Allelism of Saccharomyces cerevisiae genes PSO6, involved in survival after 3-CPs+UVA induced damage, and ERG3, encoding the enzyme sterol C-5 desaturase.
Sequencing of the yeast gene that complemented the sensitivity to the photoactivated monofunctional 3-carbethoxypsoralen of the pso6-1 mutant strain revealed that the ERG3 locus, encoding sterol C-5 desaturase involved in biosynthesis of ergosterol, is allelic to PSO6. Disruption of the ERG3 gene yielded an erg3Delta mutant viable in ergosterol-containing YEPD media with the same pleiotropic mutant phenotype known for pso6-1 and erg3 mutants, including sensitivity to hydrogen peroxide and paraquat. Thus, the erg3/pso6 yeast mutant seems to be more sensitive than the WT to 3-CPs+UVA because of the oxidative damage contributed by this treatment and not because of an impaired repair of the furocoumarin-thymine monoadducts formed in the DNA. We found a significant increase of petites amongst erg3Delta and pso6-1 yeast mutant strains grown in conditions where respiration was mandatory. Mutant pso6-1, with its lowered content of ergosterol, exhibited enhanced synthesis of chitin that was maldistributed and not confined to the bud scars. Chitin overproduction in pso6/erg3 mutants resulted in hypersensitivity to Calcofluor White.
Schmidt
C L
CL
Departamento de Biofisica/Centro de Biotecnologia, UFRGS, A. Bento Goncalves 9500, 91507-970 Porto Alegre, RS, Brazil.
Grey
M
M
Schmidt
M
M
Brendel
M
M
Henriques
J A
JA
D000483:Alleles; D002686:Chitin / Q000032:analysis / Q000096:biosynthesis; D003001:Cloning, Molecular; D011564:Furocoumarins / Q000494:pharmacology*; D005800:Genes, Fungal; D009154:Mutation; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D014466:Ultraviolet Rays
D011564:Furocoumarins; D002686:Chitin; C017104:3-carbethoxypsoralen; D010088:Oxidoreductases; C039306:sterol delta-5 desaturase