The CUP2 Gene Product, Regulator of Yeast Metallothionein Expression, Is a Copper-Activated DNA-Binding Protein

Abstract

CUP2 is a regulatory gene controlling expression of CUP1, which encodes the Cu-binding yeast metallothionein. CUP2, which is identical to the ACE1 gene, encodes a Cu-regulated DNA-binding protein. The CUP2 protein contains a cysteine-rich DNA-binding domain dependent on Cu⁺ and Ag⁺ ions which bind the cysteine residues and direct the refolding of the metal-free apoprotein. CUP2 mutant alleles from Cu-sensitive yeast strains have point mutations affecting the DNA-binding activity. These results establish CUP2 as the primary sensor of intracellular Cu⁺ in the yeast Saccharomyces cerevisiae, functioning as a Cu⁺-regulated transcriptional activator.