The Fission Yeast Copper-sensing Transcription Factor Cuf1 Regulates the Copper Transporter Gene Expression through an Ace1/Amt1-like Recognition Sequence

Abstract

Transcriptional regulation of genes encoding critical components of copper transport is essential for copper homeostasis and growth in yeast. Analysis of regulatory regions in the promoter of the ctr4 ؉ copper transporter gene in fission yeast Schizosaccharomyces pombe reveals the identity of a conserved copper-signaling element (CuSE), which is recognized by the transcription factor Cuf1. We demonstrate that CuSE is necessary for transcriptional activation in response to copper deprivation conditions. Interestingly, the CuSE element bears a strong sequence similarity to the recognition site, denoted MRE (metal regulatory element), which is recognized by a distinct class of copper sensors required for copper detoxification, including Ace1 from Saccharomyces cerevisiae and Amt1 from Candida glabrata. When a consensus MRE from S. cerevisiae is introduced into S. pombe, transcription is induced by copper deprivation in a Cuf1-dependent manner, similar to regulation by Mac1, the nuclear sensor for regulating the expression of genes encoding components involved in copper transport in S. cerevisiae. UV-cross-linking experiments show that the Cuf1 protein directly binds the CuSE. These results demonstrate that the Cuf1 nutritional copper-sensing factor possesses a module that functions similarly to domains found in the Ace1/Amt1 class of metalloregulatory factors, which allows the protein to act through a closely related MRE-like sequence to regulate copper transport gene expression in S. pombe.

The Schizosaccharomyces pombe Pccs Protein Functions in Both Copper Trafficking and Metal Detoxification Pathways

“…In response to copper limitation, Ctr6 appears to mediate the efflux of usable copper from the vacuole into the cytosol (56). Like the ctr4 ϩ and ctr5 ϩ genes, ctr6 ϩ expression is regulated by the Cuf1 transcription factor and is induced in copper-limited cells (54,56,57). Cuf1 plays an essential role in coordinating the copper-dependent transcriptional regulation of copper transporter gene expression in S. pombe.…”

“…Cuf1 plays an essential role in coordinating the copper-dependent transcriptional regulation of copper transporter gene expression in S. pombe. This regulation involves cis-acting coppersignaling elements (CuSEs) found in each of the ctr4 ϩ , ctr5 ϩ , and ctr6 ϩ promoters (56,57). Binding studies reveal that the Cuf1 N-terminal 174 amino acids are important for binding to the CuSE (58).…”

Ctr6, a Vacuolar Membrane Copper Transporter inSchizosaccharomyces pombe

“…Once copper ions are transported by the Ctr4-Ctr5 complex into the cells, they are presumably taken by putative copper chaperones, which are yet uncharacterized at the molecular level (41). A hallmark of the ctr4 ϩ and ctr5 ϩ genes is the fact that they are transcriptionally regulated according to copper need (40,42). The expression of ctr4 ϩ and ctr5 ϩ is activated under copper starvation conditions, whereas repression of these genes occurs under copper-replete conditions.…”

“…The expression of ctr4 ϩ and ctr5 ϩ is activated under copper starvation conditions, whereas repression of these genes occurs under copper-replete conditions. This regulation is mediated by the cis-acting promoter element, denoted CuSE (Cu-signaling element) with the consensus sequence 5Ј-D(T/A)DDHGCTGD-3Ј (D ϭ A, G, or T; H ϭ A, C, or T) (42). The transcription factor responsible for regulating the copper-dependent expression of genes encoding components involved in copper transport through the CuSEs is Cuf1 (40,42).…”

The PcACE1 transcription factor from Phanerochaete chrysosporium contains a Cys- and Ser-rich transactivation domain

“…Cuf1, from Schizosaccharomyces pombe, stimulates copper transport from the vacuole to the cytoplasm through ctr6 (Beaudoin and Labbé, 2001). GRISEA, the ortholog of Mac1 in Podospora anserina, activates the expression of the genes PaSOD2 and PaCtr3, encoding a mitochondrial manganese superoxide dismutase and a copper transporter, respectively (Borghouts et al, 2002).…”