Glutaredoxin GRXS17 Associates with the Cytosolic Iron-Sulfur Cluster Assembly Pathway

Abstract

Cytosolic monothiol glutaredoxins (GRXs) are required in iron-sulfur (Fe-S) cluster delivery and iron sensing in yeast and mammals. In plants, it is unclear whether they have similar functions. Arabidopsis (Arabidopsis thaliana) has a sole class II cytosolic monothiol GRX encoded by GRXS17. Here, we used tandem affinity purification to establish that Arabidopsis GRXS17 associates with most known cytosolic Fe-S assembly (CIA) components. Similar to mutant plants with defective CIA components, grxs17 loss-of-function mutants showed some degree of hypersensitivity to DNA damage and elevated expression of DNA damage marker genes. We also found that several putative Fe-S client proteins directly bind to GRXS17, such as XANTHINE DEHYDROGENASE1 (XDH1), involved in the purine salvage pathway, and CYTOSOLIC THIOURIDYLASE SUBUNIT1 and CYTOSOLIC THIOURIDYLASE SUBUNIT2, both essential for the 2-thiolation step of 5-methoxycarbonylmethyl-2-thiouridine (mcm 5 s 2 U) modification of tRNAs. Correspondingly, profiling of the grxs17-1 mutant pointed to a perturbed flux through the purine degradation pathway and revealed that it phenocopied mutants in the elongator subunit ELO3, essential for the mcm 5 tRNA modification step, although we did not find XDH1 activity or tRNA thiolation to be markedly reduced in the grxs17-1 mutant. Taken together, our data suggest that plant cytosolic monothiol GRXs associate with the CIA complex, as in other eukaryotes, and contribute to, but are not essential for, the correct functioning of client Fe-S proteins in unchallenged conditions.

Involvement of Arabidopsis glutaredoxin S14 in the maintenance of chlorophyll content

“…The participation of class II GRXs in Fe–S cluster assembly in vivo in plants remained elusive until recent reports on Arabidopsis lines expressing mitochondrial GRXS15 variant forms that displayed decreased activity of aconitase, an Fe–S cluster‐containing enzyme (Moseler et al, ), and on knockdown lines showing defects in the maturation of the mitochondrial lipoate synthase, an Fe–S enzyme (Ströher et al, ). Concerning the nucleocytosolic GRXS17, the evidence comes from its association with known cytosolic Fe–S cluster assembly components of the cytosolic machinery and with several putative Fe–S client proteins (Iñigo et al, ).…”

“…its association with known cytosolic Fe-S cluster assembly components of the cytosolic machinery and with several putative Fe-S client proteins (Iñigo et al, 2016).…”

Characterization of Glutaredoxin Fe–S Cluster-Binding Interactions Using Circular Dichroism Spectroscopy

“…CGFS glutaredoxins, either alone or in concert with BolA proteins, have been shown to accept, store, and deliver Fe-S clusters to a wide variety of acceptor proteins (Banci et al, 2014; Banci, Camponeschi, et al, 2015; Banci, Ciofi-Baffoni, et al, 2015; Bandyopadhyay et al, 2008; Boutigny et al, 2013; Frey, Palenchar, Wildemann, & Philpott, 2016; Hoffmann et al, 2011; Iñigo et al, 2016; Kim, Chung, Kim, Lee, & Roe, 2010; Mapolelo et al, 2013; Melber et al, 2016; Mühlenhoff et al, 2010; Poor et al, 2014; Shakamuri et al, 2012; Ströher et al, 2016; Uzarska et al, 2016; Vranish et al, 2016; Xia et al, 2015; Zhang et al, 2013). In S. cerevisiae , transfer of a [2Fe-2S] cluster from Grx3/4-Fra2 to the transcription factor Aft1/2 is proposed to be the key mechanism for regulating Aft1/2 activity in response to iron (Poor et al, 2014).…”

Redox response of iron-sulfur glutaredoxin GRXS17 activates its holdase activity to protect plants from heat stress

“…GRXS17 is capable of complementing the defect of the yeast grx5 deletion mutant by transferring Fe-S clusters to mitochondrial acceptor proteins (Bandyopadhyay et al, 2008; Knuesting et al, 2015). Affinity chromatography approaches with crude extracts have shown that GRXS17 associates with known cytosolic iron-sulfur protein assembly (CIA) components like Met18, Dre2, and with other cytosolic Fe-S cluster-containing proteins like xanthine dehydrogenase 1 (XDH1) and thiouridylase subunits 1 and 2 (Iñigo et al, 2016; Wang et al, 2019). GRXS17 can be additionally found in the nucleus, and it interacts with cytosolic BolA2 (Couturier et al, 2014) and with NF-YC11, a subunit of the NF-Y transcription factor complex (Knuesting et al, 2015).…”

“…However, for most of its partners, the role of the Fe-S cluster remained enigmatic. Genetic evidence from different plant species suggests a protective role of GRXS17 during thermal, genotoxic and drought stress (Cheng et al, 2011; Wu et al, 2012; Wu et al, 2017; Iñigo et al, 2016; Hu et al, 2017), in meristem development (Knuesting et al, 2015), hormonal responses (Cheng et al, 2011), and during redox-dependent processes (Yu et al, 2018).…”