SEQUENCING, DISRUPTION, AND CHARACTERIZATION OF THE CANDIDA-ALBICANS STEROL METHYLTRANSFERASE (ERG6) GENE - DRUG SUSCEPTIBILITY STUDIES IN ERG6 MUTANTS

The rise in the frequency of fungal infections and the increased resis tance noted to the widely employed azole antifungals make the developm ent of new antifungals imperative for human health. The sterol biosynt hetic pathway has been exploited for the development of several antifu ngal agents (allylamines, morpholines, azoles), but additional potenti al sites for antifungal agent development are yet to be fully investig ated. The sterol methyltransferase gene (ERG6) catalyzes a biosyntheti c step not, found in humans and has been shown to result in several co mpromised phenotypes, most notably markedly increased permeability, wh en disrupted in Saccharomyces cerevisiae. The Candida albicans ERG6 ge ne was isolated by complementation of a S. cerevisiae erg6 mutant by u sing a C. albicans genomic library, Sequencing of the Candida ERG6 gen e revealed high homology with the Saccharomyces version of ERG6. The f irst copy of the Candida ERG6 gene was disrupted by transforming with the URA3 blaster system, and the second copy was disrupted by both URA 3 blaster transformation and mitotic recombination. The resulting erg6 strains were shown to be hypersusceptible to a number of sterol synth esis and metabolic inhibitors, including terbinafine, tridemorph, fenp ropiomorph, fluphenazine, cycloheximide, cerulenin, and brefeldin A. N o increase in susceptibility to azoles was noted. Inhibitors of the ER G6 gene product would make the cell increasingly susceptible to antifu ngal agents as well as to new agents which normally would be excluded and would allow for clinical treatment at lower dosages. In addition, the availability of ERG6 would allow for its use as a screen for new a ntifungals targeted specifically to the sterol methyltransferase.