Shaikhali J, Noren L, Barajas-Lopez JD, Srivastava V, Konig J, Sauer UH, Wingsle G, Dietz KJ, Strand A
Redox-mediated mechanisms regulate DNA-binding activity of the G-group of bZIP transcription factors in Arabidopsis.
J Biol Chem. 2012, 287(33):27510-25
Plant genes which contain the Gbox in their promoters are responsive to a variety of environmental stimuli. Bioinformatic analysis of transcriptome data revealed that the Gbox element is significantly enriched in promoters of high light (HL)-responsive genes. From nuclear extracts of HL-treated Arabidopsis plants we identified the AtbZIP16 transcription factor as a component binding to the Gbox containing promoter fragment of LIGHT-HARVESTING CHLOROPHYLL A/B-BINDING PROTEIN2.4 (LHCB2.4). AtbZIP16 belongs to the G-group of Arabidopsis basic region leucine zipper (bZIP) type transcription factors. While AtbZIP16 and its close homologues AtbZIP68 and AtGBF1 bind the Gbox, they do not bind the mutated half sites of the Gbox palindrome. In addition, AtbZIP16 interacts with AtbZIP68 and AtGBF1 in the yeast two hybrid system. A conserved Cys residue was shown to be necessary for redox regulation and enhancement of DNA-binding activity in all three proteins. Furthermore, transgenic Arabidopsis lines over-expressing the wild type version of bZIP16 and T-DNA insertion mutants for bZIP68 and GBF1 demonstrated impaired regulation of LHCB2.4 expression. Finally, over expression lines for the mutated Cys variant of bZIP16 provided support for the biological significance of Cys330 in redox regulation of gene expression. Thus, our results suggest that environmentally induced changes in redox state regulate the activity of members of the G-group of bZIP transcription factors.
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