Effects of the antimicrobial drug SK-03-92 on Saccharomyces cerevisiae copper-related genes

Abstract

Faculty and students at UWL have developed and patented an antimicrobial, SK-03-92, that was derived from a stilbene produced by Comptonia peregrina (sweetfern). Work at UWL has shown that this compound is effective against a variety of gram positive bacteria but is not toxic in a mouse model. However, the precise mechanism of action of SK-03-92 has yet to be determined. We have been taking advantage of the genetics of Saccharomyces cerevisiae to provide a greater understanding of how the compound works. A large-scale RNA-seq analysis was performed on cultures of Saccharomyces cerevisiae that were treated with SK-03-93 for 60 minutes to determine the subset of genes that are dysregulated by cells in response to SK-03-92 treatment. Of the roughly 6,300 genes in yeast, the expression of 14 of the 25 genes involved in copper homeostasis was shown to be dysregulated in SK-03-92 treated yeast. Copper is an essential trace element, required for the function of many essential enzymes, but copper is also extremely toxic to cells when it is not properly sequestered. In this work, we determined that the CUP2 and LSO1 genes, both genes that are up-regulated in response to increased copper levels, were also up-regulated in response to SK-03-92 treatment. In addition, yeast strains with mutations in genes involved in copper homeostasis were affected by SK-03-92 treatment differently than wild type yeast strains. Finally, a spot assay showed that the combination of 4 μg/ml SK-03-92 and 16 mM CuSO₄ (MIC) (the MIC for each compound) caused a 10-fold decrease in survival relative to the untreated control, or either compound alone, after 30 and 60 minutes of treatment. Together, these results suggest that SK-03-92 treatment leads to a disruption of copper homeostasis in yeast cells.