7tae
From Proteopedia
Crystal Structure of the NPR1-Interacting Domain of TGA3
Structural highlights
FunctionTGA3_ARATH Transcriptional activator that binds specifically to the DNA sequence 5'-TGACG-3'. Recognizes ocs elements like the as-1 motif of the cauliflower mosaic virus 35S promoter. Binding to the as-1-like cis elements mediate auxin- and salicylic acid-inducible transcription. Required to induce the systemic acquired resistance (SAR) via the regulation of pathogenesis-related genes expression. Binding to the as-1 element of PR-1 promoter is salicylic acid-inducible and mediated by NPR1. Could also bind to the Hex-motif (5'-TGACGTGG-3') another cis-acting element found in plant histone promoters.[1] Publication Abstract from PubMedNPR1 is a master regulator of the defence transcriptome induced by the plant immune signal salicylic acid(1-4). Despite the important role of NPR1 in plant immunity(5-7), understanding of its regulatory mechanisms has been hindered by a lack of structural information. Here we report cryo-electron microscopy and crystal structures of Arabidopsis NPR1 and its complex with the transcription factor TGA3. Cryo-electron microscopy analysis reveals that NPR1 is a bird-shaped homodimer comprising a central Broad-complex, Tramtrack and Bric-a-brac (BTB) domain, a BTB and carboxyterminal Kelch helix bundle, four ankyrin repeats and a disordered salicylic-acid-binding domain. Crystal structure analysis reveals a unique zinc-finger motif in BTB for interacting with ankyrin repeats and mediating NPR1 oligomerization. We found that, after stimulation, salicylic-acid-induced folding and docking of the salicylic-acid-binding domain onto ankyrin repeats is required for the transcriptional cofactor activity of NPR1, providing a structural explanation for a direct role of salicylic acid in regulating NPR1-dependent gene expression. Moreover, our structure of the TGA32-NPR12-TGA32 complex, DNA-binding assay and genetic data show that dimeric NPR1 activates transcription by bridging two fatty-acid-bound TGA3 dimers to form an enhanceosome. The stepwise assembly of the NPR1-TGA complex suggests possible hetero-oligomeric complex formation with other transcription factors, revealing how NPR1 reprograms the defence transcriptome. Structural basis of NPR1 in activating plant immunity.,Kumar S, Zavaliev R, Wu Q, Zhou Y, Cheng J, Dillard L, Powers J, Withers J, Zhao J, Guan Z, Borgnia MJ, Bartesaghi A, Dong X, Zhou P Nature. 2022 May;605(7910):561-566. doi: 10.1038/s41586-022-04699-w. Epub 2022, May 11. PMID:35545668[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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