Iron uptake and regulation in Schizosaccharomyces pombe

• Abc3 functions in the transport of vacuolar iron stores.
• When iron is abundant, Fep1 represses genes involved in iron acquisition.
• Grx4 is an inhibitory binding partner of Fep1 under conditions of low levels of iron.
• Under low iron levels, Php4 fosters repression of genes encoding iron-using proteins.
• Grx4 is an inhibitory binding partner of Php4 under conditions of high levels of iron.

Schizosaccharomyces pombe is a useful model system for understanding many aspects of eukaryotic cell growth. Studies of S. pombe have identified novel genes that function in the regulation of iron homeostasis. In response to high levels of iron, Fep1 represses the expression of several genes involved in the acquisition of iron. When iron levels are limited, optimization of cellular iron utilization is coordinated by Php4, which represses genes encoding iron-using proteins. Results from studies in yeast have shed new light on the role of monothiol glutaredoxins (Grxs) in iron homeostasis. In S. pombe, the Grx4 protein serves as an inhibitory partner for Fep1 in response to iron deficiency, whereas it is required for the inhibition of Php4 under iron-replete conditions.