Simon Labbé’s work on iron and copper homeostasis

Figure 2 A proposed transcription model for an “iron economy”. Under low iron supply conditions, Fep1 cannot bind to DNA and php4⁺ is expressed. Once biosynthesized, Php4 interacts with the Php2/Php3/Php5 heterotrimer to mediate repression of genes that encode iron-storage (Pcl1) and iron-containing (Sdh4 and Isa1) proteins, as well as the fep1⁺ gene. Conversely, under iron-replete conditions, Fep1 binds DNA and, with the aid of Tup11 and Tup12, turns off php4⁺ gene expression. This inactivation of php4⁺ enables genes involved in storage and utilization of iron to be expressed via the Php2/Php3/Php5 heterotrimeric CCAAT binding factor.