MAC1, a nuclear regulatory protein related to Cu-dependent transcription factors is involved in Cu/Fe utilization and stress resistance in yeast.

Abstract

The related transcription factors ACE1 of Saccharomyces cerevisiae and AMT1 of Candida glabrata are involved in copper metabolism by activating the transcription of copper metallothionein genes. ACE1 and AMT1 are ‘copper‐fist’ transcription factors which possess a conserved cysteine‐rich copper binding domain required for DNA binding. Here we report the identification of a nuclear protein from S. cerevisiae, MAC1, whose N‐terminal region is highly similar to the copper and DNA binding domains of ACE1 and AMT1. Loss‐of‐function mutants of MAC1 have a defect in the plasma membrane Cu(II) and Fe(III) reductase activity, are slow growing, respiratory deficient, and hypersensitive to heat and exposure to cadmium, zinc, lead and H2O2. Conversely, a dominant gain‐of‐function mutant of MAC1 shows an elevated reductase activity and is hypersensitive to copper. We have identified two target genes of MAC1 whose altered expression in mutants of MAC1 can account for some of the observed mutant phenotypes. First, MAC1 is involved in basal level transcription of FRE1, encoding a plasma membrane component associated with both Cu(II) and Fe(III) reduction. Second, MAC1 is involved in the H2O2‐induced transcription of CTT1, encoding the cytosolic catalase. This suggests that MAC1 may encode a novel metal‐fist transcription factor required for both basal and regulated transcription of genes involved in Cu/Fe utilization and the stress response.

Dynamic Regulation of Copper Uptake and Detoxification Genes in Saccharomyces cerevisiae

“…In contrast to the CUP1 gene, each of these genes is transcriptionally activated by Cu ion starvation and inactivated by Cu ion repletion (26). Both the transcriptional activation and inactivation of these genes require Mac1p (14,24,29,48). Furthermore, the ability to properly activate, via metallation, the Ace1p DNA binding domain depends on the presence of functional yeast Cu(I) ion transport machinery (9,25).…”

“…The high-affinity Cu(I) transport genes CTR1, CTR3, and FRE1 are transcriptionally downregulated by Cu ions and induced by Cu ion starvation. This Cu ion-dependent regulation requires a wild-type Mac1p Cu metalloregulatory transcription factor (CuMRTF) (15,24,29,48). Regulation of these genes by Mac1p is highly specific for and exquisitely sensitive to Cu ions (29).…”

“…In mac1⌬ strains, transcription of CTR1 and CTR3 is undetectable and the FRE1 gene is transcribed at low levels. In addition, yeast strains which possess a dominant MAC1 up1 allele exhibit high basal levels of CTR1, CTR3, and FRE1 mRNAs, a lack of Cu-dependent repression of CTR1 and CTR3 (29), and hypersensitivity to Cu ions (24). The mutations in Mac1p that lead to a dominant MAC1 up1 allele all map to the first of two cysteine clusters found in the carboxyl-terminal half of Mac1p (16,24,48,56).…”

“…In addition, yeast strains which possess a dominant MAC1 up1 allele exhibit high basal levels of CTR1, CTR3, and FRE1 mRNAs, a lack of Cu-dependent repression of CTR1 and CTR3 (29), and hypersensitivity to Cu ions (24). The mutations in Mac1p that lead to a dominant MAC1 up1 allele all map to the first of two cysteine clusters found in the carboxyl-terminal half of Mac1p (16,24,48,56). Regulation by Mac1p requires the Cu-responsive cis-acting elements (CuREs) 5Ј-TTTTGCTC-3Ј which are arranged either in tandem or inverted repeats in the promoters of the CTR1, CTR3, and FRE1 genes (29,48).…”

Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus

“…Fungal Cu-binding TFs tightly control expression levels of genes involved in Cu uptake and export under Cu-deficient conditions or Cu-excess respectively. In Saccharomyces cerevisiae , Cu importers Ctr1 and Ctr3, located in the plasma membrane, as well as the Cu-MTs Fre1 and Fre7 are activated by the Cu-binding TF Mac1 under Cu-insufficient conditions [8,16]. Under excess Cu, the S. cerevisiae Cu-binding TF Ace1 induces the MT-encoding genes CUP1 and CRS5 , and the Cu/Zn SOD-encoding gene SOD1 [8,17].…”