Knight S A, Tamai K T, Kosman D J, Thiele D J
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0606.
Mol Cell Biol. 1994 Dec;14(12):7792-804. doi: 10.1128/mcb.14.12.7792-7804.1994.
Yeast metallothionein, encoded by the CUP1 gene, and its copper-dependent transcriptional activator ACE1 play a key role in mediating copper resistance in Saccharomyces cerevisiae. Using an ethyl methanesulfonate mutant of a yeast strain in which CUP1 and ACE1 were deleted, we isolated a gene, designated CUP9, which permits yeast cells to grow at high concentrations of environmental copper, most notably when lactate is the sole carbon source. Disruption of CUP9, which is located on chromosome XVI, caused a loss of copper resistance in strains which possessed CUP1 and ACE1, as well as in the cup1 ace1 deletion strain. Measurement of intracellular copper levels of the wild-type and cup9-1 mutant demonstrated that total intracellular copper concentrations were unaffected by CUP9. CUP9 mRNA levels were, however, down regulated by copper when yeast cells were grown with glucose but not with lactate or glycerol-ethanol as the sole carbon source. This down regulation was independent of the copper metalloregulatory transcription factor ACE1. The DNA sequence of CUP9 predicts an open reading frame of 306 amino acids in which a 55-amino-acid sequence showed 47% identity with the homeobox domain of the human proto-oncogene PBX1, suggesting that CUP9 is a DNA-binding protein which regulates the expression of important copper homeostatic genes.
由CUP1基因编码的酵母金属硫蛋白及其铜依赖性转录激活因子ACE1在介导酿酒酵母的铜抗性中起关键作用。我们使用了一个缺失CUP1和ACE1的酵母菌株的甲磺酸乙酯突变体，分离出一个名为CUP9的基因，该基因能使酵母细胞在高浓度环境铜下生长，尤其是当乳酸作为唯一碳源时。位于第十六条染色体上的CUP9基因被破坏，导致拥有CUP1和ACE1的菌株以及cup1 ace1缺失菌株丧失铜抗性。对野生型和cup9 - 1突变体的细胞内铜水平进行测量表明，细胞内总铜浓度不受CUP9的影响。然而，当酵母细胞以葡萄糖为唯一碳源生长时，CUP9的mRNA水平会被铜下调，但以乳酸或甘油 - 乙醇为唯一碳源时则不会。这种下调与铜金属调节转录因子ACE1无关。CUP9的DNA序列预测有一个306个氨基酸的开放阅读框，其中一个55个氨基酸的序列与人类原癌基因PBX1的同源框结构域有47%的同一性，这表明CUP9是一种调节重要铜稳态基因表达的DNA结合蛋白。
