SDS-associated EFL1 mutations map to key functional interfaces. SBDS C-terminal domain, magenta, space-filling representation; EFL1, cyan; eIF6, yellow (Protein Data Bank accession number 5anb), ribbon representation. EFL1 domains II, III, and IV are indicated. EFL1 residues targeted by mutations that map to the interface with SBDS are encircled. Residues mutated in SDS are indicated in black (this study) or red (Stepensky et al⁴¹ ) text; residue K976 (cyan) is targeted in the mouse model (this study). H69, rRNA helix 69.