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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
PubMed

Insights

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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