Structural basis for the regulation of plant transcription factor WRKY33 by the VQ protein SIB1

• DOI: 10.1038/s42003-024-06258-7
• Publication Date: 2024-05-11T10:06:32Z
• Authors: Xu Dong; Lulu Yu; Qiang Zhang; Ju Yang; Zhou Gong; Xiaogang Niu; Hongwei Li; Xu Zhang; Maili Liu; Changwen Jin; Yunfei Hu
• Keywords: Models, Molecular; 0303 health sciences; QH301-705.5; Arabidopsis Proteins; Arabidopsis; Article; 03 medical and health sciences; Protein Domains; Gene Expression Regulation, Plant; Amino Acid Sequence; Biology (General); Transcription Factors; Protein Binding

AbstractThe WRKY transcription factors play essential roles in a variety of plant signaling pathways associated with biotic and abiotic stress response. The transcriptional activity of many WRKY members are regulated by a class of intrinsically disordered VQ proteins. While it is known that VQ proteins interact with the WRKY DNA-binding domains (DBDs), also termed as the WRKY domains, structural information regarding VQ-WRKY interaction is lacking and the regulation mechanism remains unknown. Herein we report a solution NMR study of the interaction between Arabidopsis WRKY33 and its regulatory VQ protein partner SIB1. We uncover a SIB1 minimal sequence neccessary for forming a stable complex with WRKY33 DBD, which comprises not only the consensus “FxxhVQxhTG” VQ motif but also its preceding region. We demonstrate that the βN-strand and the extended βN-β1 loop of WRKY33 DBD form the SIB1 docking site, and build a structural model of the complex based on the NMR paramagnetic relaxation enhancement and mutagenesis data. Based on this model, we further identify a cluster of positively-charged residues in the N-terminal region of SIB1 to be essential for the formation of a SIB1-WRKY33-DNA ternary complex. These results provide a framework for the mechanism of SIB1-enhanced WRKY33 transcriptional activity.