Structure of Radical-Induced Cell Death1 Hub Domain Reveals a Common αα-Scaffold for Disorder in Transcriptional Networks

Communication within cells relies on a few protein nodes called hubs, which organize vast interactomes with many partners. Frequently, hub proteins are intrinsically disordered conferring multi-specificity and dynamic communication. Conversely, folded hub proteins may organize networks using disordered partners. In this work, the structure of the RST domain, a unique folded hub, is solved by nuclear magnetic resonance spectroscopy and small-angle X-ray scattering, and its complex with a region of the transcription factor DREB2A is provided through data-driven HADDOCK modeling and mutagenesis analysis. The RST fold is unique, but similar structures are identified in the PAH (paired amphipathic helix), TAFH (TATA-box-associated factor homology), and NCBD (nuclear coactivator binding domain) domains. We designate them as a group the αα hubs, as they share an αα-hairpin super-secondary motif, which serves as an organizing platform for malleable helices of varying topology. This allows for partner adaptation, exclusion, and selection. Our findings provide valuable insights into structural features enabling signaling fidelity. [Display omitted] •Structure determination of the RST hub domain reveals unique L-glove helix fold•RST, PAH, TAFH, and NCBD define the αα-hub family of transcriptional regulators•The αα hubs and disordered partners display various degrees of folding-upon-binding•Different helical topologies in each domain govern barcoding for network fidelity Bugge and Staby et al. determine the structure of the plant RCD1-RST hub domain illuminating details of its interactions with disordered partners of its stress-associated interactome. The study reveals structural similarities to important human hub domains defining the αα hubs of transcriptional regulators. Different helical topologies may govern barcoding for network fidelity.