A yeast sterol auxotroph (erg25) is rescued by addition of azole antifungals and reduced levels of heme

摘要

Genetic disruption of the Saccharomyces cerevi- siae C-4 sterol methyl oxidase ERG25 gene leads to sterol auxot- rophy. We have characterized a suppression system that requires two mutations to restore viability to this disrupted strain. One suppressor mutation is erg11, which is blocked in 14- demethylation of lanosterol and is itself an auxotroph. The second suppressor mutation required is either slu1 or slu2 (suppressor of lanosterol utilization). These mutations are leaky versions of HEM2 and HEM4, respectively; addition of exogenous hemin reverses the suppressing effects of slu1 and slu2. Suppression of erg25 by erg11 slu1 (or erg11 slu2) results in a slow-growing strain in which lanosterol, the first sterol in the pathway, accumulates.