Nuclear tRNA aminoacylation and its role in nuclear export of endogenous tRNAs in
            <i>Saccharomyces</i>
            <i>cerevisiae</i>

Sarkar, Soumalya; Azad, Abul Kalam; Hopper, Anita K.

doi:10.1073/pnas.96.25.14366

Cited by 133 publications

(167 citation statements)

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“…Aminoacylation also proved to be important for tRNA export in yeast, as demonstrated by analysis of tRNA synthetase mutants, amino acid starvation, and addition of inhibitors of synthetases (21,22). An added element of tRNA quality control in the yeast nucleus is the recently discovered nuclear tRNA degradation system that acts by polyadenylation of the tRNA, followed by exonucleolytic cleavage of tRNA (23).…”

Section: Problems With the Classical View Of Trna Processingmentioning

confidence: 99%

Have tRNA, will travel

Phizicky

2005

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

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Section: Problems With the Classical View Of Trna Processingmentioning

confidence: 99%

Have tRNA, will travel

Phizicky

2005

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

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“…Aminoacylated tRNAs were prepared under acidic conditions (0.3 m NaOAc, pH 4.5, and 10 mm EDTA) via glass bead lysis (Sarkar et al 1999) and RNAs were separated by electrophoresis on a 10% polyacrylamide, pH 4.5, 8 m urea gel. Cells were grown in liquid SD medium at 28°to OD 600 $1 (t ¼ 0) and then transferred for 3-8 hr to 37°.…”

Section: F35mentioning

confidence: 99%

Guanine Nucleotide Pool Imbalance Impairs Multiple Steps of Protein Synthesis and Disrupts GCN4 Translational Control in Saccharomyces cerevisiae

et al. 2011

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Purine nucleotides are structural components of the genetic material, function as phosphate donors, participate in cellular signaling, are cofactors in enzymatic reactions, and constitute the main carriers of cellular energy. Thus, imbalances in A/G nucleotide biosynthesis affect nearly the whole cellular metabolism and must be tightly regulated. We have identified a substitution mutation (G388D) that reduces the activity of the GMP synthase Gua1 in budding yeast and the total G-nucleotide pool, leading to precipitous reductions in the GDP/GTP ratio and ATP level in vivo. gua1-G388D strongly reduces the rate of growth, impairs general protein synthesis, and derepresses translation of GCN4 mRNA, encoding a transcriptional activator of diverse amino acid biosynthetic enzymes. Although processing of pre-tRNA i Met and other tRNA precursors, and the aminoacylation of tRNA iMet are also strongly impaired in gua1-G388D cells, tRNA i GTP complex (TC) and the multifactor complex (MFC) required for translation initiation accumulate $10-fold in gua1-G388D cells and, to a lesser extent, in wild-type (WT) cells treated with 6-azauracil (6AU). Consistently, addition of an external supply of guanine reverts all the phenotypes of gua1-G388D cells, but not those of gua1-G388D Dhpt1 mutants unable to refill the internal GMP pool through the salvage pathway. These and other findings suggest that a defect in guanine nucleotide biosynthesis evokes a reduction in the rate of general protein synthesis by impairing multiple steps of the process, disrupts the gene-specific reinitiation mechanism for translation of GCN4 mRNA and has far-reaching effects in cell biology and metabolism.

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“…to be aminoacylated (14)(15)(16). Even los1⌬ causes up-regulation of Gcn4, which generally occurs when there are insufficient cellular pools of aminoacylated tRNAs (31).…”

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confidence: 99%

Retrograde movement of tRNAs from the cytoplasm to the nucleus in Saccharomyces cerevisiae

Shaheen

Hopper

2005

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

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In eukaryotes, tRNAs transcribed in the nucleus function in cytoplasmic protein synthesis. The Ran-GTP-binding exportin, Los1p͞ Xpo-t, and additional pathway(s) mediate tRNA transport to the cytoplasm. Although tRNA movement was thought to be unidirectional, recent reports that yeast precursor tRNA splicing occurs in the cytoplasm, whereas fully spliced tRNAs can reside in the nucleus, require that either the precursor tRNA splicing machinery or mature tRNAs move from the cytoplasm to the nucleus. Our data argue against the first possibility and strongly support the second. Combining heterokaryon analysis with fluorescence in situ hybridization, we show that a foreign tRNA encoded by one nucleus can move from the cytoplasm to a second nucleus that does not encode the tRNA. We also discovered nuclear accumulation of endogenous cytoplasmic tRNAs in haploid yeast cells in response to nutritional deprivation. Nuclear accumulation of cytoplasmic tRNA requires Ran and the Mtr10͞Kap111 member of the importin-␤ family. Retrograde tRNA nuclear import may provide a novel mechanism to regulate gene expression in eukaryotes.amino acid deprivation ͉ heterokaryon ͉ Mtr10 ͉ tRNA nuclear import ͉ yeast E ukaryotic precursor tRNAs (pretRNAs) contain 5Ј and 3Ј extra sequences and, for Ϸ25% of Saccharomyces cerevisiae (yeast) tRNA families, introns. To be fully functional, pretRNAs are subject to several maturation steps, including removal of the extra sequences, numerous nucleoside modifications, and addition of the 3Ј terminal CCA nucleotides (1). In vertebrates, nearly all tRNA posttranscriptional processing occurs in the nucleus before export of tRNAs to the cytoplasm (1-3). In contrast, several lines of evidence show that in yeast, pretRNA intron removal occurs in the cytoplasm, not the nucleoplasm. First, the subunits of the heterotetrameric tRNA-specific splicing endonuclease, Sen15, Sen2, Sen34, and Sen54, colocalize with mitochondria (4, 5). Tethering of a noncatalytic subunit, Sen54, to mitochondria does not inhibit pretRNA splicing, whereas mutations prohibiting its mitochondrial association cause accumulation of unspliced pretRNAs (4). Moreover, cells with conditional mutations in a gene encoding a catalytic subunit, Sen2, accumulate unspliced pretRNAs in the cytoplasm (4). A previous report employing immunofluorescence and immune electron microscopy concluded that a large fraction of tRNA ligase, catalyzing second step of pretRNA splicing, resides in the nucleus (6); however, more recent reports show that there is a functional pool of tRNA ligase activity in the cytoplasm (7) and that carboxyl GFP-tagged ligase is cytosolic (5). Finally, a carboxyl GFP-tagged version of the enzyme catalyzing the third step of pretRNA splicing, removal of the residual 2Ј phosphate (8), is distributed throughout the cytoplasm (5).Splicing of pretRNAs in the cytoplasm provides an explanation for the pretRNA splicing defects observed when there are mutations in the tRNA nuclear export machinery, including the tRNA exportin, Los1p (9-11), ...

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Nuclear tRNA aminoacylation and its role in nuclear export of endogenous tRNAs in Saccharomyces cerevisiae

Cited by 133 publications

References 37 publications

Have tRNA, will travel

Have tRNA, will travel

Guanine Nucleotide Pool Imbalance Impairs Multiple Steps of Protein Synthesis and Disrupts GCN4 Translational Control in Saccharomyces cerevisiae

Retrograde movement of tRNAs from the cytoplasm to the nucleus in Saccharomyces cerevisiae

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