title: Multi-domain CGFS-type glutaredoxin Grx4 regulates iron homeostasis via direct interaction with a repressor Fep1 in fission yeast.
abstract: The fission yeast Schizosaccharomyces pombe contains two CGFS-type monothiol glutaredoxins, Grx4 and Grx5, which are localized primarily in the nucleus and mitochondria, respectively. We observed involvement of Grx4 in regulating iron-responsive gene expression, which is modulated by a repressor Fep1. Lack of Grx4 caused defects not only in growth but also in the expression of both iron-uptake and iron-utilizing genes regardless of iron availability. In order to unravel how Grx4 is involved in Fep1-mediated regulation, interaction between them was investigated. Co-immunoprecipitation and bimolecular fluorescence complementation (BiFC) revealed that Grx4 physically interacts with Fep1 in vivo. BiFC revealed localized nuclear dots produced by interaction of Grx4 with Fep1. Mutation of cysteine-172 in the CGFS motif to serine (C172S) produced effects similarly observed under Grx4 depletion, such as the loss of iron-dependent gene regulation and the absence of nuclear dots in BiFC analysis. These results suggest that the ability of Grx4 to bind iron, most likely Fe-S cofactor, could be critical in interacting with and modulating the activity of Fep1.
authors.affiliation: Laboratory of Molecular Microbiology, School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul, Republic of Korea.
authors.forename: Kyoung-Dong
authors.initials: KD
authors.lastname: Kim
authors.forename: Hyo-Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Kyung-Chang
authors.initials: KC
authors.lastname: Lee
authors.forename: Jung-Hye
authors.initials: JH
authors.lastname: Roe
mesh_terms: D020816:Amino Acid Motifs; D050980:GATA Transcription Factors / Q000235:genetics / Q000378:metabolism*; D054477:Glutaredoxins / Q000235:genetics / Q000378:metabolism*; D006706:Homeostasis; D007501:Iron / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C459859:Fep1 protein, S pombe; D050980:GATA Transcription Factors; D054477:Glutaredoxins; D029702:Schizosaccharomyces pombe Proteins; D007501:Iron; C559907:GRX4 protein, S pombe