Iron-regulated DNA binding by the AFT1 protein controls the iron regulon in yeast.

Iron deprivation of Saccharomyces cerevisiae induces transcription of genes required for high-affinity iron uptake. AFT1 mediates this transcriptional control. In this report, the 5'-flanking region of FET3, which encodes a copper-dependent oxidase required for iron transport, was analyzed and found to contain a DNA sequence responsible for AFT1-regulated gene expression. AFT1 was capable of interacting specifically with this DNA sequence. A core element within this DNA sequence necessary for the binding of AFT1 was also determined. In vivo footprinting demonstrated occupancy of the AFT1 binding site in cells deprived of iron and not in cells grown in the presence of iron. Thus, the environmental signal resulting from iron deprivation was transduced through the regulated binding of AFT1 to the FET3 promoter, followed by the activation of transcription. A regulon of genes under the control of AFT1 could be defined. AFT1 was able to bind to a consensus binding site (PyPuCACCCPu) in the 5' region of FRE1, FRE2, FTR1, FTH1 and CCC2.