Selenoproteins and selenocysteine insertion system in the model plant cell system, Chlamydomonas reinhardtii

Novoselov, Sergey V.

doi:10.1093/emboj/cdf372

Cited by 261 publications

(219 citation statements)

References 35 publications

Supporting

Mentioning

212

Contrasting

Unclassified

Order By: Relevance

“…This observation suggests a mechanism present in algae and animals but not in plants. An example of such a situation is the recently reported presence of selenoproteins in Chlamydomonas and animals but not in plants (52). In contrast, the absence of cysteine conservation might indicate a TRX regulation restricted to Chlamydomonas or algae, as in the case of inorganic pyrophosphatase.…”

Section: Figmentioning

confidence: 99%

New thioredoxin targets in the unicellular photosynthetic eukaryote Chlamydomonas reinhardtii

Lemaire

Guillon

Maréchal

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

231

188

View full text Add to dashboard Cite

Proteomics were used to identify the proteins from the eukaryotic unicellular green alga Chlamydomonas reinhardtii that can be reduced by thioredoxin. These proteins were retained specifically on a thioredoxin affinity column made of a monocysteinic thioredoxin mutant able to form mixed disulfides with its targets. Of a total of 55 identified targets, 29 had been found previously in higher plants or Synechocystis, but 26 were new targets. Biochemical tests were performed on three of them, showing a thioredoxindependent activation of isocitrate lyase and isopropylmalate dehydrogenase and a thioredoxin-dependent deactivation of catalase that is redox insensitive in Arabidopsis. In addition, we identified a Ran protein, a previously uncharacterized nuclear target in a photosynthetic organism. The metabolic and evolutionary implications of these findings are discussed.O ur knowledge on redox regulation of various physiological processes through thiol-disulfide interchange with proteins of the thioredoxin (TRX) superfamily is rapidly progressing as genome-wide approaches and functional genomics studies are expanding. In the plant biology domain, thioredoxin-dependent regulation has been first discovered for chloroplastic enzymes involved in carbon assimilation (1). The completion of the sequencing of the Arabidopsis genome revealed that TRXs constituted a multigene family and led to the assumption that numerous TRX targets were still to be discovered (2-4). Thus, proteomic approaches aimed at identifying the largest possible number of TRX targets have been developed. The first attempts took advantage of the reaction mechanism of TRXs with their targets, in which a transient heterodisulfide forms between the reduced TRX and the oxidized protein, followed by the release of the reduced target due to the attack of the mixed disulfide by the second cysteine of TRX. Model studies showed that when this second cysteine was mutated, the heterodisulfide was stabilized (5, 6). This property was applied in vivo by transforming a TRX-null mutant yeast with a monocysteinic TRX and allowed isolating a peroxiredoxin (PRX) (7). Subsequently, monocysteinic TRX mutants were used in affinity chromatography to trap interacting proteins (8-11). Native TRX affinity columns also allowed retaining some targets by electrostatic interaction (12). Another technique was also developed that consists of a reduction of a crude soluble protein extract with reduced TRX followed by a separation of the proteins on a 2D gel after derivatization of the newly appeared thiols either with a fluorescent (13) or with a radioactive (14) reagent. In one case, both techniques have been applied in parallel (15), yielding similar results.Most of the disulfide proteomics have been led with higher plants: spinach (8, 10, 12), Arabidopsis (11, 14), or cereal grains (12). A single study was led with cyanobacteria and revealed targets mostly different from those of higher plants (16). The unicellular eukaryotic green alga Chlamydomonas reinhardtii possesses a TRX syste...

show abstract

Section: Figmentioning

confidence: 99%

New thioredoxin targets in the unicellular photosynthetic eukaryote Chlamydomonas reinhardtii

Lemaire

Guillon

Maréchal

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

231

188

View full text Add to dashboard Cite

show abstract

“…When excess quaternary complexes are available in the cell, they bind the SECIS-like element and repress synthesis of SelA and SelB (Thanbichler and Bö ck 2002). Comparable pathways for selenocysteine insertion have been found in archaea (Rother et al 2003), animals (e.g., the human genome encodes 25 selenoproteins; Kryukov et al 2003), and most recently plants (Novoselov et al 2002;Rao et al 2003). The exact mechanism of insertion in archaea and eukaryotes differs from bacteria in two main aspects.…”

Section: 22mentioning

confidence: 99%

Aminoacyl-tRNAs: setting the limits of the genetic code

Ibba¹,

Söll²

2004

Genes Dev.

151

113

View full text Add to dashboard Cite

Aminoacyl-tRNAs (aa-tRNAs) are simple molecules with a single purpose-to serve as substrates for translation. They consist of mature tRNAs to which an amino acid has been esterified at the 3Ј-end. The 20 different types of aa-tRNA are made by the 20 different aminoacyl-tRNA synthetases (aaRSs, of which there are two classes), one for each amino acid of the genetic code . This would be fine if it were not for the fact that such a straightforward textbook scenario is not true in a single known living organism. aa-tRNAs lie at the heart of gene expression; they interpret the genetic code by providing the interface between nucleic acid triplets in mRNA and the corresponding amino acids in proteins. The synthesis of aa-tRNAs impacts the accuracy of translation, the expansion of the genetic code, and even provides tangible links to primary metabolism. These central roles vest immense power in aa-tRNAs, and recent studies show just how complex and diverse their synthesis is.

show abstract

“…Although having low sequence conservation, the secondary structure of eukaryotic SECIS elements is strictly conserved and thermodynamically stable (15,16). Based on these observations, several algorithms have been developed and successfully applied in genomic searches to identify these stem-loop structures, and thereby selenoprotein genes, in nucleotide sequence databases (5,7,(17)(18)(19).It has been established that the quartet is involved in the interaction with SECIS-binding protein 2 (SBP2) (20,21), which, in turn, is essential for the formation of a complex with the Sec-specific elongation factor, known as EFsec, and tRNA [Ser]Sec (22,23). This protein-RNA complex functions by inserting Sec in response to UGA codons (24).…”

mentioning

confidence: 99%

A highly efficient form of the selenocysteine insertion sequence element in protozoan parasites and its use in mammalian cells

Novoselov

Lobanov

Hua

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Selenoproteins are an elite group of proteins containing a rare amino acid, selenocysteine (Sec), encoded by the codon, UGA. In eukaryotes, incorporation of Sec requires a Sec insertion sequence (SECIS) element, a stem-loop structure located in the 3 -untranslated regions of selenoprotein mRNAs. Here we report identification of a noncanonical form of SECIS element in Toxoplasma gondii and Neospora canine, single-celled apicomplexan parasites of humans and domestic animals. This SECIS has a GGGA sequence in the SBP2-binding site in place of AUGA previously considered invariant. Using a combination of computational and molecular techniques, we show that Toxoplasma and Neospora possess both canonical and noncanonical SECIS elements. The GGGA-type SECIS element supported Sec insertion in mammalian HEK 293 and NIH 3T3 cells and did so more efficiently than the natural mammalian SECIS elements tested. In addition, mammalian type I and type II SECIS elements mutated into the GGGA forms were functional but manifested decreased Sec insertion efficiency. We carried out computational searches for both AUGA and GGGA forms of SECIS elements in Toxoplasma and detected five selenoprotein genes, including one coding for a previously undescribed selenoprotein, designated SelQ, and two containing the GGGA form of the SECIS element. In contrast, the GGGA-type SECIS elements were not detected in mammals and nematodes. As a practical outcome of the study, we developed pSelExpress1, a vector for convenient expression of selenoproteins in mammalian cells. It contains an SBP2 gene and the most efficient tested SECIS element: an AUGA mutant of the GGGA-type Toxoplasma SelT structure.genome ͉ RNA structure ͉ selenocysteine ͉ selenoprotein S elenocysteine (Sec)-containing proteins (selenoproteins) are rare but widely distributed in all domains of life (1), including bacteria (2, 3), archaea (4), and eukaryotes (5-7). The human genome possesses 25 genes encoding such proteins (7). The class of selenoproteins is defined by the occurrence of Sec, the 21st amino acid encoded by the UGA codon. Selenoproteins use the high reactivity of Sec, which is located in catalytic centers and serves redox function analogous to the functions of redox-active Cys residues (8). In addition to the UGA codon, a cis-acting element is present within selenoprotein genes, which is also essential for recognition of UGA as the Sec codon. This element is a stem-loop structure, known as the Sec insertion sequence (SECIS) located in coding regions of bacterial and in 3Ј-UTRs of archaeal and eukaryotic selenoprotein genes (9, 10).The principal features of the eukaryotic SECIS element include a segment containing four non-Watson-Crick base pairs UGAN. . . . NGAN (designated the quartet or core), an unpaired A preceding the quartet, and an unpaired AA or CC motif in the apical loop or bulge that is separated from the quartet by 11-12 nucleotides (11-14). Although having low sequence conservation, the secondary structure of eukaryotic SECIS elements is strictly conserved an...

show abstract

Selenoproteins and selenocysteine insertion system in the model plant cell system, Chlamydomonas reinhardtii

Cited by 261 publications

References 35 publications

New thioredoxin targets in the unicellular photosynthetic eukaryote Chlamydomonas reinhardtii

New thioredoxin targets in the unicellular photosynthetic eukaryote Chlamydomonas reinhardtii

Aminoacyl-tRNAs: setting the limits of the genetic code

A highly efficient form of the selenocysteine insertion sequence element in protozoan parasites and its use in mammalian cells

Contact Info

Product

Resources

About