Nickel resistance and chromatin condensation in Saccharomyces cerevisiae expressing a maize high mobility group I/Y protein.
Expression of a maize cDNA encoding a high mobility group (HMG) I/Y protein enables growth of transformed yeast on a medium containing toxic nickel concentrations. No difference in the nickel content was measured between yeast cells expressing either the empty vector or the ZmHMG I/Y2 cDNA. The ZmHMG I/Y2 protein contains four AT hook motifs known to be involved in binding to the minor groove of AT-rich DNA regions. HMG I/Y proteins may act as architectural elements modifying chromatin structure. Indeed, a ZmHMG I/Y2-green fluorescent protein fusion protein was observed in yeast nuclei. Nickel toxicity has been suggested to occur through an epigenetic mechanism related to chromatin condensation and DNA methylation, leading to the silencing of neighboring genes. Therefore, the ZmHMG I/Y2 protein could prevent nickel toxicity by interfering with chromatin structure. Yeast cell growth in the presence of nickel and yeast cells expressing the ZmHMG I/Y2 cDNA increased telomeric URA3 gene silencing. Furthermore, ZmHMG I/Y2 restored a wild-type level of nickel sensitivity to the yeast (Delta)rpd3 mutant. Therefore, nickel resistance of yeast cells expressing the ZmHMG I/Y2 cDNA is likely achieved by chromatin structure modification, restricting nickel accessibility to DNA.
Biochimie et Physiologie Moléculaire des Plantes, CNRS Unité Mixte de Recherche 5004, Université Montpellier 2, Institut National de la Recherche Agronomique, Ecole Nationale Supérieure d'Agronomie, 2 place Viala, F-34060 Montpellier Cedex 1, France.
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Forzani
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Loulergue
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Lobréaux
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Briat
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Lebrun
D000595:Amino Acid Sequence; D001483:Base Sequence; D002843:Chromatin / Q000502:physiology*; D003001:Cloning, Molecular; D004351:Drug Resistance; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D025741:HMGA1a Protein; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D008969:Molecular Sequence Data; D009532:Nickel / Q000494:pharmacology*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000235:genetics* / Q000502:physiology
D002843:Chromatin; C107092:HMGA1a Protein, plant; D006609:High Mobility Group Proteins; D008164:Luminescent Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D025741:HMGA1a Protein; D049452:Green Fluorescent Proteins; D009532:Nickel