title: The BTB/POZ domain of the Arabidopsis disease resistance protein NPR1 interacts with the repression domain of TGA2 to negate its function.
abstract: TGA2 and NONEXPRESSER OF PR GENES1 (NPR1) are activators of systemic acquired resistance (SAR) and of the SAR marker gene pathogenesis-related-1 (PR-1) in Arabidopsis thaliana. TGA2 is a transcriptional repressor required for basal repression of PR-1, but during SAR, TGA2 recruits NPR1 as part of an enhanceosome. Transactivation by the enhanceosome requires the NPR1 BTB/POZ domain. However, the NPR1 BTB/POZ domain does not contain an autonomous transactivation domain; thus, its molecular role within the enhanceosome remains elusive. We now show by gel filtration analyses that TGA2 binds DNA as a dimer, tetramer, or oligomer. Using in vivo plant transcription assays, we localize the repression domain of TGA2 to the N terminus and demonstrate that this domain is responsible for modulating the DNA binding activity of the oligomer both in vitro and in vivo. We confirm that the NPR1 BTB/POZ domain interacts with and negates the molecular function of the TGA2 repression domain by excluding TGA2 oligomers from cognate DNA. These data distinguish the NPR1 BTB/POZ domain from other known BTB/POZ domains and establish its molecular role in the context of the Arabidopsis PR-1 gene enhanceosome.
authors.affiliation: Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Boyle
authors.forename: Errol
authors.initials: E
authors.lastname: Le Su
authors.forename: Amanda
authors.initials: A
authors.lastname: Rochon
authors.forename: Heather L
authors.initials: HL
authors.lastname: Shearer
authors.forename: Jhadeswar
authors.initials: J
authors.lastname: Murmu
authors.forename: Jee Yan
authors.initials: JY
authors.lastname: Chu
authors.forename: Pierre R
authors.initials: PR
authors.lastname: Fobert
authors.forename: Charles
authors.initials: C
authors.lastname: Després
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002850:Chromatography, Gel; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D007113:Immunity, Innate / Q000235:genetics*; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015388:Organelles / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D015533:Transcriptional Activation / Q000235:genetics
chemical_list: C489413:AHBP-1b protein, Arabidopsis; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D018744:DNA, Plant; D004268:DNA-Binding Proteins; C105496:NPR1 protein, Arabidopsis; D009687:Nuclear Proteins; D012097:Repressor Proteins