Expression of one-hybrid fusions with Staphylococcus aureus lexA in Candida albicans confirms that Nrg1 is a transcriptional repressor and that Gcn4 is a transcriptional activator

In the pathogenic fungus, Candida albicans, Nrgl down-regulates the expression of morphogenetic genes and is presumed to act as a transcriptional repressor. In contrast, Gcn4 up-regulates amino acid biosynthetic genes and is presumed to be a transcriptional activator. However, these presumptions remain to be tested directly. A classic approach has been to use a one-hybrid assay that exploits the Escherichia coli lexA protein fusions. However in C albicans, the alternate decoding of CUG as serine prevents the expression of heterologous genes such as lexA, which contain numerous CUG codons. Therefore, we have developed a one-hybrid system, based on the Staphylococcus aureus lexA gene, as a tool for one-hybrid analyses of transcription factors in C. dalbicans. Using this one-hybrid system we have confirmed directly the positive and negative transcriptional activities of Nrgl and Gcn4 in C. albicans. (c) 2005 Elsevier Inc. All rights reserved.