Functional Genomics Analysis of the Saccharomyces cerevisiae Iron Responsive Transcription Factor Aft1 Reveals Iron-Independent Functions

Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario K1A 0C6, Canada.
Genetics (Impact Factor: 5.96). 05/2010; 185(3):1111-28. DOI: 10.1534/genetics.110.117531
Source: PubMed


The Saccharomyces cerevisiae transcription factor Aft1 is activated in iron-deficient cells to induce the expression of iron regulon genes, which coordinate the increase of iron uptake and remodel cellular metabolism to survive low-iron conditions. In addition, Aft1 has been implicated in numerous cellular processes including cell-cycle progression and chromosome stability; however, it is unclear if all cellular effects of Aft1 are mediated through iron homeostasis. To further investigate the cellular processes affected by Aft1, we identified >70 deletion mutants that are sensitive to perturbations in AFT1 levels using genome-wide synthetic lethal and synthetic dosage lethal screens. Our genetic network reveals that Aft1 affects a diverse range of cellular processes, including the RIM101 pH pathway, cell-wall stability, DNA damage, protein transport, chromosome stability, and mitochondrial function. Surprisingly, only a subset of mutants identified are sensitive to extracellular iron fluctuations or display genetic interactions with mutants of iron regulon genes AFT2 or FET3. We demonstrate that Aft1 works in parallel with the RIM101 pH pathway and the role of Aft1 in DNA damage repair is mediated by iron. In contrast, through both directed studies and microarray transcriptional profiling, we show that the role of Aft1 in chromosome maintenance and benomyl resistance is independent of its iron regulatory role, potentially through a nontranscriptional mechanism.

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Available from: Linda J Harris, Aug 14, 2014
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    • "Grx3p/4p can interact with Fra2p and Aft1p/Aft2p, and the Grx3p/4p- bound Fe-S clusters may function as sensors for the cytosolic iron pool (Lill and Mühlenhoff, 2008; Muhlenhoff et al., 2010). In low-Fe condition, Aft1p can shuttle between the cytosol and the nucleus in an iron-responsive manner, and functions as a transcriptional activator of iron regulon genes, which subsequently activate high-affinity iron uptake systems (Berthelet et al., 2010; Lill et al., 2012) "
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    • "Analysed genes are listed in Table S2, and many of them correspond to Gene Ontology categories related to mRNA catabolism and decay. Several previous studies have analysed the full collection of S. cerevisiae null mutants for hypersensitivity to iron-deprivation conditions (Davis-Kaplan et al., 2004; Dudley et al., 2005; Jo et al., 2009; Berthelet et al., 2010) or alterations in iron uptake (Lesuisse et al., 2005). Some coincidences are observed between our results with RNA binding protein mutants (Table S2) and the above studies. "
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    • "Thus, it is conceivable that the sensing of cellular iron content depends on the amount of ISCs generated in, and exported from, the mitochondria. Mutants of genes coding for enzymes that are central to DNA replication and DNA damage response are sensitive to the reduction of intracellular iron levels in aft1Δ cells (56). These genetic interactions reinforce the idea that a reduced availability of ISCs lowers the activity of ISC-requiring enzymes that act in DNA replication and the damage response pathways that are needed to preserve genome stability. "
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