title: Inhibition of heme biosynthesis prevents transcription of iron uptake genes in yeast.
abstract: Yeast are capable of modifying their metabolism in response to environmental changes. We investigated the activity of the oxygen-dependent high-affinity iron uptake system of Saccharomyces cerevisiae under conditions of heme depletion. We found that the absence of heme, due to a deletion in the gene that encodes delta-aminolevulinic acid synthase (HEM1), resulted in decreased transcription of genes belonging to both the iron and copper regulons, but not the zinc regulon. Decreased transcription of the iron regulon was not due to decreased expression of the iron sensitive transcriptional activator Aft1p. Expression of the constitutively active allele AFT1-1up was unable to induce transcription of the high affinity iron uptake system in heme-depleted cells. We demonstrated that under heme-depleted conditions, Aft1p-GFP was able to cycle normally between the nucleus and cytosol in response to cytosolic iron. Despite the inability to induce transcription under low iron conditions, chromatin immunoprecipitation demonstrated that Aft1p binds to the FET3 promoter in the absence of heme. Finally, we provide evidence that under heme-depleted conditions, yeast are able to regulate mitochondrial iron uptake and do not accumulate pathologic iron concentrations, as is seen when iron-sulfur cluster synthesis is disrupted.
authors.affiliation: Division of Cell Biology and Immunology, Department of Pathology, School of Medicine, University of Utah, Salt Lake City, Utah, 84132, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Crisp
authors.forename: Annette
authors.initials: A
authors.lastname: Pollington
authors.forename: Charles
authors.initials: C
authors.lastname: Galea
authors.forename: Shulamit
authors.initials: S
authors.lastname: Jaron
authors.forename: Yuko
authors.initials: Y
authors.lastname: Yamaguchi-Iwai
authors.forename: Jerry
authors.initials: J
authors.lastname: Kaplan
mesh_terms: D000483:Alleles; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D003300:Copper / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006418:Heme / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000737:chemistry; D007501:Iron / Q000378:metabolism / Q000493:pharmacokinetics*; D008164:Luminescent Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D015719:Single-Strand Specific DNA and RNA Endonucleases / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D015032:Zinc / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: C090297:AFT1 protein, S cerevisiae; D002843:Chromatin; D008164:Luminescent Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D006418:Heme; D003300:Copper; D007501:Iron; D015719:Single-Strand Specific DNA and RNA Endonucleases; D001616:beta-Galactosidase; D015032:Zinc; D010100:Oxygen