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

Transcription factor Ace1 from Saccharomyces cerevisiae regulates the expression of target genes when the copper concentration reaches 200 ìÌ levels. We are studying the ortholog of Ace1 from fungus Phanerochaete chrysosporium PcACE1, isolated by complementation in yeast. In this report we show the localization of the transactivation region of PcACE1. Different PcACE1 fragments were ligated in frame to the GAL4 DNA-binding domain by site-directed mutagenesis in a suitable yeast expression vector. Transformation of an appropriate Saccharomyces cerevisiae strain was used as host. This strain contains the fusion GAL1:lacZ in its genome under the control of promoter sequences recognized by GAL4. Finally, we measured â-galactosidase activity in each yeast clone. The activation of the reporter gene is proportional to the transactivation capacity of the transcription factor PcACE1. The results obtained indicate that PcACE1 transactivation domain is located in the carboxy terminal half and contains an array of cysteines in the form of Cys-X-Cys and Cys-X2-Cys and a 60% of Ser. Therefore, these results show that this type of Cys motif can function as transcription activating domain not only in transcription factors that respond to minimal copper concentrations but also in those that respond to high copper concentrations. This is the first transactivation domain reported in a basidiomycete fungus.

Cloning and functional characterization of the gene encoding the transcription factor Acel in the basidiomycete Phanerochaete chrysosporium

In this report we describe the isolation and characterization of a gene encoding the transcription factor Acel (Activation protein of cup 1 Expression) in the white rot fungus Phanerochaete chrysosporium. Pc-acel encodes a predicted protein of 633 amino acids containing the copper-fist DNA binding domain typically found in fungal transcription factors such as Acel, Macl and Haal from Saccharomyces cerevisiae. The Pc-acel gene is localized in Scaffold 5, between coordinates 220841 and 222983. A S. cerevisiae acel null mutant strain unable to grow in high-copper medium was fully complemented by transformation with the cDNA of Pc-acel. Moreover, Northern blot hybridization studies indicated that Pc-acel cDNA restores copper inducibility of the yeast cup 1 gene, which encodes the metal-binding protein metallothionein implicated in copper resistance. To our knowledge, this is first report describing an Acel transcription factor in basidiomycetes.