans, Dictyostelium discoideum and Tetrahymena thermophila, encode Sec tRNA in their genomes. The advantage of using both procedures is that computationally we could easily detect potential Sec tRNA genes and then confirm by sequencing that the Sec tRNA was present in the tRNA population, and thus the identified gene was not a pseudogene. Sec tRNAs from both organisms decode UGA. T. thermophila Sec tRNA, like all other sequenced Sec tRNAs, is 90 nucleotides in length, while that from D. discoideum is 91 nucleotides long making it the longest eukaryotic sequenced to date. Evolutionary analyses of known Sec tRNAs reveal the two forms identified herein are the most divergent eukaryotic Sec tRNAs thus far sequenced.
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Affiliation(s)
- Rajeev K Shrimali
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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136
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Carlson BA, Xu XM, Gladyshev VN, Hatfield DL. Selective Rescue of Selenoprotein Expression in Mice Lacking a Highly Specialized Methyl Group in Selenocysteine tRNA. J Biol Chem 2005; 280:5542-8. [PMID: 15611090 DOI: 10.1074/jbc.m411725200] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Selenocysteine (Sec) is the 21st amino acid in the genetic code. Its tRNA is variably methylated on the 2'-O-hydroxyl site of the ribosyl moiety at position 34 (Um34). Herein, we identified a role of Um34 in regulating the expression of some, but not all, selenoproteins. A strain of knock-out transgenic mice was generated, wherein the Sec tRNA gene was replaced with either wild type or mutant Sec tRNA transgenes. The mutant transgene yielded a tRNA that lacked two base modifications, N(6)-isopentenyladenosine at position 37 (i(6)A37) and Um34. Several selenoproteins, including glutathione peroxidases 1 and 3, SelR, and SelT, were not detected in mice rescued with the mutant transgene, whereas other selenoproteins, including thioredoxin reductases 1 and 3 and glutathione peroxidase 4, were expressed in normal or reduced levels. Northern blot analysis suggested that other selenoproteins (e.g. SelW) were also poorly expressed. This novel regulation of protein expression occurred at the level of translation and manifested a tissue-specific pattern. The available data suggest that the Um34 modification has greater influence than the i(6)A37 modification in regulating the expression of various mammalian selenoproteins and Um34 is required for synthesis of several members of this protein class. Many proteins that were poorly rescued appear to be involved in responses to stress, and their expression is also highly dependent on selenium in the diet. Furthermore, their mRNA levels are regulated by selenium and are subject to nonsense-mediated decay. Overall, this study described a novel mechanism of regulation of protein expression by tRNA modification that is in turn regulated by levels of the trace element, selenium.
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MESH Headings
- Animals
- Blotting, Northern
- Blotting, Western
- Female
- Fertility
- Gene Expression Regulation
- Glutathione Peroxidase/genetics
- Glutathione Peroxidase/metabolism
- Litter Size
- Male
- Methionine Sulfoxide Reductases
- Methylation
- Mice
- Proteins/analysis
- Proteins/genetics
- Proteins/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Transfer, Amino Acyl/chemistry
- RNA, Transfer, Amino Acyl/genetics
- RNA, Transfer, Amino Acyl/metabolism
- Selenium/analysis
- Selenium/metabolism
- Selenoprotein W
- Selenoproteins
- Spermatozoa/metabolism
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Affiliation(s)
- Bradley A Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, MD 20892, USA
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137
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Carlson BA, Xu XM, Gladyshev VN, Hatfield DL. Um34 in selenocysteine tRNA is required for the expression of stress-related selenoproteins in mammals. Fine-Tuning of RNA Functions by Modification and Editing 2005. [DOI: 10.1007/b106652] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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138
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Carlson BA, Xu XM, Kryukov GV, Rao M, Berry MJ, Gladyshev VN, Hatfield DL. Identification and characterization of phosphoseryl-tRNA[Ser]Sec kinase. Proc Natl Acad Sci U S A 2004; 101:12848-53. [PMID: 15317934 PMCID: PMC516484 DOI: 10.1073/pnas.0402636101] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In 1970, a kinase activity that phosphorylated a minor species of seryl-tRNA to form phosphoseryl-tRNA was found in rooster liver [Maenpaa, P. H. & Bernfield, M. R. (1970) Proc. Natl. Acad. Sci. USA 67, 688-695], and a minor seryl-tRNA that decoded the nonsense UGA was detected in bovine liver. The phosphoseryl-tRNA and the minor UGA-decoding seryl-tRNA were subsequently identified as selenocysteine (Sec) tRNA[Ser]Sec, but the kinase activity remained elusive. Herein, by using a comparative genomics approach that searched completely sequenced archaeal genomes for a kinase-like protein with a pattern of occurrence similar to that of components of Sec insertion machinery, we detected a candidate gene for mammalian phosphoseryl-tRNA[Ser]Sec kinase (pstk). Mouse pstk was cloned, and the gene product (PSTK) was expressed and characterized. PSTK specifically phosphorylated the seryl moiety on seryl-tRNA[Ser]Sec and, in addition, had a requirement for ATP and Mg2+. Proteins with homology to mammalian PSTK occur in Drosophila, Caenorhabditis elegans, Methanopyrus kandleri, and Methanococcus jannaschii, suggesting a conservation of its function across archaea and eukaryotes that synthesize selenoproteins and the absence of this function in bacteria, plants, and yeast. The fact that PSTK has been highly conserved in evolution suggests that it plays an important role in selenoprotein biosynthesis and/or regulation.
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Affiliation(s)
- Bradley A Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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139
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Carlson BA, Novoselov SV, Kumaraswamy E, Lee BJ, Anver MR, Gladyshev VN, Hatfield DL. Specific Excision of the Selenocysteine tRNA[Ser]Sec (Trsp) Gene in Mouse Liver Demonstrates an Essential Role of Selenoproteins in Liver Function. J Biol Chem 2004; 279:8011-7. [PMID: 14660662 DOI: 10.1074/jbc.m310470200] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Selenium is essential in mammalian embryonic development. However, in adults, selenoprotein levels in several organs including liver can be substantially reduced by selenium deficiency without any apparent change in phenotype. To address the role of selenoproteins in liver function, mice homozygous for a floxed allele encoding the selenocysteine (Sec) tRNA([Ser]Sec) gene were crossed with transgenic mice carrying the Cre recombinase under the control of the albumin promoter that expresses the recombinase specifically in liver. Recombination was nearly complete in mice 3 weeks of age, whereas liver selenoprotein synthesis was virtually absent, which correlated with the loss of Sec tRNA([Ser]Sec) and activities of major selenoproteins. Total liver selenium was dramatically decreased, whereas levels of low molecular weight selenocompounds were little affected. Plasma selenoprotein P levels were reduced by about 75%, suggesting that selenoprotein P is primarily exported from the liver. Glutathione S-transferase levels were elevated in the selenoprotein-deficient liver, suggesting a compensatory activation of this detoxification program. Mice appeared normal until about 24 h before death. Most animals died between 1 and 3 months of age. Death appeared to be due to severe hepatocellular degeneration and necrosis with concomitant necrosis of peritoneal and retroperitoneal fat. These studies revealed an essential role of selenoproteins in liver function.
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Affiliation(s)
- Bradley A Carlson
- Section on the Molecular Biology of Selenium, Basic Research Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland, 20892, USA
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140
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Kwon SY, Badenhorst P, Martin-Romero FJ, Carlson BA, Paterson BM, Gladyshev VN, Lee BJ, Hatfield DL. The Drosophila selenoprotein BthD is required for survival and has a role in salivary gland development. Mol Cell Biol 2003; 23:8495-504. [PMID: 14612395 PMCID: PMC262655 DOI: 10.1128/mcb.23.23.8495-8504.2003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Selenium is implicated in many diseases, including cancer, but its function at the molecular level is poorly understood. BthD is one of three selenoproteins recently identified in Drosophila. To elucidate the function of BthD and the role of selenoproteins in cellular metabolism and health, we analyzed the developmental expression profile of this protein and used inducible RNA interference (RNAi) to ablate function. We find that BthD is dynamically expressed during Drosophila development. bthD mRNA and protein are abundant in the ovaries of female flies and are deposited into the developing oocyte. Maternally contributed protein and RNA persist during early embryonic development but decay by the onset of gastrulation. At later stages of embryogenesis, BthD is expressed highly in the developing salivary gland. We generated transgenic fly lines carrying an inducible gene-silencing construct, in which an inverted bthD genomic-cDNA hybrid is under the control of the Drosophila Gal4 upstream activation sequence system. Duplex RNAi induced from this construct targeted BthD mRNA for destruction and reduced BthD protein levels. We found that loss of BthD compromised salivary gland morphogenesis and reduced animal viability.
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Affiliation(s)
- So Yeon Kwon
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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141
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Hornberger TA, McLoughlin TJ, Leszczynski JK, Armstrong DD, Jameson RR, Bowen PE, Hwang ES, Hou H, Moustafa ME, Carlson BA, Hatfield DL, Diamond AM, Esser KA. Selenoprotein-deficient transgenic mice exhibit enhanced exercise-induced muscle growth. J Nutr 2003; 133:3091-7. [PMID: 14519790 DOI: 10.1093/jn/133.10.3091] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dietary intake of selenium has been implicated in a wide range of health issues, including aging, heart disease and cancer. Selenium deficiency, which can reduce selenoprotein levels, has been associated with several striated muscle pathologies. To investigate the role of selenoproteins in skeletal muscle biology, we used a transgenic mouse (referred to as i6A-) that has reduced levels of selenoproteins due to the introduction and expression of a dominantly acting mutant form of selenocysteine transfer RNA (tRNA[Ser]Sec). As a consequence, each organ contains reduced levels of most selenoproteins, yet these mice are normal with regard to fertility, overall health, behavior and blood chemistries. In the present study, although skeletal muscles from i6A- mice were phenotypically indistinguishable from those of wild-type mice, plantaris muscles were approximately 50% heavier after synergist ablation, a model of exercise overload. Like muscle in wild-type mice, the enhanced growth in the i6A- mice was completely blocked by inhibition of the mammalian target of rapamycin (mTOR) pathway. Muscles of transgenic mice exhibited increased site-specific phosphorylation on both Akt and p70 ribosomal S6 kinase (p70S6k) (P < 0.05) before ablation, perhaps accounting for the enhanced response to synergist ablation. Thus, a single genetic alteration resulted in enhanced skeletal muscle adaptation after exercise, and this is likely through subtle changes in the resting phosphorylation state of growth-related kinases.
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Affiliation(s)
- Troy A Hornberger
- School of Kinesiology, University of Illinois, Chicago, IL 60608, USA
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142
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Rao M, Carlson BA, Novoselov SV, Weeks DP, Gladyshev VN, Hatfield DL. Chlamydomonas reinhardtii selenocysteine tRNA[Ser]Sec. RNA 2003; 9:923-30. [PMID: 12869703 PMCID: PMC1370458 DOI: 10.1261/rna.5510503] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2003] [Accepted: 05/07/2003] [Indexed: 05/19/2023]
Abstract
Eukaryotic selenocysteine (Sec) protein insertion machinery was thought to be restricted to animals, but the occurrence of both Sec-containing proteins and the Sec insertion system was recently found in Chlamydomonas reinhardtii, a member of the plant kingdom. Herein, we used RT-PCR to determine the sequence of C. reinhardtii Sec tRNA[Ser]Sec, the first non-animal eukaryotic Sec tRNA[Ser]Sec sequence. Like its animal counterpart, it is 90 nucleotides in length, is aminoacylated with serine by seryl-tRNA synthetase, and decodes specifically UGA. Evolutionary analyses of known Sec tRNAs identify the C. reinhardtii form as the most diverged eukaryotic Sec tRNA[Ser]Sec and reveal a common origin for this tRNA in bacteria, archaea, and eukaryotes.
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Affiliation(s)
- Mahadev Rao
- Section on the Molecular Biology of Selenium, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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143
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Kim M, Choi J, Carlson BA, Han JK, Rhee K, Sargent T, Hatfield DL, Lee BJ. A novel TBP-interacting zinc finger protein functions in early development of Xenopus laevis. Biochem Biophys Res Commun 2003; 306:1106-11. [PMID: 12821157 DOI: 10.1016/s0006-291x(03)01069-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A zinc finger protein that interacts with Xenopus TATA-binding protein was previously isolated by a yeast two-hybrid screen and found to serve as a transcriptional repressor. The gene was designated the negatively regulating zinc finger protein gene (NZFP). Herein, NZFP was found to be expressed maternally. After gastrulation, the level of NZFP mRNA decreased significantly throughout the neurula stage. However, mRNA levels increased at stage 35 and then began to decrease at stage 48. Eventually, no NZFP mRNA was observed in adult tissues except in the ovary. NZFP mRNA was detected in the animal hemisphere during gastrulation and observed in the neural ectoderm at the neurula stage. At the tailbud stage, NZFP was highly expressed in the head tissues such as brain, eyes, otic vesicles, lateral line placodes, and branchial arches, but weakly in somites. Depletion of NZFP in the embryos using RNA interference caused premature death at the gastrula stage or induced secondary partial axis after gastrulation. These results strongly suggest that NZFP is an essential transcription factor involved in the cell movement during gastrulation and the formation of the dorsal axis during early development in Xenopus.
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Affiliation(s)
- Mijin Kim
- Laboratory of Molecular Genetics, Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Republic of Korea
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144
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Abstract
Two model systems for examining the role of selenoproteins in health are discussed. One utilizes transgenic mice that carry mutant selenocysteine (Sec) tRNA transgenes that result in the reduction of selenoprotein expression in a protein- and tissue-specific manner. The other utilizes loxP-Cre technology to selectively remove the Sec tRNA gene in mammary epithelium that results in the reduction of only certain selenoproteins in this tissue. Both approaches provide important tools for examining the role of selenoproteins in health.
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Affiliation(s)
- Mohamed E Moustafa
- Section on the Molecular Biology of Selenium, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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145
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Kim M, Park CH, Lee MS, Carlson BA, Hatfield DL, Lee BJ. A novel TBP-interacting zinc finger protein represses transcription by inhibiting the recruitment of TFIIA and TFIIB. Biochem Biophys Res Commun 2003; 306:231-8. [PMID: 12788093 DOI: 10.1016/s0006-291x(03)00939-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We isolated a novel gene encoding a zinc finger protein from Xenopus laevis, designated NZFP that interacts with the TATA-binding protein (TBP). NZFP contains a highly conserved sequence designated finger associated box (FAX) and SUMO-1 consensus-binding motifs at the N-terminal half and 10 C2H2 type zinc finger motifs at the C-terminal half, respectively. Deletion mutants of NZFP fused with the Gal4 DNA binding domain were used to determine the function of NZFP during gene transcription by transfecting them into a Xenopus kidney cell line. Both full-length NZFP and the FAX domain repressed transcription activity by 3-5-fold. Moreover, an in vitro pull-down assay showed that the C-terminal core domain of TBP makes direct contact with the N-terminal portion of NZFP. We also found through chromatin immunoprecipitation experiments that the interaction between NZFP and TBP inhibits binding of TFIIA and TFIIB. These data strongly suggest that the repression by NZFP occurs through its binding to both DNA and TBP and the resulting NZFP-TBP-promoter complex inhibits preinitiation complex assembly by preventing binding of TFIIA and TFIIB.
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Affiliation(s)
- Mijin Kim
- Laboratory of Molecular Genetics, School of Biological Sciences, Seoul National University, 151-742, Seoul, South Korea
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146
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Kumaraswamy E, Carlson BA, Morgan F, Miyoshi K, Robinson GW, Su D, Wang S, Southon E, Tessarollo L, Lee BJ, Gladyshev VN, Hennighausen L, Hatfield DL. Selective removal of the selenocysteine tRNA [Ser]Sec gene (Trsp) in mouse mammary epithelium. Mol Cell Biol 2003; 23:1477-88. [PMID: 12588969 PMCID: PMC151713 DOI: 10.1128/mcb.23.5.1477-1488.2003] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mice homozygous for an allele encoding the selenocysteine (Sec) tRNA [Ser]Sec gene (Trsp) flanked by loxP sites were generated. Cre recombinase-dependent removal of Trsp in these mice was lethal to embryos. To investigate the role of Trsp in mouse mammary epithelium, we deleted this gene by using transgenic mice carrying the Cre recombinase gene under control of the mouse mammary tumor virus (MMTV) long terminal repeat or the whey acidic protein promoter. While both promoters target Cre gene expression to mammary epithelium, MMTV-Cre is also expressed in spleen and skin. Sec tRNA [Ser]Sec amounts were reduced by more than 70% in mammary tissue with either transgene, while in skin and spleen, levels were reduced only with MMTV-Cre. The selenoprotein population was selectively affected with MMTV-Cre in breast and skin but not in the control tissue, kidney. Moreover, within affected tissues, expression of specific selenoproteins was regulated differently and often in a contrasting manner, with levels of Sep15 and the glutathione peroxidases GPx1 and GPx4 being substantially reduced. Expression of the tumor suppressor genes BRCA1 and p53 was also altered in a contrasting manner in MMTV-Cre mice, suggesting greater susceptibility to cancer and/or increased cell apoptosis. Thus, the conditional Trsp knockout mouse allows tissue-specific manipulation of Sec tRNA and selenoprotein expression, suggesting that this approach will provide a useful tool for studying the role of selenoproteins in health.
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MESH Headings
- Alleles
- Animals
- Blotting, Northern
- Blotting, Western
- Breast/metabolism
- Chromatography
- Crosses, Genetic
- Epithelium/metabolism
- Gene Deletion
- Genes, BRCA1
- Genes, p53/genetics
- Genetic Vectors
- Glutathione Peroxidase/metabolism
- Heterozygote
- Kidney/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Models, Genetic
- Phenotype
- Promoter Regions, Genetic
- Proteins/metabolism
- RNA, Transfer, Amino Acyl/genetics
- RNA, Transfer, Amino Acyl/metabolism
- Recombination, Genetic
- Selenoproteins
- Tissue Distribution
- Transgenes
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Affiliation(s)
- Easwari Kumaraswamy
- Section on Molecular Biology of Selenium, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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147
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Xu XM, Carlson BA, Grimm TA, Kutza J, Berry MJ, Arreola R, Fields KH, Shanmugam I, Jeang KT, Oroszlan S, Combs GF, Marx PA, Gladyshev VN, Clouse KA, Hatfield DL. Rhesus monkey simian immunodeficiency virus infection as a model for assessing the role of selenium in AIDS. J Acquir Immune Defic Syndr 2002; 31:453-63. [PMID: 12473832 DOI: 10.1097/00126334-200212150-00001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The objective of this study was to determine whether simian immunodeficiency virus (SIV) infection of macaques could be used as a model system to assess the role of selenium in AIDS. Plasma and serum selenium levels were determined by standard assays in monkeys before and after inoculation of SIV. SIV-infected cells or cells expressing the HIV Tat protein were labeled with 75Se, and protein extracts were prepared and electrophoresed to analyze selenoprotein expression. Total tRNA was isolated from CEMx174 cells infected with SIV or from KK1 cells infected with HIV, and selenocysteine tRNA isoforms were characterized by reverse phase chromatography. SIV-infected monkeys show a decrease in blood selenium levels similar to that observed in AIDS with development of SAIDS. Cells infected with SIV in vitro exhibit reduced selenoprotein levels and an accumulation of small molecular weight selenium compounds relative to uninfected cells. Examination of the selenocysteine tRNA isoforms in HIV-infected KK1 cells or SIV-infected CEMx174 cells reveals an isoform distribution characteristic of selenium-deficient cells. Furthermore, transfection of Jurkat E6 cells with the Tat gene selectively altered selenoprotein synthesis, with GPX4 and Sep15 being the most inhibited and TR1 the most enhanced. Taken together, the data show that monkeys infected with SIV in vivo and cells infected with SIV in vitro will provide appropriate models for investigating the mechanism(s) responsible for reduced selenium levels that accompany the progression of AIDS in HIV disease.
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Affiliation(s)
- Xue-Ming Xu
- Section on the Molecular Biology of Selenium, Basic Research Laboratory, National Cancer Institute/NIH, Building 37, Room 2D09, Bethesda, MD 20892, USA
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148
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MESH Headings
- Animals
- Base Sequence
- Cattle
- Chromatography, Liquid
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Gene Expression
- HL-60 Cells
- Humans
- In Vitro Techniques
- Liver/metabolism
- Models, Molecular
- Molecular Sequence Data
- Nucleic Acid Conformation
- Protein Biosynthesis
- Proteins/genetics
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Transfer, Amino Acid-Specific/chemistry
- RNA, Transfer, Amino Acid-Specific/genetics
- RNA, Transfer, Amino Acid-Specific/isolation & purification
- Selenocysteine/genetics
- Selenocysteine/metabolism
- Selenoproteins
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Affiliation(s)
- Bradley A Carlson
- Section on Molecular Biology of Selenium, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Jameson RR, Carlson BA, Butz M, Esser K, Hatfield DL, Diamond AM. Selenium influences the turnover of selenocysteine tRNA([Ser]Sec) in Chinese hamster ovary cells. J Nutr 2002; 132:1830-5. [PMID: 12097655 DOI: 10.1093/jn/132.7.1830] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Selenocysteine transfer RNA (tRNA([Ser]Sec)) is a central molecule in the production of selenium-containing proteins, and may play a role in the regulation of their biosynthesis. Selenium concentration influences both the levels of tRNA([Ser]Sec) and the relative abundance of two isoforms. To study the mechanism by which selenium affects tRNA([Ser]Sec) levels, Chinese hamster ovary (CHO) cells were treated with the transcription inhibitor, actinomycin D, and tRNA([Ser]Sec) levels were determined by Northern blotting, primer extension and reverse-phase column chromatography. Turnover of tRNA([Ser]Sec) in CHO cells was faster than the total tRNA population. Supplementation of the culture media with selenium reduced turnover of tRNA([Ser]Sec), but did not influence turnover of a randomly selected serine tRNA. Inhibition of transcription with actinomycin D resulted in a relative increase in the abundance of the isoform containing methylcarboxymethyl-5'-uridine-2'-O-methylribose in the wobble position of the anticodon. Primer extension studies, which permitted the independent evaluation of the tRNA([Ser]Sec) arising from the introduced mouse gene and that derived from the host CHO gene, indicated an accelerated decline in tRNA([Ser]Sec) derived from both the transfected and the native gene. These results provide additional insight into the levels of regulation that control the translation of selenium containing proteins in mammalian cells.
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Affiliation(s)
- Ruth R Jameson
- Department of Human Nutrition, University of Illinois at Chicago, 60612, USA
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Martin-Romero FJ, Kryukov GV, Lobanov AV, Carlson BA, Lee BJ, Gladyshev VN, Hatfield DL. Selenium metabolism in Drosophila: selenoproteins, selenoprotein mRNA expression, fertility, and mortality. J Biol Chem 2001; 276:29798-804. [PMID: 11389138 DOI: 10.1074/jbc.m100422200] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Selenocysteine is a rare amino acid in protein that is encoded by UGA with the requirement of a downstream mRNA stem-loop structure, the selenocysteine insertion sequence element. To detect selenoproteins in Drosophila, the entire genome was analyzed with a novel program that searches for selenocysteine insertion sequence elements, followed by selenoprotein gene signature analyses. This computational screen and subsequent metabolic labeling with (75)Se and characterization of selenoprotein mRNA expression resulted in identification of three selenoproteins: selenophosphate synthetase 2 and novel G-rich and BthD selenoproteins that had no homology to known proteins. To assess a biological role for these proteins, a simple chemically defined medium that supports growth of adult Drosophila and requires selenium supplementation for optimal survival was devised. Flies survived on this medium supplemented with 10(-8) to 10(-6) m selenium or on the commonly used yeast-based complete medium at about twice the rate as those on a medium without selenium or with >10(-6) m selenium. This effect correlated with changes in selenoprotein mRNA expression. The number of eggs laid by Drosophila was reduced approximately in half in the chemically defined medium compared with the same medium supplemented with selenium. The data provide evidence that dietary selenium deficiency shortens, while supplementation of the diet with selenium normalizes the Drosophila life span by a process that may involve the newly identified selenoproteins.
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Affiliation(s)
- F J Martin-Romero
- Section on the Molecular Biology of Selenium, Basic Research Laboratory, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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