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The monothiol glutaredoxin Grx4 exerts an iron-dependent inhibitory effect on Php4 function.
Philippe Vachon1, Alexandre Mercier, Mehdi Jbel
1Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC, Canada.
Eukaryotic Cell
|April 24, 2012
Summary
Iron regulation in yeast involves Php4 protein interactions. Grx4
Area of Science:
- Molecular Biology
- Cellular Regulation
- Yeast Genetics
Background:
- Iron is essential for cellular function, and its scarcity triggers transcriptional repression of iron-utilizing genes in yeast.
- The transcription factor Php4 regulates this process by interacting with the CCAAT-binding core complex (Php2, Php3, Php5).
- Iron sufficiency leads to Php4 inactivation, permitting transcription of iron-requiring genes.
Purpose of the Study:
- To investigate the interaction between Php4 and the glutaredoxin Grx4.
- To elucidate the role of Grx4 domains in mediating iron-dependent regulation of Php4 activity.
Main Methods:
- Bimolecular fluorescence complementation (BiFC) assays.
- Yeast two-hybrid assays.
- Deletion mapping and site-directed mutagenesis.
Main Results:
- Php4 physically interacts with Grx4.
- The glutaredoxin (GRX) domain of Grx4 associates with Php4 in an iron-dependent manner, requiring Cys172.
- The thioredoxin (TRX) domain of Grx4 interacts constitutively with Php4, requiring Cys35, and this interaction is iron-insensitive.
Conclusions:
- The TRX domain of Grx4 constitutively interacts with Php4.
- The GRX domain-Php4 association is iron-modulated and crucial for inhibiting Php4 activity during iron repletion.
- This study reveals a novel mechanism of iron-dependent gene regulation involving specific protein-protein interactions.
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