A hapl Mutation in a Laboratory Strain of Saccharomyces cerevisiae Results in Decreased Expression of Ergosterol-Related Genes and Cellular Ergosterol Content Compared to Sake Yeast

摘要

DNA microarray and Northern blot analysis revealed that a sake yeast strain Kyokai no. 7 (K7) showed higher expression of genes encoding proteins involved in ergosterol biosynthesis than a laboratory yeast strain X2180. We hypothesized that these differences in expression levels were caused by a defect of a transcriptional factor Hapl, because strain X2180 contained a Tyl inser­tion mutation in the HAP1 gene. To confirm this, we constructed a strain X2180 derivative (strain HX) that contained the wild-type HAP1 genes originating from strain K7. The expression levels of ergosterol-related genes and cellular ergosterol content in strain HX were higher than those in strain X2180 and were almost comparable to those in strain K7. These results suggest that the dif­ferences in the expression levels of ergosterol-related genes and ergosterol content between strains K7 and X2180 were largely caused by the hapl mutation in strain X2180. Involvement of the mu­tated Hapl in the differential gene expression between strain K7 and strain X2180 was further confirmed by a lacZ reporter assay of HMG1, one of the Hapl-regulated genes. We also revealed that the HMG1 promoter region between -500 and -376 was important in the transcriptional ac­tivation by Hapl.