Zhou P, Szczypka M S, Sosinowski T, Thiele D J
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0606.
Mol Cell Biol. 1992 Sep;12(9):3766-75. doi: 10.1128/mcb.12.9.3766-3775.1992.
The opportunistic pathogenic yeast Candida glabrata elicits at least two major responses in the presence of high environmental metal levels: transcriptional induction of the metallothionein gene family by copper and the appearance of small (gamma-Glu-Cys)nGly peptides in the presence of cadmium. On the basis of a trans-activation selection scheme in the baker's yeast Saccharomyces cerevisiae, we previously isolated a C. glabrata gene which encodes a copper-activated DNA-binding protein designated AMT1. AMT1 forms multiple specific DNA-protein complexes with both C. glabrata MT-I and MT-IIa promoter DNA fragments. In this report, we localize and define the AMT1-binding sites in the MT-I and MT-IIa promoters and characterize the mode of AMT1 binding. Furthermore, we demonstrate that the AMT1 protein trans activates both the MT-I and MT-IIa genes in vivo in response to copper and that this activation is essential for high-level copper resistance in C. glabrata. Although AMT1-mediated trans activation of the C. glabrata metallothionein genes is essential for copper resistance, AMT1 is completely dispensable for cadmium tolerance. The distinct function that metallothionein genes have in copper but not cadmium detoxification in C. glabrata is in contrast to the role that metallothionein genes play in tolerance to multiple metals in higher organisms.
铜诱导金属硫蛋白基因家族的转录，以及在镉存在下出现小的（γ-谷氨酰-半胱氨酸）n甘肽。基于酿酒酵母中的反式激活选择方案，我们先前分离出了光滑念珠菌的一个基因，该基因编码一种名为AMT1的铜激活DNA结合蛋白。AMT1与光滑念珠菌MT-I和MT-IIa启动子DNA片段形成多种特异性DNA-蛋白质复合物。在本报告中，我们定位并确定了MT-I和MT-IIa启动子中的AMT1结合位点，并表征了AMT1的结合模式。此外，我们证明AMT1蛋白在体内响应铜而反式激活MT-I和MT-IIa基因，并且这种激活对于光滑念珠菌的高水平铜抗性至关重要。尽管AMT1介导的光滑念珠菌金属硫蛋白基因的反式激活对于铜抗性至关重要，但AMT1对于镉耐受性是完全可有可无的。光滑念珠菌中金属硫蛋白基因在铜解毒而非镉解毒中具有的独特功能与金属硫蛋白基因在高等生物对多种金属的耐受性中所起的作用形成对比。
