Schizosaccharomyces pombe Grx4 regulates the transcriptional repressor Php4 via [2Fe-2S] cluster binding

• Published in: Metallomics 2017-08, Vol.9 (8), p.1096-1105
• Main Authors: Dlouhy, Adrienne C, Beaudoin, Jude, Labbé, Simon, Outten, Caryn E
• Format: Article
• Language: English
• Subjects: CCAAT-Binding Factor - genetics; CCAAT-Binding Factor - metabolism; Cysteine - metabolism; Gene Expression Regulation, Fungal; Glutaredoxins - genetics; Glutaredoxins - metabolism; Iron - metabolism; Iron-Sulfur Proteins - genetics; Iron-Sulfur Proteins - metabolism; Models, Molecular; Schizosaccharomyces - growth & development; Schizosaccharomyces - metabolism; Schizosaccharomyces pombe Proteins - genetics; Schizosaccharomyces pombe Proteins - metabolism; Signal Transduction
• ISSN: 1756-5901; 1756-591X
• DOI: 10.1039/c7mt00144d

The fission yeast Schizosaccharomyces pombe expresses the CCAAT-binding factor Php4 in response to iron deprivation. Php4 forms a transcription complex with Php2, Php3, and Php5 to repress the expression of iron proteins as a means to economize iron usage. Previous in vivo results demonstrate that the function and location of Php4 are regulated in an iron-dependent manner by the cytosolic CGFS type glutaredoxin Grx4. In this study, we aimed to biochemically define these protein-protein and protein-metal interactions. Grx4 was found to bind a [2Fe-2S] cluster with spectroscopic features similar to other CGFS glutaredoxins. Grx4 and Php4 also copurify as a complex with a [2Fe-2S] cluster that is spectroscopically distinct from the cluster on Grx4 alone. In vitro titration experiments suggest that these Fe-S complexes may not be interconvertible in the absence of additional factors. Furthermore, conserved cysteines in Grx4 (Cys172) and Php4 (Cys221 and Cys227) are necessary for Fe-S cluster binding and stable complex formation. Together, these results show that Grx4 controls Php4 function through binding of a bridging [2Fe-2S] cluster.