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The yeast Malassezia furfur is a natural inhabitant of the human skin microflora that induces an allergic reaction in atopic dermatitis. To identify allergens of M. furfur, we separated a crude preparation of M. furfur antigens as discrete spots by 2‐D PAGE and detected IgE‐binding proteins using sera of atopic dermatitis patients. We identified the known allergens, Mal f 2 and Mal f 3, and determined N‐terminal amino acid sequences of six new IgE‐binding proteins including Mal f 4. The cDNA and genomic DNA encoding Mal f 4 were cloned and sequenced. The gene was mitochondrial malate dehydrogenase and encoded Mal f 4 composed of 315 amino acids and a signal sequence of 27 amino acids. We purified Mal f 4, which had a molecular mass of 35 kDa from a membrane fraction of a lysate of cultured cells. Thirty of 36 M. furfur‐allergic atopic dermatitis patients (83.3%) had elevated serum levels of IgE to purified Mal f 4, indicating that Mal f 4 is a major allergen. There was a significant correlation of the Phadebas RAST unit values of Mal f 4 and the crude antigen, but not between Mal f 4 and the known allergen Mal f 2.

We show a new transformation system for prototrophic yeast strains including those of Saccharomyces cerevisiae, Kluyveromyces lactis, K. marxianus, and Candida glabrata. This system is composed of an antibiotic, aureobasidin A (AbA), and its resistance gene AUR1-C as a selection marker. Southern analysis of genomic DNAs of the transformants indicated that the copy number of the plasmid increased from one to more than four, depending on the concentration of AbA used for selection of the transformants. The AUR1-C gene was also effective as a selection marker for gene disruption, and was able to disrupt both copies of the gene on homologous chromosomes of diploid cells by a single round of transformation. This system has a broad application in the transformation and gene disruption of prototrophic strains of a variety of yeast species.z 1998 Federation of European Biochemical Societies.

To study the mechanism of action of the antibiotic aureobasidin A (AbA) on yeasts, we isolated a dominant mutant of Schizosaccharomyces pombe which gave high resistance to AbA. From a genomic library of the mutant, an aur1R mutant gene conferring AbA resistance was isolated. One amino-acid mutation, a substitution of glycine with cysteine at residue 240, was responsible for the acquisition of AbA resistance. The wild-type aur1+ gene was essential for viability, and its over-expression enhanced significant resistance to AbA. The predicted protein of S. pombe aur1R was highly homologous in primary structure and hydropathy profile with that of Saccharomyces cerevisiae AUR1R isolated as an AbA-resistance gene. To analyze a role in cell growth of S. pombe aur1+, temperature-sensitive mutants (aur1ts) were obtained by random mutagenesis procedures using a modified PCR. The aur1ts mutation caused a defect in cell elongation at the non-permissive temperature and finally led to cell death. These results suggest that Aur1p was a target of the antibiotic AbA and was required in the cell elongation of cell-end tips and in the viability of S. pombe.

Aureobasidin A (AbA) has strong antifungal effects arising from an unusual mechanism. We show that AbA interacts with ATP-binding cassette (ABC) transporters in yeast and mammalian cells. We isolated a gene ofSaccharomyces cerevisiae that conferred resistance to AbA when the gene was present in multiple copies. The gene was identical toYOR1/YRS1, which confers resistance to oligomycin, reveromycin, and organic anions, none of which have structures similar to that of AbA. We also isolated an aur3 Rrecessive mutant of S. cerevisiae with increased resistance to AbA. Northern hybridization showed that theaur3 R mutant expressed not onlyYOR1 but also the ABC transporter-encoding genePDR5 at high levels. Genetic studies showed that theaur3 R mutant had a mutation in thePDR1 gene, which encodes a transcriptional regulator ofPDR5 and YOR1. Analysis of a yor1disruptant of the aur3/pdr1 mutant showed that both the functional YOR1 gene and the mutation in PDR1were necessary for AbA resistance. These results suggest thatYOR1 is more important than PDR5 for AbA resistance. We found in Candida albicans a novel gene whose sequence was similar to the sequence of YOR1 in S. cerevisiae. The amino acid sequence of the C. albicans YOR1 homolog showed no significant similarity to the sequences ofCDR1 and CDR2, which are ABC transporters ofC. albicans. Furthermore, AbA inhibited the efflux of the anticancer agent vincristine through P glycoproteins in cancer cells with multidrug resistance.

The AUR1 gene of Saccharomyces cerevisiae, mutations in which confer resistance to the antibiotic aureobasidin A, is necessary for inositol phosphorylceramide (IPC) synthase activity. We report the molecular cloning and characterization of the Aspergillus nidulans aurA gene, which is homologous to AUR1. A single point mutation in the aurA gene of A. nidulans confers a high level of resistance to aureobasidin A. The A. nidulans aurA gene was used to identify its homologs in other Aspergillus species, including A. fumigatus, A. niger, and A. oryzae. The deduced amino acid sequence of an aurA homolog from the pathogenic fungus A. fumigatus showed 87% identity to that of A. nidulans. The AurA proteins of A. nidulans and A. fumigatus shared common characteristics in primary structure, including sequence, hydropathy profile, and N-glycosylation sites, with their S. cerevisiae, Schizosaccharomyces pombe, and Candida albicans counterparts. These results suggest that the aureobasidin resistance gene is conserved evolutionarily in various fungi.

We cultured human hair follicle-derived keratinocytes (FDKs) from plucked hairs. To gain insight into gene expression signatures that can distinguish atopic dermatitis from non-atopic controls without skin biopsies, we undertook a comparative study of gene expression in FDKs from adult donors with atopic dermatitis and non-atopic donors. FDK primary cultures (atopic dermatitis, n = 11; non-atopic controls, n = 7) before and after interferon gamma (IFN-γ) treatment were used for microarray analysis and quantitative RT-PCR. Comparison of FDKs from atopic and non-atopic donors indicated that the former showed activated pathways with innate immunity and decreased pathways of cell growth, as indicated by increased NLRP2 expression and decreased DKK1 expression, respectively. Treatment with IFN-γ induced the enhanced expression of IL32, IL1B, IL8, and CXCL1 in the cells from atopic donors compared to that in cells from non-atopic donors at 24 h after treatment. IL1B expression in FDKs after IFN-γ treatment correlated with IL32 expression. We hypothesized that overexpression of IL32 in hair follicle keratinocytes of patients with atopic dermatitis would lead to the excessive production of pro-IL1β and that the activation of IL1β from pro-IL1β by inflammasome complex, in which NLRP2 protein might be involved, would be augmented. This is the first report to show enhanced induction of cytokine/chemokine genes by IFN-γ in atopic dermatitis using cultured FDKs.