title: The Arabidopsis NPR1 disease resistance protein is a novel cofactor that confers redox regulation of DNA binding activity to the basic domain/leucine zipper transcription factor TGA1.
abstract: The Arabidopsis NPR1 protein is essential for regulating salicylic acid-dependent gene expression during systemic acquired resistance. NPR1 interacts differentially with members of the TGA class of basic domain/Leu zipper transcription factors and regulates their DNA binding activity. Here, we report that although TGA1 does not interact with NPR1 in yeast two-hybrid assays, treatment with salicylic acid induces the interaction between these proteins in Arabidopsis leaves. This phenomenon is correlated with a reduction of TGA1 Cys residues. Furthermore, site-directed mutagenesis of TGA1 Cys-260 and Cys-266 enables the interaction with NPR1 in yeast and Arabidopsis. Together, these results indicate that TGA1 relies on the oxidation state of Cys residues to mediate the interaction with NPR1. An intramolecular disulfide bridge in TGA1 precludes interaction with NPR1, and NPR1 can only stimulate the DNA binding activity of the reduced form of TGA1. Unlike its animal and yeast counterparts, the DNA binding activity of TGA1 is not redox regulated; however, this property is conferred by interaction with the NPR1 cofactor.
authors.affiliation: Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada L2S 3A1.
authors.forename: Charles
authors.initials: C
authors.lastname: Després
authors.forename: Catherine
authors.initials: C
authors.lastname: Chubak
authors.forename: Amanda
authors.initials: A
authors.lastname: Rochon
authors.forename: Rena
authors.initials: R
authors.lastname: Clark
authors.forename: Terry
authors.initials: T
authors.lastname: Bethune
authors.forename: Darrell
authors.initials: D
authors.lastname: Desveaux
authors.forename: Pierre R
authors.initials: PR
authors.lastname: Fobert
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001419:Bacteria / Q000254:growth & development; D050976:Basic-Leucine Zipper Transcription Factors; D003545:Cysteine / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D007113:Immunity, Innate / Q000235:genetics; D016350:Leucine Zippers / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins; D010084:Oxidation-Reduction / Q000187:drug effects; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics; D020156:Salicylic Acid / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: C489413:AHBP-1b protein, Arabidopsis; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C105496:NPR1 protein, Arabidopsis; D009687:Nuclear Proteins; D010940:Plant Proteins; D014157:Transcription Factors; C068757:HBP-1b protein, plant; D003545:Cysteine; D020156:Salicylic Acid