We conducted a genome-wide screen in the budding yeast Saccharomyces cerevisiae of 4,792 homozygous diploid deletions to identify genes that function in iron metabolism. Strains unable to grow on iron-restricted medium contained deletions of genes that encode the structural components of the high affinity iron transport system (FET3, FTR1), the iron-sensing transcription factor AFT1 or genes required for the assembly of the transport system. We also identified genes that were not previously known to play a role in iron metabolism. Deletion of the gene CWH36 resulted in a severe growth defect on iron-limited medium, as well as increased sensitivity to Congo red and calcofluor white. Iron transport studies demonstrated that Δcwh36 cells have an inability to copper load apoFet3p. Furthermore, Δcwh36 cells demonstrated additional phenotypes including distorted vacuole morphology and altered kinetics of FM4-64 trafficking. We show that Δcwh36 cells have a defect in vacuolar acidification through the use of the pH-sensitive dye LysoSensor Green DND-189. In Δcwh36 cells, the vacuolar H+-ATPase is not assembled and there are reduced levels of at least one subunit of the V0 complex. The open reading frame responsible for the Δcwh36 phenotypes is YCL005W-A. This gene contains two introns, has homologues in other Saccharomyces strains, and shows weak homology to a component of the vacuolar H+-ATPase found in organisms as diverse as insect and cow.
This work was supported in part by NIDDK, National Institutes of Health Grant DK-30534. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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