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1.
PLoS One ; 6(11): e27772, 2011.
Article in English | MEDLINE | ID: mdl-22114689

ABSTRACT

Boron is an essential micronutrient for plants, and it is beneficial for animals. However, at high concentrations boron is toxic to cells although the mechanism of this toxicity is not known. Atr1 has recently been identified as a boron efflux pump whose expression is upregulated in response to boron treatment. Here, we found that the expression of ATR1 is associated with expression of genes involved in amino acid biosynthesis. These mechanisms are strictly controlled by the transcription factor Gcn4 in response to boron treatment. Further analyses have shown that boron impaired protein synthesis by promoting phosphorylation of eIF2α in a Gcn2 kinase dependent manner. The uncharged tRNA binding domain (HisRS) of Gcn2 is necessary for the phosphorylation of eIF2α in the presence of boron. We postulate that boron exerts its toxic effect through activation of the general amino acid control system and inhibition of protein synthesis. Since the general amino acid control pathway is conserved among eukaryotes, this mechanism of boron toxicity may be of general importance.


Subject(s)
Amino Acids/metabolism , Boron/adverse effects , Protein Biosynthesis/drug effects , Saccharomyces cerevisiae/drug effects , Aminoacylation/drug effects , Basic-Leucine Zipper Transcription Factors/genetics , Basic-Leucine Zipper Transcription Factors/metabolism , Biomarkers/metabolism , Blotting, Western , Gene Expression Profiling , Membrane Transport Proteins/genetics , Membrane Transport Proteins/metabolism , Oligonucleotide Array Sequence Analysis , Phosphorylation/drug effects , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , RNA, Messenger/genetics , RNA, Transfer , Real-Time Polymerase Chain Reaction , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae Proteins/metabolism , eIF-2 Kinase/genetics , eIF-2 Kinase/metabolism
2.
Biochem Biophys Res Commun ; 409(4): 748-51, 2011 Jun 17.
Article in English | MEDLINE | ID: mdl-21621519

ABSTRACT

Boron is a necessary nutrient for plants and animals, however excess of it causes toxicity. Previously, Atr1 and Arabidopsis Bor1 homolog were identified as the boron efflux pump in yeast, which lower the cytosolic boron concentration and help cells to survive in the presence of toxic amount of boron. In this study, we analyzed ATR1 paralogs, YMR279c and YOR378w, to understand whether they participate in boron stress tolerance in yeast. Even though these genes share homology with ATR1, neither their deletion rendered cells boron sensitive nor their expression was significantly upregulated by boron treatment. However, expression of YMR279, but not YOR378w, from the constitutive GAPDH promoter on a high copy plasmid provided remarkable boron resistance by decreasing intracellular boron levels. Thus our results suggest the presence of a third boron exporter, YMR279c, which functions similar to ATR1 and provides boron resistance in yeast.


Subject(s)
Boron/metabolism , Drug Resistance, Fungal , Membrane Transport Proteins/physiology , Saccharomyces cerevisiae Proteins/physiology , Saccharomyces cerevisiae/metabolism , Stress, Physiological , Antiporters/physiology , Arabidopsis Proteins/physiology , Boron/toxicity , Cell Proliferation/drug effects , Membrane Transport Proteins/genetics , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae Proteins/genetics
3.
Genomics ; 97(2): 106-11, 2011 Feb.
Article in English | MEDLINE | ID: mdl-21035538

ABSTRACT

Boron is an essential micronutrient for plants and it is either necessary or beneficial for animals. Studies identified only few genes related to boron metabolism thus far and details of how boron is imported into cells and used in cell metabolism are largely unknown. In order to identify genes that play roles in boron metabolism, we screened the entire set of yeast haploid deletion mutants and identified 6 mutants that were resistant to toxic levels of boron, and 21 mutants that were highly sensitive to boron treatment. Furthermore, we performed a proteomic approach to identify additional proteins that are significantly up-regulated by boron treatment. Our results revealed many genes and pathways related to boron stress response and suggest a possible link between boron toxicity and translational control.


Subject(s)
Boron/metabolism , Genome-Wide Association Study , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/metabolism , Stress, Physiological/genetics , Animals , Boron/pharmacology , Gene Expression Profiling , Haploidy , Saccharomyces cerevisiae/drug effects , Sequence Deletion , Up-Regulation
4.
Mol Cell Biol ; 29(13): 3665-74, 2009 Jul.
Article in English | MEDLINE | ID: mdl-19414602

ABSTRACT

Boron is a micronutrient in plants and animals, but its specific roles in cellular processes are not known. To understand boron transport and functions, we screened a yeast genomic DNA library for genes that confer resistance to the element in Saccharomyces cerevisiae. Thirty boron-resistant transformants were isolated, and they all contained the ATR1 (YML116w) gene. Atr1 is a multidrug resistance transport protein belonging to the major facilitator superfamily. C-terminal green fluorescent protein-tagged Atr1 localized to the cell membrane and vacuole, and ATR1 gene expression was upregulated by boron and several stress conditions. We found that atr1Delta mutants were highly sensitive to boron treatment, whereas cells overexpressing ATR1 were boron resistant. In addition, atr1Delta cells accumulated boron, whereas ATR1-overexpressing cells had low intracellular levels of the element. Furthermore, atr1Delta cells showed stronger boron-dependent phenotypes than mutants deficient in genes previously reported to be implicated in boron metabolism. ATR1 is widely distributed in bacteria, archaea, and lower eukaryotes. Our data suggest that Atr1 functions as a boron efflux pump and is required for boron tolerance.


Subject(s)
Boron/metabolism , Membrane Transport Proteins/metabolism , Saccharomyces cerevisiae Proteins/metabolism , Saccharomyces cerevisiae/metabolism , Amino Acid Sequence , Animals , Biological Transport/physiology , Boric Acids/metabolism , Gene Expression Profiling , Insecticides/metabolism , Membrane Transport Proteins/classification , Membrane Transport Proteins/genetics , Molecular Sequence Data , Oligonucleotide Array Sequence Analysis , Phylogeny , Protein Isoforms/genetics , Protein Isoforms/metabolism , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae Proteins/classification , Saccharomyces cerevisiae Proteins/genetics , Sequence Alignment , Sequence Homology, Amino Acid , Stress, Physiological
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