Direct activation of genes involved in intracellular iron use by the yeast iron-responsive transcription factor Aft2 without its paralog Aft1.
The yeast Saccharomyces cerevisiae contains a pair of paralogous iron-responsive transcription activators, Aft1 and Aft2. Aft1 activates the cell surface iron uptake systems in iron depletion, while the role of Aft2 remains poorly understood. This study compares the functions of Aft1 and Aft2 in regulating the transcription of genes involved in iron homeostasis, with reference to the presence/absence of the paralog. Cluster analysis of DNA microarray data identified the classes of genes regulated by Aft1 or Aft2, or both. Aft2 activates the transcription of genes involved in intracellular iron use in the absence of Aft1. Northern blot analyses, combined with chromatin immunoprecipitation experiments on selected genes from each class, demonstrated that Aft2 directly activates the genes SMF3 and MRS4 involved in mitochondrial and vacuolar iron homeostasis, while Aft1 does not. Computer analysis found different cis-regulatory elements for Aft1 and Aft2, and transcription analysis using variants of the FET3 promoter indicated that Aft1 is more specific for the canonical iron-responsive element TGCACCC than is Aft2. Finally, the absence of either Aft1 or Aft2 showed an iron-dependent increase in the amount of the remaining paralog. This may provide additional control of cellular iron homeostasis.
Courel
Maïté
M
Laboratoire d'Ingénierie des Protéines et Contrôle Métabolique, Département de Biologie des Génomes, Institut Jacques-Monod, UMR 7592 CNRS-Universités Paris 6 and 7, 2 Place Jussieu, F-75251 Paris cedex 05, France.
Lallet
Sylvie
S
Camadro
Jean-Michel
JM
Blaiseau
Pierre-Louis
PL
D027682:Cation Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D002570:Ceruloplasmin / Q000096:biosynthesis / Q000235:genetics; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D007424:Intracellular Fluid / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D018085:Regulon / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology
C090297:AFT1 protein, S cerevisiae; C436328:Aft2 protein, S cerevisiae; D027682:Cation Transport Proteins; C098723:FTR1 protein, S cerevisiae; C066986:MRS4 protein, S cerevisiae; D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; C416344:Smf3 protein, S cerevisiae; D015534:Trans-Activators; D014157:Transcription Factors; D007501:Iron; D002570:Ceruloplasmin; C085513:FET3 protein, S cerevisiae