title: CC-type glutaredoxins recruit the transcriptional co-repressor TOPLESS to TGA-dependent target promoters in Arabidopsis thaliana.
abstract: Glutaredoxins (GRXs) are small proteins which bind glutathione to either reduce disulfide bonds or to coordinate iron sulfur clusters. Whereas these well-established functions are associated with ubiquitously occurring GRXs that encode variants of a CPYC or a CGFS motif in the active center, land plants also possess CCxC/S-type GRXs (named ROXYs in Arabidopsis thaliana) for which the biochemical functions are yet unknown. ROXYs and CC-type GRXs from rice and maize physically and genetically interact with bZIP transcription factors of the TGA family to control developmental and stress-associated processes. Here we demonstrate that ROXYs interact with transcriptional co-repressors of the TOPLESS (TPL) family which are related to Tup1 in fungi and Groucho/TLE in animals. In ROXYs, the functionally important conserved A(L/I)W(L/V) motif at the very C terminus mediates the interaction with TPL. A ternary TGA2/ROXY19/TPL complex is formed when all three proteins are co-expressed in yeast. Loss-of-function evidence for the role of TPL in ROXY19-mediated repression was hampered by the redundancy of the five members of the TPL gene family and developmental defects of higher order tpl mutants. As an alternative strategy, we ectopically expressed known TPL-interacting proteins in order to out-compete the amount of available TPL in transiently transformed protoplasts. Indeed, ROXY19-mediated transcriptional repression was strongly alleviated by this approach. Our data suggest a yet unrecognized function of GRXs acting as adapter proteins for the assembly of transcriptional repressor complexes on TGA-regulated target promoters.
authors.affiliation: Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany.
authors.forename: Joachim F
authors.initials: JF
authors.lastname: Uhrig
authors.affiliation: Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany.
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Huang
authors.affiliation: Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany.
authors.forename: Sina
authors.initials: S
authors.lastname: Barghahn
authors.affiliation: Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Willmer
authors.affiliation: Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany.
authors.forename: Corinna
authors.initials: C
authors.lastname: Thurow
authors.affiliation: Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany. Electronic address: cgatz@gwdg.de.
authors.forename: Christiane
authors.initials: C
authors.lastname: Gatz
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D056970:Co-Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D054477:Glutaredoxins / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011523:Protoplasts / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D015003:Yeasts / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D056970:Co-Repressor Proteins; D054477:Glutaredoxins; D005978:Glutathione; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C511291:At1g15750 protein, Arabidopsis
keywords: Arabidopsis thaliana; Gene expression; Glutaredoxins; ROXYs; TGA transcription factors; TOPLESS