The copper-dependent ACE1 transcription factor activates the transcription of the mco1 gene from the basidiomycete Phanerochaete chrysosporium

We have previously identified and functionally characterized the transcription factor ACE1 (Pc-ACE1) from Phanerochaete chrysosporium. In Saccharomyces cerevisiae, ACE1 activates the copper-dependent transcription of target genes through a DNA sequence element named ACE. However, the possible target gene(s) of Pc-ACE1 were unknown. An in silico search led to the identification of putative ACE elements in the promoter region of mco1, one of the four clustered genes encoding multicopper oxidases (MCOs) in P. chrysosporium. Since copper exerts an effect at the transcriptional level in MCOs from several organisms, in this work we analysed the effect of copper on transcript levels of the clustered MCO genes from P. chrysosporium, with the exception of the transcriptionally inactive mco3. Copper supplementation of cultures produced an increment in transcripts from genes mco1 and mco2, but not from mco4. Electrophoretic mobility-shift assays revealed that Pc-ACE1 binds specifically to a probe containing one of the putative ACE elements found in the promoter of mco1. In addition, using a cell-free transcription system, we showed that in the presence of cuprous ion, Pc-ACE1 induces activation of the promoter of mco1, but not that of mco2.