Copper ions and the regulation of Saccharomyces cerevisiae metallothionein genes under aerobic and anaerobic conditions.
We have previously reported that the Saccharomyces cerevisiae CRS5 metallothionein gene is negatively regulated by oxygen. The mechanism of this repression was the focus of the current study. We observed that the aerobic repression of CRS5 is rapid and occurs within minutes of exposing anaerobic cultures to air. Furthermore, the CUP1 metallothionein gene of S. cerevisiae was found to be subject to a similar downregulation of gene expression. We provide evidence that the aerobic repression of yeast metallothioneins involves copper ions and Ace1, the copper trans-activator of CUP1 and CRS5 gene expression. A functional Ace1 binding site was found to be necessary for the aerobic repression of CRS5. Moreover, the aerobic down-regulation of the metallothioneins was abolished when cells were treated with elevated levels of copper. Our studies show that anaerobic cultures accumulate higher levels of copper than do aerobic cells and that this copper is rapidly lost when cells are exposed to air. In fact, the kinetics of this copper loss closely parallels the kinetics of CUP1 and CRS5 gene repression. The yeast metallothionein genes, therefore, serve as excellent markers for variations in copper accumulation and homeostasis that occur in response to changes in the oxidative status of the cell.
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Department of Environmental Health Sciences, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205, USA.
Culotta
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D001483:Base Sequence; D002352:Carrier Proteins; D003300:Copper / Q000378:metabolism*; D019327:Copper Sulfate; D004271:DNA, Fungal; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D007477:Ions; D008668:Metallothionein / Q000235:genetics*; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000378:metabolism
C089939:CRS5 protein, S cerevisiae; C500769:CUP1-1 protein, S cerevisiae; C060256:CUP2 protein, S cerevisiae; D002352:Carrier Proteins; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D007477:Ions; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C007121:copper thionein; D003300:Copper; D008668:Metallothionein; D019327:Copper Sulfate; D010100:Oxygen