Residues in dsRBDs 3 and 4 make base-directed contacts with ARF1 SBS. Residues in dsRBDs 3 and 4 make base-directed contacts with ARF1 SBS. (A) Schematic representation of ARF1 SBS. Dotted lines indicate contacts between residues in hStau1 dsRBD3A (dark blue), dsRBD3B (blue), or dsRBD4 (cyan), and the RNA. Red dots mark residues interacting with the RNA bases (colored in the scheme). (B–E) Detailed views of the base-directed interactions, with hydrogen bonds indicated as dotted lines. The view is down the RNA helix axis. Nucleotides of the ARF1 SBS sense and antisense strand are in black and gray, respectively. (F)Kd values determined by FA using 5ʹ-fluorescein-labeled ARF1 SBS, either single or double stranded, or a dsRNA of the same length and of a random AU sequence (dsAU). Daniela Lazzaretti et al. LSA 2018;1:e201800187 © 2018 Crown copyright. The government of Australia, Canada, or the UK ("the Crown") owns the copyright interests of authors who are government employees. The Crown Copyright is not transferable.