Speaker
Description
Optimizing auxin-mediated plant development is critical for global food security, as this phytohormone regulates plant architecture and environmental adaptation. This process relies on a chromatin-based regulatory switch in which activator Auxin Response Factors (ARFs), particularly AtARF5/MONOPTEROS, recruit the BRAHMA (BRM) ATPase-associated SWI/SNF chromatin remodeling complex to modulate target gene expression, as demonstrated in vivo.
In this context, we aim to resolve the full-length structure of BRAHMA from Arabidopsis thaliana, a long-standing objective in our research group. However, the large size of BRM presents significant challenges for recombinant expression and structural characterization. To overcome these limitations, we propose a domain-based dissection strategy focusing on three key regions: the bromodomain, the ATPase domain, and an α-helical domain. The bromodomain acts as a histone mark reader by recognizing acetylated lysine residues on histone tails, thereby contributing to genomic targeting. The ATPase domain, a helicase-like catalytic core, uses ATP hydrolysis to reposition nucleosomes through sliding or ejection. The α-helical regions are expected to provide structural stability and mediate protein–protein interactions within the complex.
In addition, we describe the production of regulatory subunits ARP4 and ARP7, actin-related proteins that contribute to the stability and function of SWI/SNF complexes. Understanding their roles will help clarify how BRM-containing complexes are assembled and regulated during chromatin remodeling. Although this strategy successfully yielded crystals of the BRM bromodomain, the diffraction data obtained were not of sufficient quality to solve the structure. Therefore, optimizing the crystallization conditions remains a critical challenge for obtaining high-quality datasets and achieving structural determination.
These results provide a foundation for reconstructing the architecture of full-length BRM. By integrating this structural characterization with our group’s “molecular caliper” model, we aim to establish a mechanistic framework for how AtARF5 dimers engage the chromatin remodeling machinery to regulate gene expression through structural characterization of BRAHMA in Arabidopsis.